Journal of Applied and Computational Mechanics
https://jacm.scu.ac.ir/
Journal of Applied and Computational Mechanicsendaily1Thu, 01 Apr 2021 00:00:00 +0430Thu, 01 Apr 2021 00:00:00 +0430Approximate Solutions of Coupled Nonlinear Oscillations: Stability Analysis
https://jacm.scu.ac.ir/article_15752.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.Non-similar Solutions of MHD Mixed Convection over an Exponentially Stretching Surface: Influence of Non-uniform Heat Source or Sink
https://jacm.scu.ac.ir/article_14133.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.Multiscale Numerical Modeling of Solute Transport with Two-Phase Flow in a Porous Cavity
https://jacm.scu.ac.ir/article_15842.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&rsquo;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&rsquo;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.Numerical Simulation of Unsteady Flow toward a Stretching/Shrinking Sheet in Porous Medium Filled with a Hybrid Nanofluid
https://jacm.scu.ac.ir/article_14641.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.Comparative Study of Plane Poiseuille Flow of Non-isothermal Couple Stress Fluid of Reynold Viscosity Model using Optimal Homotopy Asymptotic Method and New Iterative Method
https://jacm.scu.ac.ir/article_15878.html
In this paper, we have explored the steady Poiseuille flow of couple stress fluid between two parallel plates under &lrm;the influence of non-isothermal effects of Reynold viscosity model, using Optimal Homotopy Asymptotic Method &lrm;&lrm;(OHAM) and New Iterative Method (NIM). We obtained expressions for velocity profile, temperature distribution, &lrm;average velocity, volume flux and shear stress. The solutions obtained using these methods are in the form of &lrm;infinite series; therefore, they can be easily computed. Comparative results of solutions obtained by both methods &lrm;are given using different tables and graphs.MHD Casson Nanofluid Past a Stretching Sheet with the Effects of Viscous Dissipation, Chemical Reaction and Heat Source/Sink
https://jacm.scu.ac.ir/article_14804.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.Variational Principles for Two Compound Nonlinear Equations with Variable Coefficients
https://jacm.scu.ac.ir/article_15918.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.Heat Transfer of Hybrid-nanofluids Flow Past a Permeable Flat Surface with Different Volume Fractions
https://jacm.scu.ac.ir/article_14842.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.Meshfree Collocation Method for the Numerical Solution of Higher Order KdV Equation
https://jacm.scu.ac.ir/article_15919.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||&infin;&nbsp;and ||L||2 error norms.Topology Optimization of Laminated Composite Plates and Shells using Optimality Criteria
https://jacm.scu.ac.ir/article_14895.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.The Method of Lines Analysis of Heat Transfer of Ostwald-de Waele Fluid Generated by a Non-uniform Rotating Disk with a Variable Thickness
https://jacm.scu.ac.ir/article_15263.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 K&aacute;rm&aacute;n&rsquo;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 &nbsp;increases, while local tangential skin friction coefficient decreases, the local Nusselt number decrease, both the thickness of the velocity and temperature boundary layer increase.&nbsp;Thermal Buckling Analysis of Circular Bilayer Graphene Sheets Resting on an Elastic Matrix Based on Nonlocal Continuum Mechanics
https://jacm.scu.ac.ir/article_14896.html
In this article, the thermal buckling behavior of orthotropic circular bilayer graphene sheets embedded in the Winkler&ndash;Pasternak elastic medium is scrutinized. Using the nonlocal elasticity theory, the bilayer graphene sheets are modeled as a nonlocal double&ndash;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&ndash;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.On the Dynamics of the Logistic Delay Differential Equation with Two Different Delays
https://jacm.scu.ac.ir/article_15933.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.&nbsp;Evaluating the Delamination in the Drilling Process of a Melamine Coated Medium Density Fiberboard (MDF)
https://jacm.scu.ac.ir/article_14900.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.In-Plane Shear-Axial Strain Coupling Formulation for Shear-Deformable Composite Thin-Walled Beams
https://jacm.scu.ac.ir/article_16052.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&ndash;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.Effects of Inclined Magnetic Field and Porous Medium on Peristaltic Flow of a Bingham Fluid with Heat Transfer
https://jacm.scu.ac.ir/article_15007.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.Design of Cooling Water System (CWS) for CRAFT Lower Hybrid Current Driven (LHCD) System
https://jacm.scu.ac.ir/article_15889.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.Numerical Analysis of an Edge Crack Isotropic Plate with Void/Inclusions under Different Loading by Implementing XFEM
https://jacm.scu.ac.ir/article_15010.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.Close Loop Design in Glucose Insulin Model with Effect of Physical Exercise
https://jacm.scu.ac.ir/article_16042.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.Numerical Solution of the Time Fractional Reaction-advection-diffusion Equation in Porous Media
https://jacm.scu.ac.ir/article_15019.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&rsquo;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&rsquo; 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.Random Walk Particle Tracking for Convection-diffusion Dominated Problems in Shallow Water Flows
https://jacm.scu.ac.ir/article_15977.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.Optimum Design of Nano-Scaled Beam Using the Social Spider Optimization (SSO) Algorithm
https://jacm.scu.ac.ir/article_15044.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.Numerical Analysis of the Deformation of a Shearing Machine Tool under Excessive Blade Clearance
https://jacm.scu.ac.ir/article_16072.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.Distributed-parameter Dynamic Modeling and Bifurcation Analysis of a Trapezoidal Piezomagnetoelastic Energy Harvester
https://jacm.scu.ac.ir/article_15085.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.Free Vibration Analysis of FG Porous Sandwich Plates under Various Boundary Conditions
https://jacm.scu.ac.ir/article_16055.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&rsquo;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.Nonlinear Convective Flow of Maxwell Fluid over a Slendering Stretching Sheet with Heat Source/Sink
https://jacm.scu.ac.ir/article_15143.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.Heat Transport Exploration of Free Convection Flow inside Enclosure Having Vertical Wavy Walls
https://jacm.scu.ac.ir/article_16045.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 &ndash; 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.Investigation of Rousselier Model and Gurson-Tvergaard-Needleman Model in Ductile Fracture of API X65 Gas Pipeline Steel
https://jacm.scu.ac.ir/article_15239.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.Computational Study of Flow around 2D and 3D Tandem Bluff Bodies
https://jacm.scu.ac.ir/article_15976.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&rsquo;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.Polymeric Dissipative Convection Flow from an Inclined Plane with Chemical Reaction: Numerical Study
https://jacm.scu.ac.ir/article_15241.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&rsquo;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&nbsp;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.Uniformly Convergent Numerical Method for Two-parametric Singularly Perturbed Parabolic Convection-diffusion Problems
https://jacm.scu.ac.ir/article_15999.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.Reduction in Space for Dynamic Finite Element Analysis of Assemblies of Beam-columns when the Mass is Available in Digitized Format
https://jacm.scu.ac.ir/article_15244.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.Effects of Non-Linear Thermal Radiation and Chemical Reaction on Time Dependent Flow of Williamson Nanofluid With Combine Electrical MHD and Activation Energy
https://jacm.scu.ac.ir/article_15973.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.A Hybrid SVM-RVM Algorithm to Mechanical Properties in the Friction Stir Welding Process
https://jacm.scu.ac.ir/article_15253.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.A Robust Three-Level Time-Split MacCormack Scheme for Solving Two-Dimensional Unsteady Convection-Diffusion Equation
https://jacm.scu.ac.ir/article_16029.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&infin;(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.Numerical Simulations of Unsteady 3D MHD Micropolar Fluid Flow over a Slendering Sheet
https://jacm.scu.ac.ir/article_15260.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.Conformable Double Sumudu Transform with Applications
https://jacm.scu.ac.ir/article_16014.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.Heating Capacity of an Earth to Air Heat Exchanger in Arid Regions - Experimental Investigation
https://jacm.scu.ac.ir/article_15262.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&deg;C at a depth of 1.5 meters. The EAHE made of 66 meters of PVC tube is demonstrated a heating capacity of 13&deg;C and a cooling capacity of 7&deg;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.Conjugate Mixed Convection in a Horizontal Cylindrical Duct under the Solid Shell Internal Heat Generation
https://jacm.scu.ac.ir/article_16103.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&cent;/Di and local Nusselt Nu(Ri) number in the hydrodynamics establishment zone are proposed and compared with the present numerical results.Size-dependent Nonlinear Forced Vibration Analysis of Viscoelastic/Piezoelectric Nano-beam
https://jacm.scu.ac.ir/article_15269.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&rsquo;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.Axisymmetric Problem of the Elasticity Theory for the Radially Inhomogeneous Cylinder with a Fixed Lateral Surface
https://jacm.scu.ac.ir/article_15541.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 on 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.Magnetohydrodynamic Bio-convective Casson Nanofluid Flow: A Numerical Simulation by Paired Quasilinearisation
https://jacm.scu.ac.ir/article_15273.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.Experimental and Numerical Investigation of Heat and Mass Transfer Processes for Determining the Optimal Design of an Accumulator with Phase Transformations
https://jacm.scu.ac.ir/article_16118.html
Applying the methods of mathematical and experimental modeling, the processes of heat and mass transfer in heat accumulator with phase transformations, where heat sources are made in the form of tube bundles staggered have been studied. The analysis of these processes is carried out and the main phases of heat accumulation and extraction at heat accumulator &ldquo;charging&rdquo; and &ldquo;discharging&rdquo; have been determined. The geometry of the location of heat sources (runoffs) is found, at which the rate of heat accumulation (extraction) from the unit of PCM is the maximum. As a result of the conducted investigations a new improved design of heat accumulator, which can be used when developing heat accumulators of a similar type has been suggested.Investigation of Jeffery-Hamel Flow for Nanofluid in the Presence of Magnetic Field by a New Approach in the Optimal Homotopy Analysis Method
https://jacm.scu.ac.ir/article_15275.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.Analytical Simulation for Transient Natural Convection in a Horizontal Cylindrical Concentric Annulus
https://jacm.scu.ac.ir/article_16119.html
In this study, a new scheme is suggested to find the analytical approximating solutions for a two-dimensional transient natural convection in a horizontal cylindrical concentric annulus bounded by two isothermal surfaces. The new methodology depends on combining the algorithms of Yang transform and the homotopy perturbation methods. Analytical solutions for the core, the outer layer and the inner layer at small times are found by a new method. Also, the effect of Grashof number, Prandtl number and radius proportion on the heat transfer and the flow of fluid (air) at different values was studied. Moreover, the study calculates the mean of the Nusselt number along with the effect of the Grashof number and radius proportion on it as parameters which acts as clues for heat transfer calculations of the natural convection for the annulus. The results, obtained by using the new method, prove that it is efficient and has high exactness compared to the other methods, used to find the analytical approximate solution for the transient natural convection in a horizontal cylindrical concentric annulus. The convergence of the new method was also discussed theoretically by referring to some theorems, and experientially by a verification of the solutions resulting from the simulations of the convergent condition. Furthermore, the graphs of the new solutions show the veracity, utility and exigency of the new method, and come in line with solutions offered by previous studies.Design, Analysis and Manufacturing of a Bone Cutting Ultrasonic Horn-Tool and Verification with Experimental Tests
https://jacm.scu.ac.ir/article_15307.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.Non-linear Radiation and Navier-slip effects on UCM Nanofluid Flow past a Stretching Sheet under Lorentzian Force
https://jacm.scu.ac.ir/article_16132.html
