Journal of Applied and Computational MechanicsJournal of Applied and Computational Mechanics
https://jacm.scu.ac.ir/
Fri, 27 Nov 2020 06:49:37 +0100FeedCreatorJournal of Applied and Computational Mechanics
https://jacm.scu.ac.ir/
Feed provided by Journal of Applied and Computational Mechanics. Click to visit.Non-similar Solutions of MHD Mixed Convection over an Exponentially Stretching Surface: ...
https://jacm.scu.ac.ir/article_14133_0.html
In this paper, an analysis of magnetohydrodynamic (MHD) mixed convection over an exponentially stretching surface in the presence of a non-uniform heat source/sink and suction/injection is presented. The governing boundary layer equations are transformed into a set of non-dimensional equations by using a group of non-similar transformations. The resulting highly non-linear coupled partial differential equations are solved by using the implicit finite difference method in combination with the quasilinearization technique. Numerical results for the velocity, temperature and concentration profiles, as well as the skin friction coefficient, wall heat transfer and mass transfer rates are computed and presented graphically for various parameters. The results indicate that the velocity profile reduces, while the temperature profile increases in presence of the effects of magnetic field and suction at the wall. The velocity ratio parameter increases the skin-friction coefficient and the Schmidt number decreases the wall mass transfer rate. The temperature profile increases for the positive values of Eckert number and space as well as temperature dependent heat source/sink parameters, while the opposite behavior is observed for negative values of same parameters.Mon, 18 Feb 2019 20:30:00 +0100Editorial
https://jacm.scu.ac.ir/article_16114_1889.html
In recent years, thanks to the great progresses in numerical approaches, computational procedures ‎are increasingly applied to different braches of science, and more specifically to engineering and ‎related physical sciences. Fluid and solid mechanics are known as two separate fields of ‎mechanical science and technology including several applications from solids and structures ‎analyses to fluid flow and heat transfer problems. The mentioned topics are of much interest to ‎physicists, mathematicians and in particular, mechanical engineers. The objective of this special ‎issue is to establish a unique collection in the subject of computational solid and structural ‎mechanics, fluid dynamics, nanolfluids heat and mass transfer and of course multiphysics ‎problems emphasizing the applications of advanced computational approaches. Modeling, ‎simulation and solution of engineering problems are of great interest and mostly welcome in this ‎special collection.Mon, 30 Nov 2020 20:30:00 +0100Poiseuille Flow with Couple Stresses Effect and No-slip Boundary Conditions
https://jacm.scu.ac.ir/article_15238_1889.html
In this paper, the problem of Poiseuille flow with couple stresses effect in a fluid layer using the linear instability and nonlinear stability theories is analyzed. Also, the nonlinear stability eigenvalue problems for x,z and y,z disturbances are derived. The Chebyshev collocation method is adopted to arrive at the eigenvalue equation, which is then solved numerically, where the equivalent of the Orr-Sommerfeld eigenvalue problem is solved using the Chebyshev collocation method. The difficulties which arise in computing the spectrum of the Orr-Sommerfeld equation are discussed. The critical Reynolds number Rc, the critical wave number ac, and the critical wave speed cc are computed for wide ranges of the couple stresses coefficient M. It is found that the couple stresses coefficient M has great stabilizing effects on the fluid flow where the fluid flow becomes more unstable as M increases.Mon, 30 Nov 2020 20:30:00 +0100Numerical Simulation of Unsteady Flow toward a Stretching/Shrinking Sheet in Porous Medium ...
https://jacm.scu.ac.ir/article_14641_0.html
The purpose of this study is to present simulation and numerical solutions to the unsteady flow and heat transfer near stagnation point over a stretching/shrinking sheet in porous medium filled with a hybrid nanofluid. Water (base fluid), nanoparticles of titania and copper were considered as a hybrid nanofluid. It is worth mentioning that evaluating the heat transfer enhancement due to the use of hybrid nanofluids has recently become the center of interest for many researchers. The coupled non-linear boundary-layer equations governing the flow and heat transfer are derived and reduced to a set of coupled non-dimensional equations using the appropriate transformations and then solved numerically as a nonlinear boundary value problem by bvp4c scheme from MATLAB. To validate the modeling of hybrid nanofluid and also numerical procedure, the value of the skin friction and the heat transfer rate for the limited cases of pure water, titania/water and copper/water is obtained and compared with previously reported results that demonstrate an excellent agreement. In the present investigation, the thermal characteristics of hybrid nanofluid are found to be higher in comparison to the base fluid and fluid containing single nanoparticles, respectively. It can be concluded that both skin friction coefficient and local Nusselt number enhance almost linearly with increasing the copper nanoparticle volume fraction (as second nanoparticle). Besides, the porosity and the magnetic effect amplify heat transfer rate, while the unsteadiness parameter has a reducing effect on heat transfer rate in problem conditions.Sat, 03 Aug 2019 19:30:00 +0100Miscellaneous Modeling Approaches and Testing of a Satellite Honeycomb Sandwich Plate
https://jacm.scu.ac.ir/article_15240_1889.html
The honeycomb sandwich structures are commonly and efficiently adopted in the development of light mass satellite structures as a result of their inherent high stiffness and strength properties. Through a comprehensive study, the equivalent finite element modeling of honeycomb sandwich structures utilizing miscellaneous modeling approaches is introduced. For the sake of validating results, both theoretical analysis and experimental modal testing are implemented upon a honeycomb sandwich plate utilizing free-free boundary conditions. Based on the results, the sandwich theory and its related shell-volume-shell approach introduce a good match with the experimental results. The aforementioned approach is utilized extensively during the process of satellite structural design and modeling. In addition, a parametric study is executed so as to relate the geometric and material variations to the resonant modal frequencies. The study results indicate a crucial influence of both honeycomb core and facing sheets thicknesses on the modal frequency values.Mon, 30 Nov 2020 20:30:00 +0100MHD Casson Nanofluid Past a Stretching Sheet with the Effects of Viscous Dissipation, Chemical ...
https://jacm.scu.ac.ir/article_14804_0.html
The effects of viscous dissipation, chemical reaction and activation energy on the two-dimensional hydromagnetic convective heat and mass transfer flow of a Casson nanofluid fluid over a stretching sheet with thermal radiation, have been discussed in detail. The formulated highly nonlinear equations for the above-mentioned flow are converted into first-order ordinary differential equations (ODEs). The shooting method along with Adams-Bash forth Moulton method is used to solve the BVP by using the Fortran language program. The numerical results are computed by choosing different values of the involved physical parameters and compared with earlier published results and excellent validation of the present numerical results has been achieved for local Nusselt number and local Sherwood number. The graphical numerical results of different physical quantities of interest are presented to analyze their dynamics under the varying physical quantities. From the results, it has been remarked that the heat transfer rate escalates for the large values of radiation parameter, viscous dissipation for the Casson nanofluid.Tue, 08 Oct 2019 20:30:00 +0100Numerical Study on Subsurface Stress in Hertzian Contacts under Pure Sliding Conditions
https://jacm.scu.ac.ir/article_15243_1889.html
In this study, the two-dimensional numerical simulation on the subsurface stress field in Hertzian contact under the pure sliding condition for different speeds and coefficients of friction is presented. The Hertzian contacts are represented by a dry contact between a rigid flat surface and an elastic cylinder with radius R=12.5 mm. Simulation is carried out through two steps, the first one is for applying normal load and the second one is for applying angular speed for the cylinder. The results of subsurface stress filed for pure sliding are compared to non-moving Hertzian contact. The results show that pure sliding speed has a major effect on the value of maximum von Mises stress in the subsurface of contact. The effect of sliding speed is attributed to tangential forces and elastic deformation in the contact. On the other hand, the coefficient of friction has a primary effect on the position of maximum stress and the shift of the contact region. Indeed, when pure sliding motion is introduced with a low value of friction coefficient, the shift of the contact region is negligible compared to non-moving Hertzian contact. The study is extended to investigate the effect of contact geometry on subsurface stress for Hertzian contact in the cam-follower interface. The shape of the follower has a significant effect on the value and distribution of Hertzian stress, thus, the fatigue life of rubbing surfaces of the cam-follower interface.Mon, 30 Nov 2020 20:30:00 +0100Heat Transfer of Hybrid-nanofluids Flow Past a Permeable Flat Surface with Different Volume ...
https://jacm.scu.ac.ir/article_14842_0.html
Nowadays, the preparation, characterization, and modeling of nanofluids are deliberated in plenty to improve the heat transfer effects. Therefore, this paper centers on the heat transfer effects of three separate hybrid nanoparticles such as Al2O3-SiO2, Al2O3-TiO2, and TiO2-SiO2 with a base fluid such as water to gratify the advances. Analytical investigations for the Marangoni convection of different hybrid nanofluids over the flat surface for the cases such as suction, injection and impermeable were analyzed. A validation table for the comparison between analytical and numerical studies is tabulated. The influence of the hybrid nanoparticles solid volume fraction and the wall mass transfer parameter are mentioned through graphs at the side of the heat transfer rate tabulation. The impact of solid volume fraction decelerates the velocity distribution and raises the temperature distribution for all the three hybrid nanofluids in the cases of suction, impermeable, and injection. While relating the surface velocity and heat transfer rate of the three hybrid nanofluids, Al2O3-SiO2/water has a higher surface velocity, TiO2-SiO2/water has a higher heat transfer rate and Al2O3-TiO2/water has lower surface velocity and heat transfer rate for the increment of wall mass transfer parameter.Tue, 15 Oct 2019 20:30:00 +0100Hybrid Solution for the Analysis of MHD Micropolar Fluid Flow in a Vertical Porous ...
https://jacm.scu.ac.ir/article_15397_1889.html
In this paper, we analyze the transient magnetohydrodynamic (MHD) flow of an incompressible micropolar fluid between a porous parallel-plates channel. The fluid is electrically-conducting subjected to radiation described by the Cogley-Vincent-Gilles formulation and with convective thermal boundary conditions at the plates. The solution methodology employed is the hybrid numerical-analytical approach known as the Generalized Integral Transform Technique (GITT). The consistency of the integral transform method in handling such a class of problem is illustrated through convergence analyses, and the influence of physical parameters such as radiation, and micropolar parameters, and Hartman number. The wall shear stress, the coupled stress coefficient, and heat flux at the walls were also calculated, demonstrating that increasing the gyroviscosity decreases the wall stresses magnitudes. Furthermore, the results show that increasing the radiation heat transfer decreases the fluid temperature distribution. Additionally, the velocity is damped, and the angular velocity is increased by the Lorentz force in the presence of a magnetic field.Mon, 30 Nov 2020 20:30:00 +0100Topology Optimization of Laminated Composite Plates and Shells using Optimality Criteria
https://jacm.scu.ac.ir/article_14895_0.html
Laminated composite materials have the advantage of desired properties and are vastly replacing the existing traditional materials in Civil Engineering construction. In the present study, it is aimed to extend the study on the analysis of laminated composites plates and shells towards structural optimization. Topology optimization is performed using two different objective functions namely strain energy and fundamental frequency. The results of optimization have shown clearly that the distribution of material is dependent on the laminae. The optimal arrangement of material is obtained after using a cut-off relative density. It is confirmed to be a well-connected grid and is examined in detail. The results have shown that the optimal arrangement of material for a simply supported plate carrying a uniformly distributed load is at the centre of the edges and not towards the corners, Hence, the optimal arrangement of beams using strain energy is to align by joining the centre of the edges similar to plus (+) sign.Sat, 09 Nov 2019 20:30:00 +0100Third-grade Fluid Flow of Stretching Cylinder with Heat Source/Sink
https://jacm.scu.ac.ir/article_15316_1889.html
In this research, the impact of heat transfer on mixed convection steady third-grade fluid flow over an impermeable stretching cylinder with heat source is scrutinized. The investigation of mixed convection with non-Newtonian fluid is significant in geophysical and engineering fields. Appropriate transformations are alleged to obtain ordinary differential equations, which are later computed by using an analytical approach called the homotopy analysis methodology (HAM), and the interval of convergence is computed. Local Nusselt number and coefficient of skin friction values are computed numerically for novel parameters.Mon, 30 Nov 2020 20:30:00 +0100Thermal Buckling Analysis of Circular Bilayer Graphene Sheets Resting on an Elastic Matrix ...
https://jacm.scu.ac.ir/article_14896_0.html
In this article, the thermal buckling behavior of orthotropic circular bilayer graphene sheets embedded in the Winkler–Pasternak elastic medium is scrutinized. Using the nonlocal elasticity theory, the bilayer graphene sheets are modeled as a nonlocal double–layered plate that contains small scale effects and van der Waals (vdW) interaction forces. The vdW interaction forces between the layers are simulated as a set of linear springs using the Lennard–Jones potential model. Using the principle of virtual work, the set of equilibrium equations are obtained based on the first-order shear deformation theory (FSDT) and nonlocal differential constitutive relation of Eringen. Differential quadrature method (DQM) is employed to solve the governing equations for simply-supported and clamped boundary conditions. Finally, the effects of the small scale parameter, vdW forces, aspect ratio, elastic foundation, and boundary conditions are considered in detail.Mon, 11 Nov 2019 20:30:00 +0100Numerical Calculation of an Air Centrifugal Separator Based on the SARC Turbulence Model
https://jacm.scu.ac.ir/article_15362_1889.html
The numerical results of mathematical modeling of a two-phase swirling turbulent flow in the separation zone of a centrifugal apparatus are presented. The motion of the carrier gas flow was modeled using the averaged Navier-Stokes equations, for the closure of which the well-known turbulence model by Schur and Spalart was used, the amendment to the Spalart-Allmaras SARC model. Based on the obtained field of averaged velocities of the carrier medium, taking into account turbulent diffusion. The article compares the results taking into account the influence of the solid phase on the dynamics of the air environment and without taking it into account with experimental data.Mon, 30 Nov 2020 20:30:00 +0100Evaluating the Delamination in the Drilling Process of a Melamine Coated Medium Density ...
https://jacm.scu.ac.ir/article_14900_0.html
Medium density fiberboard (MDF) is an engineering product that is used in many industrial and general applications such as the furniture industry and kitchen cabinets. Generally, MDF products are generated by screw joints using the drilling process. However, the drilling process of the MDF panels leads to the delamination at the entrance and exit of the drill bit that should be controlled. In this work, the effect of the processing parameters including the feed rate and cutting speed on the delamination of melamine coated MDF is investigated. For this, two different tools with different tool geometry (a brad point drill bit and a commonly used twist drill bit) are examined. Image processing is used to measure the conventional delamination factor together with a new delamination factor referred to as area delamination factor for the drilled holes. It that the delamination value decreases with increasing cutting speed and increases with increasing feed rate. Though, there were some fluctuations in the results. The trend of changing the delamination respect to the investigated parameters was the same for both applied drill bits; however, the smaller value of delamination is obtained using the twist drill bit. Using the proposed area delamination factor, the effect of process parameters on the delamination is presented with higher magnitudes but with the same behavior. This, together with the ability of characterization of the water absorption of drilled holes has made the area delamination factor a more appropriate parameter to evaluate the delamination. The overall results are consistent with previously published works.Thu, 14 Nov 2019 20:30:00 +0100Entropy Analysis of a Radiating Magnetic Liquid Film along a Slippery Inclined Heated Surface ...
https://jacm.scu.ac.ir/article_15252_1889.html
The hydromagnetic flow of a Newtonian incompressible and electrically conducting variable-viscosity liquid film along an inclined isothermal or isoflux hydrophobic surface is investigated numerically. It is assumed that the fluid is subjected to a convective cooling at the free surface in the presence of a transversely imposed magnetic field. We incorporated in the energy equation, the viscous dissipation, Joule heating due to the magnetic field and the local radiative heat flux term for optically thick gray fluid reported by Roseland approximation. The governing non-linear differential equations are obtained and solved numerically using the shooting method coupled with a fourth-order Runge-Kutta method. The effects of some parameters on velocity and temperature profiles, skin friction, Nusselt number entropy generation rate, and the Bejan number profiles are analyzed graphically and discussed.Mon, 30 Nov 2020 20:30:00 +0100Effects of Inclined Magnetic Field and Porous Medium on Peristaltic Flow of a Bingham Fluid ...
https://jacm.scu.ac.ir/article_15007_0.html
The current paper aims to explain the peristaltic mechanism of a Bingham fluid with varying viscosity. The fluid is considered to flow within a porous medium and subjected to a magnetic field with significant inclination. Heat transfer characteristics are studied with convective conditions and variable thermal conductivity. The solution is obtained by the perturbation technique, where small values of variable liquid properties are utilized. The graphs plotted indicate that variation in viscosity as well as thermal conductivity actively contribute to reduce the pressure gradient. Further, for a higher radius of the plug flow region, a higher pressure rise occurs. The magnetic parameter and Grashof number influence the trapping phenomenon by reducing the dimensions of the bolus.Mon, 25 Nov 2019 20:30:00 +0100Forced-based Shear-flexure-interaction Frame Element for Nonlinear Analysis of Non-ductile ...
https://jacm.scu.ac.ir/article_15480_1889.html
An efficient frame model with inclusion of shear-flexure interaction is proposed here for nonlinear analyses of columns commonly present in reinforced concrete (RC) frame buildings constructed prior to the introduction of modern seismic codes in the Seventies. These columns are usually characterized as flexure-shear critical RC columns with light and non-seismically detailed transverse reinforcement. The proposed frame model is developed within the framework of force-based finite element formulation and follows the Timoshenko beam kinematics hypothesis. In this type of finite element formulation, the internal force fields are related to the element force degrees of freedom through equilibrated force shape functions and there is no need for displacement shape functions, thus eliminating the problem of displacement-field inconsistency and resulting in the locking-free Timoshenko frame element. The fiber-section model is employed to describe axial and flexural responses of the RC section. The modified Mergos-Kappos interaction procedure and the UCSD shear-strength model form the core of the shear-flexure interaction procedure adopted in the present work. Capability, accuracy, and efficiency of the proposed frame element are validated and assessed through correlation studies between experimental and numerical responses of two flexure-shear critical columns under cyclic loadings. Distinct response characteristics inherent to the flexure-shear critical column can be captured well by the proposed frame model. The computational efficiency of the force-based formulation is demonstrated by comparing local and global responses simulated by the proposed force-based frame model with those simulated by the displacement-based frame model.Mon, 30 Nov 2020 20:30:00 +0100Numerical Analysis of an Edge Crack Isotropic Plate with Void/Inclusions under Different ...
https://jacm.scu.ac.ir/article_15010_0.html
In the present work, the effect of various discontinuities like voids, soft inclusions and hard inclusions of the mixed-mode stress intensity factor (MMSIF), crack growth and energy release rate (ERR) of an edge crack isotropic plate under different loading like tensile, shear, combine and exponential by various numerical examples is investigated. The basic formulation is based on the extended finite element method (XFEM) through the M interaction approach using the level set method. The effect of single and multi voids and inclusions with position variation on MMSIF and crack growth are also investigated. The presented results would be applicable to enhancing the better fracture resistance of cracked structures and various loading conditions.Tue, 26 Nov 2019 20:30:00 +0100Unsteady Stokes Flow through a Porous Pipe with Periodic Suction and Injection with Slip Conditions
https://jacm.scu.ac.ir/article_15478_1889.html
The problem of unsteady Stokes flow of certain Newtonian fluids in a circular pipe of uniform cross section is discussed. The pipe is uniformly porous. The unsteady Navier-Stokes equations for the system in cylindrical polar coordinates have been solved analytically to obtain a complete description of the flow. The solution of the flow equations subject to the slip boundary conditions leads to the detailed expressions for axial and radial components of velocity and the pressure distribution depending on position coordinates and time. As a special case we have presented the situation when no-slip boundary conditions are implemented. The velocity profile is analyzed for different values of the flow parameters like Womersley number, slip length and time.Mon, 30 Nov 2020 20:30:00 +0100Numerical Solution of the Time Fractional Reaction-advection-diffusion Equation in Porous Media
https://jacm.scu.ac.ir/article_15019_0.html
In this work, we obtained the numerical solution for the system of nonlinear time-fractional order advection-reaction-diffusion equation using the homotopy perturbation method using Laplace transform method with fractional order derivatives in Liouville-Caputo sense. The solution obtained is very useful and significant to analyze many physical phenomenons. The present technique demonstrates the coupling of homotopy perturbation method and the Laplace transform technique using He’s polynomials, which can be applied to numerous coupled systems of nonlinear fractional models to find the approximate numerical solutions. The salient features of the present work is the graphical presentations of the numerical solution of the concerned nonlinear coupled equation for several particular cases and showcasing the effect of reaction terms on the nature of solute concentration of the considered mathematical model for different particular cases. To validate the reliability, efficiency and accuracy of the proposed efficient scheme, a comparison of numerical solutions and exact solution are reported for Burgers’ coupled equations and other particular cases of concerned nonlinear coupled systems. Here we find high consistency and compatibility between exact and numerical solution to a high accuracy. Presentation of absolute errors for given examples are reported in tabulated and graphical forms that ensure the convergence rate of the numerical scheme.Tue, 26 Nov 2019 20:30:00 +0100Different Groups of Variational Principles for Whitham-Broer-Kaup Equations in Shallow Water
https://jacm.scu.ac.ir/article_15509_1889.html
Because the variational theory is the theoretical basis for many kinds of analytical or numerical methods, it is an essential but difficult task to seek explicit functional formulations whose extrema are sought by the nonlinear and complex models. By the semi-inverse method and designing trial-Lagrange functional skillfully, two different groups of variational principles are constructed for the Whitham-Broer-Kaup equations, which can model a lot of nonlinear shallow-water waves. Furthermore, by a combination of different variational formulations, new families of variational principles are established. The obtained variational principles provide conservation laws in an energy form and are proved correct by minimizing the functionals with the calculus of variations. All variational principles are firstly discovered, which can help to study the symmetries and find conserved quantities, and might find lots of applications in numerical simulation. The procedure reveals that the semi-inverse method is highly efficient and powerful, and can be extended to more other nonlinear equations.Mon, 30 Nov 2020 20:30:00 +0100Optimum Design of Nano-Scaled Beam Using the Social Spider Optimization (SSO) Algorithm
https://jacm.scu.ac.ir/article_15044_0.html
In this research study, the optimum cross-sectional dimensions of nano-scale beam elements are investigated under different load conditions. Euler-Bernoulli beam model based on nonlocal elasticity theory is utilized for the analysis of the beam. Two types of nano-scaled beams are modeled; carbon nanotubes (CNTs) and Boron nitride nanotubes (BNNTs). The novel meta-heuristic based optimization algorithm called Social Spider Optimization (SSO) algorithm is employed to find the beam designs with the objective of minimizing the cross-sectional area. Furthermore, the obtained optimum cross-sectional dimensions, critical stress and displacement values of the beams are compared according to the material type, beam length, and load conditions.Fri, 29 Nov 2019 20:30:00 +0100A Simple Approach to Volterra-Fredholm Integral Equations
https://jacm.scu.ac.ir/article_15724_1889.html
This paper suggests a simple analytical method for Volterra-Fredholm integral equations, the solution process is similar to that by variational-based analytical method, e.g., Ritz method, however, the method requires no establishment of the variational principle for the discussed problem, making the method much attractive for practical applications. The examples show the method is straightforward and effective, and the method can also be extended to other nonlinear problems.Mon, 30 Nov 2020 20:30:00 +0100Distributed-parameter Dynamic Modeling and Bifurcation Analysis of a Trapezoidal ...