In the present article, the novel contributions are modelling of Upper convected Maxwell nanoflow under Lorentzian influence over a stretching surface and investigating it using bvp4c procedure with MATLAB software. The boundary is set fixed with axial slip. Non-linear energy distribution is incorporated. Similarity variables are utilized to transmute non-linear PDEs of the basic fluid model to coupled system of ODEs. Computed numerical results are better compared with the past literature work to evidence its efficacy. The nanoflow momentum, energy, species diffusion are visualized graphically and analyzing the performance of proficient physical quantities on shear stress, energy dispersion coefficient, mass diffusion coefficient scatter of the system are seen through tables. Presence of magnetic field reduces friction at the wall and acts as a cooling agent.Navier slip increases the friction factor near the wall. Non-linear radiation transfers more heat from the system. Energy transfer coefficient is high in linear thermal rather than non-linear thermal distribution.Numerical Solution of Time Fractional Cable Equation via the Sinc-Bernoulli Collocation Method
https://jacm.scu.ac.ir/article_15318.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.Robust P-H∞ Integrated Controller for Flexible Link Manipulator System in the Presence of Disturbance
https://jacm.scu.ac.ir/article_16137.html
Flexible link manipulators have recently high attention in research due to the numerous advantages over traditional manipulators. However, flexible link manipulators still have critical problem of less position accuracy due to the tip vibration. Thus, this research contributes by developing a robust P-H&infin; integrated controller for a flexible link manipulator (FLM). The P-H&infin; integrated controller is a combination of Proportional (p ) controller and H&infin; controller which helps of possession several advantages such as optimal position tracking, effective vibration repression, and robust to reject disturbances. The proposed P-H&infin; integrated controller has been simulated to control the FLM system using MATLAB/Simulink toolbox. The results have demonstrated satisfactory performance of the proposed P-H&infin; integrated controller in terms of position tracking, vibration repression, and disturbance rejection.Structural Strength Analysis and Fabrication of a Straight Blade of an H-Darrieus Wind Turbine
https://jacm.scu.ac.ir/article_15352.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.A General Multibody Approach for the Linear and Nonlinear Stability Analysis of Bicycle Systems. Part I: Methods of Constrained Dynamics
https://jacm.scu.ac.ir/article_16125.html
This investigation is the first contribution of a two-part research work concerning the theoretical development of a multibody approach to analyze the constrained dynamics of articulated mechanical systems. In this paper, a method for investigating the linear and nonlinear stability of the dynamic behavior of mechanical systems modeled as multibody systems subjected to holonomic and nonholonomic constraints is presented. To this end, the nonlinear equations of motions that assume a complex index-three differential-algebraic form are systematically formulated and directly linearized by using an automatic procedure based on a hybrid symbolic-numeric approach devised in this work. The proposed stability analysis method, therefore, is based on the formulation of a generalized eigenvalue problem and represents a viable computer-aided approach suitable for analyzing multibody mechanical systems having different degrees of complexity. Furthermore, an extension of the generalized coordinate partitioning algorithm is introduced in this paper for handling nonholonomic multibody systems leading to a robust and general multibody computational procedure referred to as the Robust Generalized Coordinate Partitioning Algorithm (RGCPA). Since the methodologies employed in this paper to study the stability of multibody mechanical systems are general and versatile, they can be easily implemented in general-purpose multibody computer programs and readily used to analyze several mechanical applications having engineering interest.Investigation on the Crack Effect in the Cylinder and Matrix on the Backscattering Field Frequency Specifications using the Finite Element Method
https://jacm.scu.ac.ir/article_15354.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&rsquo;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&rsquo;s information and the analytical and experimental form functions in addition to the comparison of the aluminum cylinder form function and reference form function.A General Multibody Approach for the Linear and Nonlinear Stability Analysis of Bicycle Systems. Part II: Application to the Whipple-Carvallo Bicycle Model
https://jacm.scu.ac.ir/article_16126.html
This paper represents the second contribution of a two-part research work presenting the application of the proposed multibody analysis approach to bicycle systems and the relative numerical results found. In this work, a nonlinear multibody model of a bicycle system is developed and implemented to perform a parametric analysis to understand the influence of the variation of the principal model parameters on the system stability under investigation. To demonstrate the effectiveness of the proposed approach, the case study considered in this paper is the dynamic analysis of the Whipple-Carvallo bicycle model. Considering the combined use of a robust numerical technique for nonlinear dynamical simulations with a specifically devised linearization procedure, the effects of the different geometric parameters and inertial properties on the bicycle stability are investigated. The numerical results obtained in this work using the proposed multibody techniques are useful to gain insight information about the dynamic behavior of the bicycle system in a straight motion. The proposed multibody methodology also demonstrated a high potential for analyzing complex multibody mechanical systems in virtue of the generality of the analytical and computational approaches adopted.Mathematical Analysis of Poiseuille Flow of Casson Fluid past Porous Medium
https://jacm.scu.ac.ir/article_15394.html
In this article, the influence of microstructure in the Casson fluid flow through a porous medium is investigated, by extending the Buckingham-Reiner&rsquo;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&rsquo;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&rsquo;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.A Novel Fractional-Order System: Chaos, Hyperchaos and Applications to Linear Control
https://jacm.scu.ac.ir/article_16138.html
Chaos and hyperchaos are generated from a new fractional-order system. Local stability of the system&rsquo;s three equilibria is analyzed when the fractional parameter belongs to (0,2]. According to Hopf bifurcation theory in fractional-order systems, approximations to the periodic solutions around the system&rsquo;s three equilibria are explored. Lyapunov exponents, Lyapunov spectrum and bifurcation diagrams are computed and chaotic (hyperchaotic) attractors are depicted. Furthermore, a linear control technique (LFGC) based on Lyapunov stability theory is implemented to derive the hyperchaotic states of the proposed system to its three equilibrium points. Numerical results are used to validate the theoretical results.Comparative Study of Mixed Convective MHD Cu-Water Nanofluid Flow over a Cone and Wedge using Modified Buongiorno’s Model in Presence of Thermal Radiation and Chemical Reaction via Cattaneo-Christov Double Diffusion Model
https://jacm.scu.ac.ir/article_15395.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.An analytical Technique for Solving New Computational Solutions of the Modified Zakharov-Kuznetsov Equation Arising in Electrical Engineering
https://jacm.scu.ac.ir/article_16153.html
The modified (G'/G)-expansion method is an efficient method that has appeared in recent times for solving new computational solutions of nonlinear partial differential equations (NPDEs) arising in electrical engineering. This research has applied this process to seek novel computational results of the developed Zakharov-Kuznetsov (ZK) equation in electrical engineering. With 3D and contour graphical illustration, mathematical results explicitly exhibit the proposed algorithm's complete honesty and high performance.Thermal Performance of Oscillating Blade with Various Geometries in a Straight Channel
https://jacm.scu.ac.ir/article_15420.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.Numerical Study and Geometric Investigation of Corrugated Channels Subjected to Forced Convective Flows
https://jacm.scu.ac.ir/article_16188.html
The employment of heat exchangers with complex channels has increasing importance in several engineering problems as commercial refrigeration and cooling of electronic packages. One important subject in this kind of device is the design of corrugated channels. Therefore, the present work aims at the geometric optimization of trapezoidal blocks mounted in channels subjected to steady, incompressible, laminar, two-dimensional forced convective flows. The computational domain studied here mimics the corrugated channels commonly found in micro-channel heat exchangers. For the geometrical investigation, it is employed the Constructal Design Method. The numerical simulations were performed for two Reynolds numbers (ReH) equal to 60 and 160 and constant Prandtl number (Pr = 6.99). Results demonstrated that the length/height ratios of both studied blocks (given by L1/H1 and L2/H2 ratios) have the highest sensibility over the thermal performance, showing the importance of the channel's blocks intrusion. It was also shown that the combined analysis of the ratios L1/H1 and L2/H2 was much more efficient for the improvement of the heat transfer rate in the corrugated channels. The thermal performance increased by nearly 65% when the best and worst configurations were compared.Buckling and Vibration Analysis of a Double-layer Graphene Sheet Coupled with a Piezoelectric Nanoplate
https://jacm.scu.ac.ir/article_15421.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&rsquo;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.Analytical Expressions for the Singularities Treatment in the Three-dimensional Elastostatic Boundary Element Method
https://jacm.scu.ac.ir/article_16211.html
The Boundary Element Method (BEM) is one of the most used numerical methods to solve engineering problems. This method has several advantages over other domain methods. However, BEM requires the use of the fundamental solution of the integral formulation that governs the problem under analysis. Furthermore, these fundamental solutions present, in their majority, singular and hyper-singular terms that impair the stability of the numerical solution when the source point is in the element to be integrated. In order to regularize unstable kernels present in the BEM's three-dimensional elastostatic formulation, the present work develops expressions, in Laurent's series, for treatment of the singularity. The precision of the developed expressions is verified on a standard curved triangular element. The results show excellent efficiency in the regularization of singular and hyper-singular kernels for the problem under analysis.Computational Fluid Dynamic Analysis of Amphibious Unmanned Aerial Vehicle
https://jacm.scu.ac.ir/article_15424.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&deg; 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.Laminar Flow Control and Drag Reduction using Biomimetically Inspired Forward Facing Steps
https://jacm.scu.ac.ir/article_16220.html
This paper explores the use of shark-skin inspired two-dimensional forward facing steps to attain laminar flow control, delay boundary layer transition and to reduce drag. Computation Fluid Dynamics (CFD) simulations are carried out on strategically placed forward facing steps within the laminar boundary layer using the Transition SST model in FLUENT after comprehensive benchmarking and validation of the simulation setup. Results presented in this paper indicate that the boundary layer thickness to step height ratio (d/h), as well as the location of the step within the laminar boundary layer (x/L), greatly influence transition onset. The presence of a strategically placed forward facing step within the laminar boundary layer might damp disturbances within the laminar boundary layer, reduce wall shear stress and energize the boundary layer leading to transition onset delay and drag reduction as compared to a conventional flat plate. Results presented in this paper indicate that a transition delay of 20% and a drag reduction of 6% is achievable, thereby demonstrating the veracity of biomimicry as a potential avenue to attain improved aerodynamic performance.Validation of Model-Based Real-Time Hybrid Simulation for a Lightly-Damped and Highly-Nonlinear Structural System
https://jacm.scu.ac.ir/article_15427.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.New Exact Traveling Wave Solutions for Fractional Order System Describing the Second Grade Fluid through Medium with Heat Transfer
https://jacm.scu.ac.ir/article_16235.html
The aim of this paper is to determine the time-dependent MHD fractionalized three-dimensional flow of viscoelastic fluid in porous medium with heat transfer by traveling wave solution. The governing nonlinear partial differential equations are altered by utilizing the wave parameter &xi; = lx + my + nz + &omega;t&beta;/&Gamma;(&beta;+1) into ordinary differential equations. The exact solutions are attained by applying a traveling wave method for two different cases. Here we discuss some precise cases, the solution of MHD Newtonian fluid in porosity can be obtained by substituting &alpha;1&nbsp;&rarr; 0&nbsp;in general solution. The impact of important governing parameters on the movement of a fluid is examined as well as the comparison of Newtonian and non-viscous fluids have been made by 2D and 3D graphical analysis.Theoretical and Experimental Investigation on Mechanical Behavior of Aluminum to Aluminum Tubular Bonded Lap Joint under Pure Torsion and a Finite Element Comparison with Hybrid Rivet/Bonded Joint
https://jacm.scu.ac.ir/article_15433.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&rsquo;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.The Rank Upgrading Technique for a Harmonic Restoring Force of Nonlinear Oscillators
https://jacm.scu.ac.ir/article_16236.html
An enhanced analytical technique for nonlinear oscillators having a harmonic restoring force is proposed. The approach is passed on the change of the auxiliary operator by another suitable one leads to obtain a periodic solution. The fundamental idea of the new approach is based on obtaining an alternative equation free of the harmonic restoring forces. This method is a modification of the homotopy perturbation method. The approach allows not only an actual periodic solution but also the frequency of the problem as a function of the amplitude of oscillation. Three nonlinear oscillators including restoring force, the simple pendulum motion, the cubic Duffing oscillator, the Sine-Gordon equation are offered to clarify the effectiveness and usefulness of the proposed technique. This approach allows an effective mathematical approach to noise and uncertain properties of nonlinear vibrations arising in physics and engineering.Nanostructure, Molecular Dynamics Simulation and Mechanical Performance of PCL Membranes Reinforced with Antibacterial Nanoparticles
https://jacm.scu.ac.ir/article_15466.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.Nonlinear Control for Attitude Stabilization of a Rigid Body Forced by Nonstationary Disturbances with Zero Mean Values
https://jacm.scu.ac.ir/article_16234.html
A rigid body forced by a nonstationary perturbing torque with zero mean value is under consideration. The control strategy for attitude stabilization of the rigid body is based on the usage of dissipative and restoring torques. It is assumed that the dissipative torque is linear, while restoring and perturbing torques are purely nonlinear. A theorem on sufficient conditions for asymptotic stability of the body angular position is proved on the basis of the decomposition method, the Lyapunov direct method and the averaging technique. Computer simulation results illustrating the theorem are presented.A Note on the Hydromagnetic Blasius Flow with Variable Thermal Conductivity
https://jacm.scu.ac.ir/article_15467.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.Sensitivity Analyses of Structural Damage Indicators and Experimental Validations
https://jacm.scu.ac.ir/article_16238.html
The vibration-based damage detection (VBDD) has been widely used in structural health monitoring (SHM). However, different damage indicators have different effects on SHM. It is necessary to analyze the sensitivity of structural damage indicators to study the correlation between these indicators and damages. In this paper, the sensitivities of the mode shape, modal strain energy (MSE) and strain mode are numerically studied and experimentally validated. The damage is simulated by the reduction in the cross-sectional area of the rods of a 3-D steel frame. The sensitivity of the three damage indicators are obtained and compared by using the finite element (FE) analyses of the frame; the modal parameters are obtained through the experimental modal analysis, and the sensitivity of the three damage indicators are calculated to validate whether they could identify the structural damage. The results indicate that, generally, the sensitivity of the modal strain is the highest, followed by the MSE, and the sensitivity of the mode shape is the lowest. Nevertheless, the MSE shows high sensitivity in the cases of multiple damages. The sensitivity of the damage indicators varies for different damage locations; the sensitivity decreases from the mid span to the end of the steel frame. The above results provide a theoretical basis for the selection of damage indicators in the damage detection.Experimental and Finite Element Study to Determine the Mechanical Properties and Bond Between Repair Mortars and Concrete Substrates
https://jacm.scu.ac.ir/article_15470.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.Design Optimization and Experimental Validation of Low-Cost Flat Plate Collector Under Central Qasssim Climate
https://jacm.scu.ac.ir/article_16247.html
In Saudi Arabia, hot water for domestic uses consumes a great portion of home electricity. Thus, solar collectors can be considered as an important alternative to reduce the amount of consumed electricity. Therefore, in recent researches, a great attention was given to develop flat plate collector (FPC) with optimal performance. In this paper, a multi-objective modified imperialist competitive algorithm (MOMICA) was employed for optimizing the performance of a FPC. The optimization results showed a capability to reach higher FPC efficiency with a relatively small collector area and hence lower price. It has also been proved that the change of the insulator depth from 0.02 to 0.05 m has a strong influence on the system&rsquo;s efficiency.A Closed-Form Solution for Electro-Osmotic Flow in Nano-Channels
https://jacm.scu.ac.ir/article_15479.html
In this article&lrm;, &lrm;a fluid dynamic code is implemented to investigate a non-linear model for electro-osmotic flow through a one-dimensional Nano-channel&lrm;. &lrm;Certain mathematical techniques are simultaneously utilized to convert the coupled system of equations into a non-linear differential correlation&lrm;. &lrm;This correlation is based on the mole fraction of anion&lrm;. &lrm;By using a modified homotopy perturbation method&lrm;, &lrm;the achieved non-linear differential equation is converted into a few linear differential equations&lrm;. &lrm;The mole fraction of anion across the channel is found by solving the linear differential equations&lrm;. &lrm;Finally&lrm;, &lrm;the distribution of the mole fraction of cation&lrm;, &lrm;electrical potential, and velocity are accurately derived based on the mole fraction of anion&lrm;. &lrm;The present study confirms that by application of a modified homotopy perturbation method&lrm;, &lrm;the results are in acceptable agreement with the previously validated data&lrm;. &lrm;However, using the proposed method here&lrm;, &lrm;a closed-form of the solution is achieved&lrm;.Finite Element and Experimental Investigation on the Effect of Repetitive Shock in Corrugated Cardboard Packaging
https://jacm.scu.ac.ir/article_16278.html
The primary concern of the current study is estimating the repetitive shock induced damages leading to cumulative fatigue on corrugated cardboard boxes experimentally and numerically. Repetitive shock tests were performed on boxes using a vibration table to construct a Damage Boundary Curve (DBC). To computationally determine this curve, a finite element approach is proposed using an elastoplastic homogenization model for corrugated cardboard. The proposed model was implemented in the finite element software ABAQUS. Thanks to adopted model simplifications, a box can be easily and reliably modelled as a homogenized structure. A calibration method is used to compute a set of effective parameters in homogenized model in order to keep its behavior qualitatively and quantitatively close to the response of a full structural model. For verification, the identified model is used to simulate the box compression test. To replicate the experimental tests, simulations of successive repetitive shock pulses are carried with the proposed model for oligocyclique and limited endurance fatigue. To reduce computational costs, we propose a simple method for unlimited endurance fatigue by extrapolating a trend line after some training cycles. The proposed method shows good agreement with experimental results.Biomechanical Evaluation of Bone Quality Effect on Stresses at Bone-Implant Interface: A Finite Element Study
https://jacm.scu.ac.ir/article_15481.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 &times; 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.Structural and Aerodynamical Parametric Study of Truss-Core Gas Turbine Rotor Blade
https://jacm.scu.ac.ir/article_16279.html
Improvement of turbine blades is currently the prime area of research dedicated to the development of more efficient gas turbines. This study examines the structural performance of the gas turbine rotor and stator blades with the implementation of Kagome truss-core structure as inner topology. The truss-core structure was hypothesised to improve the stress behaviour of the blade by reducing the mass and, hence, the centrifugal force induced by rotation, while remaining robust enough to withstand bending stress induced by the flow. In order to analyse the stress state of the truss-core model, fluid flow analysis of transonic turbomachinery was performed via the Frozen Rotor technique in ANSYS CFX and then coupled with ANSYS Mechanical. As a result, the combined surface load of the rotor was obtained and used to estimate the structural performance. By examining the obtained complex stress state of the rotor blades, the truss-core density-dependent structural performance was derived for the given initial and boundary conditions.Improvement of Numerical Manifold Method using Nine-node Quadrilateral and Ten-node Triangular Elements along with Complex Fourier RBFs in Modeling Free and Forced Vibrations
https://jacm.scu.ac.ir/article_15484.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.Impacts of Volume of Carbon Nanotubes on Bending for Carbon-Kevlar Hybrid Fabrics
https://jacm.scu.ac.ir/article_16308.html
Carbon nanotubes indicate mechanical properties ideally examined for reinforced Carbon/Kevlar hybrid fabrics in the intact specimens by SEM and EDX observations an Carbon nanotubes indicated mechanical properties that were examined for reinforced Carbon/Kevlar hybrid fabrics in the intact specimens by SEM and EDX observations and after attempting six successful ballistic impacts, at various targets&rsquo; angles: normal impact (0-degree), 10-degree, 20-degree, 30-degree, and 40-degree) with the different volume of CNT% (0, 0.1, 0.3, 0.5, 0.7, 1, and 1.5) after attempting six successful ballistic impacts, at various targets&rsquo; angles: normal impact (0-degree), 10-degree, 20-degree, 30-degree, and 40-degree) with the different volume of CNT% (0, 0.1, 0.3, 0.5, 0.7, 1, and 1.5). Each sample was fabricated by the same curing unit and then evaluated by the three‐point bending universal testing machine model (INSTRON-3369). Flexural Stress-Strain curves under 3-points bending in CNT epoxy composite laminates calculated flexural modulus of elasticity and bending toughness at room temperature.Thermal-Aerodynamic Performance Measurement of Air Heat Transfer Fluid Mechanics over S-shaped Fins in Shell-and-tube Heat Exchangers
https://jacm.scu.ac.ir/article_15485.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-&epsilon; 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 (&mu;t), 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.Method of Unsteady Hydrodynamic Characteristics Determination in Turbulent Boundary Layer
https://jacm.scu.ac.ir/article_16310.html
This paper presents the method of the turbulent flow simulation. The method may be used to address the computational aeroacoustics (CAA) problems, where the vortex noise&rsquo;s sources have to be determined. This method is an alternative to both large-eddy simulation (LES) methods and stochastics turbulence simulation techniques. The proposed method is more computationally efficient compared to LES and, unlike stochastic approaches, it does not require empirical constants. The simulation according to this method is achieved in two main stages. During the first step the averaged flow&rsquo;s properties are obtained using the RANS simulation. These properties are used for the formulation of the discrete vortex model on the second step. Vortices&rsquo; intensities are oscillating with amplitudes and frequencies obtained from the RANS simulation with random phase shifts. Turbulent velocity field is then determined as the sum of averaged flow velocities, velocities induced by the pulsing vortices and velocities induced by the trailing vortices (Kelvin circulation theorem). The method is verified by considering the test problem. The developed turbulent boundary layer near the horizontal wall is simulated by means of both the presented method and the LES method. A good agreement between these two methods indicates on the viability of the approach presented in this paper. However, a thorough investigation of the method is still yet to be accomplished.Scattering and Backscattering Study of Mechanical Plane Wave in Composite Materials Plates (Earth model 1066B and LiNbO3)
https://jacm.scu.ac.ir/article_15486.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.Schmidt-Ishlinskii Yield Criterion and a Rotating Cylinder with a Rigid Inclusion
https://jacm.scu.ac.ir/article_16311.html
An elastoplastic rotating cylinder with a rigid inclusion and fixed ends is investigated. The analysis is based on infinitesimal strain theory, Schmidt-Ishlinskii yield criterion, and its associated flow rule and perfectly plastic material behavior. Both loading and unloading stages are studied. The closed-formed solutions for all stages of deformation including secondary plastic flow are obtained. The results are illustrated by the distributions of the stresses and plastic strains in a cylinder rotating at different speeds.Comparison of Functionally Graded Hip Stem Implants with Various Second-Generation Titanium Alloys
https://jacm.scu.ac.ir/article_15498.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.Thermoelastic Memory-dependent Responses to an Infinite Medium with a Cylindrical Hole and Temperature-dependent Properties
https://jacm.scu.ac.ir/article_16350.html