https://jacm.scu.ac.ir/article_15085_0.html
In this paper, the effect of the bimorph profile on the nonlinear dynamic behavior and performance of a vibratory piezomagnetoelastic energy harvester is investigated. The proposed model is composed of upper and lower piezoelectric layers on a trapezoidal cantilever beam with one attached tip magnet as well as two external magnets. The magnetic field of two external magnets generates magnetic forces and moment on the tip magnet. The bimorph structure is considered as a distributed-parameter system, and the external forces are obtained by analyzing the magnetic field of the external magnets. Equations of motion are obtained using electromagnetic Lagrange equations based on the generalized Hamilton principle and the Euler-Bernoulli beam theory. The proposed model for the bimorph and magnetic forces is validated by previously published experimental results. In order to compare the nonlinear behavior of the rectangular and trapezoidal beam profiles, the bifurcation diagrams are depicted for various control parameters such as the separation distances of the magnets, beam root width, and beam tip width. Verification of the bifurcation diagrams is performed by the phase plane portraits and Poincare maps. Also, the harvested power level is compared for different profiles of the bimorph. Moreover, the simultaneous effects of exciting frequency and bifurcation parameters on the system performance are investigated by the waterfall diagrams. The obtained results show that the trapezoidal beam profile with a lower tip width has higher performance than the rectangular beam. In trapezoidal beam profiles, the subharmonic and chaotic motions have relatively higher output powers than periodic motions.Thu, 05 Dec 2019 20:30:00 +0100A Radial Basis Function Collocation Method for Space-dependent Inverse Heat Problems
https://jacm.scu.ac.ir/article_15512_1889.html
In this study, a radial basis function collocation method (RBFCM) is proposed for the numerical treatment of inverse space-wise dependent heat source problems. Multiquadric radial basis function is applied for spatial discretization whereas for temporal discretization Runge-Kutta method of order four is employed. Numerical experiments for one, two and three-dimensional cases are included to test the efficiency and accuracy of the suggested method. Both non-rectangular and rectangular geometries with uniform and non-uniform points are taken into consideration and the obtained results are compared with the exact as well as with the techniques presented in recent literature.Mon, 30 Nov 2020 20:30:00 +0100Effect of Two Baffles on MHD Natural Convection in U-Shape Superposed by Solid Nanoparticle ...
https://jacm.scu.ac.ir/article_15654_1889.html
In this paper, numerical Galerkin Finite Element Method (GFEM) applies for natural convection heat transfer of U-shaped cavity filled by Fe3O4-water nanofluid under the magnetic field and including two baffles. The above boundaries of the cavity are at low temperatures and bottom boundary is in a variable function temperature. It is assumed that two baffles in the cavity make vortexes to enhance heat transfers. The dimensionless governing equations including velocity, pressure, and temperature formulation are solved by the Galerkin finite element method. The results are discussed based on the governing parameters such as a nanoparticle volume fraction, Hartmann and Rayleigh numbers, magnetic field angle and nanoparticles shapes. As a main result, increasing both Aspect Ratio (AR) and Ra numbers enhanced heat transfer process and improved the average Nusselt numbers, while increasing the Hartmann number decreased the Nusselt number. Furthermore, it concluded that AR=0.4 had the maximum ψ and Nusselt numbers among the other examined aspect rations. Also, platelet, cylindrical, brick and spherical shapes had the maximum Nusselt numbers in sequence.Mon, 30 Nov 2020 20:30:00 +0100Nonlinear Convective Flow of Maxwell Fluid over a Slendering Stretching Sheet with Heat Source/Sink
https://jacm.scu.ac.ir/article_15143_0.html
In this study, the features of Maxwell fluid flow through a stretching sheet (variable thickness) with heat source/sink and melting heat transfer are analyzed. Leading equations of the course are transmuted with suitable similarity transmutations and resolved the subsequent equations mathematically with shooting technique. The effects of the valid parameters on the regular profiles (velocity, concentration, temperature) are elucidated through graphs in two cases (presence and absence of melting). And also, friction factor, transfer rates (mass, heat) are examined with the same parameters and the outcomes are presented in tabular form. A few of the findings are (a) the elastic parameter upsurges the velocity (b) heat source parameter raises the temperature (c) mass transfer rate is lowered by chemical reaction.Thu, 12 Dec 2019 20:30:00 +0100Computational Analysis of Turbulent Flow over a Bluff Body with Drag Reduction Devices
https://jacm.scu.ac.ir/article_15614_1889.html
Reducing aerodynamic drag of heavy trucks is crucially important for the reduction of fuel consumption and hence results in less air pollution. One way to reduce the aerodynamic drag is the deployment of drag reduction devices at the rear of trucks and this paper describes a numerical study of flow over a bluff body with rear drag devices using the Reynolds-Averaged-Navier-Stokes (RANS) approach to investigate the drag reduction mechanisms and also to assess accuracy of the RANS approach for this kind of flow. Four cases, a baseline case without any drag reduction devices and three cases with different drag reduction devices, have been studied and the predicted mean and turbulent quantities agree well with the experimental data. Drag reduction varies hugely from a few percent in one case to more than 40% in another case and detailed analysis of flow fields has been carried out to understand such a difference and to elucidate the drag reduction mechanism, which ultimately can lead to better design of future drag reduction devices.Mon, 30 Nov 2020 20:30:00 +0100Modified Variational Iteration Technique for the Numerical Solution of Fifth Order KdV-type ...
https://jacm.scu.ac.ir/article_15511_1889.html
In this article, a simple and new algorithm is proposed, namely the modified variational iteration algorithm-I (mVIA-I), for obtaining numerical solutions to different types of fifth-order Korteweg de-Vries (KdV) equations. In order to verify the precision, accuracy and stability of the mVIA-I method, generated numerical results are compared with the Laplace decomposition method, Adomian decomposition method, Homotopy perturbation transform method and the modified Adomian decomposition method. Comparison with the mentioned methods reveals that the mVIA-I is computationally attractive, exceptionally productive and achieves better accuracy than the others.Mon, 30 Nov 2020 20:30:00 +0100Investigation of Rousselier Model and Gurson-Tvergaard-Needleman Model in Ductile Fracture of ...
https://jacm.scu.ac.ir/article_15239_0.html
In this research, the micromechanical Rousselier damage model, which is not available in commercial software is accomplished with a subroutine in Abaqus finite element analysis software. Ductile fracture behavior of API X65 steel is evaluated by simulation of tensile test of smooth and round notch bar specimens of base metal in hoop direction and weld metal. The Rousselier model and its parameters of this model are determined for API X65 steel based on experimental data. In this work, the Rousselier and Gurson damage model is compared for API X65 steel. Results of the tensile test and simulation for the Gurson model show inaccuracy in the final stage of the load-displacement plot. This is because in the Gurson model it is assumed that the fracture surface is flat and shear fracture does not occur in specimens, but in the Rousselier model, the shear fracture is considered. The Rousselier model shows more accurate results compared with experimental data in the final stage of loading. Furthermore, the Rousselier model shows little error comparing with the experiment around maximum load since the void growth due to nucleation is ignored in this model. Also, the Rousselier model shows better convergence when the grooving radius of tensile test specimen increasing but the Gurson model behaves differently.Tue, 24 Dec 2019 20:30:00 +0100Analysis of a Jet Pump Performance under Different Primary Nozzle Positions and Inlet ...
https://jacm.scu.ac.ir/article_15714_1889.html
A jet pump operates under the Venturi effect, where a fluid enters through a primary nozzle and, when passing through a convergent-divergent nozzle, it reaches supersonic conditions, originating a vacuum pressure in a secondary fluid. Fluid-dynamics simulations of jet pumps are performed here using standard k-ε turbulence model. Numerical results are compared to those obtained with an analytical model previously developed, concluding that both approaches predict a similar behavior of Match number, fluid pressure and fluid velocity. A parametric study is done to determine the influence of inlet pressure and primary nozzle position in jet pump performance, Mach number field and total pressure profile. Both parameters have an important influence in those variables, but this is not monotonic in all cases.Mon, 30 Nov 2020 20:30:00 +0100Bending of Functionally Graded Sandwich Nanoplates Resting on Pasternak Foundation under ...
https://jacm.scu.ac.ir/article_15529_1889.html
This article proposes a refined higher order nonlocal strain gradient theory for stresses and deflections of new model of functionally graded (FG) sandwich nanoplates resting on Pasternak elastic foundation. Material properties of the FG layers are supposed to vary continuously through-the-thickness according to a power function or a sigmoid function in terms of the volume fractions of the constituents. The face layers are made of FG material while the core layer is homogeneous and made of ceramic. In this study, an analytical approach is proposed using the higher-order shear deformation plate theory and nonlocal strain gradient theory with combination of various boundary conditions. Numerical outcomes are reported to display the impact of the material distribution, boundary conditions, elastic foundation parameters and the sandwich nanoplate geometry on the deflections and stresses of FG sandwich nanoplates. The exactness of this theory is determined by comparing it to other published outcomes.Mon, 30 Nov 2020 20:30:00 +0100Polymeric Dissipative Convection Flow from an Inclined Plane with Chemical Reaction: Numerical Study
https://jacm.scu.ac.ir/article_15241_0.html
An analytical model is developed to study the effects of viscous dissipation and chemical reaction in viscoelastic convection from an inclined plate as a simulation of electro-conductive polymer materials processing. The Jeffery’s viscoelastic model is deployed to describe the non-Newtonian characteristics of the fluid and provides a good approximation for polymers, which constitutes a novelty of the present work. The normalized nonlinear boundary value problem is solved computationally with the Keller-Box implicit finite-difference technique. Extensive solutions for velocity, surface temperature and concentration, skin friction, heat, and transfer rates are visualized numerically and graphically for various thermophysical parameters. Validation is conducted with earlier published work for the case of a vertical plate in the absence of viscous dissipation, chemical reaction, and non-Newtonian effects. The boundary layer flow is accelerated with increasing Deborah number whereas temperatures and concentrations are decelerated slightly. Temperatures and concentration are boosted with increasing inclination parameter whereas velocity is lowered. A reverse trend is seen for increasing Richardson number. Increasing chemical reaction reduces velocity and concentration whereas it enhances temperature. Increasing the viscous dissipation parameter is found to enhance velocity and temperature whereas it suppresses concentration.Wed, 25 Dec 2019 20:30:00 +0100Application of Atangana-Baleanu Fractional Derivative to Carbon Nanotubes Based ...
https://jacm.scu.ac.ir/article_15608_1889.html
Single and multi-walled carbon nanotubes (SWCNTs & MWCNTs) comprise a large group of nanometer-thin hollow fibrous nanomaterials having physico-chemical characteristics like atomic configuration, length to diameter ratios, defects, impurities and functionalization. This manuscript is devoted for the analysis of carbon nanotubes based non-Newtonian nanofluid suspended in ethylene glycol taken as base fluid. The problem is modeled through modern method of fractional calculus namely Atangana-Baleanu fractional derivative and then solved analytically by invoking Laplace transform. The analytic solutions are established for the temperature and velocity distribution and expressed in terms of special function. The graphical results are depicted through computational software Mathcad and discussed for carbon nanotubes with various embedded parameters. An interesting comparison is explored graphically between single and multi-walled carbon nanotubes subject to the single and multi-walled carbon nanotubes are suspended in ethylene glycol. The several similarities and differences suggested that carbon nanotubes are accelerated and decelerated, while for unit time t = 1s, carbon nanotubes have identical velocities with and without fractional approach.Mon, 30 Nov 2020 20:30:00 +0100Explicit and Implicit Finite -Volume Methods for Depth Averaged Free-Surface Flows
https://jacm.scu.ac.ir/article_15468_1889.html
In recent years, much progress has been made in solving free-surface flow variation problems in order to prevent flood environmental problems in natural rivers. Computational results and convergence acceleration of two different (explicit and implicit numerical techniques) finite-volume based numerical algorithms, for depth-averaged subcritical and/or supercritical, free-surface, steady flows in channels, are presented. The implicit computational model is a bi-diagonal, finite-volume numerical scheme, based on MacCormack’s predictor-corrector technique and uses the semi-linearization matrices for the governing Navier-Stokes equations which are expressed in terms of diagonalization. This implicit numerical scheme puts primary emphasis to solution convergence using non-orthogonal local coordinate system. The explicit formulation uses volume integrals to solve the governing flow equations. Computational results and convergence performance between the implicit and the explicit finite-volume numerical schemes, for incompressible, viscous, depth-averaged free-surface, steady flows are presented. Implicit and explicit computational results are satisfactorily compared with available measurements. The implicit bi-diagonal technique yields fast convergence compared to the explicit one at the expense of programming effort. Iterations require to achieve convergence solution error of less than 10-5, can be reduced down to 90.0 % in comparison to analogous flows with using explicit numerical technique.Mon, 30 Nov 2020 20:30:00 +0100Reduction in Space for Dynamic Finite Element Analysis of Assemblies of Beam-columns when the ...
https://jacm.scu.ac.ir/article_15244_0.html
In 2008, a technique was proposed to reduce run-times in analysis of semi-discretized equation of motion against dynamic excitations available in digitized format. Later, the technique was successfully adapted to reduce numbers of degrees of freedom in finite element analysis of assemblies of beam-columns subjected to static digitized loads. In this paper, attention is paid to dynamic finite element analysis of assemblies of beam-columns. It is shown that, when the mass is available in digitized format, after small modifications in the original technique, the adaptation can simplify the analysis, regardless of the models' sizes, their linearity or non-linearity, and whether the damping is classical or non-classical. The reductions in run-time and in-core memory are considerable, while the changes in accuracy can be negligible.Sat, 28 Dec 2019 20:30:00 +0100The Brick Thermal Performance Improvement using Phase Change Materials
https://jacm.scu.ac.ir/article_15531_1889.html
The problems of heat and mass transfer in phase change materials are of great engineering interest. The absorption and storage of energy in the form of latent heat makes it possible to use them in the construction industry to smooth out the effects of temperature transitions in the environment. This work is devoted to the study of heat transfer in a building block with paraffin inserts under unsteady external conditions. The influence of the geometric dimensions of the block and the volume fraction of the phase change material on the effect of restraining external temperature fluctuations was studied. The unsteady conjugate melting problem was solved in a closed rectangular region with two cavities filled with PCM. The temperature of the environment on the left boundary changes in harmonic law. Thermal distributions were obtained at various points in time.Mon, 30 Nov 2020 20:30:00 +0100A Periodic Solution of the Newell-Whitehead-Segel (NWS) Wave Equation via Fractional Calculus
https://jacm.scu.ac.ir/article_15685_1889.html
The Newell-Whitehead-Segel (NWS) equation is one of the most significant amplitude equations with a wider practical applications in engineering and applied physics. It describes several line patterns; for instance, see lines from seashells and ripples in the sand. In addition, it has several applications in mathematical, chemical, and mechanical physics, as well as bio-engineering and fluid mechanics. Therefore, the current research is concerned with obtaining an approximate periodic solution of a nonlinear dynamical NWS wave model at three different powers. The fractional calculus via the Riemann-Liouville is adopted to calculate an analytical periodic approximate solution. The analysis aims to transform the original partial differential equation into a nonlinear damping Duffing oscillator. Then, the latter equation has been solved by utilizing a modified Homotopy perturbation method (HPM). The obtained results revealed that the present technique is a powerful, promising, and effective one to analyze a class of damping nonlinear equations that appears in physical and engineering situations.Mon, 30 Nov 2020 20:30:00 +0100A Hybrid SVM-RVM Algorithm to Mechanical Properties in the Friction Stir Welding Process
https://jacm.scu.ac.ir/article_15253_0.html
The friction stir welding method is one of the solid-state welding methods for non-homogeneous metals. In this study, the 5XXX series aluminum sample and pure copper are subjected to four passes friction welding process and then the mechanical and metallurgical properties of the welded samples are compared with the prototype. For this purpose, the effect of welding parameters including rotational speed, forward speed and pin angle of the tool is tested by the full factorial method. In this process, hardness estimation and tensile testing are based on input process parameters in order to obtain mechanical properties is an important issue. For this purpose, a mathematical model of mechanical properties must be defined based on the input process parameters. Due to the complex nature of the effect of input process parameters on mechanical properties, this modeling is a complex mathematical problem in which the use of supervised learning algorithms is considered as an efficient alternative. In this paper, a new combination of Relevance Vector Machine (RVM) and Support Vector Machine (SVM) is presented which has a higher degree of accuracy.Mon, 30 Dec 2019 20:30:00 +0100Analysis of Entropy Generation in Hydromagnetic Micropolar Fluid Flow over an Inclined ...
https://jacm.scu.ac.ir/article_15138_1889.html
A numerical analysis is performed on entropy generation in a radiative and dissipative hydromagnetic micropolar fluid prompted by a nonlinearly stretching sheet with the impact of non-uniform heat source/sink, variable magnetic field, electrical conductivity, and dynamic viscosity. The main equations are computationally solved via shooting techniques in the company with Runge-Kutta algorithms. The impact of the prominent controlling parameters is graphically checked on the velocity, temperature, microrotation, entropy generation, and Bejan number. An excellent relationship exists between the results obtained with related studies previously reported in the literature in the limiting conditions. More so, it is revealed by the findings that the irreversibility due to heat transfer is dominant over viscous dissipation irreversibility as the radiation parameter advances while the trend changes with the Brikman number parameter.Mon, 30 Nov 2020 20:30:00 +0100Numerical Simulations of Unsteady 3D MHD Micropolar Fluid Flow over a Slendering Sheet
https://jacm.scu.ac.ir/article_15260_0.html
The purpose of the present analysis is to explore the numerical investigation on the time-dependent 3D magnetohydrodynamic flow of micropolar fluid over a slendering stretchable sheet. The prevailing PDEs are rehabilitated into coupled non-linear ODEs with the aid of appropriate similarity variables and then numerically calculated by applying the 4th RKM incorporate with shooting scheme. The contributions of various interesting variables are shown graphically. Emerging physical parameters on velocity, microrotation, and the surface drag coefficient are portrayed graphically. It is noticed that the microrotation profiles highly influenced by the vortex viscosity parameter and the micro-inertia density parameter. It is also concluded that the microrotation profiles (h2) are promoted by increasing the spin gradient viscosity parameter. Excellent accuracy of the present results is observed with the formerly published as a result of a special case.Wed, 08 Jan 2020 20:30:00 +0100A Novel Quadrilateral Element for Dynamic Response of Plate Structures Subjected to Blast Loading
https://jacm.scu.ac.ir/article_15704_1889.html
We study the dynamic response of plate structures subjected to blast loading. This load is introduced in dynamically excited form over time. Two assumptions are given to ensure the physical properties of dynamic problems. The plate structures are studied its response under explosion. The governing equation with respect to the motion is solved by using a novel quadrilateral element SQ4T related to the twice interpolation strategy (TIS) and the average acceleration method of Newmark’s family. Our solutions are compared with reference solutions to confirm the accuracy of the proposed element.Mon, 30 Nov 2020 20:30:00 +0100Heating Capacity of an Earth to Air Heat Exchanger in Arid Regions - Experimental Investigation
https://jacm.scu.ac.ir/article_15262_0.html
Heating capacity of an earth to air heat exchanger EAHE equipped with an exterior fan in the arid region like the Southwest of Algeria is investigated experimentally. In-situ measurement of annual undisturbed subsoil vertical temperature profile is shown that it was 28°C at a depth of 1.5 meters. The EAHE made of 66 meters of PVC tube is demonstrated a heating capacity of 13°C and a cooling capacity of 7°C and a big dependence on local climate conditions. Great potentials and thermal comfort with less energy consumption are represented by earth to air or air-ground heat exchanger in the arid regions like the South of Algeria.Sat, 11 Jan 2020 20:30:00 +0100Simultaneous Flow of Three Immiscible Fractional Maxwell Fluids with the Clear and ...
https://jacm.scu.ac.ir/article_15626_1889.html
One-dimensional transient ﬂows of three layers immiscible fractional Maxwell ﬂuids in a cylindrical domain have been investigated in the presence of a porous medium. In the ﬂow, the domain is considered the concentric regions namely one clear region and other two annular regions are ﬁlled with a homogeneous porous medium saturated by a generalized Maxwell ﬂuid. The studied problem is based on a mathematical model focused on the ﬂuids with memory described by a constitutive equation with time-fractional Caputo derivative. Analytical solutions to the problem with initial-boundary conditions and interface ﬂuid-ﬂuid conditions are determined by employing the integral transform method (the Laplace transform, the finite Hankel transform and the ﬁnite Weber transform). The memory effects and the inﬂuence of the porosity coefficient on the ﬂuid motion have been studied. Numerical results and graphical illustrations, obtained with the Mathcad software, have been used to analyze the ﬂuid behavior. The inﬂuence of the memory on the ﬂuid motion is signiﬁcant at the beginning of motion and it is attenuated in time.Mon, 30 Nov 2020 20:30:00 +0100The Method of Lines Analysis of Heat Transfer of Ostwald-de Waele Fluid Generated by a ...
https://jacm.scu.ac.ir/article_15263_0.html
In this article, it is aimed to address one of Ostwald-de Waele fluid problems that either, has not been addressed or very little focused on. Considering the impacts of heat involving in the Non-Newtonian flow, a variant thickness of the disk is additionally considered which is governed by the relation z = a (r/RO+1)-m. The rotating Non-Newtonian flow dynamics are represented by the system of highly nonlinear coupled partial differential equations. To seek a formidable solution of this nonlinear phenomenon, the application of the method of lines using von Kármán’s transformation is implemented to reduce the given PDEs into a system of nonlinear coupled ordinary differential equations. A numerical solution is considered as the ultimate option, for such nonlinear flow problems, both closed-form solution and an analytical solution are hard to come by. The method of lines scheme is preferred to obtain the desired solution which is found to be more reliable and in accordance with the required physical expectation. Eventually, some new marvels are found. Results indicate that, unlike the flat rotating disk, the local radial skin friction coefficients and tangential decrease with the fluid physical power-law exponent increases, the peak in the radial velocity rises which is significantly distinct from the results of a power-law fluid over a flat rotating disk. The local radial skin friction coefficient increases as the disk thickness index increases, while local tangential skin friction coefficient decreases, the local Nusselt number decrease, both the thickness of the velocity and temperature boundary layer increase. Sun, 12 Jan 2020 20:30:00 +0100Size-dependent Nonlinear Forced Vibration Analysis of Viscoelastic/Piezoelectric Nano-beam
https://jacm.scu.ac.ir/article_15269_0.html
In this paper, the nonlinear forced vibration of isotropic viscoelastic/ piezoelectric Euler-Bernoulli nano-beam is investigated. For this purpose, the consistent couple stress theory is utilized for modeling the viscoelastic/piezoelectric nano-beam. Hamilton’s principle is also employed to obtain the governing equations of motion. Further, the Galerkin method is used in order to convert the governing partial differential equations to a nonlinear second-order ordinary differential one, and then multiple scale method is used to solve motion equation.Mon, 13 Jan 2020 20:30:00 +0100Magnetohydrodynamic Bio-convective Casson Nanofluid Flow: A Numerical Simulation by Paired ...
https://jacm.scu.ac.ir/article_15273_0.html
A study on the effects of gyrotactic microorganism and nanoparticles in the bio-convection magnetohydrodynamic flow of Casson fluid at the nonlinear stretching boundary is investigated. Irregular heat source/sink, Joule and viscous dissipations, Brownian motion, and thermophoresis are included in the energy equation. The model outlining the flow system is non-dimensionalised and retained in the same form. The equations are worked out by pairing, i.e. first pair momentum and gyrotactic micro-organism density equation and second pair energy and nanoparticle concentration equation. This technique is termed as a paired quasilinearisation method (PQLM). Convergence and accuracy of PQLM are shown. Obtained numerical results are depicted in graphs in order to observe further insight into the flow pattern. Interesting aspects of various controlling parameters in flow, heat, nanoparticle concentration and microorganism density are discussed.Tue, 14 Jan 2020 20:30:00 +0100Investigation of Jeffery-Hamel Flow for Nanofluid in the Presence of Magnetic Field by a New ...