The present research discusses a generalized thermoelastic model with variable thermal material properties and derivatives based on memory. Based on this new model, an infinitely long homogeneous, isotropic elastic body with a cylindrical hole is analyzed for thermal behavior analysis. The governing equations are deduced by the application of the principle of memory-dependent derivatives and the generalized law on heat conduction. In a numerical form, the governing differential equations are solved utilizing the Laplace transform technique. Numerical calculations are shown in graphs to explain the effects of the thermal variable material properties and memory dependent derivatives. In addition, the response of the cylindrical hole is studied through the effects of many parameters such as time delay, the kernel function and boundary conditions. The results obtained with those from previous literature are finally verified.Haar Wavelet Method for Solving High-Order Differential Equations with Multi-Point Boundary Conditions
https://jacm.scu.ac.ir/article_15499.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.Moving Least Squares Method and its Improvement: A Concise Review
https://jacm.scu.ac.ir/article_16360.html
The concise review systematically summarises the state-of-the-art variants of Moving Least Squares (MLS) method. MLS method is a mathematical tool which could render cogent support in data interpolation, shape construction and formulation of meshfree schemes, particularly due to its flexibility to form complex arithmetic equation. However, the conventional MLS method is suffering to deal with discontinuity of field variables. Varied strategies of overcoming such shortfall are discussed in current work. Although numerous MLS variants were proposed since the introduction of MLS method in numerical/statistical analysis, there is no technical review made on how the methods evolve. The current review is structured according to major strategies on how to improvise MLS method: the modification of weight function, the manipulation of discrete norms, the inclusion of iterative feature for residuals minimising and integration of these strategies for more robust computation. A wide range of advanced MLS variants have been compiled, summarised, and reappraised according to its underlying principle of improvement. In addition, inherent limitation of MLS method and its possible strategy of improvement is discussed too in this article. The current work could render valuable reference to implement and develop advanced MLS schemes, whenever complexity of the specific scientific problems arose.Chaos Control in Gear Transmission System using GPC and SMC Controllers
https://jacm.scu.ac.ir/article_15500.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.Parameter Estimation in Population Balance through Bayesian Technique Markov Chain Monte Carlo
https://jacm.scu.ac.ir/article_16365.html
In this work, the Markov Chain Monte Carlo is applied to estimate parameters that represent mechanisms that describe particles' dynamics in particulate systems from the literature's proposed models. Initially, the reduced sensitivity coefficient is evaluated to verify which parameters could be estimated simultaneously. The technique is then applied to estimate the models' parameters in different numerical scenarios to determine the rates that influence population dynamics. After the analyzes are performed, the estimates show good precision, accuracy, and a good fit between the measured and estimated state variables. The results show that the Markov chain Monte Carlo can determine the rates of population balance phenomenon.Numerical Scheme based on Non-polynomial Spline Functions for the System of Second Order Boundary Value Problems arising in Various Engineering Applications
https://jacm.scu.ac.ir/article_15501.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.Diffusion-thermo Effects in Stagnation Point Flow of Second Grade Fluid past a Stretching Plate
https://jacm.scu.ac.ir/article_16370.html
Transmission of heat and mass in boundary layer flows over stretching surfaces play a significant role in metallurgy and polymer industry. In Current article the assisting and opposing flow of a second grade fluid towards a stretching sheet is analyzed to examine the heat and mass transfer in stagnation point boundary layer flow. Different flow parameters such as concentration, surface temperature and stretching velocity are supposed to variate linearly. The basic transport equations are transformed into non-linear ordinary differential equations by means of boundary layer approximation and similarity transmutations, which are then solved by employing nonlinear shooting (NLS) and Keller-box methods (KBM). These techniques are very useful for solving boundary-layer problems and are applicable to other general situations than that presented current study. The outcomes of velocity, temperature, concentration profile, skin-friction coefficient, heat and mass transfer coefficients are analyzed briefly in graphical and tabular formats. The mass transmission rate was found to be in direct relation with Schmidt number. Moreover, we predict that a rise in Prandtl number leads to a decline in temperature and thermal layer of boundary thickness for both supporting and contrasting flows. The outcomes of this article are important for the analysts in the field of second grade fluids. We believe that the article is very well prepared and the results are original and useful from both theoretical and application point of views.Hydrodynamic Behavior in Solar Oil Heat Exchanger Ducts Fitted with Staggered Baffles and Fins
https://jacm.scu.ac.ir/article_15502.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.Nonlinear Dynamic Behavior of Hyperbolic Paraboloidal Shells Reinforced by Carbon Nanotubes with Various Distributions
https://jacm.scu.ac.ir/article_16374.html
The analytical solution of the nonlinear dynamic behavior of CNT-based hyperbolic paraboloidal shallow shells (HYPARSSs) with various distribution shapes is presented. A theoretical model was created for HYPARSSs reinforced with CNTs using the von K&aacute;rm&aacute;n -type nonlinearity. Then the nonlinear basic equations are reduced to ordinary nonlinear differential equations using Galerkin methods and the correlation for frequency-amplitude relationship is obtained using the Grigolyuk method. In addition, the nonlinear frequency/linear frequency (NL/L) ratio is determined as a function of amplitude. Comparisons with reliable results in the literature were made to test the accuracy of the formulas. Finally, a systematic investigate is performed to control the influences of CNTs in the matrix, CNT distribution types and nonlinearity on the vibration frequency-amplitude relationship.Effect of Throughflow on the Convective Instabilities in an Anisotropic Porous Medium Layer with Inconstant Gravity
https://jacm.scu.ac.ir/article_15514.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. In this study, two types of gravity field digression were examined: (a) linear and (b) parabolic. It is found that the throughflow parameter Pe, the thermal anisotropy parameter &eta;&nbsp;and gravity deviation parameter&nbsp;&lambda; postpone the beginning of convective activity, whereas the mechanical anisotropy parameter&nbsp;&xi; rapids the onset of convective activity. The dimension of the convection cells enhances on enhancing the thermal anisotropy parameter &eta;, the mechanical anisotropy parameter&nbsp;&xi; and gravity deviation parameter&nbsp;&lambda; while, the throughflow parameter Pe decreases the extent of the convective cells. It is also noted that the structure with linear variation of gravity force is more stable.Applicability Evidence of Constructal Design in Structural Engineering: Case Study of Biaxial Elasto-Plastic Buckling of Square Steel Plates with Elliptical Cutout
https://jacm.scu.ac.ir/article_16376.html
The application of the Constructal Design method in Heat Transfer and Fluid Mechanics areas is an already consecrated approach to geometrically evaluate these flow engineering systems. However, this approach in Mechanics of Materials realm is not yet widely used, since one can find only few publications about it in literature. The Constructal Design is based on the Constructal Law, a physical law that explains the universal phenomenon of evolution of any finite size flow system. Therefore, the main goal here is to show that the Constructal Design can also be used in dedicated Structural Engineering problems as an effective method for geometric evaluation. The obtained results prove the Constructal Design applicability definitively in Mechanics of Materials.Effect of Inlet Air Locations on Particle Concentration using Large Eddy Simulation based on Multi Relaxation Time Lattice Boltzmann Method
https://jacm.scu.ac.ir/article_15515.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 &micro;m) in a modeled room. Simulation results showed that for the displacement ventilation system with the inlet air register on the floor, the number of 10&micro;m 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 10&micro;m 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 1&micro;m particle motion, and the numbers of the particles that remain suspended in the room are roughly the same for both ventilation systems.Unsteady MHD Mixed Convection Flow of Water over a Sphere with Mass Transfer
https://jacm.scu.ac.ir/article_16379.html
This paper examines the unsteady magnetohydrodynamic (MHD) mixed convection flow over a sphere combined with variable fluid properties. An implicit finite difference scheme, together with the quasi-linearization, is used to find non-similar solutions for the governing equations. The vanishing skin friction is prevented or at least delayed by enhancing the mixed convection in both the cases of steady and unsteady fluid flow. Both skin friction and heat transfer coefficients are found to be increasing with an increase in time or MHD parameter.Metal and Metallic Oxide Nanofluid over a Shrinking Surface with Thermal Radiation and Heat Generation/Absorption
https://jacm.scu.ac.ir/article_15518.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.Nonlinear Biodynamic Models of the Hand-arm System and Parameters Identification using the Vibration Transmissibility or the Driving-point Mechanical Impedance
https://jacm.scu.ac.ir/article_16397.html
This study aims at deriving nonlinear expressions of the transmissibility and the driving-point mechanical impedance (DPMI) of two nonlinear biodynamic hand-arm models having active restoring and dissipative parameters. It aims also in computing explicitly the non-directly measurable stiffness and damping coefficients of the human hand-arm system (HAS). Multivariate Pad&eacute; approximants are used to express the dependence of the HAS mechanical properties on various influencing factors. The harmonic balance method is used to derive analytical expressions of the transmissibility and the DPMI. Then, the models parameters are identified by minimizing constrained error functions between the theoretical DPMI or transmissibility and the measured data. The developed workflow is applied to three experimental data sets of Z-direction vibrations where the excitation frequency and/or the grip force are varied. Using the ISO-10068 (2012) limit DPMI values versus the excitation frequency, we derived upper and lower limits of the overall stiffness coefficient and damping ratio for the human HAS. Furthermore, the model reproduces with high accuracy experimental measurements of the transmissibility, the DPMI and the vibration power absorption.Modeling beam-like planar structures by a one-dimensional continuum: an analytical-numerical method
https://jacm.scu.ac.ir/article_15523.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.Two-Dimensional Numerical Study of the Transient Flow Conditions in Complete Shock Tunnel
https://jacm.scu.ac.ir/article_16406.html
In the current research, an axisymmetric model is developed to study high-speed unsteady flow in the test section of a 7 meter-long shock tunnel. The computational calculations of the shock tunnel are conducted using the Fluent CFD solver. The Finite Volume Method (FVM) is used to discretize the governing equations of mass, momentum, and energy. The accuracy of the numerical model is investigated with first-order upwind, second-order upwind, and third-order MUSCL schemes. Adaptive mesh refinement is implemented to resolve the shock wave and contact surface regions accurately. The numerical results are compared with theoretical calculations and experimental data from experimental tests and the comparison shows good agreement. Different test gases of Helium, Air and CO2, are utilized in the current study. The results show that steady test conditions are maintained for a longer test time by adjusting the pressure ratio and gas combination across the diaphragm. The highest shock wave speed and strength are achieved for a gas combination of Helium-CO2, but a longer test duration is observed when using Air as the test gas.Thermodynamic and Environmental Assessment of Mounting Fin at the Back Surface of Photovoltaic Panels
https://jacm.scu.ac.ir/article_15524.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&deg;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.Fatigue Life Analysis of Bus Body based on User Target Load Spectrum
https://jacm.scu.ac.ir/article_16400.html
In this article, fatigue life of a bus body is analyzed based on the user target load spectrum. A finite element model of the bus body is built with characteristics. The static analysis result is obtained by using the inertia release method and a multi-body dynamic model is established by using the rigid flexible coupling method. According to user investigation, the user load spectrum is obtained through dynamic simulation. The average value and amplitude of each level of stress are extracted from the load spectrum information. With the fatigue properties of the material, the damage value of the bus body is determined by using the S-N curve method and Miner linear cumulative damage theory. The simulation gives the fatigue life and damage values of the most dangerous position of the body structure. Calculation shows that the fatigue life of the bus body meets durability requirements.Elastic Limit Angular Velocity and Acceleration Investigation in Non-Uniform Rotating Disk under Time-Dependent Mechanical Loading