https://jacm.scu.ac.ir/article_15275_0.html
In this article, numerical study of nanofluid flow between two inclined planes is carried out under the influence of magnetic field. Water-based nanofluid with nanoparticle of Copper (Cu) is taken into consideration for the present investigation. An efficient numerical method namely Optimal Homotopy Analysis Method (OHAM) is employed to get an approximate series solution for the related governing differential equation. A new approach is proposed to determine the convergence controller parameters used in OHAM. For the validation of the proposed technique, the convergence of the obtained results is shown for different values of involved parameters. Moreover, residual errors for the different number of terms in the obtained series solution are represented graphically. Obtained numerical results from the proposed method are incorporated with the previous results and they are found to be in very good agreement. Impacts of involved parameters like nanoparticle volume fraction, Hartmann number and Reynolds number on non-dimensional velocity are also discussed.Tue, 14 Jan 2020 20:30:00 +0100Design, Analysis and Manufacturing of a Bone Cutting Ultrasonic Horn-Tool and Verification with ...
https://jacm.scu.ac.ir/article_15307_0.html
Horn is one of the main components of ultrasonic cutting systems. The most important characteristics of the horn design are its resonant frequency and amplification factor. Closed-form equations can be used only for the design of simple horns and do not apply to more complex shapes like surgical tools. In This paper, a designing technique based on the finite element method and experimental tests is presented. The conventional design methods are improved, and designing a high performance surgical ultrasonic horn for bone cutting tools is facilitated. The new and complex bone cutting tool has both the knife-edge and toothed-edge, which could cut the bone easily and accurately. The investigations of cutting forces applied to the tool edges show less force in the toothed edge than the knife edge.Sat, 01 Feb 2020 20:30:00 +0100Numerical Solution of Time Fractional Cable Equation via the Sinc-Bernoulli Collocation Method
https://jacm.scu.ac.ir/article_15318_0.html
An important equation usually used in modeling neuronal dynamics is cable equation. In this work, a numerical method for the fractional cable equation which involves two Riemann-Liouville fractional derivatives is proposed. Our computational technique is based on collocation idea where a combination of Bernoulli polynomials and Sinc functions are used to approximate the solution to this problem. The constructed approximation by our method convert the fractional cable equation into a set of algebraic equations. Also, we provide two numerical examples to confirm the accuracy and effectiveness of the present method.Fri, 07 Feb 2020 20:30:00 +0100Fractional Sumudu Decomposition Method for Solving PDEs of Fractional Order
https://jacm.scu.ac.ir/article_15348_0.html
. In this paper, the fractional Sumudu decomposition method (FSDM) is employed to handle the time-fractional PDEs and system of time-fractional PDEs. The fractional derivative is described in the Caputo sense. The approximate solutions are obtained by using FSDM, which is the coupling method of fractional decomposition method and Sumudu transform. The method, in general, is easy to implement and yields good results. Illustrative examples are included to demonstrate the validity and applicability of the proposed technique.Mon, 17 Feb 2020 20:30:00 +0100Structural Strength Analysis and Fabrication of a Straight Blade of an H-Darrieus Wind Turbine
https://jacm.scu.ac.ir/article_15352_0.html
Small H-Darrieus wind turbines have become popular in the wind power market because of their many advantages, which include simplicity of design, low construction costs, and they are thought to represent an adequate solution even in unconventional installation regions. The blade is generally considered as the most important component of the wind turbine system because it controls the efficiency of the turbine. The blade structure must be designed to support the difficult environmental conditions (e.g., wind, and snow) encountered during the operational life of the wind turbine. This current study uses three-dimensional (3D) modeling and structural strength analysis to fabricate two straight blades (aluminum and galvanized steel) for a small H-Darrieus wind turbine. The 3D modeling of the blade structure is performed using SolidWorks, a computer-aided design (CAD) software package, and the structural strength analysis uses the Finite Element Analysis (FEA) technique to identify the stiffness, resistance, and reliability of the blade structure. The simulation results obtained indicate that no structural failures are predicted for either of the two structures tested because the factors of safety are larger than one, and the all maximum deflections are within the allowable deformation limits for the materials. Manufacturing processes for the two structures are described.Wed, 19 Feb 2020 20:30:00 +0100Thermoelastic Model with Higher-order Time-derivatives and Two Phase-lags for an Infinitely ...
https://jacm.scu.ac.ir/article_15353_0.html
In this work, a generalized higher-order time-derivatives model with phase-lags has been introduced. This model is applied to study the thermal heat problem of a homogeneous and isotropic long cylinder due to initial stress and heat source. We use the Laplace transform method to solve the problem. The numerical solutions for the field functions are obtained numerically using the numerical Laplace inversion technique. The effect of the higher-order parameters, the initial stress, the magnitude of the heat source and the instant time on the temperature field, the displacement field, and the stress fields have been calculated and displayed graphically and the obtained results are discussed. The results are compared with those obtained previously in the contexts of some other models of thermoelasticity.Wed, 19 Feb 2020 20:30:00 +0100Investigation on the Crack Effect in the Cylinder and Matrix on the Backscattering Field ...
https://jacm.scu.ac.ir/article_15354_0.html
A novel method to determine the health of the industrial parts is using the ultrasound scattering waves. Any changes in the structure of the scattering object or in the boundary conditions will cause a change in the scattering field. The frequency spectrum of the scattering time signal has valuable information, which is studied by resonant ultrasound spectroscopy (RUS). Since any defect, property changes, or changes in boundary conditions can affect the scattering field. Therefore, the possible defects in the piece are detected using the response of the scattering field. One possible defect in the fiber-reinforced composites is the existence of a crack in the matrix or fibers. In the present study, the effect of crack on the far-field backscattering amplitude spectrum is investigated using the finite element method (FEM). To this end, the effect of the crack’s direction in the cylinder and matrix on the form function is scrutinized. The results show that the Rayleigh frequency modes are more sensitive to the cracks existing in the epoxy matrix than the Whispering-gallery frequency modes. Also, the existence of the crack in the aluminum cylinder has the most effect on the Whispering-gallery frequency modes. Besides, the existence of a horizontal crack in the aluminum cylinder leads to a significant reduction in these frequency modes. The validation of the research is determined by comparing the steel cylinder form function obtained from the finite element method’s information and the analytical and experimental form functions in addition to the comparison of the aluminum cylinder form function and reference form function.Wed, 19 Feb 2020 20:30:00 +0100Numerical Modeling of Heat Transfer and Hydrodynamics in Compact Shifted Arrangement Small ...
https://jacm.scu.ac.ir/article_15391_0.html
Numerical modeling of heat and hydrodynamics processes in the channels of compact small diameter tube bundles with different transverse shifted arrangement is carried out. The fields of velocities, temperatures, and pressures in the tube bundle channels were obtained, and their influence on heat transfer conditions and hydraulic losses were analyzed. The calculation of the thermohydraulic efficiency for different constructions of the tube bundles had been carried out, and their results with data of well-known tube bundles of different geometry are compared.Sun, 01 Mar 2020 20:30:00 +0100Mathematical Analysis of Poiseuille Flow of Casson Fluid past Porous Medium
https://jacm.scu.ac.ir/article_15394_0.html
In this article, the influence of microstructure in the Casson fluid flow through a porous medium is investigated, by extending the Buckingham-Reiner’s one-dimensional model to plane-Poiseuille flow and Hagen-Poiseuille flow geometries. While analyzing the flow characteristics in single-channel/pipes or multiple channels/pipes of different width/radius, four different probability density functions are used to model the pores widths/radii distributions. It is found that when the pressure gradient increases, the Buckingham-Reiner function raises slowly in the plane-Poiseuille flow, whereas in Hagen-Poiseuille flow, it rises rapidly. In all kinds of distribution of pores, the fluid’s mean velocity and porosity of the flow medium are considerably higher in the Hagen-Poiseuille flow than in the plane-Poiseuille flow, and this behavior is reversed for the permeability of the flow medium. The fluid’s mean velocity, porosity, and permeability of the flow medium increases appreciably with the rise of the channel width and pipe radius. The porosity of the flow medium slumps with the rise of the periodof the channels and pipes distribution from 1 to 2, and it decreases very slowly with the further rise of the period H of the channels and pipes from 2 to 11.Mon, 29 Nov 1999 20:30:00 +0100Comparative Study of Mixed Convective MHD Cu-Water Nanofluid Flow over a Cone and Wedge using ...
https://jacm.scu.ac.ir/article_15395_0.html
The steady Cu-water nanofluid flow in presence of magnetic field is investigated numerically under the effects of mixed convection, thermal radiation and chemical reaction. For investigating the nanofluid flow, the flow over two different geometries, cone and wedge have been considered. The Tiwari and Das nanofluid model is implemented together with Buongiorno nanofluid model. Thermal and concentration diffusion are studied using the Cattaneo-Christov double diffusion model. At the boundary of the surface, no slip and zero mass flux condition are implemented to control the nanoparticle volume fraction at surface. Constitutive laws of flow are obtained in form of ordinary differential equations by the use of similarity transformation. The modeled flow problem is solved numerically by the Runge-Kutta-Fehlberg method and shooting scheme. Variation in flow properties due to parameters involved is presented graphically and through tabular values. The effect of thermal radiation and thermal relaxation parameter is to increase heat transfer. The temperature of nanofluid and drag force at surface increases due to enhanced magnetic field. The nanoparticles are found to be concentrated near the surface of cone and wedge but concentration decreases with chemical reaction parameter and Schmidt number as fluid moves towards far field.Mon, 02 Mar 2020 20:30:00 +0100Thermal Performance of Oscillating Blade with Various Geometries in a Straight Channel
https://jacm.scu.ac.ir/article_15420_0.html
In this study, the effect of stationary and oscillating blades on the forced convection heat transfer in a channel is studied numerically. Simulations are performed in a fully-developed, laminar, unsteady, and incompressible flow with Reynolds number and Prandtl number equal to 100 and 1, respectively. The effects of the blade geometry, oscillating speed and oscillation angle on heat transfer and pressure drop are studied. The results are presented in terms of time-averaged Nusselt number, temperature, and vorticity distribution and the pressure drop. The results indicate that the oscillation angle, oscillating speed of the blade, and the number of the blades, affect the thermal performance of the channel. In most cases, it is observed that the effect of the oscillation angle is more than that for the oscillating speed on heat transfer enhancement. However, increasing the number of blades does not necessarily help to enhance the heat transfer, but it can slightly decrease the pressure drop.Mon, 09 Mar 2020 20:30:00 +0100Buckling and Vibration Analysis of a Double-layer Graphene Sheet Coupled with a ...
https://jacm.scu.ac.ir/article_15421_0.html
In this article, the vibration and buckling of a double-layer Graphene sheet (DLGS) coupled with a piezoelectric nanoplate through an elastic medium (Pasternak and Winkler models) are investigated. DLGS are subjected to biaxial in-plane forces and van der Waals force existing between each layer. Polyvinylidene fluoride (PVDF) piezoelectric nanoplate is subjected to an external electric potential. For the sake of this study, sinusoidal shear deformation theory of orthotropic plate expanded with Eringen’s nonlocal theory is selected. The results indicate that nondimensional frequency and nondimensional critical buckling load rise when the ratio of width to thickness increases. Furthermore, incrementing the effect of elastic medium parameter results in increasing the stiffness of the system and, consequently, rising nondimensional frequency and critical buckling load.Mon, 09 Mar 2020 20:30:00 +0100Computational Fluid Dynamic Analysis of Amphibious Unmanned Aerial Vehicle
https://jacm.scu.ac.ir/article_15424_0.html
Unmanned Aerial Vehicles (UAVs) are becoming popular due to its versatile maneuvering and high pay load carrying capabilities. Military, navy and coastal guard makes crucial use of the amphibious UAVs which includes the working functionalities of both hover craft and multi-rotor systems. Inculcation of these two systems and make it as amphibious UAV for water quality monitoring, sampling and analysis is essential to serve the human-kind for providing clean water. On this note, an amphibious UAV is designed for carrying a water sampler mechanism with an on-board sensor unit. In order to examine the stability of designed UAV under diverse wind load conditions and to examine the aerodynamic performance characteristics, computational fluid dynamic analysis (CFD) is performed. For various flight conditions such as pitch, roll, yaw and hovering, the flow characteristics around the vehicle body is examined. The aerodynamic phenomenon at the rotor section, vortex, turbulent regions, wake and tip vortex are identified. In addition, CFD analysis are conducted to determine the thrust forces during forward and hovering conditions through varying the wind speed 3 to 10 m/sec and speed of rotor 2000 to 5000 rpm. The effect of non-dimensional parameters such as advance ratio and induced inflow ratio on estimating the thrust characteristics are studied. Simulation results suggested that at 5° angle of attack and 8 m/sec wind speed condition, the aerodynamic performance of the vehicle is superior and stable flight is guaranteed. The amphibious UAV with flying and gliding modes for collecting water samples in remote water bodies and also in-situ water quality measurement can be well utilized for water quality monitoring.Wed, 11 Mar 2020 20:30:00 +0100Validation of Model-Based Real-Time Hybrid Simulation for a Lightly-Damped and Highly-Nonlinear ...
https://jacm.scu.ac.ir/article_15427_0.html
Hybrid simulation (HS) is a cost-effective alternative to shake table testing for evaluating the seismic performance of structures. HS structures are partitioned into linked physical and numerical substructures, with actuators and sensors providing the means for the interaction. Load application in conventional HS is conducted at slow rates and is sufficient when material rate-effects are negligible. Real-time hybrid simulation (RTHS) is a variation of the HS method, where no time-scaling is applied. Despite the recent strides made in RTHS research, the body of literature validating the performance of RTHS, compared to shake table testing, remains limited. In the few available studies, the tested structures and assemblies are linear or modestly nonlinear, and artificial damping is added to the numerical substructure to ensure convergence and stable execution of the simulation. The objective of this study is the validation of a recently proposed model-based RTHS framework, focusing on lightly-damped and highly-nonlinear structural systems; such structures are particularly challenging to consider using RTHS. The boundary condition in the RTHS tests are enforced via displacement and acceleration tracking. The modified Model-Based Control (mMBC) compensator is employed for the tracking action. A two-story steel frame structure with a roof-level track nonlinear energy sink (NES) device is selected due to its light damping, high nonlinearity, and repeatability. The complete structure is first tested on a shaking table, and then substructured and tested via the RTHS method. The model-based RTHS approach is shown to perform similar to the shake table method, even for lightly-damped and highly-nonlinear structures.Sun, 15 Mar 2020 20:30:00 +0100Theoretical and Experimental Investigation on Mechanical Behavior of Aluminum to Aluminum ...
https://jacm.scu.ac.ir/article_15433_0.html
The combination of mechanical and bonded joints creates a new connection type, called hybrid joint which has the benefits of both mechanical and bonded joints. In this research, the mechanical behavior of the tubular bonded lap joint between aluminum tubes subjected to pure torsion has been investigated experimentally and numerically, and the results have been compared. The mechanical behavior of the hybrid (rivet/bonded) joint has been investigated numerically and the outcomes have been compared. The adhesive and rivets have cohesive elements and bushing connector elements, respectively. The results from the hybrid joints and the damage mechanism show that the rivets change the interface shear stress and the stress distribution of the joint, and affect the joint’s torque capacity and strengths. It has been observed that for specimens with overlap lengths close to effective length, the hybrid joint is more effective.Sun, 15 Mar 2020 20:30:00 +0100Nanostructure, Molecular Dynamics Simulation and Mechanical Performance of PCL Membranes ...
https://jacm.scu.ac.ir/article_15466_0.html
Recently, the application of porous bio-nanocomposites has been considered by many researchers for orthopedic application. Since experimental tests for obtaining the mechanical and physical properties of these nanostructured biomaterials are very expensive and time-consuming, it is highly recommended to model and simulate these bio-nanoscale materials to predict their mechanical and physical properties. In this study, three-phase porous bio-nanocomposite membranes were fabricated with Titanium oxide (TiO2), Hydroxyapatite (HA) and Polycaprolactone (PCL) polymer. HA and TiO2 are both biocompatible and biodegradable. The samples were fabricated with various amounts of titanium oxide and the materials characterization has been performed on selected sample. The molecular dynamics technique (MD) have been used to predict the mechanical performance of the nanocomposite models. The MD simulations were performed for single phase material and the developed for two phases equivalent components as a new approach in using MD simulation results. The results indicated the close relationship between the experimental data and simulation values for the selected sample. Moreover, phase and morphology of these nanostructures have been investigated using SEM results. Therefore, based on the proposed approach, MD simulation can be applicable for predicting the properties of porous bio-nanocomposite membrane.Thu, 26 Mar 2020 19:30:00 +0100A Note on the Hydromagnetic Blasius Flow with Variable Thermal Conductivity
https://jacm.scu.ac.ir/article_15467_0.html
In this paper, the influence of the transverse magnetic field is unraveled on the development of steady flow regime for an incompressible fluid in the boundary layer limit of a semi-infinite vertical plate. The sensitivity of real fluids to changes in temperature suggests a variable thermal conductivity modeling approach. Using appropriate similarity variables, solutions to the governing nonlinear partial differential equations are obtained by numerical integration. The approach used here is based on using the shooting method together with the Runge-Kutta-Fehlberg integration scheme. Representative velocity and temperature profiles are presented at various values of the governing parameters. The skin-friction coefficient and the rate of heat transfer are also calculated for different parameter values. Pertinent results are displayed graphically and discussed. It is found that the heat transfer rate improves with an upsurge in a magnetic field but lessens with an elevation in the fluid thermal conductivity.Sun, 29 Mar 2020 19:30:00 +0100Experimental and Finite Element Study to Determine the Mechanical Properties and Bond ...
https://jacm.scu.ac.ir/article_15470_0.html
The separation between repair mortars and the concrete substrate is one of the serious problems in repairing concrete structures. One of the main causes of this separation is the lack of proper curing and, consequently, excessive shrinkage of the repair mortar, which reduces the bond strength between the concrete substrate and the repair layer and has an adverse effect on the compressive and tensile strength of the repair mortars. In this paper, the mechanical properties, shrinkage of repair mortars, as well as their shear and tensile bond strength is investigated on the concrete substrate of different ages under the curings of "abandoned in the laboratory space," "water-submerged" and "curing agent." In-situ "friction-transfer" and "pull-off" methods are used to measure adhesion. Furthermore, the relationships between compressive strength, tensile strength, and readings are obtained from "friction-transfer" and "pull-off" methods on repair mortars and the stress distribution method used in the above-mentioned methods are presented using nonlinear finite element analysis (Abaqus/CAE). The results indicate a significant effect of curing method on shrinkage and mechanical properties of repair mortars; as a result, effective curing increases the shear and tensile bond strength at the substrate and repair layer joint boundary. It is also observed that there is a linear relationship between the experimental results obtained from the two methods used in this study with a high correlation coefficient, highly consistent with the results obtained from nonlinear finite element analysis. Thus, they can be used as in-situ methods for determining the compressive and tensile strength of repair mortars.Fri, 03 Apr 2020 19:30:00 +0100A Closed-Form Solution for Electro-Osmotic Flow in Nano-Channels
https://jacm.scu.ac.ir/article_15479_0.html
In this article‎, ‎a fluid dynamic code is implemented to investigate a non-linear model for electro-osmotic flow through a one-dimensional Nano-channel‎. ‎Certain mathematical techniques are simultaneously utilized to convert the coupled system of equations into a non-linear differential correlation‎. ‎This correlation is based on the mole fraction of anion‎. ‎By using a modified homotopy perturbation method‎, ‎the achieved non-linear differential equation is converted into a few linear differential equations‎. ‎The mole fraction of anion across the channel is found by solving the linear differential equations‎. ‎Finally‎, ‎the distribution of the mole fraction of cation‎, ‎electrical potential, and velocity are accurately derived based on the mole fraction of anion‎. ‎The present study confirms that by application of a modified homotopy perturbation method‎, ‎the results are in acceptable agreement with the previously validated data‎. ‎However, using the proposed method here‎, ‎a closed-form of the solution is achieved‎.Sat, 11 Apr 2020 19:30:00 +0100Biomechanical Evaluation of Bone Quality Effect on Stresses at Bone-Implant Interface: A Finite ...
https://jacm.scu.ac.ir/article_15481_0.html
The aim of this study is to evaluate the effect of the alveolar bone quality on von Mises stress at the bone-implant interface during occlusal loading. Four (3D) finite element models of fully osteointegrated 3-mm diameter × 11.5-mm length dental implant indifferent alveolar bone with different cortical bone thickness are created, using SolidWorks computer aided design software. The alveolar bone cortical-spongy bone ratio modelled includes I) 90%-10%, II) 60%-40%, III) 40%-60%, and IV) 10%-90%. These models are then exported to ABAQUS software and stress analyses are run under an occlusal load of 70 N acting on the platform face of the dental implant. Results of this study show that the implants are subjected to similar stress distributions in all models; maximum stress values are confined in the outer cervical plate of the cortical bone around the neck. This could explain bone loss and implant de-osseointegration. Peak stresses are lowest in the model with 90% cortical bone (14.2 MPa) and almost doubled in the model with 10% cortical bone (26.6 MPa). The stress values gradually reduce towards the apical area, demonstrating masticatory force transfer from implant to bone. Furthermore, both cortical and spongy bone structures exhibit highest stress values in the model with thinnest cortical layer. The high interfacial stress concentration near the implant-cortical bone junction could lead to bone failure or implant instability induced by fatigue or overload risk. Results of our study could be a first step towards the development of a clinical pre-operative planning tool for dental implantolgy.Tue, 14 Apr 2020 19:30:00 +0100Dynamic Investigation of Non-linear Behavior of Hydraulic Cylinder in Mold Oscillator using PID ...
https://jacm.scu.ac.ir/article_15483_0.html
To learn the dynamic characteristics of a mold oscillator, we establish a model that describes the relationship between force equilibrium of a hydraulic cylinder and mold under various oscillation conditions. The non-linearity caused by the servo-value and the operating fluid is considered as excitation, and is calculated as control error between an input signal and mold oscillation in real-time by a PID control process. Based on the non-linear property, we determine that the dynamic behavior is caused by mold oscillation displacement and hydraulic cylinder pressure. We define excitation frequency and harmonic terms, and determine that the sources of the harmonic peak frequency and high peak frequency; (50n ± exciting frequency ωexc) are friction between the piston and hydraulic cylinder, and variable stiffness of the operating fluid. Finally, a mathematical model of the hydraulic chamber that can represent the unknown non-linear phenomenon is derived.Wed, 15 Apr 2020 19:30:00 +0100Improvement of Numerical Manifold Method using Nine-node Quadrilateral and Ten-node ...
https://jacm.scu.ac.ir/article_15484_0.html
In this paper, the numerical manifold method (NMM) with a 9-node quadrilateral element and a 10-node triangular element is developed. Furthermore, complex Fourier shape functions are used to improve the 9-node quadrilateral NMM. Also, the two approaches of higher-order NMM construction are compared, increasing the order of weight functions or local approximation ones; for this purpose, six-node triangular and three-node triangular using second-order and third-order NMM is used. For validation of the suggested method, one free vibration and two forced vibration numerical examples are assessed. The results show that the proposed methods are more accurate than conventional NMM. In addition, the superiority of complex Fourier shape functions compared to classical Lagrange ones in improving accuracy is perceived.Thu, 16 Apr 2020 19:30:00 +0100Thermal-Aerodynamic Performance Measurement of Air Heat Transfer Fluid Mechanics over ...
https://jacm.scu.ac.ir/article_15485_0.html
Forced-convection heat transfer of pure air-fluid inside an open channel as a section of a shell-and-tube heat exchanger is evaluated numerically. S-shaped obstacles are used in the mentioned channel. Airflow inside the channel is considered as a turbulence flow. Governing equations are solved throughout the computational Finite Volume Method (FVM). These equations are analyzed using the standard k-ε model. The results are designed based on the geometry of S-shaped obstacles. Mentioned results are shown in the form of turbulent kinetic energy (k), turbulent intensity (TI), turbulent viscosity (μt), temperature (T), Nusselt numbers (Nux local, and Nu average), friction coefficients (Cf local, and f average), and the thermal aerodynamic performance factor (TEF), for a Reynolds number (Re) of 12,000 to 32,000. This type of analysis is very useful in many industries and engineering-related problems for getting a good idea about the physical model whenever the analytic solution is out of reach.Fri, 17 Apr 2020 19:30:00 +0100Scattering and Backscattering Study of Mechanical Plane Wave in Composite Materials Plates ...
https://jacm.scu.ac.ir/article_15486_0.html
Reflection and refraction phenomenon pattern of elastic plane wave at the interface between anisotropic monoclinic elastic half-space and isotropic elastic half-spaces is studied. Closed-form expression for phase velocity is obtained. Reflection and transmission coefficients are obtained using the method of Cramer's rule in determinant form. Also, the energy ratios are calculated in terms of reflection and transmission coefficients. Numerical examples are considered to exhibit all the findings graphically. The energy conservation law is implemented at each angle of incidence to validate the numerical results, and it is found that energy ratios are in good agreement with the energy conservation law.Sun, 19 Apr 2020 19:30:00 +0100Comparison of Functionally Graded Hip Stem Implants with Various Second-Generation Titanium ...
https://jacm.scu.ac.ir/article_15498_0.html
Total hip Arthroplasty (THA) is performed every year at a very high frequency to improve the quality of life of thousands of patients all over the globe. Nevertheless, the expected service life of such surgery remains unsuitable for patients under 50 years old. This is mainly related to stress shielding and the potential adverse tissue reaction to some of the elements of the market-dominant implant materials. In this research, functionally graded (FG) implant designs of several titanium alloys layered with hydroxyapatite (HA) are proposed to provide lower implant stiffness compared to a solid stem to approach the requirements of human bone. Moreover, TNZT (Ti35Nb7Zr5Ta), and TMZF (Ti12Mo6Zr2Fe) second-generation titanium alloys are studied as a replacement for the famous Ti6Al4V alloy to avoid the adverse tissue reactions related to aluminum and vanadium elements. The different FG models are numerically tested using a 3D finite element simulation after virtual implantation in a femur bone under the dynamic load of a patient descending stairs. In the numerical study, the variation in stress distribution and strain energy in a femur bone is assessed for different FG hip stems as well as the axial stiffness of the hip stems. Results indicated an increase in strain energy and von Mises stress in the cortical and cancellous bones using FG hip stems. Additionally, the axial stiffness is reduced for all FG hip stems relative to the commercial Ti6Al4V hip stem.Tue, 21 Apr 2020 19:30:00 +0100Haar Wavelet Method for Solving High-Order Differential Equations with Multi-Point Boundary ...
https://jacm.scu.ac.ir/article_15499_0.html
In This paper, the developed Haar wavelet method for solving boundary value problems is described. As known, the orthogonal Haar basis functions are applied widely for solving initial value problems, but In this study, the method for solving systems of ODEs associated with multipoint boundary conditions is generalized in separated or non-separated forms. In this technique, a system of high-order boundary value problems of ordinary differential equations is reduced to a system of algebraic equations. The experimental results confirm the computational efficiency and simplicity of the proposed method. Also, the implementation of the method for solving the systems arising in the real world for phenomena in fluid mechanics and construction engineering approves the applicability of the approach for a variety of problems.Thu, 23 Apr 2020 19:30:00 +0100Chaos Control in Gear Transmission System using GPC and SMC Controllers
https://jacm.scu.ac.ir/article_15500_0.html
Chaos is a phenomenon that occurs in some non-linear systems. Therefore, the output of the system will be heavily dependent on the initial conditions. Since the main characteristic of the chaos is an abnormal behavior of the system output, it should be considered in designing control systems. In this paper, controlling chaos phenomenon in a time-variant non-linear gear transmission system is investigated. To do this, a non-linear model for the system is introduced considering the effective parameters of the system, and then it is shown that chaos appears in the system by plotting phase plane of state-space variables. It should be noted that there is a great difference between random and chaotic behavior. In random cases, the model or input contains uncertainty, and therefore, the system behavior and output are not predictable. However, in chaotic behavior, there is only a brief uncertainty in the system model, input or initial conditions, and designing controller based on output prediction could be achieved. Therefore, model predictive control (MPC) algorithms are used to control the chaos, using the output prediction concept. In many cases, perturbation term also can be considered as uncertainty, and therefore, a robust controller family can be used for eliminating chaos. Both generalized predictive controller (GPC) and sliding mode controller (SMC) are used for chaos control here. The simulation results show the efficiency of the proposed algorithms.Sat, 25 Apr 2020 19:30:00 +0100Numerical Scheme based on Non-polynomial Spline Functions for the System of Second Order ...
https://jacm.scu.ac.ir/article_15501_0.html
Several applications of computational science and engineering, including population dynamics, optimal control, and physics, reduce to the study of a system of second-order boundary value problems. To achieve the improved solution of these problems, an efficient numerical method is developed by using spline functions. A non-polynomial cubic spline-based method is proposed for the first time to solve a linear system of second-order differential equations. Convergence and stability of the proposed method are also investigated. A mathematical procedure is described in detail, and several examples are solved with numerical and graphical illustrations. It is shown that our method yields improved results when compared to the results available in the literature.Sat, 25 Apr 2020 19:30:00 +0100Hydrodynamic Behavior in Solar Oil Heat Exchanger Ducts Fitted with Staggered Baffles and Fins
https://jacm.scu.ac.ir/article_15502_0.html
The attachment of turbulators, such as baffles, fins, ribs, bars, and blocks, inside the thermal solar receiver ducts, is among the most effective mechanisms for important thermal exchange by creating the turbulence, extending the trajectory of the flow, increasing the surface of heat exchange, forcing recycling cells, and hence a high thermal exchange. The solar finned and baffled heat exchangers are employed in a wide application interval, and it is important to examine the design of a duct for this configuration of the flow field and its effect on the heat transport phenomenon. In This study, dynamic field simulations are reported in horizontal rectangular form ducts, using three obstacles with oil HTF (heat transfer fluid). Two various finned and baffled duct configurations are treated, i.e., case (A) with one fin and two baffles, and case (B) with two fins and one baffle. Different hydrodynamic fields, i.e., X-velocity and Y-speed, as well as various X-velocity profiles in many flow stations, related to Re value, are analyzed. A computational approach is applied in order to simulate the oil flow, using finite volume (FV) integration method, SIMPLE discretization algorithm, QUICK interpolation scheme, Standard k-epsilon turbulence model, and ANSYS FLUENT 12.0 software. Simulation results reported an unstable flow structure, with powerful recycling cells, on the backsides of each fin and baffle, as a result of fluid detachment at their upper front sharp edges, in both studied models (A and B). As expected, the first duct model, i.e., Case A, has better X- and Y-velocity values, due to its large recirculation regions. In This paper, many physical phenomena, such as the turbulence, instability, flow separation, and the appearance of reverse secondary currents, are reported. As its data confirmed by many previous numerical and experimental results, the suggested new models of finned and baffled heat exchangers filled with high thermal conductivity oil, allow an improvement in the dynamic thermal-energy behavior of many thermal devices such as flat plate solar collectors.Sat, 25 Apr 2020 19:30:00 +0100Effect of Throughflow on the Convective Instabilities in an Anisotropic Porous Medium Layer ...
https://jacm.scu.ac.ir/article_15514_0.html
The significance of inconstant gravity force and uniform throughflow on the start of convective movement in an anisotropic porous matrix is investigated numerically utilizing large-term Galerkin procedure. The porous layer is acted to uniform upright throughflow and inconstant downward gravitational force which changes with the height from the layer. We examined two types of gravity field digression: (a) linear and (b) parabolic. It is found that the throughflow parameter , the thermal anisotropy parameter and gravity deviation parameter postpone the beginning of convective activity, whereas the mechanical anisotropy parameter rapids the onset of convective activity. The dimension of the convection cells enhances on enhancing the thermal anisotropy parameter , the mechanical anisotropy parameter and gravity deviation parameter while, the throughflow parameter decreases the extent of the convective cells. It is also noted that the structure with linear variation of gravity force is more stable.Wed, 29 Apr 2020 19:30:00 +0100Effect of Inlet Air Locations on Particle Concentration using Large Eddy Simulation based on ...
https://jacm.scu.ac.ir/article_15515_0.html
In this work, turbulent indoor airflow was considered by Large Eddy Simulation (LES) based on Multi Relaxation Time Lattice Boltzmann Method (MRT-LBM). The Lagrangian approach was utilized to investigate the effect of inlet air location on transport and concentration of different sizes of particles (1-10 µm) in a modeled room. Simulation results showed that for the displacement ventilation system with the inlet air register on the floor, the number of 10µm particles that exit through the outlet is more than the case for the mixing ventilation system with the inlet register on the ceiling. Also, for the latter case, when the inlet air is on the ceiling, the number of suspended 10µm particles in the room is less than for the displacement ventilation system with inlet register on the floor. In addition, the results showed that the location of the inlet air register does not have a considerable effect on the small 1µm particle motion, and the numbers of the particles that remain suspended in the room are roughly the same for both ventilation systems.Thu, 30 Apr 2020 19:30:00 +0100Metal and Metallic Oxide Nanofluid over a Shrinking Surface with Thermal Radiation and Heat ...
https://jacm.scu.ac.ir/article_15518_0.html
In transport as well as manufacturing industries, the two basic aspects are heating and cooling. The use of metal or metallic oxide nanofluids has an effective cooling technique than that of conventional fluids. Therefore, the work is aimed at describing the three-dimensional MHD flow of metal and metallic oxide nanofluids past a stretching/shrinking sheet embedding with a permeable media. Further, thermal properties are enhanced by incorporating heat generation/absorption and radiative heat energy in the heat equation, enhancing the efficiency of temperature profiles. The convective boundary condition for temperature is used, which affects the temperature profile. Suitable similarity transformation is used to transform the governing equations to ordinary differential equations. The approximate analytical solution is obtained for these transformed differential equations employing the Adomian Decomposition Method (ADM). The influences of characterizing parameters are obtained and displayed via graphs, and the computation results of the heat transfer rate for various values of constraints are shown in a table. It is observed that both the momentum and energy profiles decrease with an enhance in the porosity parameter. Also, the fluid temperature decreases with an increasing thermal radiation parameter, but the opposite effect is encountered for the energy generation/absorption parameter.Fri, 01 May 2020 19:30:00 +0100Modeling beam-like planar structures by a one-dimensional continuum: an analytical-numerical method
https://jacm.scu.ac.ir/article_15523_0.html
In this paper, beam-like structures, macroscopically behaving as planar Timoshenko beams, are considered. Planar frames, made by periodic assemblies of micro-beams and columns, are taken as examples of these structures and the effectiveness of the equivalent beam model in describing their mechanical behavior, is investigated. The Timoshenko beam (coarse model) is formulated via the direct one-dimensional approach, by considering rigid cross-sections and flexible axis-line, while its constitutive laws is determined through a homogenization procedure. An identification algorithm for evaluation of the constitutive constants is illustrated, based on Finite Element analyses of the cell of the periodic system. The inertial properties of the equivalent model are instead analytically identified under the hypothesis the masses are lumped at the joints. The advantages in using the equivalent model are discussed with reference to the linear static and dynamic responses of some planar frames, taken as case-studies, for which both analytical and numerical tools are used. Numerical results, obtained by the equivalent model, are compared with Finite Element analyses on planar frames (fine models), considering both symmetric and not-symmetric layouts, in order to show to effectiveness of the proposed algorithm. A comparison with analytical results is carried out to validate the limits of applicability of the method.Wed, 06 May 2020 19:30:00 +0100Thermodynamic and Environmental Assessment of Mounting Fin at the Back Surface of ...
https://jacm.scu.ac.ir/article_15524_0.html
Nowadays, researches on different kinds of renewable energies including photovoltaic technology are developing rapidly. It is proved that the output power of a PV cell is reduced by increasing the temperature. In this paper, mounting aluminum fins at the back surface of the PV module is proposed as a simple and low-cost method to decrease the PV cell temperature. It was found that using aluminum fins caused more than 7°C reduction in the cell temperature. Besides, it was shown that the entropy generation of the PV module with fin, was 3.5% lower than the conventional one. Also, the positive environmental impacts of using fins at the back surface of the PV module were estimated by RETScreen software, so that it, leads to enhance the performance of the PV power plant by more than 25 %, from an environmental viewpoint.Thu, 07 May 2020 19:30:00 +0100Elastic Limit Angular Velocity and Acceleration Investigation in Non-Uniform Rotating Disk ...
https://jacm.scu.ac.ir/article_15526_0.html
An analytical effort is made to achieve cognition on the effect of time-dependent mechanical loading ‎on the stress fields of rotating disks with non-uniform thickness and density. At high variable angular ‎velocities and accelerations, evaluation of the effect of shear stress on the values of von Mises stress is ‎significant and it is excellent to consider shear stress in this equivalent stress calculation alongside the ‎radial and tangential stress. In the proposed analytical model, the Homotopy perturbation method (HPM) ‎solves the general structure of rotating disks equilibrium equations in both radial and tangential ‎directions. HPM is an efficient tool to solve linear and nonlinear equations, providing solutions in quick ‎converging series. The results obtained through this process are then confirmed using the finite ‎difference method and the exact solution in the literature. The effect of parameters in angular velocity ‎and acceleration functions with the parameter in the thickness function and the effect of boundary ‎conditions on the values of elastic limit angular velocity and acceleration are established by performing ‎numerical examples. Furthermore, the effect of shear stress on the maximum values of ‎von Mises stress is discussed. It is shown that shear stress has more influence on the distribution of ‎equivalent von Mises stress in the elastic region. It is shown the introduced analytical model is useful for ‎evaluating rotating disk with any arbitrary shape of thickness and density function, without using the ‎commercial finite element simulation software.Sat, 09 May 2020 19:30:00 +0100Stability analysis of Casson nanofluid over an extending/contracting wedge and stagnation point
https://jacm.scu.ac.ir/article_15528_0.html
This numerical study is conducted to scrutinize the dual solutions and stability analysis of the flow of Casson nanofluid past a permeable extending/contracting wedge and stagnation point. Momentum, heat and mass transfer behaviors of the Casson nanofluid has been modeled with the use of the Buongiorno nanofluid model. Suitable self-similarity variables are employed to convert the fluid transport equations into ordinary differential equations and the bvp4c MATLAB solver is used to solve the equations. The impacts of active parameters on fluid transport properties are illustrated graphically. The outcomes of the present analysis reveal that the influence of Casson fluid parameter on velocity and temperature distributions obtained from the first and second solutions exhibit the opposite natures. From the stability analysis, it is found that the thermophoresis and Brownian motion effects acquire the same critical point value on Nusselt number. The temperature distribution of the Casson nanofluid is higher over the wedge than stagnation point. The two solutions are found for the limited range of extending/contracting parameter. The detailed stability test is carried out to determine which of the two solutions is physically realizable and stable.Sat, 09 May 2020 19:30:00 +0100Optimization of air distribution patterns by arrangements of air inlets and outlets: case study ...
https://jacm.scu.ac.ir/article_15534_0.html
In this research, possible methods to improve the air distribution patterns of an operating room (OR) employing CFD method were investigated. Laminar airflow (LAF), turbulent airflow (TAF), and LAF with the air curtain were examined. It was found that LAF and LAF with the air curtain cases were superior to TAF-based cases. The study showed that the LAF and LAF with the air curtain cases as the proposed configurations have an acceptable capability to maintain the indoor air conditions within the range recommended by the standards. According to the simulations, the LAF with the air curtain case is the most suitable case in terms of the contamination risk, and it was recommended to be implemented in the existing OR.Thu, 14 May 2020 19:30:00 +0100A new modified Hamilton-Crosser and Nan models for thermal conductivity of different lengths ...
https://jacm.scu.ac.ir/article_15535_0.html
In order to investigate the shape effect of nanoadditives on thermal conductivity of nanofluids, different length carbon nanotubes (CNTs) were made and using a two-step method, different nanofluids were prepared. The CNTs were cut by functionalization at different refluxing times of 1, 2 and 4 hours. To probe the effect of aspect ratio of CNTs on the obtained data, modified Hamilton-Crosser and Nan models were developed. It was found that the original Hamilton-Crosser and Nan models could not predict the experimental thermal conductivities. By replacing n=6+x L/D instead of the shape factor of n=6 in the Hamilton- Crosser, where L and D were length and diameter of CNTs and also by replacing φ(x "D" /"L" ) instead of φ (volume fraction) in the Nan model, the prediction of modified equations had very good accordance with the experimental data which means the shape of nanoadditives has high impact on nanofluid’s properties.Fri, 15 May 2020 19:30:00 +0100Multi-objective optimization of shot-peening parameters using design of experiments and finite ...
https://jacm.scu.ac.ir/article_15536_0.html
Shot-peening is a mechanical surface treatment used extensively in the industry to enhance the performance of metal parts against fatigue. Therefore, it is important to determine its main parameters and find the optimal values. The purpose of this study is to obtain a statistical model to determine the important parameters of the shot-peening process by considering the effect of sample thickness on the responses and to use this model to obtain multi-objective optimal parameters. For this purpose, response surface methodology was used to determine the governing models between the response variable and the input parameters. Shot velocity, shot diameter, coverage percentage and sample thickness are chosen as shot-peening parameters. Residual compressive stress, its depth and roughness are considered as the response variable. Using finite element analysis, shot-peening process has been simulated. The desirability function approach is used to multi-objective optimization so the optimal shot-peening parameters that simultaneously provide two response variables in optimal mode are obtained. The results shows that surface stress and maximum residual stress are independent of shot velocity, but the depth of the compressible stress and roughness are directly related to shot velocity. In addition, thickness influences on surface stress and the depth of the compressible stress. We can achieve optimal conditions for surface stress, maximum compressive stress, and roughness simultaneously with high-coverage and low-velocity.Fri, 15 May 2020 19:30:00 +0100AXISYMMETRIC PROBLEM OF THE ELASTICITY THEORY FOR THE RADIALLY INHOMOGENEOUS CYLINDER WITH A ...
https://jacm.scu.ac.ir/article_15541_0.html
By the method of the asymptotic integration of the equations of elasticity theory, the axisymmetric problem of elasticity theory is studied for a radially inhomogeneous cylinder of small thickness. It is considered that the elasticity moduli are arbitrary positive continuous functions of the radius of the cylinder. It is also assumed that the lateral surface of the cylinder is fixed, and stresses are imposed at the end faces of the cylinder, which leave the cylinder in equilibrium. The analysis is carried out when the cylinder thickness tends to zero. It is shown that solutions corresponding to the first and second iterative processes that determine the internal stress-strain state of the radially inhomogeneous cylinder with a fixed surface do not exist. The third iterative process defines solutions that have the boundary layer character equivalent to the Saint-Venant end effect in the theory of inhomogeneous plates. The stresses determined by the third iterative process are localized at the ends of the cylinder and decrease exponentially with distance from the ends. The asymptotic integration method is used to study the problem of torsion of the radially inhomogeneous cylinder of small thickness. The nature of the stress-strain state is analyzed.Tue, 19 May 2020 19:30:00 +0100A Comparative Study on the Efficiency of Compiled Languages and MATLAB/Simulink for Simulation ...
https://jacm.scu.ac.ir/article_15549_0.html
In the present paper, a comparison between the simulation performance of a highly nonlinear model in MATLAB/Simulink and in a compiled language has been drawn. A complete powertrain layout was drawn in Simulink and the same model was developed from scratch in Fortran 2003 which led to creating a complete simulation software program named Powertrain Simulator. The results show that for a system with not many details and phase changes, both of the simulation environments offer acceptable performance. However, when the modeling layout is overly complicated, developing the model in a compiled language is a smarter choice.Sun, 24 May 2020 19:30:00 +0100Unsteady separated stagnation point flow of nanofluid past a moving flat surface in the ...
https://jacm.scu.ac.ir/article_15550_0.html
This paper explores energy and mass transport behavior of unstable separated stagnation point flow of nanofluid over a moving flat surface along with Buongiorno’s model. Characteristic of Brownian diffusion and thermophoresis are considered. Additionally, characteristics of chemical reaction took into account. A parametric investigation is performed to investigate the outcome of abundant parameters such as temperature, velocity and concentration. An appropriate equation is converting into a set of ODEs through employing appropriate transformation. The governing equations has been solved numerically by using the classical fourth-order Runge-Kutta integration technique combined with the conventional shooting procedure after adapting it into an initial value problem. Our findings depicts that the temperature field θ(ζ) improves for augmenting values of theromophoresis parameter (Nt) with dual solutions of attached flow without inflection and flow with inflection. Also, the difference of Brownian motion parameter (Nb) with two different solutions of attached flow exists with energy profile. It can found that an energy profile θ(ζ) elevates due to augmenting values of (Nb). It has been perceives that thermal boundary layer thickness elevates due to large amount of Brownian motion parameter (Nb).Sun, 24 May 2020 19:30:00 +0100Analysis and Optimization of Truss Structures, Constrained Handling using Genetic Algorithm
https://jacm.scu.ac.ir/article_15552_0.html
In this study, an attempt is made to minimize the weight of Howe roof and ten member-6 Node trusses, separately. Two constraints, maximum allowable deflection and maximum allowable member stresses have been considered. For the first truss, permissible deflection is not known from the literature; therefore, it is determined using exhaustive search method. Once magnitudes of the constraints are identified, member cross-sectional areas are varied to get the optimal weight. Both exhaustive search method and the genetic algorithm have been implemented for this purpose. During this optimization, we have seen that some members tend to form a string and thus they may be eliminated from the structure. Doing this, we could further reduce the weights of the trusses and even less than the minimum available in the literature. The second truss is an indeterminate structure and Maxwell Betti reciprocal theorem is applied to calculate the member forces. Also, further reduction of members is made for this truss keeping in mind that the truss becomes determinate with the decrease in the member(s).Tue, 26 May 2020 19:30:00 +0100Thermal Analysis of Radiating Film Flow of Sodium Alginate using MWCNT Nanoparticles
https://jacm.scu.ac.ir/article_15577_0.html
Heat transfer of fluids plays an important role in process flows, as this has significant impacts in process configurations, energy pricing and utilization. Therefore, this paper, the heat and mass transfer of a radiating non-Newtonian Sodium alginate transported through parallel squeezing plates is examined. The radiating-squeezing fluid flows through the parallel plates arranged vertically against each other with multi walled carbon nanotube (MWCNT) particles. Transport mechanics and thermal conditions of the Sodium alginate is studied using systems of coupled nonlinear models. This higher order, governing ordinary differential models are used to analyze the thermal and mass transfer of the nanofluid using the adomian decomposition method. Results obtained from analytical study displayed graphically are used to investigate effect of thermal radiation on film flow of MWCNT nanoparticles on the Sodium alginate. As revealed from result, concentration increase of MWCNT nanoparticles increases thermal profile significantly. This can be physically explained owing to increasing concentration, increases thickness of thermal boundary due to conductivity enhancement of fluid. Improved thermal diffusivity drops thermal gradient which reduces heat transfer. Whereas, radiation effect on fluid transport shows decrease in heat transfer as thermal conductivity becomes lower than temperature gradient of the flow. Obtained analysis when compared against other methods of solution (numerical and approximate analytical) proves satisfactory. Therefore, the results obtained from the work provides a good basis for the application and improvement of the Sodium alginate in medical, pharmaceutical and manufacturing industries among other practical application.Sun, 31 May 2020 19:30:00 +0100Precision Shape Control of Ultra-thin Shells with Strain Actuators
https://jacm.scu.ac.ir/article_15579_0.html
This paper is part of an effort conducted at Université libre de Bruxelles (ULB) on behalf of European Space Agency (ESA) to control the shape of thin polymer shell structures with a unimorph layer of strain actuators (Polyvinylidenefluoride-co-trifluoroethylene, PVDF-TrFE), to achieve high quality light-weight foldable reflectors for space observation. The paper discusses the influence of the electrode size on the morphing capability of the system and addresses the difficulty associated with the ill-conditioning when controlling a very large set of electrodes. The final part of the paper describes a technology demonstrator currently under development and presents some simulation results fitting low order optical modes.Mon, 01 Jun 2020 19:30:00 +0100Structural Health Monitoring of Multi-Storey Frame Structures using Piezoelectric ...