https://jacm.scu.ac.ir/article_15526.html
An analytical effort is made to achieve cognition on the effect of time-dependent mechanical loading &lrm;on the stress fields of rotating disks with non-uniform thickness and density. At high variable angular &lrm;velocities and accelerations, evaluation of the effect of shear stress on the values of von Mises stress is &lrm;significant and it is excellent to consider shear stress in this equivalent stress calculation alongside the &lrm;radial and tangential stress. In the proposed analytical model, the Homotopy perturbation method (HPM) &lrm;solves the general structure of rotating disks equilibrium equations in both radial and tangential &lrm;directions. HPM is an efficient tool to solve linear and nonlinear equations, providing solutions in quick &lrm;converging series. The results obtained through this process are then confirmed using the finite &lrm;difference method and the exact solution in the literature. The effect of parameters in angular velocity &lrm;and acceleration functions with the parameter in the thickness function and the effect of boundary &lrm;conditions on the values of elastic limit angular velocity and acceleration are established by performing &lrm;numerical examples. Furthermore, the effect of shear stress on the maximum values of &lrm;von Mises stress is discussed. It is shown that shear stress has more influence on the distribution of &lrm;equivalent von Mises stress in the elastic region. It is shown the introduced analytical model is useful for &lrm;evaluating rotating disk with any arbitrary shape of thickness and density function, without using the &lrm;commercial finite element simulation software.Solution of the Problem of Analytical Construction of Optimal Regulators for a Fractional Order Oscillatory System in the General Case
https://jacm.scu.ac.ir/article_16462.html
An algorithm is proposed for solving the problem of analytical constructing of an optimal fractional-order regulator (OFOR) in the general case. By inscribing the extended functional, the corresponding fractional order Euler-Lagrange equation is determined. Then, using the Mittag-Leffler function, a fundamental solution to the corresponding Hamiltonian system is constructed. It is shown that to obtain an analogue of the analytical construction of AM Letov's regulators, the order of the fractional derivatives must be a rational number, the denominator and numerator of which are odd numbers. Numerical illustrative examples are provided.Stability Analysis of Casson Nanofluid Flow over an Extending/Contracting Wedge and Stagnation Point
https://jacm.scu.ac.ir/article_15528.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 have 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.Influence of Pressure on the Frequency Spectrum of Micro and Nanoresonators on Hinged Supports
https://jacm.scu.ac.ir/article_16491.html
Eigenfrequencies of bending oscillations are determined for a resonator with rectangular cross-sections mounted on hinged supports. Consideration is given to the surface effect caused by the interaction between gas pressure and the difference in the areas of the resonator&rsquo;s convex and concave surfaces. Changes in the frequency spectrum are examined at the presence of both concentrated and uniformly distributed masses attached to the resonator&rsquo;s surface. The solution of the inverse problem enables the identification of attached masses using changes of eigenfrequencies.Optimization of Air Distribution Patterns by Arrangements of Air Inlets and Outlets: Case Study of an Operating Room
https://jacm.scu.ac.ir/article_15534.html
In this research, possible methods to improve the air distribution patterns of an operating room (OR) employing CFD method are investigated. Laminar airflow (LAF), turbulent airflow (TAF), and LAF with the air curtain are examined. It is found that LAF and LAF with the air curtain cases are superior to TAF-based cases. The study shows 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 is recommended to be implemented in the existing OR.Quasi-bifurcation and Imperfection-sensitivity of Cylindrical Shells under Pressures due to an Explosion
https://jacm.scu.ac.ir/article_16514.html
The static and dynamic behavior of a horizontal cylindrical shell (as used to store fuels in tanks) is investigated in this work by means of computational modeling. Under a distributed pressure commonly used to model effects due to explosions, the geometrically nonlinear behavior is explored to identify bifurcation and limit points along the static equilibrium path, and the associated displacements. Critical load reductions due to imperfections are found in the order of 25%. The dynamic analysis is next presented to identify the possibility of reaching a quasi-bifurcation. It is found that the first peak in the transient response at which the displacement reaches the same value as in the limit static case occurs for a load which is about 3.5 times the static bifurcation load. The velocity is zero at this state and is identified as a quasi-bifurcation, at which the shell is expected to display a static instability. Imperfection-sensitivity of the quasi-bifurcation load is found to be of the same order as the static one. This is the first quasi-bifurcation study of a shell to identify dynamic buckling due to a nearby explosion.A New Modified Hamilton-Crosser and Nan Models for Thermal Conductivity of Different Lengths Carbon Nanotubes Water-based Nanofluids
https://jacm.scu.ac.ir/article_15535.html
In order to investigate the shape effect of nanoadditives on thermal conductivity of nanofluids, different length carbon nanotubes (CNTs) are made and using a two-step method, different nanofluids are prepared. The CNTs are cut into different lengths by functionalization at different refluxing times of 1, 2 and 4 hours. To probe the effect of aspect ratio of CNTs on the obtained experimental data, modified Hamilton-Crosser and Nan models are developed. It is found that the original Hamilton-Crosser and Nan models could not predict the experimental thermal conductivities. By replacing n = 6 + xL/D&nbsp;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&nbsp;&phi;&nbsp;(xL/D) instead of &phi;&nbsp;(volume fraction) in the Nan model, the prediction of modified equations show very good accordance with the experimental data which means the shape of nanoadditives has high impact on nanofluids&rsquo; properties.Multi-objective Optimization of Shot-peening Parameters using Design of Experiments and Finite Element Simulation: A Statistical Model
https://jacm.scu.ac.ir/article_15536.html
Shot-peening is a mechanical surface treatment used extensively in the industry to enhance the performance of metal parts against fatigue. Thus, it is important to determine main parameters of shot-peening in order to obtain its optimal values. The purpose of this study is to achieve a statistical model to determine the important parameters of the shot-peening process by considering the effect of sample thickness on the responses and achieving the multi-objective optimal parameters. To do this, response surface methodology are used to determine the governing models between the response variable and the input parameters. Shot velocity, shot diameter, coverage percentage and sample thickness are selected as shot-peeningparameters. Residual compressive stress, its depth and roughness are considered as the response variable. Using finite element analysis, shot-peening process are simulated. The desirability function approach is used for multi-objective optimization so that the optimal shot-peeningparameters, which simultaneously provide two response variables in optimal mode, are obtained. The results show that surface stress and maximum residual stress are independent of shot velocity, whereas, the depth of the compressible stress and roughness are directly related to shot velocity. In addition, thickness modifies surface stress and the depth of the compressible stress. The optimal conditions for surface stress, maximum compressive stress, and roughness simultaneously with high-coverage and low-velocity can be achieved as well.A Comparative Study on the Efficiency of Compiled Languages and MATLAB/Simulink for Simulation of Highly Nonlinear Automotive Systems
https://jacm.scu.ac.ir/article_15549.html
In the present paper, a comparison between the simulation performance of a highly nonlinear model in MATLAB/Simulink and a compiled language has been drawn. A complete powertrain layout was formed 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.Unsteady Separated Stagnation Point Flow of Nanofluid past a Moving Flat Surface in the Presence of Buongiorno's Model
https://jacm.scu.ac.ir/article_15550.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&rsquo;s model. Characteristic of Brownian diffusion and thermophoresis are considered. Additionally, characteristics of chemical reaction is taken 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 depict that the temperature field &theta;(&zeta;) 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 be found that an energy profile &theta;(&zeta;) elevates due to augmenting values of (Nb). It has been perceived that thermal boundary layer thickness elevates due to large amount of Brownian motion parameter (Nb).Analysis and Optimization of Truss Structures, Constrained Handling using Genetic Algorithm
https://jacm.scu.ac.ir/article_15552.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 the exhaustive search method. Once magnitudes of the constraints are identified, member cross-sectional areas are varied to get the optimal weight. Both the exhaustive search method and the genetic algorithm have been implemented for this purpose. During the optimization, members tending to form a string 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).Thermal Analysis of Radiating Film Flow of Sodium Alginate using MWCNT Nanoparticles
https://jacm.scu.ac.ir/article_15577.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.Precision Shape Control of Ultra-thin Shells with Strain Actuators
https://jacm.scu.ac.ir/article_15579.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.Structural Health Monitoring of Multi-Storey Frame Structures using Piezoelectric Incompatibility Filters: Theory and Numerical Verification
https://jacm.scu.ac.ir/article_15616.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 paperInvestigation of Nanoﬂuid Natural Convection Heat Transfer in Open Ended L-shaped Cavities utilizing LBM
https://jacm.scu.ac.ir/article_15620.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 = 103, 104, 105, 106), cavity aspect ratio (AR = 0.2, 0.4, 0.6) and volume concentration of Cu nanoparticles (0 &le;&nbsp;&Phi; &le; 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 = 106 with AR = 0.4 (32.76%) occurs. Results illustrate that increasing the cavity aspect ratio decreases heat transfer rate for Ra = 103&nbsp;and Ra = 104. The least and most heat transfer rate for Ra = 105 occurs in enclosures by aspect ratios of 0.2 and 0.4 respectively, while it was observed at Ra = 106 for minimum and maximum rate of heat transfer the opposite behavior that at Ra = 105 occurs.ADM Solution for Cu/CuO –Water Viscoplastic Nanofluid Transient Slip Flow from a Porous Stretching Sheet with Entropy Generation, Convective Wall Temperature and Radiative Effects
https://jacm.scu.ac.ir/article_15622.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&rsquo;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.A Modified Thermoelastic Fractional Heat Conduction Model with a Single-Lag and Two Different Fractional-Orders
https://jacm.scu.ac.ir/article_15630.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.Effect of Cattaneo-Christov Heat Flux on Radiative Hydromagnetic Nanofluid Flow between Parallel Plates using Spectral Quasilinearization Method
https://jacm.scu.ac.ir/article_15631.html
In this paper, we numerically solve 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.&nbsp;Numerical Study of Three-dimensional Boundary-layer Flow over a Wedge: Magnetic Field Analysis
https://jacm.scu.ac.ir/article_15643.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 couple 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 behavior. Both numerical and asymptotic solutions give good agreement in predicting the velocity behaviors 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.Analytical Solutions and Analyses of the Displacement Separating Point in Diffusers
https://jacm.scu.ac.ir/article_15663.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.Twin Screw Expanders Profile Optimization Using Surrogate-Based Modelling
https://jacm.scu.ac.ir/article_15667.html
Twin screw machines can be used as an expander to recover the lost power in various processes causing pressure energy loss. Twin screw expanders (TSEs) have caught the attention of many researchers due to low capital, maintenance and operation costs, long lifespan and their application in two-phase fluids. However, substantial efforts required to enhance their performance. This research describes the optimization of the profile of a TSE with 4-6 lobe configuration - using surrogate-based modeling (SBM). To do so, based on the in-house code developed within FORTRAN, a TSE profile is designed and validated against available data. Then, a mathematical model is developed viaof experiments (DOE). Next, the effects of four main profile parameters are investigated on the expander performance in the entire design space. Finally, an optimized combination of parameters is offered using a multi-objective genetic algorithm. 3D computational fluid dynamics (CFD) results show that the optimized profile had more than 7% exergy efficiency compared to the base profile.Natural frequencies and internal resonance of beams with arbitrarily distributed axial loads
https://jacm.scu.ac.ir/article_15668.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 loadsMagneto-bio-thermal Convection in Rotating Nanoliquid containing Gyrotactic Microorganism
https://jacm.scu.ac.ir/article_15676.html
The magneto-convection influenced by a gyrotactic behavior of algal suspensions along with rotation in the nanoliquid 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) &gt; 6) and shooting method (by taking forcing condition) are 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 slow down the convective motion of microorganisms across the layer and destabilizes the system.Variational Inference for Nonlinear Structural Identification
https://jacm.scu.ac.ir/article_15678.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.Vibration Mitigation of Rail Noise Barriers by Hysteretic Absorbers
https://jacm.scu.ac.ir/article_15680.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.Higher-Order Slope Limiters for Euler Equation
https://jacm.scu.ac.ir/article_15684.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.Nonlinear Primary Frequency Response Analysis of Self-Sustaining Nanobeam Considering Surface Elasticity
https://jacm.scu.ac.ir/article_15686.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.&nbsp;Non-similar Radiative Bioconvection Nanofluid Flow under Oblique Magnetic Field with Entropy Generation
https://jacm.scu.ac.ir/article_15687.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 an 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.An Automatic Program of Generation of Equation of Motion and Dynamic Analysis for Multi-body Mechanical System using GNU Octave
https://jacm.scu.ac.ir/article_15689.html
Multi-body dynamics is used to 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 derive 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.On/off Nodal Reconfiguration for Global Structural Control of Smart 2D Frames
https://jacm.scu.ac.ir/article_15690.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&ndash;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.Characterization of the Nonlinear Biaxial Mechanical Behavior of Human Ureter using Constitutive Modeling and Artificial Neural Networks
https://jacm.scu.ac.ir/article_15696.html
Characterization of the mechanical properties of soft biological tissues is a fundamental&nbsp;issue in a variety of medical applications. As such, constitutive modeling of biological tissues that serves to establish a relationship between the kinematic variables has been used to formulate the tissue&rsquo;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, at first, 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 (RMSE&lt;0.02). Such results confirmed that neural networks can be a reliable alternative for modeling the nonlinear mechanical behavior of soft biological tissues.Improving the linear stability of the visco-elastic Beck's beam via piezoelectric controllers
https://jacm.scu.ac.ir/article_15706.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.Numerical Investigation on Flow Transition through a Curved Square Duct with Negative Rotation
https://jacm.scu.ac.ir/article_15707.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 (-10 &le; Tr &le; -1500). The other useful parameters such as Dean number (Dn), Curvature (d), Grashof number (Gr), and Prandtl number (Pr) are considered fixed. The investigations are divided into four parts. In the first portion, linear stability of the flows through the duct is discussed. Then time evolution calculations of the unsteady solutions for different Taylor numbers are demonstrated in the &ldquo;time vs. heat flux&rdquo; plane. This inquiry shows that the flow undergoes various instabilities for increasing the Taylor number. Thirdly, two types of flow velocity, axial flow and secondary flow and the temperature profiles are represented. It is obtained that two up to six vortex secondary flows are found for the regular and irregular oscillation and the flow patterns are different for a fixed period for regular oscillation. To show more clarity of the periodic and chaotic flow, power spectrum density is further examined. However, it is observed that the flows are mixed and enhanced heat transfer because of the acting of centrifugal force, Coriolis force, and heating induced buoyancy force on the duct. Finally, the numerical results are compared with the experimental data which shows that the numerical data fully matches with the experimental outcome.About Earthquakes in Subduction Zones with the Potential to Cause a Tsunami
https://jacm.scu.ac.ir/article_15712.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.A Simple Approach for Dealing with Autonomous Conservative Oscillator under Initial Velocity
https://jacm.scu.ac.ir/article_15713.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&rsquo;s velocity become zero. When oscillator&rsquo;s speed is zero and placed out of movement&rsquo;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.MHD Double-Diffusive Natural Convection in a Closed Space Filled with Liquid Metal: Mesoscopic Analysis
https://jacm.scu.ac.ir/article_15715.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 &le; Ra &le; 105), Lewis number (2 &le; Le &le; 10), buoyancy ratio (-2 &le; N &le; 2), Hartmann number (0 &le; Ha &le; 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.Manifold Learning Algorithms Applied to Structural Damage Classification
https://jacm.scu.ac.ir/article_15730.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.Stress Control of a Piezoelectric Lumped-element Model − Theoretical Investigation and Experimental Realization
https://jacm.scu.ac.ir/article_15731.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&minus;4900&nbsp;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.Rotating Cylinder Turbulator Effect on the Heat Transfer of a Nanofluid Flow in a Wavy Divergent Channel
https://jacm.scu.ac.ir/article_15732.html
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,&nbsp;&Phi; 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.Numerical Study on Heat Transfer and Pressure Drop in a Mini-Channel with Corrugated Walls
https://jacm.scu.ac.ir/article_15733.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&deg;, 40&deg; and 60&deg;. 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-&epsilon;) 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.Transient Response of Longitudinal Fins under Step Changes in Base Temperature and Heat Flux using Lattice Boltzmann Method
https://jacm.scu.ac.ir/article_15760.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 thermophysical 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.Predictive Control with Dynamic Hysteresis Reference Trajectory: Application to a Structural Base-Isolation Model
https://jacm.scu.ac.ir/article_15794.html
Over the last decades, in the field of control engineering, Model Predictive Control (MPC) has been successfully &lrm;employed in many industrial processes. This due to, among other aspects, its capability to include constrains within &lrm;the design control formulation and also its ability to perform on-line optimization. For instance, in the civil &lrm;engineering field, different MPC approaches have been well developed to formulate active control algorithms able &lrm;to reduce civil structural responses to earthquakes. Thus, in this paper, a customized version of a conventional &lrm;Predictive Control (PC) strategy is proposed to mitigate the displacement on a base-isolated system with a &lrm;nonlinear hysteresis behavior, that is excited by a seismic event. The proposal consists of including a dynamic &lrm;hysteresis system into the control scheme to generate a reference trajectory that will softly drive the base-isolated &lrm;structure to a rest status. The proposed control scheme is evaluated through numerical experiments, and then its &lrm;performance is compared with respect to the conventional Predictive Control methodology. According to the &lrm;numerical experiments, the approach here presented results more efficient than the conventional method due to &lrm;the use of a suitable linear model of the structural system plus a new Driver Block with dynamic hysteresis within &lrm;the Predictive Control scheme&lrm;.An Experimental Comparison between Wing Root and Wingtip Corrugation Patterns of Dragonfly Wing at Ultra-low Reynolds Number and High Angles of Attack
https://jacm.scu.ac.ir/article_15936.html
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&deg; to 30&deg;. 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 &alpha;=25&deg;, 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.Nonlinear dynamics and stability of a homogeneous model of tall buildings under resonant action
https://jacm.scu.ac.ir/article_15959.html
A homogeneous model of beam-like structure, roughly portraying&nbsp; the mechanical behavior of a tall building, is considered to address nonlinear dynamic response in case of external resonant excitation. A&nbsp; 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.Modeling of Flight of the Line Thrower Projectile
https://jacm.scu.ac.ir/article_15978.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&rsquo;s flight distance on the projectile departure angle is constructed for several values of the tensile rigidity of the line.Optimization of Spark Ignition Engine Performance using a New Double Intake Manifold: Experimental and Numerical Analysis
https://jacm.scu.ac.ir/article_16030.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%.&nbsp;Influence of Thermophysical Features on MHD Squeezed Flow of Dissipative Casson fluid with Chemical and Radiative Effects
https://jacm.scu.ac.ir/article_16033.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 free convective flow of unsteady 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.On the Active Vibration Control of Nonlinear Uncertain Structures
https://jacm.scu.ac.ir/article_16039.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.On Stokes' Second Problem for Burgers' Fluid over a Plane Wall
https://jacm.scu.ac.ir/article_16044.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. It is observed that the velocity and the boundary layer thickness were observed to be decreased in the presence of the side walls. Moreover, the Maxwell fluid was observed to be the speediest and the Newtonian was the slowest.Turbulent Forced Convection and Entropy Generation of Impinging Jets of Water-Al2O3 Nanofluid on Heated Blocks
https://jacm.scu.ac.ir/article_16051.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 (&phi;), 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 &phi;. 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.Flexural-Torsional Galloping of Prismatic Structures with Double-Symmetric Cross-Section
https://jacm.scu.ac.ir/article_16056.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.Heat Transfer Improvement in an Open Cubic Cavity using a Hybrid Nanofluid
https://jacm.scu.ac.ir/article_16057.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 (300 &lt; Re &lt; 700), the solid volume fraction (0 &lt;&nbsp;&phi; &lt; 0.08), and heat source location (1cm &lt; d &lt; 3cm). Results indicate that by increasing Re,&nbsp;&phi; and dh, the heat transfer is improved. Moreover, nanohybrid gives better heat transfer than nanofluid, and the use of nanoparticles contributes to the minimization of entropy generation. Compared with the vertical location of the heat source, the horizontal location gives an increase in heat transfer. The Nuav correlations are determined for the nanofluid and hybrid nanofluid. This study may help to enhance the heat transfer of electronic equipment.Combined Impacts of Fin Surface Inclination and Magnetohydrodynamics on the Thermal Performance of a Convective-Radiative Porous Fin
https://jacm.scu.ac.ir/article_16073.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 thatthe 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.&nbsp;A New Approach for Exergoeconomics Evaluation by Considering Uncertainty with Monte Carlo Method
https://jacm.scu.ac.ir/article_16189.html
The exergoeconomics analysis combines thermodynamic assessments based on exergy analysis with economic concepts. this article suggests a new method for exergoeconomics analysis and evaluation of energy systems by considering uncertainty in economic parameters. As the first step, the future values of economic parameters that influence the operating cost of the energy system are forecasted by the Monte Carlo Method. Then, as a novel approach, principles of exergoeconomics analysis method are coupled with the Monte Carlo Method for exergoeconomics evaluation of energy systems. Also, three new parameters, i.e. Risk Factor (RF), Risk Factor Sensitivity (RFS), and Product Cost Sensitivity (PCS), are proposed. Two different approaches are considered in the evaluation process to improve the system: a) decreasing the total cost of products and b) reducing the risk of the cost of products. Also, the proposed method is applied to the CGAM system as a benchmark. Eventually, the results of the first and second approaches show that the total cost of products can be reduced 4.1% (from 22.270 $/GJ to 21.358 $/GJ) and also the risk of the cost of the products can be reduced 5.8% (from 25.8% to 24.3%).An Exact Analytical Solution for Heat Conduction in a Functionally Graded Conical Shell
https://jacm.scu.ac.ir/article_16222.html
In this study, an exact analytical solution for the heat conduction problem in a truncated conical shell is presented. The cone is made of functionally graded materials and it is considered that the material properties vary according to power-law functions. The general thermal boundary conditions are applied to cover a wide variety of actual applications. The results are successfully validated. Two examples, which are tried to mimic practical conditions, are studied using the derived solution, and a parametric study is done to shed light on the problem. The outcomes of this research provide useful information for understanding the nature of heat transfer behavior in the specific geometry of a cone. Regarding the specific applications of conical shells, the results can be used in the prefabrication process of these shells and tailoring the design parameter of functionally graded materials.A Novel Approach to Compute the Numerical Solution of Variable Coefficient Fractional Burgers' Equation with Delay