https://jacm.scu.ac.ir/article_15616_0.html
In the present paper, we develop a novel method for structural health monitoring of multi-storey frame structures with the capability to detect and localise local damage. The method uses so-called spatial incompatibility filters, which are continuously distributed strain-type sensors only sensitive to incompatibilities. In the first part of the paper the concept of incompatibility filters is introduced for multi-storey frame structures and it is shown how these filters can be used to detect and localise local cracks in frame structures. In the second part of the paper we study the use of incompatibility filters put into practice by piezoelectric sensor networks for structural health monitoring of a three-storey frame structure. The design of the piezoelectric sensor network is based on an analytical analysis of the frame structure within the framework of the method developed in the first part of the paper and a numerical verification using three-dimensional Finite Elements completes the paperFri, 12 Jun 2020 19:30:00 +0100Investigation of nanoﬂuid natural convection heat transfer in open ended L-shaped cavities ...
https://jacm.scu.ac.ir/article_15620_0.html
In this paper, laminar natural convection of copper/water nanofluid in an open-ended L-shaped cavity is investigated by Lattice Boltzmann Model (LBM). The results are compared by previous studies, that are in good agreement. Influences of Rayleigh number (Ra=〖10〗^3,〖10〗^4,〖10〗^5,〖10〗^6), cavity aspect ratio (AR=0.2, 0.4, 0.6) and volume concentration of Cu nanoparticles (0≤φ≤0.1) on the momentum, thermal ﬁelds and heat transfer in the enclosure are studied. Also, the effect of changing the boundary conditions, on the heat transfer rate has been investigated. It is observed that maximum heat transfer enhancement by adding the nanoparticles for Ra=〖10〗^6 with AR=0.4 (32.76%) occurs. Results illustrate that increasing the cavity aspect ratio decreases heat transfer rate for Ra=〖10〗^3 and Ra=〖10〗^4. The least and most heat transfer rate for Ra=〖10〗^5 occurs in enclosures by aspect ratios of 0.2 and 0.4 respectively, while it was observed at Ra=〖10〗^6 for minimum and maximum rate of heat transfer the opposite behavior that at Ra=〖10〗^5 occurs.Sat, 13 Jun 2020 19:30:00 +0100ADM solution for Cu/CuO –Water viscoplastic nanofluid transient slip flow from a porous ...
https://jacm.scu.ac.ir/article_15622_0.html
A mathematical model is presented for entropy generation in transient hydromagnetic flow of an electroconductive magnetic Casson (non-Newtonian) nanofluid over a porous stretching sheet in a porous medium. The model employed is Cattaneo-Christov heat flux to simulate non-Fourier (thermal relaxation) effects. A Rosseland flux model is implemented to model radiative heat transfer. The Darcy model is employed for the porous media bulk drag effect. Momentum slip is also included to simulate non-adherence of the nanofluid at the wall. The transformed, dimensionless governing equations and boundary conditions (featuring velocity slip and convective temperature) characterizing the flow are solved with the Adomian Decomposition Method (ADM). Bejan’s entropy minimization generation method is employed. Cu-water and CuO-water nanofluids are considered. Extensive visualization of velocity, temperature, and entropy generation number profiles is presented for variation in pertinent parameters. The calculation of skin friction and local Nusselt number are also studied. The ADM computations are validated with simpler models from the literature. The solutions show that with elevation in the volume fraction of nanoparticle and Brinkman number, the entropy generation magnitudes are increased. An increase in Darcy number also upsurges the friction factor and heat transfer at the wall. Increasing volume fraction, unsteadiness, thermal radiation, velocity slip, Casson parameters, Darcy, and Biot numbers are all observed to boost temperatures. However, temperatures are reduced with increasing non-Fourier (thermal relaxation) parameter. The simulations are relevant to the high temperature manufacturing fluid dynamics of magnetic nano liquids, smart coating systems.Sun, 14 Jun 2020 19:30:00 +0100A Modified Thermoelastic Fractional Heat Conduction Model with A Single-Lag and Two Different ...
https://jacm.scu.ac.ir/article_15630_0.html
Recently, fractional calculus theory has been successfully employed in generalized thermoelasticity theory and several models with fractional order have been introduced. In this work, a fractional thermoelastic modified Fourier's Law with phase lag and two different fractional-orders has been constructed. The previous fractional models of thermoelasticity introduced by Sherief et al. [1], Ezzat [2] and Lord and Shulman [3] as well as classical coupled thermoelasticity [4] follow as limiting cases. This proposed model is applied to an infinitely annular cylinder that is subject to time-dependent surface temperatures, and whose surfaces are free of traction. The method of the Laplace transform is employed to get the solutions of the field variables. A numerical technique is utilized to invert the Laplace transforms. Some results are presented in tables and figures to extract the effects of fractional order parameters on all variables studied. The theory's predictions have been checked and compared to previous models.Fri, 19 Jun 2020 19:30:00 +0100Effect of Cattaneo-Christov heat flux on radiative hydromagnetic nanofluid flow between ...
https://jacm.scu.ac.ir/article_15631_0.html
We solve numerically the equations for hydromagnetic nanofluid flow past semi-infinite parallel plates where thermal radiation and a chemical reaction are assumed to be present and significant. The objective is to give insights on the important mechanisms that influence the flow of an electrically conducting nanofluid between parallel plates, subject to a homogeneous chemical reaction and thermal radiation. These flows have great significance in industrial and engineering applications. The reduced nonlinear model equations are solved using a Newton based spectral quasilinearization method. The accuracy and convergence of the method is established using error analysis. The changes in the fluid properties with various parameters of interest is demonstrated and discussed. The spectral quasilinearization method was found to be rapidly convergent and accuracy is shown through the computation of solution errors.Fri, 19 Jun 2020 19:30:00 +0100Numerical study of three-dimensional boundary-layer flow over a wedge: magnetic field analysis
https://jacm.scu.ac.ir/article_15643_0.html
The magnetohydrodynamic flow of a viscous fluid over a constant wedge in three-dimensional boundary-layer has been analyzed both numerically and asymptotically. The magnetic field is applied normal to the flow. The mainstream flows aligned with wedge surface are assumed to be proportional to the power of the coordinate distances. The system is described using three-dimensional MHD boundary-layer equations which are converted to coupled nonlinear ordinary differential equations using similarity transformations. The resulting equations are solved numerically using the Keller-box method which is second-order accurate and asymptotically for far-field behaviour. Both numerical and asymptotic solutions give good agreement in predicting the velocity behaviours and wall shear stresses. The effects of Hartmann number, pressure gradient and shear-to-strain-rate on the velocity fields are studied. Particularly, it is shown that the solutions of three-dimensional boundary-layer for variable pressure gradient exist, its effects are important on the boundary-layer flow. Results show that there are new families of solutions for some range of shear-to-strain-rate and there exists a threshold value of it beyond which no solutions exist. For some range of parameters, there is a reverse flow at which our boundary-layer assumptions are no longer valid. Various results for the velocity profiles, wall-shear stresses and displacement thicknesses are also obtained. The physical mechanisms behind these results are discussed.Tue, 23 Jun 2020 19:30:00 +0100Analytical Solutions and Analyses of the Displacement Separating Point in Diffusers
https://jacm.scu.ac.ir/article_15663_0.html
The main purpose of this study is to develop an understanding of the turbulent boundary layer calculation to analyze displacement of the separating point in diffusers. An approximate method has been used which is based on an analogy with the rheological power law and is applied in the study of non-linear viscous flows. At first, the method has been validated with the experimental data in the same experimental cases study. An appropriate geometric with and without the Nano-fluids in the straight-wall and curved-wall conical diffusers has been investigated. Its analyses output was compared with the results obtained by a numerical code. Also, the proposed method is more practical and can be used in diffuser design procedures.Sun, 05 Jul 2020 19:30:00 +0100Twin Screw Expanders Profile Optimization Using Surrogate-Based Modelling
https://jacm.scu.ac.ir/article_15667_0.html
Abstract. Twin screw machines can be used as an expander to recover the lost power in various processes that cause pressure exergy loss. Twin screw expanders (TSEs) have caught the attention of many researchers due to low capital, maintenance, and operation costs, longer lifespan, and usage in two-phase fluids. However, many efforts need to be made to enhance their performance. This research described the optimization of the profile of a TSE with 4-6 lobe configuration - using surrogate-based modeling (SBM). For this purpose, based on the in-house code developed within FORTRAN, a TSE profile was designed and validated against available data. Then, a mathematical model was developed by the design of experiments (DOE), and the effects of four main profile parameters were investigated on the expander performance in the entire design space. Finally, an optimized combination of parameters was derived using a multi-objective genetic algorithm. 3D computational fluid dynamics (CFD) results showed that the optimized profile had more than 7% exergy efficiency compared to the base profile.Tue, 07 Jul 2020 19:30:00 +0100Natural frequencies and internal resonance of beams with arbitrarily distributed axial loads
https://jacm.scu.ac.ir/article_15668_0.html
An exact analytical solution for transversal free vibrations of a beam subjected to an arbitrary distributed axial load and a tip tension is obtained by means of a power series representation, whose coefficients are determined recursively in an easy way. The dependence on the natural frequencies on the load is then investigated, and the buckling load (corresponding to vanishing frequency) is also discussed. Next, the 1:3 internal resonance between the first and the second mode is deeply studied, and an interesting (and unexpected) property is found for linearly distributed axial loadsTue, 07 Jul 2020 19:30:00 +0100Numerical Analysis of the Baffles Inclination on Fluid Behavior in a Shell and Tube Heat ...
https://jacm.scu.ac.ir/article_15669_0.html
The thermo-hydraulic performances of the shell-and-tube heat exchangers with different baffles inclination angle α =10°, α =20°, and α = 40° are investigated. The numerical analysis has been evaluated using ANSYS Fluent with the finite volume method for Reynolds number varying between 24000 and 27000. In all heat exchangers, the characteristics studied are the velocity, the temperature in the shell, the heat transfer coefficient, the pressure. The results showed small dead zones for the baffles inclination angle of 40°. The results showed that the temperature increases by 3.4 K, the heat transfer coefficient decreased by 0.983 %, the pressure drop decreased by 0.992 %, the overall performance factor decreased by 0.83 % when the baffles inclination angle α is increased from 10° to 40°.Wed, 08 Jul 2020 19:30:00 +0100Magneto-Bio-Thermal Convection in Rotating Nanoliquid containing Gyrotactic Microorganism
https://jacm.scu.ac.ir/article_15676_0.html
The magneto-convection influenced by a gyrotactic behavior of algal suspensions along with rotation in the nanofluid layer is investigated. Linear theory based on normal mode analysis is used to find out the inquisitive results of the problem for rigid-free and rigid-rigid boundaries. Both Galerkin-method (Number of terms (N)>6) and shooting method (by taking forcing condition) is utilized to find the critical value of the Rayleigh number (both thermal and bio) in case of non-oscillatory stability. Both thermal and bio Rayleigh numbers are dependent on each other, thus advance or delay the convection. Rotation and magnetic field slowed down the convective motion of microorganisms across the nanofluid layer and destabilizes the system.Sun, 12 Jul 2020 19:30:00 +0100Variational Inference for Nonlinear Structural Identification
https://jacm.scu.ac.ir/article_15678_0.html
Research interest in predictive modeling within the structural engineering community has recently been focused on Bayesian inference methods, with particular emphasis on analytical and sampling approaches. In this study, we explore variational inference, a relatively unknown class of Bayesian inference approaches which has potential to realize the computational speed, accuracy, and scalability necessary for structural health monitoring applications. We apply this method to the predictive modeling of a simulated Bouc-Wen system subject to base vibration and compare the performance of this inference approach to that of the unscented Kalman filter. From this investigation, we find that though variational inference is more computationally intensive than the unscented Kalman filter, it exhibits superior performance and flexibility.Sun, 19 Jul 2020 19:30:00 +0100Vibration Mitigation of Rail Noise Barriers by Hysteretic Absorbers
https://jacm.scu.ac.ir/article_15680_0.html
A strategy is proposed to mitigate the noise barrier vibrations due to the train passage in high speed lines employing a hysteretic vibration absorber. The barrier is modelled as a generalized single degree of freedom system; the absorber consists of a light mass attached to the main structure by a hysteretic element whose restoring force is described by the Bouc-Wen model. The resulting two degrees of freedom system is studied, and it is shown that, for control purposes, beneficial conditions are obtained when the two oscillators are close to the resonance conditions (1:1). A procedure for a preliminary design of the absorber is highlighted; a parametric analysis varying the absorber characteristics is carried out and the optimal values are obtained by maximizing the barrier response performance. The absorber is then realized exploiting high damping rubber elements whose constitutive parameters have been identified through experimental tests. The effectiveness of the realized absorber is assessed by performing dynamic analysis of the two degrees of freedom system under the train excitation at a reference speed and comparing its performances with those of the designed one, observing a similar reduction of the barrier response. Finally, a sensitivity analysis of the performances varying the train speed shows that, even if the stiffness and damping of the absorber are amplitude dependent, its efficiency is confirmed in the speed range of high speed trains.Sun, 19 Jul 2020 19:30:00 +0100Higher-Order Slope Limiters for Euler Equation
https://jacm.scu.ac.ir/article_15684_0.html
High-resolution schemes are designed for resolving shocks without significant numerical dissipation and dispersion. Achieving higher-order and high-resolution is a challenging task because of the non-monotonicity of the higher-order schemes. In this article, we have presented second-order and third-order slope limiters having an improved shock resolution and accuracy. The present limiters are tested on one-dimensional and two-dimensional unstructured grids and compared with the existing limiters. The numerical result shows that the present limiters have an excellent shock resolving property and accuracy than other limiters. In blast wave problems, it has shown over 200% more accurate results than the other limiters.Mon, 27 Jul 2020 19:30:00 +0100An 8-Node Solid-Shell Finite Element based on Assumed Bending Strains and Cell-Based ...
https://jacm.scu.ac.ir/article_15705_1889.html
In this paper, a new 8-node solid-shell finite element is proposed. The transverse shear strains and transverse normal strains of the element are separately interpolated and related to the C0-displacement approximation at tying points to overcome the shear- and trapezoidal-locking phenomena. From the bending strain approximation suggested for degenerated shell elements, the assumed bending strains for the solid-shell element are firstly established. The membrane strains of the element are smoothed on domains defined by dividing the middle surface's element into 1, 2, 3 or 4 sub-cells in accordance with the cell-based strain smoothing (CS) technique. The formulations of the membrane stiffness matrices are explicitly integrated on the boundary lines of the smoothing sub-cells. The proposed CSn-Q8 element, in which n is the number of smoothing sub-cells, is verified through static analysis of several benchmark plate and shell problems. Numerical results show the improved performance of the CSn-Q8 element in comparison with other references.Mon, 30 Nov 2020 20:30:00 +0100Discretization of the 2D Convection–Diffusion Equation Using Discrete Exterior Calculus
https://jacm.scu.ac.ir/article_15728_1889.html
While the Discrete Exterior Calculus (DEC) discretization of the diffusive term of the Transport Equation is well understood, the DEC discretization of the convective term, as well as its stabilization, is an ongoing area of research. In this paper, we propose a local discretization for this term based on DEC and geometric arguments, considering the particle velocity field prescribed at the vertices of the primal mesh. This formulation is similar to that of the Finite Element Method with linear interpolation functions (FEML) and can be stabilized using known stabilization techniques, such as Artificial Diffusion. Using this feature, numerical tests are carried out on simple stationary and transient problems with domains discretized with coarse and fine simplicial meshes to show numerical convergence.Mon, 30 Nov 2020 20:30:00 +0100Singular Stresses at a Vertex and Along a Singular Line in Three-dimensional Piezoelectric ...
https://jacm.scu.ac.ir/article_15716_1889.html
Singular stress fields in three-dimensional piezoelectric bonded joints are investigated at a vertex and along a free edge (the singular line) of an interface. Two perfectly bonded joints, which are different in the side surface shapes, are considered. The joints consist of multi-terms of singularity. Two-major terms of singularity are investigated in details. The orders of singularity at the vertex and along the singular line are calculated using three-dimensional finite element eigen-analysis. The intensities of singularity are calculated using the conservative integral. The intensities of singularity at several points located on the singular line are examined. The relationships between the intensities of singularity and the distances from the vertex are plotted to determine how the vertex singularity affects the singularity along the singular line. Finally, the relationships between singular stress fields at the vertex and along the singular line are considered.Mon, 30 Nov 2020 20:30:00 +0100Pre-drilling Effect on Thermal Friction Drilling of Cast Aluminum Alloy Using ...
https://jacm.scu.ac.ir/article_15729_1889.html
Thermal friction drilling is a non-conventional hole making process, which uses a rotating tool to penetrate the workpiece and create a bushing. Friction drilling of brittle cast alloys is likely to result in severe petal forming and radial fracturing. This research investigates the effect of pre-drilling diameter and depth on the produced bushing cracks and petal formations while drilling cast aluminum alloy (A380). A three-dimensional finite element model of high-temperature deformation and large plastic strain is performed by using ABAQUS software. Modeling by using dynamic, temperature-displacement, explicit, as well as the adaptive meshing, element deletion, interior contact, and mass scaling techniques, is necessary to enable the convergence of the solution. The finite element analysis results predict that the pre-drilling has a significant effect on the produced bushing shape. The effect of initial deformation decreases with pre-drilling, leading to fewer cracks and petal formations. Hence, the obtained bushing length increases, so providing a more load-bearing surface that leads to a stiffer joint. Additionally, the effect of pre-drilling on the produced temperature is studied, and the results reveal that by increasing the pre-drilling diameter or depth the temperature decreases. Therefore, less workpiece material melting occurs, which leads to less adhering on the tool surface, so fewer cracks and petal formations.Mon, 30 Nov 2020 20:30:00 +0100The Permutation Entropy and its Applications on Fire Tests Data
https://jacm.scu.ac.ir/article_15738_1889.html
Based on the data gained from a full-scale experiment, the order/disorder characteristics of the compartment fire temperatures are analyzed. Among the known permutation/encoding type entropies used to analyze time series, we look for those that fit better in the fire phenomena. The literature in its major part does not focus on time series with data collected during full-scale fire experiments, therefore we do not only perform our analysis and report the results, but also discuss methods, algorithms, the novelty of our entropic approach and details behind the scene. The embedding dimension selection in the complexity evaluation is also discussed. Finally, more research directions are proposed.Mon, 30 Nov 2020 20:30:00 +0100Stability Analysis of a Damped Nonlinear Wave Equation
https://jacm.scu.ac.ir/article_15751_1889.html
The current manuscript is concerned with extracting an analytical approximate periodic solution of a damped cubic nonlinear Klein-Gordon equation. The Riemann-Liouville fractional calculus is utilized to obtain an analytic approximate solution. The Homotopy technique is absorbed in the multiple time-spatial scales. The approved scheme yields a generalization of the Homotopy equation; whereas, two different small parameters are adapted. The first parameter concerns with the temporal perturbation, simultaneously, the second one is accompanied by the spatial one. Therefore, the analytic approximate solution needs the two perturbation expansions. This approach conducts more advantages in handling the classical multiple scales method. Furthermore, the initial conditions are included throughout the multiple scale method to achieve a special solution of the governing equation of motion. The analysis ends up deriving two first-order equations within the extended variables and their actual solution is achieved. The procedure adopted here is very promising and powerful in managing similar numerous nonlinear problems arising in physics and engineering. Furthermore, the linearized stability of the corresponding ordinary Duffing differential equation is analyzed. Additionally, some phase portraits are shown.Mon, 30 Nov 2020 20:30:00 +0100The Relations between the Various Critical Temperatures of Thin FGM Plates
https://jacm.scu.ac.ir/article_15787_1889.html
This work investigates the relations between the critical temperature of the thin FGM plates under various temperature distributions through the thickness resting on the Pasternak elastic foundation. Both rectangular and skew plates are investigated. The uniform, linear, and nonlinear temperature distributions through the plate’s thickness are considered. Formulations are derived based on the classical plate theory (CPT) considering the von Karman geometrical nonlinearity taking the physical neutral plane as the reference plane. The partial differential formulation is separated into two sets of ordinary differential equations using the extended Kantorovich method (EKM). The stability equations and boundary conditions terms are derived according to Trefftz criteria using the variational calculus expressed in an oblique coordinate system. Novel multi-scale plots are presented to show the linear relations between the critical temperatures under various temperature distributions. The critical temperature of plates with different materials are also found linearly related. Resulting relations should be a huge time saver in the analysis process, as by knowing one critical temperature of the one FGM plate under one temperature distribution many other critical temperatures of many other FGM plates under any temperature distributions can be obtained instantly.Mon, 30 Nov 2020 20:30:00 +0100Two Modifications of the Homotopy Perturbation Method for Nonlinear Oscillators
https://jacm.scu.ac.ir/article_16040_1889.html
Nonlinear vibration arises in engineering and physics, and the periodic motion of these nonlinear oscillatory systems have rich dynamics. An estimation of amplitude-frequency relationship of a nonlinear oscillator is much needed, therefore, well-known homotopy perturbation method is employed for this purpose. In this paper, two last modifications of the homotopy perturbation method are briefly reviewed, which couples with either the parameter-expansion technology or the enhanced perturbation method. Both modifications are extremely effective for nonlinear oscillators, and the cubic-quintic-septic Duffing oscillator is used as an example to elucidate the solution processes.Mon, 30 Nov 2020 20:30:00 +0100Larin Parameterization to Solve the Problem of Analytical Construction of the Optimal ...
https://jacm.scu.ac.ir/article_16048_1889.html
The problem of the analytical construction of the optimal regulator of oscillatory systems with liquid ‎dampers on the complex plane is considered. Since the fractional derivative is included in the differential ‎equation describing the oscillatory systems with liquid dampers movement, the corresponding input-output ‎transfer function also contains fractional rational orders, the general Larin parameterization scheme is ‎modifying for this case. The results are illustrated by numerical examples and it is shown that they coincide ‎with Letov’s А.М. analytical construction of the optimal regulator.Mon, 30 Nov 2020 20:30:00 +0100Theoretical Analysis of the Motorcycle Front Brake Heating Process during High Initial Speed ...
https://jacm.scu.ac.ir/article_16050_1889.html
Motorcycles are a common mode of transport. They are used both for a conventional purpose - as a way to cover the distance from A to B, but more and more often they are a way of recreation. The choice of bikes is huge on the market: from scooters, threw small city bikes, to high-speed performance or racing machines. High speeds is closely related to high kinetic energy of movement. In case of emergency stopping, the brakes may overheat and cause fading. In this study, it was decided to check how the initial speed affects the motorcycle brake heating process. FEM was used for this purpose.Mon, 30 Nov 2020 20:30:00 +0100Multiobjective Geometric Analysis of Stiffened Plates under Bending through Constructal ...
https://jacm.scu.ac.ir/article_16110_1889.html
Constructal design, finite element method and exhaustive search are applied to analyze different arrangements of steel plates with rectangular or trapezoidal stiffeners. As performance parameters, the maximum deflection and maximum von Mises stress are considered. A non-stiffened plate adopted as reference is studied together with 25 plates with rectangular stiffeners and 25 plates with trapezoidal stiffeners. The results show that trapezoidal stiffeners are more effective in minimizing the maximum deflection in comparison with rectangular stiffeners. However, regarding the minimization of stress, the rectangular stiffeners normally present better performance. When both performance parameters are concomitantly considered, a slight advantage of 4.70% for rectangular geometry is identified.Mon, 30 Nov 2020 20:30:00 +0100Nonlinear Primary Frequency Response Analysis of Self-Sustaining Nanobeam Considering Surface ...