https://jacm.scu.ac.ir/article_16487.html
In this article, we come up with a novel numerical scheme based on Haar wavelet (HW) along with nonstandard &lrm;finite difference (NSFD) scheme to solve time-fractional Burgers&rsquo; equation with variable diffusion coefficient and &lrm;time delay. In the solution process, we discretize the fractional time derivative by NSFD &lrm; formula and spatial &lrm;derivative by HWs series expansion. We use the quasilinearisation process to linearize the nonlinear term. Also, &lrm;the convergence of the scheme is discussed. The efficiency and correctness of the proposed scheme are assessed &lrm;by &lrm;L&infin;-error and L2&lrm; &lrm;-error norms.&lrm;Behavior of Nanofluid with Variable Brownian and Thermal Diffusion Coefficients Adjacent to a Moving Vertical Plate
https://jacm.scu.ac.ir/article_16488.html
This work was motivated by studying the behavior of nanofluid adjacent to a moving vertical plate. A non-homogeneous distribution of nanoparticles inside the boundary layer was considered with variable Brownian and thermal diffusion coefficients throughout the layer. Employing group similarity transformation method transformed the governing mathematical model into a system of ordinary differential equations. The resultant system was numerically solved using shooting method. The numerical investigation was carried out for different parameters namely: Prandtl number, Pr, temperature difference ratio, &Upsilon;, and the ratio of nanoparticles volumetric fraction difference, &Upsilon;&phi;, and the attained results were illustrated graphically to examine their effect on different fluid characteristics. The results showed that increasing Pr values decreased the nanofluid velocity, shear stress, temperature distribution and nanoparticles volumetric fraction, while it increased the heat flux and nanoparticles gradient inside the boundary layer. On the other hand, increasing&nbsp;&Upsilon; values increased the nanofluid velocity, shear stress and heat flux but it decreased the temperature distribution. Also, increasing &Upsilon;&phi;&nbsp;values decreased the nanofluid velocity, shear stress and temperature distribution but it increased the heat flux. The characteristics of nanofluids were studied to enhance the thermal conductivity and the efficiency of heat transfer systems. A comparison between the obtained results and the previous published results indicated an excellent agreement.Temperature Dependent Damping in Additively Manufactured Polymer Structures
https://jacm.scu.ac.ir/article_16492.html
Temperature effects are predominantly ignored when computing the dynamic response of structures. Yet, in applications where large changes in temperature occur, the dynamic response can drastically change. This is particularly true for polymers. While the temperature effects on modulus and loss factor are often available for most polymers, this change is not addressed or corrected for. Meanwhile, the recent research on additively manufactured polymer metastructures has yet to consider the effects of temperature change on their ability to suppress vibrations. In order to fill this gap, the study presented in this paper focuses on the effects of temperature change on additively manufactured structures.MHD Non-Newtonian Fluid Flow past a Stretching Sheet under the Influence of Non-linear Radiation and Viscous Dissipation
https://jacm.scu.ac.ir/article_16509.html
This work reports the heat and mass transfer of the 2- D MHD flow of the Casson and Williamson motions under the impression of non-linear radiation, viscous dissipation, and thermo-diffusion and Dufour impacts. The flow is examined through an extending zone along with inconsistent thickness. The partial differential equations are extremely nonlinear and lessen to ODEs throughout of the appropriate similarity transformation. The system of nonlinear and coupled ODEs is handled applying a numerical approach with shooting procedure. Numerical solutions for momentum and energy descriptions are deliberated through graphs and tabular form for the impacts of magnetic parameter, Soret and Dufour variables, momentum power index variable, Schmidt number, wall thickness variable, without dimensions velocity slip, heat jump and mass jump variable. Outcomes illustrate that the momentum, temperature, and concentration transfer of the laminar boundary layers of equally non-Newtonian liquid motions are non-consistent. A comparison made with the existing literature which shows an good agreement and confidence of the present outcomes. It shows that Casson parameter restricted the skin friction, local heat and mass transfer while l enhanced the skin friction, local heat and mass transfer. Velocity slip constant decreases the skin friction, local heat and mass transfer and a similar observation for thermal slip constant while an opposite phenomena for the solutal slip constant.&nbsp;How Wavelike Bumps Mitigate the Vortex-induced Vibration of a Drilling Riser
https://jacm.scu.ac.ir/article_16515.html
In this paper, computational fluid dynamics is used to study how wavelike bumps influence the suppression of drilling-riser vortex-induced vibration (VIV). The numerical model involves two-dimensional unsteady incompressible turbulent flow around a cylinder, with the flow characteristics regarded as being constant. The results show that wavelike bumps are effective in mitigating the VIV, but the degree of mitigation does not increase indefinitely with the number of bumps. The mitigation is greatest with either 5 or 7 wavelike bumps, reducing the vibration amplitudes of the cylinder in the in-line and cross-flow directions to negligible levels. To know how equipping a circular cylinder with wavelike bumps affected its VIV response, cases with wavelike bumps of 1, 3, 5, 7, 9, and 11 are studied.&nbsp;Four Legged Guará Robot: From Inspiration to Implementation
https://jacm.scu.ac.ir/article_16560.html
Design of legged robots is still an open problem with several implementation challenges and there is little material available to guide new designs. Moreover, usually the actuator sets of the robot are heavy and bulky and are placed near the joints, which increases the weight and inertia of the legs and consequently results in instability, slower movement and high energy consumption. This paper presents the design, modeling, and control of the Guar&aacute;, a sixteen-degree-of-freedom (DOF) legged robot, covering all stages of development of a quadruped robot, including experiments with a prototype. The system is composed by four legs, each one with 4 DOF. To reduce the leg&rsquo;s weight and inertia, here we present a design concept for the legs where the actuators are positioned on the robot platform and timing belt transmissions are used to drive the joints. Moreover, the design of the legs mimics the human leg by presenting the knees faced forward and its locomotion pattern mimics the quadruped wave gait. With this configuration, the robot is able to walk on straight lines or free curved paths. The control system of the robot consists of a high-level state machine and a lower level PID position controller. The electronics are embedded over a flat platform coupled to the legs. The kinematics of the robot was studied and an integrated environment was provided for walking simulation, adjustment, and diagnosis of operation. The experimental results are focused on the kinematics of the legs and the stability of the robot and show a good agreement between the designed and executed movements. This paper is presented as a framework that can be generalized to other systems and can be a useful reference for the design of other legged robots.Effect of Temperature and Moisture on the Impact Behaviour of Adhesive Joints for the Automotive Industry
https://jacm.scu.ac.ir/article_16573.html
This study focuses on evaluating the impact of aluminum adhesive joints as a function of temperature and moisture, in an effort to understand how these conditions affect their mechanical properties and behavior. After preparing the required specimens (using two different adhesives and adherend thicknesses), several tests have been made in order to determine these properties and compare their values to the predictions made using analytical methods. These tests were repeated with several distinct combinations of temperatures and moisture levels so that the effect of these properties can be properly interpreted. It was observed that higher temperatures strongly increase the ductility of the adhesive but mixed with moisture this can degrade them. Moisture can increase the energy absorbed through increased plastic deformation of the adhesive and improve behaviour at low temperatures.Solving Duffing-Van der Pol Oscillator Equations of Fractional Order by an Accurate Technique
https://jacm.scu.ac.ir/article_16575.html
In this paper, an accurate technique is used to find an approximate solution to the fractional-order Duffing-Van der Pol (DVP, for short) oscillators equation which is reproducing kernel Hilbert space (RKHS, for short ) method. The numerical results show that the n-term approximation is a rapidly convergent series representation and they present also the high accuracy and effectiveness of this method. The efficiency of the proposed method has been proved by the theoretical predictions and confirmed by the numerical experiments.Dynamically Consistent NSFD Methods for Predator-prey System
https://jacm.scu.ac.ir/article_16577.html
In this paper, we introduce two nonstandard finite difference (NSFD) methods for solving the mathematical model of the Rosenzweig-MacArthur predator-prey system. These new proposed numerical methods have important features such as positivity and elementary stability. Numerical comparisons between the proposed methods and the other methods such as second-order and forth order Runge-Kutta methods (we refer them RK2 and RK4, respectively), Euler method, and NSFD method presented in [6] indicate that the new methods have better accuracy and convergence.On Integrability up to the Boundary of the Weak Solutions to a Class of non-Newtonian Compressible Fluids with Vacuum
https://jacm.scu.ac.ir/article_16582.html
In this paper, we study the integrability up to the boundary of the weak solutions of non-Newtonian compressible fluid with a nonlinear constitutive equation in ℝ3 bounded domain. Galerkin approximation will be used for existence of weak solutions and by applying the bounded linear operator B, introduced by Bogovskii, we prove the square integrability of the density up to the boundary.Nonlinear Vibration of an Electrostatically Actuated Functionally Graded Microbeam under Longitudinal Magnetic Field
https://jacm.scu.ac.ir/article_16607.html
In this work, we develop a model of an electrostatically actuated functionally graded (FG) microbeam under a longitudinal magnetic field based on the Euler-Bernoulli beam and nonlocal strain gradient theories to investigate the nonlinear vibration problem. The FG microbeam is placed between two electrodes, a DC voltage applied between the two fixed electrodes causes an electrostatic force to be exerted on the FG microbeam. The FG microbeam is composed of metal and ceramic in which the properties of these materials are assumed to change in the thickness direction according to the simple power-law distribution. The Galerkin method and the Hamiltonian Approach are employed to find the approximate frequency of the FG microbeam. The accuracy of the present solution is verified by comparing the obtained results with the numerical results and the published results in the literature. Effects of the power-law index, the material length scale parameter, the nonlocal parameter, the applied voltage and the magnetic force on the nonlinear vibration behaviour of the FG microbeam are studied and discussed.Description of Anomalous Behavior of Aluminum Alloys with Hill48 Yield Criterion by Using Different Experimental Inputs and Weight Coefficients
https://jacm.scu.ac.ir/article_16651.html
The anomalous behavior of aluminum alloys is modeled with quadratic Hill48 yield criterion in this study. An identification method based on minimization of the error function is applied and the effect of the number of experimental input and weight coefficients used in the identification are investigated. Two highly anisotropic aluminum alloys (AA2090-T3 and AA5182-O) are selected in the study. Firstly, Hill48 parameters are determined with four different experimental data set, then the effect of the weight coefficients for each set is investigated. In-plane variations of plastic properties and yield surfaces of the materials are predicted with determined Hill48 parameters and the most appropriate pair (experimental data set and weight coefficient) are selected by comparison of the predicted results with experiment.&nbsp;On the Effect of the End-effector Point Trajectory on the Joint Jerk of the Redundant Manipulators
https://jacm.scu.ac.ir/article_16660.html
This paper is focused on investigating the joints jerk of industrial serial redundant manipulators with 6 degrees of freedom (6-DOF) under the variation of the end-effector point (EEP) trajectory in the workspace. The EEP trajectories are initially built in the basic planes because of their simplicity, verification and experimentation are smooth, and most of the actual welded structures are performed on these basic planes. The jerk is determined by solving the inverse kinematics problem of the redundant system. This problem is solved based on the algorithm which is used for adjusting the increments of the generalized coordinate vector (AGV). The efficiency of this algorithm is shown through the error between a given trajectory and the recalculated trajectory through the forward kinematics problem. The result of this study allows us to evaluate the effect of the change of the trajectory on the kinematics characteristics of the robot in general and the jerk of the joints in particular. On the other hand, these results can be used as the basis for planning the EEP trajectory for redundant robots, developing algorithms to reduce joint jerky, increase the life of robot systems, and improve the accuracy of the redundant robot movement.Free Vibration Analysis of Functionally Graded Porous Nano-plates with Different Shapes Resting on Elastic Foundation