https://jacm.scu.ac.ir/article_15686_0.html
This paper is focused to investigate the effects of nonlinear sources, including viscoelastic foundation and geometrical nonlinearity along with the surface elasticity and residual surface stress effects on the primary frequency response of a harmonically excited nanoscale Bernoulli-Euler beam. Due to large surface-area-to-volume ratio, the theory of surface elasticity as well as residual surface stress effects are taken into account within the beam models. The Galerkin approach accompanied by trigonometric shape functions is utilized to reduce the governing PDEs of the system to ODEs. The multiple scales perturbation method theory is applied to compute the nonlinear frequency response of nanobeam. The effects of linear and nonlinear viscoelastic damping coefficient of the medium, crystallographic directions of [100] and [111] of anodic alumina, geometrical nonlinear term and geometrical property on the nonlinear primary frequency response of nanoscale beam are investigated. The results show that theses parameters have a significant effect on the nonlinear frequency response of nanobeams in the case of primary resonance.Mon, 27 Jul 2020 19:30:00 +0100Non-Similar Radiative Bioconvection Nanofluid Flow under Oblique Magnetic Field with Entropy ...
https://jacm.scu.ac.ir/article_15687_0.html
Motivated by exploring the near-wall transport phenomena involved in bioconvection fuel cells combined with electrically conducting nanofluids, in the present article, a detailed analytical treatment using homotopy analysis method (HAM) is presented of non-similar bioconvection flow of a nanofluid under the influence of magnetic field (Lorentz force) and gyrotactic microorganisms. The flow is induced by a stretching sheet under the action of a oblique magnetic field. In addition, nonlinear radiation effects are considered which are representative of solar flux in green fuel cells. A second thermodynamic law analysis has also been carried out for the present study to examine entropy generation (irreversibility) minimization. The influence of magnetic parameter, radiation parameter and bioconvection Rayleigh number on skin friction coefficient, Nusselt number, micro-organism flux and entropy generation number (EGN) is visualized graphically with detailed interpretation. Validation of the HAM solutions with published results is also included for the non-magnetic case in the absence of bioconvection and nanofluid effects. The computations show that the flow is decelerated with increasing magnetic body force parameter and bioconvection Rayleigh number whereas it is accelerated with stronger radiation parameter. EGN is boosted with increasing Reynolds number, radiation parameter and Prandtl number whereas it is reduced with increasing inclination of magnetic field.Tue, 28 Jul 2020 19:30:00 +0100An Automatic Program of Generation of Equation of Motion and Dynamic Analysis for Multi-body ...
https://jacm.scu.ac.ir/article_15689_0.html
Multi-body dynamics can calculate the physical quantities required for component design, such as calculating the dynamic response of mechanical components and the time history of dynamic loads. Advances in analysis software, including DADS, ADAMS, RecurDyn, and DAFUL, have made it possible to easily calculate dynamic responses by defining relationships between components and operating environments from 3D modeling on user-created components. However, when the understating of dynamic analysis is lacking, it is difficult to apply multi-body dynamics analysis in the design process, and it is difficult to analyze the acquired response data. In this study, we developed an automatic code to de-rive equations of motion in the matrix format and calculate dynamic responses of multi-body systems using GNU Octave, a free high-level language. In particular, the process of defining matrices and vectors such as inertia matrix, stiffness matrix, and external force vector concerning the degrees of freedom of components by using Euler-Lagrange equations is shown to understand the structure and process of dynamic analysis. The code application by explaining how to use the code in a different mechanical system is also shown to help understand the usage method for who wants to study Multi-body dynamics.Wed, 29 Jul 2020 19:30:00 +0100On/off Nodal Reconfiguration for Global Structural Control of Smart 2D Frames
https://jacm.scu.ac.ir/article_15690_0.html
This paper proposes an on/off semi-active control approach for mitigation of free structural vibrations, designed for application in 2D smart frame structures. The approach is rooted in the Prestress–Accumulation Release (PAR) control strategies. The feedback signal is the global strain energy of the structure, or its approximation in the experimental setup. The actuators take the form of on/off nodes with a controllable ability to transfer moments (blockable hinges). Effectiveness of the approach is confirmed in a numerical simulation, as well as using a laboratory experimental test stand.Fri, 31 Jul 2020 19:30:00 +0100Characterization of the Nonlinear Biaxial Mechanical Behavior of Human Ureter Using ...
https://jacm.scu.ac.ir/article_15696_0.html
Characterization of the mechanical properties of soft tissues is a fundamental issue in a variety of medical applications. As such, constitutive modeling of tissues that serves to establish a relationship between the kinematic variables has been used to formulate the tissue’s mechanical response under various loading conditions. However, the validation of the developed analytical and numerical models is accompanied by a length of computation time. Hence, the need for new advantageous methods like artificial intelligence (AI), aiming at minimizing the computation time for real-time applications such as in robotic-assisted surgery, sounds crucial. In this study, the mechanical nonlinear characteristics of human ureter were obtained from planar biaxial test data, in which the examined specimens were simultaneously loaded along their circumferential and longitudinal directions. To do so, the biaxial stress-strain data was used to fit the well-known Fung and Holzapfel-Delfino hyperelastic functions using the genetic optimization algorithm. Next, the potential of Artificial Neural Networks (ANN), as an alternative method for prediction of the mechanical response of the tissue was evaluated such that, multilayer perceptron feedforward neural network with different architectures was designed and implemented and then, trained with the same experimental data. The results showed both approaches were practically able to predict the ureter nonlinearity and in particular, the ANN model can follow up the tissue nonlinearity during the entire loading phase in both low and high strain amplitudes (RMSESun, 02 Aug 2020 19:30:00 +0100Improving the linear stability of the visco-elastic Beck's beam via piezoelectric controllers
https://jacm.scu.ac.ir/article_15706_0.html
Control strategies for the visco-elastic Beck's beam, equipped with distributed piezoelectric devices and suffering from Hopf bifurcation triggered by a follower force, are proposed in this paper. The equations of motion of the Piezo-Electro-Mechanical (PEM) system are derived through the Extended Hamilton Principle, under the assumption that the piezoelectric patches are shunted to the so-called zero-order network and zero-order analog electrical circuit. An exact solution for the eigenvalue problem is worked out for the PEM system, while an asymptotic analysis is carried out to define three control strategies, recently developed for discrete PEM systems, that are here adapted to improve the linear stability of the visco-elastic Beck's beam. An extensive parametric study on the piezo-electrical quantities, based on an exact linear stability analysis of the PEM system, is then performed to investigate the effectiveness of the controllers.Thu, 06 Aug 2020 19:30:00 +0100Numerical Investigation on the Flow Transition through a Curved Square Duct with Negative Rotation
https://jacm.scu.ac.ir/article_15707_0.html
Application of the rotational phenomena in the curved ducts plays an important role in many engineering areas, so researchers are attracted to innovate something new in this area nowadays. In this regard, the current paper has performed the fluid flow through the curved duct for an extensive range of negative rotation (-10Fri, 07 Aug 2020 19:30:00 +0100About Earthquakes in Subduction Zones with the Potential to Cause a Tsunami
https://jacm.scu.ac.ir/article_15712_0.html
The problem of occurrence of starting earthquakes in subduction zones is considered. Subduction is the phenomenon of movement of the oceanic lithospheric plate under the continental one. The oceanic lithospheric plate at a certain depth melts from below and can slide. The paper considers the occurrence of starting earthquakes under the assumption that lithospheric plates have different contact conditions, being on a rigid base in the subduction zone. A molten lithospheric plate has no tangential contact stresses, while the other, oceanic, is rigidly connected to the base. The block element method is used to study the occurrence of the starting earthquake and the peculiarity of its consequences. The conditions to generate of tsunamis as a result of such earthquakes are being studied. Solutions to boundary value problems that are constructed precisely, rather than approximatively, allow us to reveal the mechanisms of destruction of the environment that were not previously known. In particular, the results obtained allowed us to detect a new type of crack that was not previously described. They destroy the environment in a different way than Griffiths cracks, which is demonstrated in this paper and is important in engineering practice.Tue, 11 Aug 2020 19:30:00 +0100A Simple Approach for Dealing with Autonomous Conservative Oscillator under Initial Velocity
https://jacm.scu.ac.ir/article_15713_0.html
The current study is involved to analytical solution of nonlinear oscillators under initial velocity. By using energy conservation principle, system initial condition converts to condition which oscillator’s velocity become zero. When oscillator’s speed is zero and placed out of movement’s origin, the relation between frequency and amplitude could be extracted. By paying attention to energy conservation principle and relation between the initial velocity and amplitude, the frequency-amplitude relation is extended to frequency-initial velocity relationship. In order to demonstrate the effectiveness of proposed method, Duffing oscillator with cubic nonlinearity and oscillator with discontinuity are considered. Comparison of results with numerical solution shows good agreement. The proposed method is simple and efficient enough to achieve the analytical approximation of nonlinear autonomous conservative oscillator with initial velocity.Wed, 12 Aug 2020 19:30:00 +0100MHD Double-Diffusive Natural Convection in A Closed Space Filled with liquid metal: Mesoscopic ...
https://jacm.scu.ac.ir/article_15715_0.html
In this paper, the lattice Boltzmann approach is carried out to study the double-diffusive natural convection in a space encapsulating liquid metal is presented. The Uniform magnetic field is applied horizontally at the square domain and an insulated rectangular block is kept stationary at the center of the cavity. The linear increment of temperature and concentration is used at the left wall and cold temperature is applied at the right wall. Horizontal walls are adiabatic conditions. Horizontal walls are adiabatic conditions. The numerical analysis is performed at the range of Rayleigh number (103 ≤ Ra ≤ 105), Lewis number (2 ≤ Le ≤ 10), buoyancy ratio (-2 ≤ N ≤ 2), Hartmann number (0 ≤ Ha ≤ 50) with Prandtl number (Pr) = 0.054. Results show that the increase in Ra tends to maximize heat and mass transfer rate while increasing Ha, decreases the same. The rise in Le diminishes heat transfer marginally but increasing the mass transfer significantly. The effect of N differs with different operating conditions, in general, the rate of heat and mass transfer is found to decrease with a decrease of N value.Sat, 15 Aug 2020 19:30:00 +0100Manifold Learning Algorithms Applied to Structural Damage Classification
https://jacm.scu.ac.ir/article_15730_0.html
A comparative study of four manifold learning algorithms was carried out to perform the dimensionality reduction process within a proposed methodology for damage classification in structural health monitoring (SHM). Isomap, locally linear embedding (LLE), stochastic proximity embedding (SPE), and laplacian eigenmaps were used as manifold learning algorithms. The methodology included several stages that comprised: data normalization, dimensionality reduction, classification through K-Nearest Neighbors (KNN) machine learning model and finally holdout cross-validation with 25% of data for training and the remaining 75% of data for testing. Results evaluated in an experimental setup showed that the best classification accuracy was 100% when the methodology uses isomap algorithm with a hyperparameter k of 170 and 8 dimensions as a feature vector at the input to the KNN classification machine.Wed, 26 Aug 2020 19:30:00 +0100Stress Control of a Piezoelectric Lumped-element Model − Theoretical Investigation and ...
https://jacm.scu.ac.ir/article_15731_0.html
This contribution focuses on force- and stress-tracking of a multi-degree of freedom system by eigenstrain actuation. The example under consideration is an axially excited piezoelectric bar which can be modeled as a lumped parameter system. The piezoelectric effect serves as actuation source and the question is answered how to prescribe the piezoelectric actuation in order to achieve a desired stress distribution, or, in the lumped case, a desired distribution of internal forces. First, the equations of motion are set up in matrix notation where the state vector contains the displacement components. After some basic manipulations, the governing equation can be written in terms of the internal force vector. Now, if one intends to have a certain desired internal force distribution, it is straightforward to find a condition for the piezoelectric control actuation. The developed theory is first verified by using a continuous piezoelectric bar, where the motion of one end is prescribed. Then the theory is experimentally verified: a lumped two-degree of freedom system is investigated and the goal is to reduce the stress or the internal force in order to avoid mechanical damage. The force-controlled configuration is exposed to a sweep-signal excitation between 1000−4900 Hz, running for 22 minutes without any signs of damage. Then the same system is excited by the same excitation but without piezoelectric control. After some seconds the test sample is visibly damaged, going along with a significant reduction of the first eigenfrequency. This gives strong evidence for the appropriateness of the proposed stress or force control methodology.Wed, 26 Aug 2020 19:30:00 +0100Rotating Cylinder Turbulator Effect on The Heat Transfer of a Nanofluid Flow in a Wavy ...
https://jacm.scu.ac.ir/article_15732_0.html
Abstract. In this research study, the numerical Galerkin Finite Element Method (GFEM) is used for forced laminar convection heat transfer of Cu-water nanofluid in a divergent wavy channel including a rotating cylinder turbulator. The above boundary of the channel is in low temperatures and the bottom boundary is in hot temperatures as well as the cylinder wall temperature. It is assumed that the cylinder rotates in the cavity and makes vortexes to enhance heat transfers. The dimensionless governing equations including velocity, pressure, and temperature formulation are solved by the Galerkin finite element method. The results are discussed based on the governing factors such as nanoparticle volume fraction, Reynolds number, cylinder diameter and rotating velocity. As a main result, among the all studied parameters (Re, u, φ and r), increasing the Re number has the most effect on heat transfer which has 4.8 and 1.6 Average Nu for the cylinder wall and wavy wall, respectively.Sat, 29 Aug 2020 19:30:00 +0100Numerical study on heat transfer and pressure drop in a mini-channel with corrugated walls
https://jacm.scu.ac.ir/article_15733_0.html
This study presents the numerical results relative to the development of heat transfer and pressure drop inside a corrugated channel, under constant heat flux conditions applied to the walls; the working fluid is air. The test section is a channel with two plates having trapezoidal-shaped corrugations with V-folds. The corrugated plates were placed inside a 12.5 m high channel and tested for three different inclination angles, i.e. 20°, 40° and 60°. The model was simulated for a heat flux of 0.58 kW /m2, while the Reynolds numbers were considered within the interval ranging from 600 to 1400. The standard turbulent model (k-ε) was employed to simulate the flow and heat transfer developments within the channel. In addition, the governing equations were solved using the finite volume method in a structured uniform grid arrangement. Moreover, the effects of the geometric parameters on heat transfer and flow evolution were discussed as well. It is also worth noting that the corrugated surface had a significant impact on the enhancement of heat transfer and pressure drop due to breakage and destabilization occurring in the thermal boundary layer.Sun, 30 Aug 2020 19:30:00 +0100Approximate Solutions of Coupled Nonlinear Oscillations: Stability Analysis
https://jacm.scu.ac.ir/article_15752_0.html
The current article is concerned with a comprehensive investigation in achieving approximate solutions of coupled nonlinear oscillations with high nonlinearity. These equations are highly nonlinear second-order ordinary differential equations. Via a coupling of the Homotopy perturbation method and Laplace transforms, which is so-called the He-Laplace method, traditional approximate solutions involving the secular terms are accomplished. On the other hand, in order to cancel the secular terms, an expanded frequency technique is adapted to accomplish periodic approximate solutions. Therefore, a nonlinear frequency, for each differential equation, is achieved. Furthermore, for more convenience, these solutions are pictured to indicate their behavior. The multiple time-scales with the aid of the Homotopy concept are utilized to judge the stability criteria. The analyses reveal the resonance as well as the non-resonant cases. Additionally, numerical calculations are carried out, graphically, to address the regions that guaranteed the bounded solutions. It is found that the latter method, is the most powerful mathematical tool in extracting the stability analysis of the considered system.Fri, 04 Sep 2020 19:30:00 +0100TRANSIENT RESPONSE OF LONGITUDINAL FINS UNDER STEP CHANGES IN BASE TEMPERATURE AND HEAT FLUX ...
https://jacm.scu.ac.ir/article_15760_0.html
The present article reports the transient response of longitudinal fins having linear and non-linear temperature dependent thermal conductivity, convection coefficient and internal heat generation under two cases of base boundary condition, (i) step change in base temperature and (ii) step change in base heat flux. The fin tip is assumed to be adiabatic. Both, linear and non-linear, temperature dependency of thermo-physical properties is addressed in the mathematical formulation and the solution for the above cases is obtained using Lattice Boltzmann method (LBM) implemented in an in-house source code. LBM, being a dynamic method, simulates the macroscopic behavior by using a simple mesoscopic model and offers enormous advantages in terms of simple algorithm to handle even the most typical of boundary conditions that are easy and compact to program even in case of complicated geometries too. Although the transient response of longitudinal fins has been reported earlier, however power law variation of thermo physical properties for the above two base condition has not been reported till date. The present article first establishes the validity of LBM code with existing result and then extends the code for solving the transient response of the longitudinal fin under different sets of application-wise relevant conditions that have not been treated before. Results are reported for several combination of thermal parameter and are depicted in form of graphs.Sat, 05 Sep 2020 19:30:00 +0100A Fractal Rheological Model for SiC Paste using a Fractal Derivative
https://jacm.scu.ac.ir/article_15793_0.html
The rheological property plays an important role in a free-form extrusion 3D printing process, no rheological model was available in open literature that could effectively take into account effects of both the non-Newtonian viscosity and the concentration of nano/micro particles in a paste. Here a fractal law for non-Newtonian fluids is suggested using a fractal derivative, the law can predict correctly the boundary effect of a viscous flow, and can model effectively the nonlinear velocity distribution across the section. A systematic derivation of a fractal rheological model is suggested using the basic laws in the fluid mechanics, which can provide a deep insight into the two-scale fractal interpretation of non-Newtonian fluids. An experiment was carefully designed to verify the model and to elucidate the relationship between the shear rate and viscosity of the SiC paste. 15wt.%, 25wt.%, 35wt.% and 45wt.% SiC pastes were prepared by using mixing, stirring and ball milling processes. The rheology of the paste can be controlled primarily through the SiC concentration, which affects the fractal order. The fractal model sheds a bright light on a simple but accurate approach to non-Newtonian fluids.Tue, 08 Sep 2020 19:30:00 +0100Predictive Control with Dynamic Hysteresis Reference Trajectory: Application to a ...
https://jacm.scu.ac.ir/article_15794_0.html
Over the last decades, in the field of control engineering, Model Predictive Control (MPC) has been successfully ‎employed in many industrial processes. This due to, among other aspects, its capability to include constrains within ‎the design control formulation and also its ability to perform on-line optimization. For instance, in the civil ‎engineering field, different MPC approaches have been well developed to formulate active control algorithms able ‎to reduce civil structural responses to earthquakes. Thus, in this paper, a customized version of a conventional ‎Predictive Control (PC) strategy is proposed to mitigate the displacement on a base-isolated system with a ‎nonlinear hysteresis behavior, that is excited by a seismic event. The proposal consists of including a dynamic ‎hysteresis system into the control scheme to generate a reference trajectory that will softly drive the base-isolated ‎structure to a rest status. The proposed control scheme is evaluated through numerical experiments, and then its ‎performance is compared with respect to the conventional Predictive Control methodology. According to the ‎numerical experiments, the approach here presented results more efficient than the conventional method due to ‎the use of a suitable linear model of the structural system plus a new Driver Block with dynamic hysteresis within ‎the Predictive Control scheme‎.Tue, 08 Sep 2020 19:30:00 +0100Analysis of Dual Solutions of Unsteady Micropolar Hybrid Nanofluid Flow over a ...
https://jacm.scu.ac.ir/article_15795_0.html
An unsteady boundary layer flow of a micropolar hybrid nanofluid over a stretching/shrinking sheet is analyzed. The nonlinear ordinary differential equations of the problem have been solved using the efficient implicit Runge–Kutta–Butcher method along with Nachtsheim–Swigert iteration technique. For a certain set of parameters, numerical results expose dual solutions with the change of the velocity ratio parameter. The dual solutions are presented in a wide range of the physical parameters. Using a lot of numerical data, the critical values of the velocity ratio parameter, local friction factor, local couple-stress and local Nusselt number for the existence of dual solutions are expressed as a function of the physical parameters. These expressions might be useful for the development of new technology or for the future experimental investigation.Thu, 10 Sep 2020 19:30:00 +0100Thermoelastic Vibrations of Nonlocal Nanobeams Resting on a Pasternak Foundation via DPL Model
https://jacm.scu.ac.ir/article_15797_0.html
The present work introduces the thermoelastic vibrations of nonlocal nanobeams resting on a two-parameter foundation. The governing equations are formulated for linear Winkler–Pasternak foundation type based on the generalized dual-phase-lag heat conduction and nonlocal beams theories. The nanobeam is subjected to a temperature ramping function. The coupled equations of the problem are formulated and solved by Laplace transform technique. The effects of the nonlocal parameter and different foundation parameters on the field variables are illustrated graphically and discussed. The results obtained are consistent with previous analytical and numerical results.Fri, 11 Sep 2020 19:30:00 +0100Assessment of Drag Reduction Devices Mounted on a Simplified Tractor-Trailer Truck Model
https://jacm.scu.ac.ir/article_15815_0.html
Aerodynamic drag reduction of tractor-trailer combination trucks is critically important to improve their fuel consumption which consequently results in lower emissions. One practical method to reduce aerodynamic drag of a truck is by mounting drag reduction devices on the truck. This paper presents a numerical study of turbulent flow over a simplified tractor-trailer truck with different drag reduction devices mounted on the truck using the Reynolds Averaged Navier-Stokes (RANS) approach to assess the effectiveness of those devices in drag reduction around the tractor-trailer gap region. Three cases with different drag reduction devices have been studied and significant drag reduction (above 30%) has been achieved for all three cases. Detailed analysis of the flow field has been carried out to understand drag reduction mechanisms, and it shows that no matter what drag reduction devices are deployed the drag reduction is mainly due to the reduced pressure on the front face of the trailer, and a small proportion of the drag reduction is due to the reduced turbulent kinetic energy in the gap region.Sat, 12 Sep 2020 19:30:00 +0100Role of Magnetic field on the Dynamical Analysis of Second Grade Fluid: An Optimal Solution ...
https://jacm.scu.ac.ir/article_15829_0.html
The dynamical analysis of MHD second grade fluid based on their physical properties has stronger resistance capabilities, low-frequency responses, lower energy consumption, and higher sensitivities; due to these facts externally applied magnetic field always takes the forms of diamagnetic, ferromagnetic and paramagnetic. The mathematical modeling based on the fractional treatment of governing equation subject to the temperature distribution, concentration, and velocity field is developed within a porous surfaced plate. Fractional differential operators with and without non-locality have been employed on the developed governing partial differential equations. The mathematical analysis of developed fractionalized governing partial differential equations has been established by means of systematic and powerful techniques of Laplace transform with its inversion. The fractionalized analytical solutions have been traced out separately through Atangana-Baleanu and Caputo-Fabrizio fractional differential operators. Our results suggest that the velocity profile decrease by increasing the value of the Prandtl number. The existence of a Prandtl number may reflect the control of the thickness of momentum and enlargement of thermal conductivity.Sun, 13 Sep 2020 19:30:00 +0100The Integrated Analysis of Vibrations of Quartz Crystal Plates through Artificial Coupling ...
https://jacm.scu.ac.ir/article_15839_0.html
We introduce smaller artificial factors into the elastic constants matrix and manage to make Mindlin first-order plate theoryequations of motions coupled for a uniform and integrated analysis. The energy distributions of the five coupled modes are obtained and all the five vibration modes are identified through the energy calculation. This analytical approach based on artificial couplings of vibration modes suggests that all vibration modes of structural components can be analyzed through the same procedure and computer code if the right elastic constants are modified and the mode identification can be done with the energy method. This is a new technique to study multimode vibrations of structures in a broad frequency range with just one procedure and calculation tool for simplification.Mon, 14 Sep 2020 19:30:00 +0100Multiscale Numerical Modeling of Solute Transport with Two-Phase Flow in a Porous Cavity
https://jacm.scu.ac.ir/article_15842_0.html
This paper introduces dimensional and numerical investigation of the problem of solute transport within the two-phase flow in a porous cavity. The model consists of momentum equations (Darcy’s law), mass (saturation) equation, and solute transport equation. The cavity boundaries are constituted by mixed Dirichlet-Neumann boundary conditions. The governing equations have been converted into a dimensionless form such that a group of dimensionless physical numbers appear including Lewis, Reynolds, Bond, capillary, and Darcy numbers. A time-splitting multiscale scheme has been developed to treat the time derivative discretization. Also, we use the Courant-Friedrichs-Lewy (CFL) stability condition to adapt the time step size. The pressure is calculated implicitly by coupling Darcy’s law and the continuity equation, then, the concentration equation is solved implicitly. Numerical experiments have been conducted and the effects of the dimensionless numbers have been on the saturation, concentration, pressure, velocity, and Sherwood number have been investigated.Mon, 14 Sep 2020 19:30:00 +0100Comparative Study of Plane Poiseuille Flow of Non-isothermal Couple Stress Fluid of ...
https://jacm.scu.ac.ir/article_15878_0.html
In this paper, we have explored the steady Poiseuille flow of couple stress fluid between two parallel plates under ‎the influence of non-isothermal effects of Reynold viscosity model, using Optimal Homotopy Asymptotic Method ‎‎(OHAM) and New Iterative Method (NIM). We obtained expressions for velocity profile, temperature distribution, ‎average velocity, volume flux and shear stress. The solutions obtained using these methods are in the form of ‎infinite series; therefore, they can be easily computed. Comparative results of solutions obtained by both methods ‎are given using different tables and graphs.Fri, 18 Sep 2020 19:30:00 +0100Symmetry Reduction and Exact Solutions of a Class of Wave Equations
https://jacm.scu.ac.ir/article_15879_0.html
In this paper, the Lie symmetries and similarity reduction of a class of wave equations are investigated. First, Lie algorithm is used to get the determining equations of symmetry for the given equations which are complicated and difficult to be solved. Next, differential form of Wu’s method is used to solve this problem. Moreover, a special case of differential invariant method is used to get similarity reduction of the given equations.Fri, 18 Sep 2020 19:30:00 +0100Exp-function Method and Reduction Transformations for Rogue Wave Solutions of the ...
https://jacm.scu.ac.ir/article_15881_0.html
A pair of rogue wave solutions of the Davey-Stewartson (DS) equations are obtained by using the exp-function method and reduction transformations. Firstly, the Davey-Stewartson equations are transformed into two easy-to-solve equations, one of which is the deformed nonlinear Schrödinger (NLS) equation and the other is a polynomial equation. Secondly, based on the existing known solutions of the deformed NLS equation constructed by the exp-function method, rogue wave solutions of the DS equations are obtained. Finally, some spatial and spatiotemporal structures and dynamical evolutionary plots of the obtained rogue wave solutions are shown.Sat, 19 Sep 2020 19:30:00 +0100Forced Vibration Responses of Axially Functionally Graded Beams by using Ritz Method
https://jacm.scu.ac.ir/article_15883_0.html
This work presents forced vibration responses of a cantilever beam made of functionally graded material under a harmonic load. The material properties of beam vary along the axial direction. The kinematics of the beam are considered within Timoshenko beam theory. The governing equations of problem are derived by using the Lagrange procedure. In the solution of the problem the Ritz method is used and algebraic polynomials are used with the trivial functions for the Ritz method. In the solution of the forced vibration problem, the Newmark average acceleration method is used in the time history. In this study, free and forced vibration responses of the axially functionally graded beam are investigated in detail. In the numerical examples, the effects of material graduation, geometric and dynamic parameters on the free and forced vibration response of axially graded beam are investigated.Sun, 20 Sep 2020 20:30:00 +0100MHD Oldroyd-B Fluid with Slip Condition in view of Local and Nonlocal Kernels
https://jacm.scu.ac.ir/article_15884_0.html
We examine the velocity field of an incompressible Oldroyd-B fluid over a horizontal plate of continual length in a permeable medium with magnetohydrodynamics effect. Firstly, the results for the dimensionless classical model (governing equation) have been studied analytically then the study is extended for different fractional operators. The relations to determine the velocity fields of this problem are found by Laplace transformation and different numerical inversion algorithms. The impact of physical parameters on velocity profiles is analyzed graphically for integer and non-integer models. Non-integer operators are used to analyzing the impact of fractional parameters on the fluid curves of the fluid.Sun, 20 Sep 2020 20:30:00 +0100Design of Cooling Water System (CWS) for CRAFT Lower Hybrid Current Driven (LHCD) System
https://jacm.scu.ac.ir/article_15889_0.html
Lower hybrid current driven (LHCD) system, as the most efficient non-inductive current drive method in the tokamak, is an integral part of the Comprehensive Research Facility for Fusion Technology (CRAFT). The cooling water system (CWS) is necessary to be designed to remove the thermal power generated by the clients of the LHCD system so that system could operate safely. Therefore, a thermal hydraulic model is developed by AFT Fathom aimed at investigating thermal hydraulic behavior of the system under the normal operation. According to the calculation results, the CWS can provide required pressure, temperature and flow rate to address the client requirements of LHCD system. The study could provide a design reference for the construction of cooling water system for LHCD system and other CRAFT subsystems.Sun, 20 Sep 2020 20:30:00 +0100Nonlinear Winkler-based Frame Element with Inclusion of Shear-Flexure Interaction Effect for ...
https://jacm.scu.ac.ir/article_15890_0.html
Non-ductile reinforced concrete (RC) members are common in the existing RC frame buildings with the old seismic code (lightly and inadequately detailed transverse reinforcement) and may suffer shear failure or flexure-shear failure. To investigate the failure behaviors of those RC structures, performance-based numerical models are needed. Thus, a new fiber frame element on Winkler-based foundation including the interaction effects between shear and flexure was developed to analyze non-ductile RC frames resting on foundation, in this study. The proposed element is formulated for implementation in displacement-based finite element formulation under the kinematic assumptions of Timoshenko beam theory. As a result, axial and flexural mechanisms are automatically coupled through the fiber-section model, while shear and flexural actions interact via the UCSD shear-strength model within the framework of modified Mergos-Kappos interaction procedure to evaluate sectional shear force and shear stiffness within the shear constitutive law. Therefore, the presented model is simple, but able to capture several salient behaviors of non-ductile RC frames resting on foundation, including interaction between shear and flexure, soil-structure interaction, degradation of shear strength due to inelastic flexural deformation, and shear failure. Those features and efficiency of the proposed model are demonstrated by two numerical simulations in this work.Tue, 22 Sep 2020 20:30:00 +0100Forced Response of a Low-Pressure Turbine Blade using Spectral/hp Element Method: Direct ...
https://jacm.scu.ac.ir/article_15891_0.html
The Spectral/HP element method has been applied to perform Direct Numerical Simulations (DNS) over a single T106A turbine blade-row using the open source software Nektar++. The main goal of the current study is to perform preliminary investigations at modest Reynolds and Mach numbers, 8000 and 0.1 respectively, for uniform, steady flow past the aerofoil by employing Nektar++’s solver for the 2D Navier-Stokes equations for incompressible flow. The mesh was firstly validated against results obtained using the same software and for a similar set of parameter values. One dimensional, pitch-wise harmonic vibrations were subsequently imposed on the blade by means of a coordinate transformation. A parametric study in terms of the frequency and amplitude of the vibrations was carried out. The effects of the vibrations on entire domain, along the blade surface and in its wake were assessed. The pressure on the blade surface and the wake loss were each decomposed into components arising due to the mean flow and due to the vibrations. In each case the dominant components were then identified for the values of frequency and amplitude considered here.Tue, 22 Sep 2020 20:30:00 +0100Control of Actuators Torques for Optimal Movement along a Given Trajectory for the DexTAR Robot
https://jacm.scu.ac.ir/article_15892_0.html
The control problem of the dynamics of actuators is considered to obtain a given optimal movement of the end-effector for a parallel Dexterous Twin Arms Robot (DexTAR). The trajectory is assumed to be known in advance, and the law of motion along the trajectory is given from some optimality conditions. The equations of dynamics of the robot are written under the condition that the leading rods are driven by torques of a symmetrically arranged pair of engines. The solutions of the direct and inverse kinematic problems are presented as auxiliary material. The resulting nonlinear motion equations are derived. A numerical example shows that the equations can be simplified neglecting the change in the angle between the rods at the end-effector. Numerical examples of calculating the torques are given.Thu, 24 Sep 2020 20:30:00 +0100New Analytical Study for Nanofluid between Two Non-Parallel Plane Walls (Jeffery-Hamel Flow)
https://jacm.scu.ac.ir/article_15893_0.html
The aim of this paper is to analyze the problem of magneto hydrodynamic Jeffrey-Hamel flow (JHF) with nanoparticles. The governing equations for this problem are reduced to an ordinary differential equation and it is solved using new analytical method (NAM) and fourth-order Runge-Kutta Method (RK ∼ 4). The NAM is an iterative method that relies mainly on derivatives with Taylor expansion interference. In addition, the velocity profile has been computed and shown for various values of physical parameters. The objective of the present work is to investigate the effect of the angles between the plates, Reynold number, magnetic number and nanoparticles volume fraction on the velocity profile.Sat, 26 Sep 2020 20:30:00 +0100A Simple Approach for the Fractal Riccati Differential Equation
https://jacm.scu.ac.ir/article_15895_0.html
In this paper, a fractal modification of the Riccati differential equation is presented, and the two-scale transform method combined with Taylor series is used to solve the equation. Two examples are given to verify the correctness and effectiveness of the proposed method.Sat, 26 Sep 2020 20:30:00 +0100Fractal Variational Theory for Chaplygin-He Gas in a Microgravity Condition
https://jacm.scu.ac.ir/article_15896_0.html
On the microgravity condition, gravity affects the motion of objects and the flow of fluids, and the continuum assumption is not valid, therefore, a fractal Chaplygin-He gas model is developed by a new fractal derivative in microgravity space. A fractal variational principle is successfully established via the fractal semi-inverse method.Sat, 26 Sep 2020 20:30:00 +0100Heat and Mass Transfer of Natural Convective Flow with Slanted Magnetic Field via Fractional ...
https://jacm.scu.ac.ir/article_15904_0.html
This article explores the MHD natural convective viscous and incompressible fluid flow along with radiation and chemical reaction. The flow is confined to a moving tilted plate under slanted magnetic field with variable temperature in a porous medium. Non-dimensional parameter along Laplace transformation and inversion algorithm are used to investigate the solution of system of dimensionless governing equations. Fractional differential operators namely, Caputo (C), Caputo-Fabrizio (CF) and Atangana-Baleanu in Caputo sense (ABC) are used to compare graphical behavior of for velocity, temperature and concentration for emerging parameters. On comparison, it is observed that fractional order model is better in explaining the memory effect as compared to classical model. Velocity showing increasing behavior for fractional parameter a whereas there is a decline in temperature, and concentration profiles for a. Fluid velocity goes through a decay due to rise in the values of M, Sc and j. However, velocity shows a reverse profile for augmented inputs of Kp , Gr and S. Tabular comparison is made for velocity and Nusselt number and Sherwood number for fractional models.Sun, 27 Sep 2020 20:30:00 +0100An Efficient Spectral Method-based Algorithm for Solving a High-dimensional Chaotic Lorenz System
https://jacm.scu.ac.ir/article_15911_0.html
In this paper, we implement the multidomain spectral relaxation method to numerically study high dimensional chaos by considering the nine-dimensional Lorenz system. Chaotic systems are characterized by rapidly changing solutions, as well as sensitivity to small changes in initial data. Most of the existing numerical methods converge slowly for this kind of problems and this results in inaccurate approximations. Spectral methods are known for their high accuracy. However, they become less accurate for problems characterised by chaotic solutions, even with an increase in the number of grid points. As a result, in this work, we adopt the multidomain approach which assumes that the main interval can be decomposed into a finite number of subdomains and the solution obtained in each of the subdomains. This approach remarkably improves the results as well as the efficiency of the method.Thu, 01 Oct 2020 20:30:00 +0100Variational Principles for Two Compound Nonlinear Equations with Variable Coefficients
https://jacm.scu.ac.ir/article_15918_0.html
It is very important to seek explicit variational principles for nonlinear partial differential equations, which are theoretical bases for many methods to solve or analyze the nonlinear phenomena and problems. By designing the modified trial-Lagrange functional, different variational formulations are successfully and firstly established by the semi-inverse method for two kinds of compound nonlinear equation, i.e. the KdV-Burgers equation and the Burgers-BBM equation, respectively. Both of them contain the variable coefficients, which are time-dependent. Furthermore, the obtained variational principles are proved correct by minimizing the functionals with the calculus of variations.Sun, 04 Oct 2020 20:30:00 +0100Meshfree Collocation Method for the Numerical Solution of Higher Order KdV Equation
https://jacm.scu.ac.ir/article_15919_0.html
In this paper, an efficient meshfree collocation scheme based on meshfree radial basis function is implemented for the numerical solution of 7th-order Korteweg-de Vires (KdV) equations. The demand of meshless techniques increment because of its meshless nature and simplicity of usage in higher dimensions. The proposed numerical scheme is tested on several test problems. The efficiency and accuracy of the suggested scheme is analyzed via ||L||∞ and ||L||2 error norms.Mon, 05 Oct 2020 20:30:00 +0100Applications of Higher-Order Derivatives to the Subclasses of Meromorphic Starlike Functions
https://jacm.scu.ac.ir/article_15932_0.html
In this paper, we introduce and study some new classes of multivalent (p -valent) meromorphically starlike functions involving Higher-Order derivatives. For these multivalent classes of functions, we derive several interesting properties including sharp coefficient bounds, neighborhoods, partial sums and inclusion relationships. For validity of our results relevant connections with those in earlier works are also pointed out.Wed, 07 Oct 2020 20:30:00 +0100On the Dynamics of the Logistic Delay Differential Equation with Two Different Delays
https://jacm.scu.ac.ir/article_15933_0.html
Here, we study the logistic delay differential equation with two different delays. First of all, we disscuse the local stability and Hopf bifurcation conditons. The method of steps is used to get a discretized analogue of the original system. Local stability and bifurcation analysis of the discretized system is investigated. Finally, we carry out some numerical simulations such as bifurcation diagram, Lyapunov exponent and phase portraits to verify the theoretical results and to illustrate complex dynamics of the considered system. Thu, 08 Oct 2020 20:30:00 +0100An Experimental Comparison between Wing root and Wing tip Corrugation Patterns of Dragonfly ...
https://jacm.scu.ac.ir/article_15936_0.html
Abstract. This study presents the empirical comparison between the wing root and wingtip corrugation patterns of dragonfly wing in the newly-built wind-tunnel at the IAUN. The main objective of the research is to investigate the effect of wingtip and wing root corrugations on aerodynamic forces and the flow physics around the cross-sections at Re=10000 and the angle of attack of 0° to 30°. For this aim, two cross-sections are extracted from wing root (first cross-section) and wingtip (second cross-section). The first cross-section has corrugations with higher density than the second cross-section. The comparison of lift coefficients obtained from pressure distribution and force measurement indicates an acceptable agreement between the results. Also, Particle Image Velocity (PIV) technique is used to measure the velocity field. The results show that all corrugation patterns do not have positive effects on the aerodynamic forces. The second cross-section can generate considerable aerodynamic forces compared to the first cross-section. At α=25°, the lift coefficient generated by the second cross-section is 90% and 25% higher than that of the first cross-section and the flat plate, respectively. Based on results, corrugations in the wing root's vicinity have a crucial role in the solidity of insect wings; however, corrugations in the wing tip's vicinity play a vital role in generating adequate aerodynamic forces. The comparison conducted in the current research reveals the second cross-section is an appropriate replacement for the flat plate in MAVs due to generating more essential forces for flight.Sat, 10 Oct 2020 20:30:00 +0100A Case Study of Combined Application of Smart Materials in a Thermal Energy Harvester with ...
https://jacm.scu.ac.ir/article_15958_0.html
This paper demonstrates a case study of a combined application of smart materials in a thermal energy harvester with vibrating action. The conceptual design of the harvester is based on a Shape Memory Alloy wire attached to the free end of a piezoelectric flexible cantilever beam intended for generation of electrical energy utilizing a constant heat source. A mathematical model containing three differential equations describing the dynamics of the mechanical, electrical and thermal subsystems is developed. The Shape Memory Alloy hysteretic behaviour is considered in the mathematical model. An essential observation is the system oscillates at two frequencies lower one of which depends on the temperature time constant and the higher one is determined by the natural frequency of the mechanical subsystem. The comparison of the numerical solutions and the experimentally obtained graphs of the harvester output characteristics shows a good degree of coincidence.Sun, 25 Oct 2020 20:30:00 +0100Nonlinear dynamics and stability of a homogeneous model of tall buildings under resonant action
https://jacm.scu.ac.ir/article_15959_0.html
A homogeneous model of beam-like structure, roughly portraying the mechanical behavior of a tall building, is considered to address nonlinear dynamic response in case of external resonant excitation. A symmetric layout of the building is considered, so as to allow the existence of an in-plane response, whose features are evaluated by means of the Multiple Scale Method and accounting for internal resonance, necessarily occurring in the model. Furthermore, to take into account the three-dimensional nature of the problem, stability of the in-plane response to out-of-plane disturbances is addressed, solving the associated parametrically excited linear system.Sun, 25 Oct 2020 20:30:00 +0100Prognosis and Detection of Experimental Failures in Open Field Diesel Engines Applying ...
https://jacm.scu.ac.ir/article_15971_0.html
The high costs of open-field diesel engines arise from the lack of maintenance of these systems. Thus, the maintenance of this equipment has been treated as a great challenge, as some methods of data monitoring are not possible to be implemented, given the inadequate sensing conditions, plant location, local climate, facilities, even the methods and maintenance routines. In a second step, the labor is not qualified and of sufficient quantity to meet the demand, resulting in a slow and inefficient system. One of the challenges of predictive systems is to inform damage and failures in real time of the operating conditions of these machines and equipment. This work demonstrates the possibility of analyzing and detecting failures in open field predictive systems, using the concepts of vibration and acoustics in artificial intelligence. One of the results of this work demonstrates the robustness of the negative selection artificial immune system algorithm, whose application of the Wiener filter was of fundamental need. The other result demonstrates the versatility of conditioned use both or just one of the concepts between vibration and acoustics, in prognosis and fault detection. Considering the versatility of using these two techniques, it is possible to affirm that, the predictive systems of real time analysis have an effective solution directed to the area and, if implemented, it is of low cost and high efficiency.Mon, 26 Oct 2020 20:30:00 +0100Effects of Non-Linear Thermal Radiation and Chemical Reaction on Time Dependent Flow of ...
https://jacm.scu.ac.ir/article_15973_0.html
The current article will present the impact of the heat and mass transfer of combine electrical MHD flow of time dependent Williamson fluid with nanoparticles by the incorporating the influences of non-linear thermal radiation and the chemical reaction through wedge shape geometry. The fluid flows past a porous stretching wedge with convected Nield boundary conditions. The several (geometrical and physical) conditions have been included to provide more practicable results. The effects of activation energy further discussed. Due to relevant similarity transformation, set of partial differential equations which is non-linear and complicated is converted into simplest system of ordinary differential equations. To obtain the desired solution, famous numerical technique (shooting) used with the help of bvp4c MATLAB coding. The variation physical quantities namely velocity, temperature, concentration of nanoparticles, local Sherwood number, coefficient of skin friction and local Nusselt number have been observed under the influence of emerging parameters. The elaborated discussion presented with graphical and tabular illustrations.Tue, 27 Oct 2020 20:30:00 +0100Application of Complex Functional of Quality in Optimal Control of Spacecraft Motion
https://jacm.scu.ac.ir/article_15974_0.html
The problem of optimal control of the reorientation of a spacecraft as a solid body from an arbitrary initial ‎position into a prescribed final angular position is considered and solved. The case is ‎studied in detail when the ‎minimized index combines, in a given proportion, the integral of modulus of angular momentum and duration of ‎maneuver. It is proved that the accepted optimality ‎criterion guarantees the motion of a spacecraft with modulus of ‎angular momentum not exceeding the required value. Formalized equations and expressions for the synthesis of ‎the optimal rotation program are obtained using quaternion models. It is shown that the optimal solution corresponds to the strategy “acceleration - rotation with constant modulus of angular momentum-‎braking”, the ‎angular momentum and the controling moment are perpendicular during optimal rotation between acceleration and ‎braking. On the basis of necessary optimality conditions, the ‎main properties, laws, and key characteristics ‎‎(parameters, constants, integrals of motion) of the ‎optimal solution of the control problem, including the turn time ‎and the maximum angular momentum for the optimal motion, are determined. An estimation of the influence of the ‎bounded ‎controling moment on the character of the optimal motion and on the indicators of quality is ‎made. The ‎construction of an optimal control program of rotation is based on the quaternion variables and Pontryagin’s ‎maximum principle. The value of maximal angular momentum magnitude is calculated by condition of ‎transversality. The designed method is universal and invariant ‎relative to the moments of inertia. For dynamically ‎symmetric spacecraft, a complete solution of ‎the reorientation problem in closed form is presented. An example ‎and results of mathematical ‎modeling of the motion of a spacecraft under optimal control are presented, ‎demonstrating the ‎practical feasibility of the method for controlling spacecraft's spatial orientation.Tue, 27 Oct 2020 20:30:00 +0100Computational Study of Flow around 2D and 3D Tandem Bluff Bodies
https://jacm.scu.ac.ir/article_15976_0.html
Numerical simulations have been carried out to advance our current understanding of flow around two dimensional (2D) and three dimensional (3D) square shaped tandem bluff bodies at a Reynolds number of 22,000, especially to shed light on the sudden change of the downstream body’s drag coefficient. The Reynolds-Averaged Navier-Stokes (RANS) approach has been employed in the present study and the predicted drag coefficients compare reasonably well with available experimental data. Better understanding of flow fields has been achieved by analyzing streamlines, velocity vectors for both 2D and 3D cases in a horizontal plane and a vertical symmetric plane. The sudden jump in drag coefficient of the downstream body for the 2D case is well captured numerically, which is due to the flow over the upstream body impinging onto the front face of the downstream body at a critical gap size between those two bodies. For the 3D case the drag coefficient is predicted to increase gradually, consistent with the previous experimental finding. This is due to the fact that the vortical structures formed in the 3D case are very different, resulting in a reasonably smooth change of the flow field around the upstream body and hence leading to a gradual, not sudden, increase in the drag coefficient of the downstream body.Wed, 28 Oct 2020 20:30:00 +0100Random Walk Particle Tracking for Convection-diffusion Dominated Problems in Shallow Water Flows
https://jacm.scu.ac.ir/article_15977_0.html
This paper deals with a Lagrangian stochastic approach to solve the advection-diffusion equation of a scalar tracer inflow based on random walk particle tracking (RWPT) of a fine number of particles that describe the tracer. The water flow is governed by the shallow water equations that are solved using a finite volume upwinding scheme on a non-structured triangular mesh. Results are presented for two problems, pure advection in a square cavity and pollutant advection in the strait of Gibraltar, that demonstrate the performance, accuracy, and the flexibility of the RWPT method to examine the process of pollutant convection by comparing predictions with those from the Eulerian approach. The Lagrangian approach is shown to have advantages in terms of the high level of simplicity and stability relative to the Eulerian approach.Wed, 28 Oct 2020 20:30:00 +0100Modeling of Flight of the Line Thrower Projectile
https://jacm.scu.ac.ir/article_15978_0.html
The actual problem of increasing the flight range of line thrower projectile which is a container with a line (thin rope) inside. The line leaves the container during the flight, i.e. the projectile has a variable mass. Mathematical model of the projectile flight is constructed using the Lagrange equations of the second kind. The projectile is considered as a material particle, the line considered as an elastic thread with the tensile Cauchy strain. An approximation of the projectile flight trajectory is introduced in terms of three generalized coordinates. The dependence of the projectile’s flight distance on the projectile departure angle is constructed for several values of the tensile rigidity of the line.Thu, 29 Oct 2020 20:30:00 +0100Uniformly Convergent Numerical Method for Two-parametric Singularly Perturbed Parabolic ...
https://jacm.scu.ac.ir/article_15999_0.html
This paper deals with the numerical treatment of two-parametric singularly perturbed parabolic convection-diffusion problems. The scheme is developed through the Crank-Nicholson discretization method in the temporal dimension followed by fitting the B-spline collocation method in the spatial direction. The effect of the perturbation parameters on the solution profile of the problem is controlled by fitting a parameter. As a result, it has been observed that the method is a parameter-uniform convergent and its order of convergence is two. This is shown by the boundedness of the solution, its derivatives, and error estimation. The effectiveness of the proposed method is demonstrated by model numerical examples, and more accurate solutions are obtained as compared to previous findings available in the literature.Sat, 31 Oct 2020 20:30:00 +0100Performance of Two Types of High Speed, High Efficiency Axisymmetric Intakes
https://jacm.scu.ac.ir/article_16010_0.html
Performance of two axisymmetric air intakes are compared at conditions suitable for Mach number range from 2 to 8. First is the Busemann intake and second is the reversed isentropic nozzle. The isentropic nozzle is built by the method of characteristics. The contour of this nozzle is taken as a compression surface for the incoming flow. Performances of these two intakes are compared by comparison of both viscous and inviscid CFD calculations at Mach 6. Viscous flow calculations show that the total pressure recovery in compression section is 0.8316 in the Busemann intake and 0.869 in the reversed isentropic nozzle intake.Sun, 01 Nov 2020 20:30:00 +0100Conformable Double Sumudu Transform with Applications
https://jacm.scu.ac.ir/article_16014_0.html
Recently, a new deformation of the Sumudu transforms namely, conformable Sumudu transform has been introduced. In this article, we generalize the concept of one-dimensional conformable Sumudu transform into two-dimensional conformable Sumudu transform namely, conformable double Sumudu transform. Further, we present and prove some main properties and theorems related to the introduced transform. In order to illustrate the validity, efficiency, and applicability of the proposed transform, we apply the conformable double Sumudu transform to solve initial and boundary value problems of conformable fractional partial differential equations.Sun, 01 Nov 2020 20:30:00 +0100A Robust Three-Level Time-Split MacCormack Scheme for Solving Two-Dimensional Unsteady ...
https://jacm.scu.ac.ir/article_16029_0.html
A three-level time-split MacCormack method has been developed for solving the two-dimensional time-dependent convection-diffusion equation. The differential operator "splits" the two-dimensional problem into two pieces so that each subproblem is easy to solve using the original MacCormack procedure. The obtained scheme is temporal second-order convergent and spatial fourth-order accurate. This considerably reduces the computational cost of the algorithm. Under a suitable time-step restriction, both stability and convergence of the proposed technique are analyzed in the L∞(0, T; L2)-norm. A large set of numerical examples which provide the convergence rate of the new algorithm are presented. Overall, the considered approach is found to lie in the class of robust numerical schemes for solving general systems of partial differential equations.Mon, 02 Nov 2020 20:30:00 +0100Optimization of Spark Ignition Engine Performance Using a New Double Intake Manifold: ...
https://jacm.scu.ac.ir/article_16030_0.html
In this study, the effect of different intake manifold geometries on the performance of a spark-ignited engine is investigated both numerically and experimentally. 1D and 1D-3D simulations are carried out to find the optimal dimensions of different intake manifold designs. The numerical simulations are successfully validated with real data. The results show that the manifold design utilizing two-valve throttle has a better performance. The superior design is constructed and mounted on the engine to compare the output result with the base design. The operation tests are performed at various rotational speeds in the range of 1000-6000 rpm. Regarding the experimental tests, the superior double intake manifold increases the engine brake power and torque by 6.814%.Tue, 03 Nov 2020 20:30:00 +0100Constructal Design of an Idealize Arterial Bypass Graft: Effect of the Bypass Attachment ...
https://jacm.scu.ac.ir/article_16031_0.html
This paper aims to investigate, through the 3D numerical analysis of an idealized arterial bypass graft, the dependence of the resistance to flow on the bypass insertion point. The computational model assumes a laminar steady-state Newtonian fluid flow and three different Reynolds numbers: 150, 250, and 400. In this study, the constructal theory has been employed, a self-standing law in physics which covers the statement of minimum flow resistance to optimize morphing architectures, i.e. the coronary artery bypass grafting. According to the Constructal Design method, the constraints are stenosis degree, junction angle, and diameter ratio, while the attachment point is defined as a design parameter. The results demonstrate that the distance between the bypass attachment point and the stenosis influences the pressure drop; more specifically, the pressure drop decreases with the augmentation of the distance. In this regard, a different distribution of the mass flows between the bypass, and the artery is observed and seemed to be the main reason for that behavior. The application of the Constructal Design method in hemodynamics is a tool to describe the biological system to search for better flow performance since it is based on the natural evolution of living systems.Tue, 03 Nov 2020 20:30:00 +0100Measuring Crack-type Damage Features in Thin-walled Composite Beams using De-noising and a ...
https://jacm.scu.ac.ir/article_16032_0.html
A new method is described, allowing to locate and also measure the length and orientation of crack-type damage features in thin-walled composite beams (TWCB), a capability not previously reported. The method is based on a modal-analysis technique and is shown to work on a hollow composite beam, going beyond previous work limited to simple beams and plates. The method is shown to be capable to function down to signal-to-noise ratios (SNR) of about 15, corresponding to far noisier conditions than in most previous work. This capability is achieved by a combination of wavelet de-noising and the use of a 2D Continuous Wavelet Transform (CWT), applied to two modal analysis metrics, COMAC and Mode Shape Differences (MSD). The length and orientation of the crack can be determined accurately using a 2D curve fitting approach. Using either COMAC or MSD produces reliable results, but MSD is found to be somewhat more noise-tolerant. The new method is believed to be useful for the measurement of damage features in a variety of thin-walled composite beams such as aircraft wings and wind turbine blades, among others.Thu, 05 Nov 2020 20:30:00 +0100Influence of Thermophysical Features on MHD Squeezed Flow of Dissipative Casson fluid with ...
https://jacm.scu.ac.ir/article_16033_0.html
Theoretical investigation of variable mass diffusivity, thermal conductivity, and viscosity on unsteady squeezed flow of dissipative Casson fluid is presented. Physically, for any effective heat and mass transfer process, a proper account of thermophysical properties in such a system is required to attain the desired production output. The magnetized flow of free convective, and unsteady motion of Casson fluid encompassing Joule dissipation, radiation, and chemical reactive influence is induced as a result of squeezing property. The governing model assisting the magnetized flow is formulated and transformed via an appropriate similarity transformation. The resulting set of ordinary differential equations is solved numerically using Chebyshev based Collocation Approach (CCA). However, variable viscosity, thermal conductivity, and mass diffusivity effects are seen to diminish the fluid flow velocities, temperature, and concentration respectively along with the lower plate. Heat and mass transfer coefficient, skin friction downsized to an increasing value of variable thermal and mass diffusivity parameters while variable viscosity pronounces the skin friction coefficient. Furthermore, the present analysis is applicable in polymer processing, such as injection molding, extrusion, thermoforming among others.Thu, 05 Nov 2020 20:30:00 +0100Buckling Analysis of Functionally Graded Shells under Mixed Boundary Conditions Subjected ...
https://jacm.scu.ac.ir/article_16035_0.html
In this study, the buckling problem of shells consisting of functionally graded ‎materials (FGMs) under uniform compressive lateral pressure is solved at mixed ‎boundary conditions. After creating the FGM models, the basic differential equations ‎of FGM shells under compressive lateral pressure are derived within the scope of ‎classical shell theory (CST). The basic differential equations are solved with the help ‎of Galerkin method and the formula for the lateral buckling pressure is obtained. The ‎minimum values of the lateral buckling pressure are found numerically by minimizing ‎the obtained expression according to the numbers of transverse and longitudinal ‎waves. The accuracy is confirmed by comparing the numerical values for the lateral ‎buckling pressure of homogeneous and FGM shells with the results in the literature. ‎The influences of FGM profiles and shell characteristics on the magnitudes of lateral ‎buckling pressure are investigated in detail by performing specific numerical analyzes.Fri, 06 Nov 2020 20:30:00 +0100On the Active Vibration Control of Nonlinear Uncertain Structures
https://jacm.scu.ac.ir/article_16039_0.html
This study proposes an active nonlinear control strategy for effective vibration mitigation in nonlinear dynamical systems characterized by uncertainty. The proposed scheme relies on the coupling of a Bayesian nonlinear observer, namely the Unscented Kalman Filter (UKF) with a two-stage control process. The UKF is implemented for adaptive joint state and parameter estimation, with the estimated states and parameters passed onto the controller. The controller comprises a first task of feedback linearization, allowing for subsequent integration of any linear control strategy, such as addition of damping, LQR control, or other, which then operates on the linearized state equations. The proposed framework is validated on a Duffing oscillator characterized by light damping and an uncertain nonlinear parameter under harmonic and stochastic disturbance. The demonstrated performance suggests that the proposed Bayesian approach offers a competitive approach for active vibration suppression in nonlinear uncertain systems.Sun, 08 Nov 2020 20:30:00 +0100A Variational Principle for a Nonlinear Oscillator Arising in the Microelectromechanical System
https://jacm.scu.ac.ir/article_16041_0.html
A nonlinear oscillator arising in the microelectromechanical system is complex and it is difficult to obtain a variational principle. This paper begins with a wrong variational formulation and uses the semi-inverse method to obtain a genuine variational principle. Additionally, this paper gives simple formula for the fast frequency estimation of the nonlinear oscillator. Only simple calculation is needed to have a relatively high accuracy results when compared with the other methods.Mon, 09 Nov 2020 20:30:00 +0100Close Loop Design in Glucose Insulin Model with Effect of Physical Exercise
https://jacm.scu.ac.ir/article_16042_0.html
The minimal mathematical models for exercise and its extension is included the major exercise effects on plasma glucose and insulin levels. Model expectations for glucose and insulin dynamics are steady with current literature statistics. The extended model offers innovative disruption test stage for the enlargement of closed-loop glucose control algorithms. Stability analysis as well as qualitative analysis has been made for the model. We treat the controllability and observability of the system for glucose insulin regulatory system during feedback design. Numerical simulation has been carried out to check the effectiveness and actual behavior for the proposed system.Mon, 09 Nov 2020 20:30:00 +0100Scaling Law of Permeability and Porosity for Fluid Transport Phenomena in Porous PCM Media
https://jacm.scu.ac.ir/article_16043_0.html
The present paper reports the numerical results of fluid flow in porous phase change materials (PCM) media. This is an important topic in potential scientific, technological and engineering field’s especially latent heat storage. In this paper, we are only interested in the correlation between permeability and porosity of the porous media and not in latent storage. Fluid flow is characterized by many parameters mainly permeability and porosity. Many models have been proposed for the study of this phenomenon over the years. However, it can be modeled using the complex model that studies the characteristics of pore microstructure and fluid flow in porous media. This model is more accurate and realistic compared to previous models. It predicts permeability and porosity with a good agreement with experimental data. In this paper, the complex model is used to determine the impact of the tortuosity and the density of capillary distribution on the relation between permeability and porosity and check their scaling laws with universal exponents independently of other parameters. The results show that the permeability-porosity relation is proportional to the standard deviation of capillary distribution and its density. The tortuosity affects porosity proportionally, and permeability inversely. The relation between porosity and permeability follows a power law with universal exponents β = 4.06 ± 0.12 for different values of the expectation of distribution, the density of capillaries and the tortuosity; and β = 1.69 ± 0.01 for different values of the standard deviation, density of capillaries and tortuosity. The universality of these exponents further validates the complex model with various previous experimental and numerical studies.Mon, 09 Nov 2020 20:30:00 +0100On Stokes' second problem for Burgers' fluid over a plane wall
https://jacm.scu.ac.ir/article_16044_0.html
The Stokes' second problem for a Burgers' fluid over a plane wall is considered in this paper. The motion of the fluid is induced by the oscillation of the plane wall between two side walls perpendicular to the plane wall. The exact analytical solutions for the velocity field and the adequate shear stress are established in simple forms by means of integral transforms. The solutions that have been obtained, presented as a sum of the steady and the transient solutions, satisfy all imposed initial and boundary conditions. In the absence of the side walls they reduce to the similar solutions over an infinite plate. Finally, the results for the velocity, as well as a comparison between models, are displayed graphically for pertinent parameters to show interesting aspects of the solutions.Mon, 09 Nov 2020 20:30:00 +0100Heat Transport Exploration of Free Convection Flow inside Enclosure Having Vertical Wavy Walls
https://jacm.scu.ac.ir/article_16045_0.html
This paper expresses a numerical study of flow features and heat transport inside enclosure. Governing equations will be discretized by finite-element process with a collected variable arrangement. The assumptions of the Grashof number (103 - 106), aspect ratio (1.0 – 2.0), wave ratio (0.0 - 0.40) concerning a fluid with Pr = 0.71. Streamlines and isotherm lines are utilized to show the corresponding flow and thermal field inside a cavity. Global and local distributions Nusselt numbers are displayed for the before configuration. Finally, velocity and temperature profiles are displayed for some selected positions inside an enclosure for a better perception of the flow and thermal field.Mon, 09 Nov 2020 20:30:00 +0100Accelerating the Convergence of Multiphase Flow Simulations when Employing Non-Uniform ...
https://jacm.scu.ac.ir/article_16046_0.html
Non-uniform grids inevitably arise in multiphase flow simulation scenarios due to the need to resolve near-wall phenomena and/or large L/D ratios associated with the reactor configuration. This in conjunction with large density ratios of the constituent phases can retard the convergence of the pressure-correction equation that results from applying operator-splitting methods to the incompressible Navier-Stokes equations. Various pre-conditioning strategies to this ill-conditioned pressure-correction matrix are explored in this study for a class of bubbling bed simulations encompassing: different particle densities, bed-heights and dimensions (2D/3D). The right-side Block Jacobi preconditioning option resulted in a 20 - 35% decrease in CPU time that correlated well with a decrease in the number of iterations to reach a specified tolerance.Tue, 10 Nov 2020 20:30:00 +0100On the Usefulness of Pre-processing Methods in Rotating Machines Faults Classification using ...
https://jacm.scu.ac.ir/article_16049_0.html
This work presents a multi-fault classification system using artificial neural network (ANN) to distinguish between different faults in rotating machines automatically. Rotation frequency and statistical features, including mean, entropy, and kurtosis were considered in the proposed model. The effectiveness of this model lies in using Synthetic Minority Over-sampling Technique (SMOTE) to overcome the problem of imbalance data classes. Furthermore, the Relief feature selection method was used to find the most influencing features and thus improve the performance of the model. Machinery Fault Database (MAFAULDA) was deployed to evaluate the performance of the prediction models, achieving an accuracy of 97.1% which surpasses other literature that used the same database. Results indicate that handling imbalance classes hold a key role in increasing the overall accuracy and generalizability of multi-layer perceptron (MLP) classifier. Furthermore, results showed that considering only statistical features and rotational speed are good enough to get a model with high classification accuracy.Tue, 10 Nov 2020 20:30:00 +0100Turbulent forced convection and entropy generation of impinging jets of water-Al2O3 nanofluid ...
https://jacm.scu.ac.ir/article_16051_0.html
A computational analysis on water-Al2O3 nanofluid turbulent forced convection is performed to analyze heat transfer and entropy production in a channel containing heated blocks, cooled by impinging jets. The two phase mixture model (TPMM) is used. The increase in the Reynolds number (Re) and the volume fraction of nanoparticles (φ), the decrease in spacing between the heated block (Db) and moving the location of the second jet (J2) to the first jet (J1) contribute to increasing the heat transfer rate (HTR).In addition, the TPMM gives higher values of average Nusselt number (Nu) ̅ than the single-phase model (SPM). The thermal (𝑆𝑔̇ ,𝑡ℎ), frictional (𝑆𝑔̇ ,𝜈) and total (𝑆𝑔̇ ,𝑡) entropy generation values increase with Re and φ. When Db is reduced, 𝑆𝑔̇,𝑡 increases. However, 𝑆𝑔̇ ,𝑡 increases when the jet position vary from J2 to J1. Different correlations are proposed for Nu ̅. Our results are compared with data available in the literature.Tue, 10 Nov 2020 20:30:00 +0100In-Plane Shear-Axial Strain Coupling Formulation for Shear-Deformable Composite Thin-Walled Beams
https://jacm.scu.ac.ir/article_16052_0.html
This paper presents an improved description of the in-plane strain coupling in Librescu-type shear-deformable composite thin-walled beams (CTWB). Based on existing descriptions for Euler-type CTWB, an analogous formulation for shear-deformable CTWB is here developed by building, via the Mindlin–Reissner theory and an orthotropic constitutive law of the shell wall, an alternate equation for the in-plane shear force which effectively couples the axial and shear in-plane strains. It is observed that this strain coupling formulation includes some of the transversal (out-of-plane) shear strain terms, thus also functioning as a path for transferring transversal shear energy to the in-plane strain field and therefore improving shear-deformability. The performance of the new CTWB model is compared against that of previously available CWTB (i.e. Euler-type with strain coupling and Timoshenko-type without strain coupling) for several aspect ratios, fibre-orientations and laminate types. Error measures are calculated by comparing several relevant stiffness coefficients and displacement shapes to reference results provided by corresponding 3D shell-based ANSYS finite-element models. Results indicate that for cases involving significant shear energy (i.e. short aspect ratios) and/or in-plane shear-axial strain coupling (i.e. off-axis or asymmetric/unbalanced laminates), the new CTWB model proposed in this work can attain an accuracy level comparable to that associated to more sophisticated models, two to three orders of magnitude larger, at a fraction of the computational cost.Thu, 12 Nov 2020 20:30:00 +0100Free Vibration Analysis of FG Porous Sandwich Plates under Various Boundary Conditions
https://jacm.scu.ac.ir/article_16055_0.html
In the present work, free vibration analysis of the square sandwich plate with functionally graded (FG) porous face sheets and isotropic homogenous core is performed under various boundary conditions. For this purpose, the material properties of the sandwich plate are supposed to vary continuously through the thickness direction according to the volume fraction of constituents defined with the modified rule of the mixture including porosity volume fraction with four different types of porosity distribution over the cross-section. Furthermore, a hyperbolic shear displacement theory is used in the kinematic relation of the FG porous sandwich plate, and the equations of motion are derived utilizing Hamilton’s principle. Analytical solutions are achieved for free vibration analysis of square sandwich plates with FG porous face sheets under various boundary conditions, i.e. combinations of clamped (C), simply supported (SS), and free (F) edges are presented. Several parametrical studies are conducted to examine the effects of porosity volume fraction, type of porosity distribution model, lay-up scheme, side to thickness ratio, and boundary conditions on the free vibration of the FG sandwich plates. Finally, it is concluded that the investigated parameters have significant effects on the free vibration of the FG sandwich plates and the negative effects of porosity may be reduced by adopting suitable values for said parameters, considerably.Sat, 14 Nov 2020 20:30:00 +0100Flexural-Torsional Galloping of Prismatic Structures with Double-Symmetric Cross-Section
https://jacm.scu.ac.ir/article_16056_0.html
The linear galloping of prismatic structures having double-symmetric cross-section, subjected to steady wind flow acting along a symmetry axis, is investigated. The continuous system is reduced to a three degree-of-freedom system via a Galerkin approach. The quasi-steady assumption for the aerodynamic forces is applied, under the hypothesis that the galloping instability is well-separated from the vortex induced vibration phenomenon. Due to the structural symmetry conditions and accounting for the aerodynamic coupling, galloping is of flexural-torsional type, occurring in the direction orthogonal to the incident wind. Moreover, coupling is stronger close to the resonance between the flexural and torsional degrees of freedom. A linear stability diagram is built up in a two-parameter space, highlighting the role of coupling in modifying the critical wind velocity, and in producing a veering phenomenon between the two modes. The existence of points at which a double-Hopf bifurcation manifests itself is detected. Both exact and perturbation solutions are provided, these latter in the non-resonant and resonant cases, useful to throw light on the interactive mechanisms. The resonant perturbation solution permits to analytically investigate under which conditions coupling has a detrimental effect on galloping, which manifests at a wind velocity lower than the flexural and torsional critical velocities. Situations where coupling between modes leads to beneficial effect with respect to the Den Hartog's critical wind velocity are also highlighted. As an application, galloping of a family of multi-story tower buildings having a square cross-section is studied.Sun, 15 Nov 2020 20:30:00 +0100Heat Transfer Improvement in an Open Cubic Cavity using a Hybrid Nanofluid
https://jacm.scu.ac.ir/article_16057_0.html
Numerical simulation of convection heat transfer and entropy generation in an open cubic cavity filled with a hybrid nanofluid is carried out. This configuration is heated uniformly by a constant volumetric heat source qv. All the walls are adiabatic. The hybrid nanofluid flow (Al2O3-Cu/water) penetrates in the cavity at a uniform velocity U0 and a temperature T0. To solve the mathematical equations, we used Ansys-Fluent 14.5 software. Results are validated with other works found in the literature. We present our results in terms of streamlines, isotherms, velocity, temperature, local and average Nusselt numbers profiles, and entropy generation for the Reynolds number (300Sun, 15 Nov 2020 20:30:00 +0100Numerical Analysis of the Deformation of a Shearing Machine Tool under Excessive Blade Clearance
https://jacm.scu.ac.ir/article_16072_0.html
Guillotine shearing machines for metal sheet may be inadvertently operated at increased blade clearance. Typical cases were studied using commercially available finite element software with an explicit solver. Loads causing elastic deformation to the machine structure arise from plastic deformation of the sheet metal being processed, its behavior being modelled by modified Johnson-Cook law. Excessive clearance was found to overload the machine considerably compared to normal clearance, owing to considerable lateral forces. As a result, the guillotine and much less so the base of the machine, undergo oscillatory deformation and the sheet is partly sheared and mostly bent. Such analysis helps the designer understand structural issues of the machine tool in extreme situations and modify the design appropriately.Mon, 16 Nov 2020 20:30:00 +0100Combined Impacts of Fin Surface Inclination and Magnetohydrodynamics on the Thermal Performance ...
https://jacm.scu.ac.ir/article_16073_0.html
In this work, the combined impacts of magnetohydrodynamics and fin surface inclination on thermal performance of convective-radiative porous fin with temperature-invariant thermal conductivity is numerically study using finite difference method. Parametric studies reveal that as the inclination of fin, convective, radiative, magnetic and porous parameters increase, the adimensional fin temperature decreases which leads to an increase in the heat transfer rate through the fin and the thermal efficiency of the porous fin. It is established that the porous fin is more efficient and effective for low values of convective, inclination angle, radiative, magnetic and porous parameters. The thermal performance ratio of the fin increases with the porosity parameter.Wed, 18 Nov 2020 20:30:00 +0100Conjugate Mixed Convection in a Horizontal Cylindrical Duct under the Solid Shell Internal Heat ...
https://jacm.scu.ac.ir/article_16103_0.html
This paper deals with three-dimensional, mixed convection in a cylindrical duct horizontally. This latter is partially subjected to a uniform volumetric heat generation at the solid-liquid interface. The working fluid (water) with a parabolic velocity profile and a constant temperature T0 enters the tube. The study was carried out for different Richardson numbers values Ri=0.1-8 at Reynolds number Re=600. Results were conducted so that to show the influence of Richardson number Ri on the dynamic and thermal fields and local Nusselt number Nu(q,z) and peripherally averaged axial Nusselt number Nu(z). Also, analyses of the results showed that the hydrodynamic effects are manifested by the existence of secondary flow, inducing temperature gradient at a cross-section between the top and bottom of the duct. The reversed flow is observed for a low Reynolds number Re=10. A significant increase in heat exchange is observed in mixed convection compared to pure forced convection flow. Correlations for the variation of average Nusselt number Nu (Ri,z) at the entrance region with Ri and z=z¢/Di and local Nusselt Nu(Ri) number in the hydrodynamics establishment zone are proposed and compared with the present numerical results.Tue, 24 Nov 2020 20:30:00 +0100