https://jacm.scu.ac.ir/article_16661.html
This paper proposes a finite element method (FEM) based on a nonlocal theory for analyzing the free vibration of the functionally graded porous (FGP) nano-plate with different shapes lying on the elastic foundation (EF). The FGP materials with two-parameter are the power-law index (k) and the porosity volume fraction (&xi;) in two cases of even and uneven porosity. The EF includes Winkler stiffness (k1) and Pasternak stiffness (k2). Some numerical results in our work are compared with other published to verify accuracy and reliability. Moreover, the influence of geometric parameters, materials on the free vibration of the FGP nano-plates resting on the EF is comprehensively investigated.Nonstandard Dynamically Consistent Numerical Methods for MSEIR Model
https://jacm.scu.ac.ir/article_16581.html
In this paper, two numerical methods for solving the MSEIR model are presented. In constructing these methods, the non-standard finite difference strategy is used. The new methods preserve the qualitative properties of the solution, such as positivity, conservation law, and boundedness. Numerical results are presented to express the efficiency of the new methods.Theoretical Investigation of Viscosity and Thermal Conductivity of a Gas along a Non-isothermal Vertical Surface in Porous Environment with Dissipative Heat: Numerical Technique
https://jacm.scu.ac.ir/article_16667.html
The prime objective of the current investigation is to explore the variation of viscosity and thermal conductivity impacts on MHD convective flow over a moving non-isothermal vertical plate in presence of the viscous-dissipative heat and thermal-radiation. The compatible transformation of similarity are employed to obtain the non-linear ODE with the appropriate boundary conditions from the governing equations and the numerical solution of the boundary value problem so obtained are solved via MATLAB bvp4c solver. Naturally, the fluid viscosity and thermal-conductivity may vary from liquid to metal with temperatures and therefore, the impact of viscosity and thermal-conductivity in this investigation is quite significant. The physical parameters along with several influences on momentum, temperature, and concentration are explicated and portrayed with graphs. In addition, the velocity, temperature and concentration gradients at the surface are evaluated and displayed in tabular form. A decent agreement is found in the present outcomes with previously issued work. Furthermore, it is found that the growth of the thermal-radiation increases the gas temperature. The present study is useful for various industrial applications like metal and polymer extrusion, continuous casting, cooling process, nuclear plant and many more.Numerical Investigation of an Unsteady and Anisotropic Turbulent Flow Downstream a 90° Bend Pipe with and without Ribs
https://jacm.scu.ac.ir/article_16671.html
In this work, a numerical study of the dynamical behavior of unsteady and anisotropic turbulent flow downstream a 90&deg; bended pipe was presented. For this purpose, comparative computations are carried out employing two flow configurations, bend pipe with ribs and bend pipe without ribs with a curvature radius ratio Rc/D=2.0. In the bend pipe with ribs, the pitch ratios Pt/e=40 and the rib height to pipe diameter e/D is 0.1. This model has been utilized to assess the effect of ribs on flow where the presence of the ribs leads to a complex velocity field with regions of flow separation upstream and downstream of the ribs. The Reynolds-Averaged Navier&ndash;Stokes (RANS) approach is employed and the computational model is validated by comparisons with the existing experimental data. The simulations are conducted with the commercials CFD software FLUENT for Dean number varying from 5000 to 40000. The result analysis shows that the higher resistance generated by the ribs produced relatively larger velocity gradient (&part;U/&part;y) compared to the case of bend pipe without ribs where a more uniform mean velocity profile is observed. The turbulence intensities are higher in the ribbed bend pipe compared to those in the non-ribbed case and depend faintly on the Dean number. The levels of the Reynolds shear stresses are significantly enhanced by the ribs compared to the case without ribs. This increasing is explained by significantly higher levels of turbulence production over those ribs produced by large values of &part;U/&part;y.Nonlinear Multiscale Modelling and Design using Gaussian Processes
https://jacm.scu.ac.ir/article_16678.html
A method for nonlinear material modeling and design using statistical learning is proposed to assist in the mechanical analysis of structural materials. Conventional computational homogenization schemes are proven to underperform in analyzing the complex nonlinear behavior of such microstructures with finite deformations. Also, the higher computational cost of the existing homogenization schemes inspires the inception of a data-driven multiscale computational homogenization scheme. In this paper, a statistical nonlinear homogenization scheme is discussed to mitigate these issues using the Gaussian Process Regression technique. A data-driven model is trained for different strain states of microscale unit cells. In the macroscale, nonlinear response of the macroscopic structure is analyzed, for which the stresses and material responses are predicted by the trained surrogate model.A Generalized Identification of Joint Structural State and Unknown Inputs Using Data Fusion MKF-UI
https://jacm.scu.ac.ir/article_16680.html
The classical Kalman filter (KF) can estimate the structural state online in real time. However, the classical KF presupposes that external excitations are known. The existing methods of Kalman filter with unknown inputs (KF-UI) have limitations that require observing the acceleration response at the excitation point or assuming the unknown force. To surmount the above defects, an innovative modal Kalman filter with unknown inputs (MKF-UI) is proposed in this paper. Modal transformation and modal truncation are used to reduce the dimensionality of the structural state, and the accelerations at the excitation positions do not need to observe. Besides, the proposed MKF-UI does not require the assumption of unknown external excitation. Therefore, the proposed approach is suitable for the generalized identification of dynamic structural states and unknown loadings. The effectiveness and feasibility of the proposed identification approach are ascertained by some numerical simulation examples.Numerical and Experimental Investigation on Post-buckling Behavior of Stiffened Cylindrical Shells with Cutout subject to Uniform Axial Compression
https://jacm.scu.ac.ir/article_16692.html
In this paper, post buckling behavior of thin steel and aluminum cylindrical shells with rectangular cutouts under axial loading was studied experimentally and also using the finite element method. Riks method is used for analyzing the cylindrical shells. The effect of longitudinal and circumferential stiffeners (ribs and stringer) was studied on the buckling load and the post buckling behavior as the stiffeners used individually and in combination with each other. It was shown that by adding stringer, the buckling load improves and the rib has a positive effect on the post buckling behavior of the structure. Some tests were performed by ZwickRoell tensile/compression testing machine and it was carried out for both types of steel and aluminum shells with and without stiffeners. Comparing the experimental results with the FEA results shows good agreement. Nonlinear analysis of cylindrical steel and aluminum shells with cutout have demonstrated that, in some cases, a local buckling called snap-back can be seen in the load-displacement path. Snap-back which is a decrease in the amount of both load and displacement indicates this local buckling. This phenomenon is because of appearing mode shapes sequentially during the numerical buckling analysis of shells. Although these local buckling happened, the structure is still endured the higher loads.Variational Principles and Solitary Wave Solutions of Generalized Nonlinear Schrödinger Equation in the Ocean
https://jacm.scu.ac.ir/article_16696.html
Internal solitary waves are very common physical phenomena in the ocean, which play an important role in the transport of marine matter, momentum and energy. Because the generalized nonlinear Schr&ouml;dinger equation can well explain the effects of nonlinearity and dispersion in the ocean, it is more suitable for describing the deep-sea internal wave propagation and evolution than other mathematical models. At first, by designing skillfully the trial-Lagrange functional, different kinds of variational principles are successfully established for a generalized nonlinear Schr&ouml;dinger equation by the semi-inverse method. Then, the constructed variational principles are proved correct by minimizing the functionals with the calculus of variations. Furthermore, some kinds of internal solitary wave solutions are obtained and demonstrated by semi-inverse variational principle for the generalized nonlinear Schr&ouml;dinger equation.Stability Analysis of Articulated Bus in Straight-ahead Running Manoeuvre
https://jacm.scu.ac.ir/article_16702.html
A comprehensive study on the stability of a planar linearized single-track model of a two-section pusher articulated bus is presented with the aid of a complete set of stability maps. The two sections of the vehicle model are connected at the hitch point by a revolute joint; an equivalent visco-elastic characteristic function describes its rotational visco-elastic properties, playing a major role in stability control and therefore in passive safety. The equations of motion are derived in analytical form, allowing easy implementation of the non-linear model (eventually including a non-linear viscoelastic characteristic functions of the joint). Stability of the linearized model is then studied in equilibrium configurations by means of sensitivity analysis with respect to the model&rsquo;s governing parameters. Stability maps are drawn on the basis of sets of parameter values related to straight-ahead running, steady-state manoeuvres. The most important parameters controlling the onset of unstable motions are identified, paying attention to the role played by the equivalent rotational damping coefficient and the equivalent torsional stiffness characterizing the connection joint, with the aim of finding criteria for its design.Free Convection of Micropolar Fluid over an Infinite Inclined Moving Porous Plate
https://jacm.scu.ac.ir/article_16703.html
The present paper analyzes free convective heat and mass transfer of non-conducting micropolar fluid flow over an infinitely inclined moving porous plate in the presence of heat source and chemical reaction. Moreover, the effect of thermal radiation is also taken care of in the same study. The present investigation is relevant to the fabrication system in industries corresponding to the materials composed with high-temperature. Similarity technique is adopted with similarity variable to transform the non-dimensional form of the partial differential equations into ordinary differential equations. To get the approximate solution of these transformed complex nonlinear set of ODEs we have employed fourth order Runge&ndash;Kutta method in conjunction with shooting technique. The validation of the present result as well as critical issues is addressed in the discussion section refereeing to the previously published work as a particular case. The behavior of physical parameters governs the flow phenomena are displayed via graphs and tables.Parametric Optimization of a Cyclogiro Aircraft Design for Efficient Hover with Aeroelastic Considerations
https://jacm.scu.ac.ir/article_16704.html
A minimization procedure is proposed to orient the design of a vertical take-off and landing drone towards sustainability. The vehicle is a novel cycloidal rotor drone and the principal objective is to yield the best ratio of payload to power consumption. The drone blades, rotor arms, and frame are designed for fused deposition modeling additive manufacturing with polylactic acid. 10 variables for the geometry, operation parameters, and material infill percentages are explored in search of the optimum design. A special derivation procedure allows obtaining the symbolic equations for the weight and power consumption of the drone. This permits optimization with a hybrid genetic and gradient method and exploring a broad range of aircraft sizes. 7 constraint equations ensure that the necessary assumptions made for the derivation remain valid and that the structural strength is adequate. For each new configuration, this method allows to quickly find a new optimum design using a desktop computer. Also, modifying the constraints, variables, or objective function is straightforward. Finally, the resulting design has a power loading of 0.0876 N/W.Finite Element Modelling and Simulation of the Hysteretic Behaviour of Single- and Bi-metal Cantilever Beams using a Modified Non-linear Beta-damping Model
https://jacm.scu.ac.ir/article_16709.html
This paper explores a novel non-linear hysteresis model obtained from the modification of the conventional Kelvin-Voigt model, to produce a non-viscous hysteretic behaviour that is closer to metal damping. Two case studies are carried out for a vibrating cantilever beam under tip loading (bending), the first considering a single uniform material and the second considering a bimetallic structure. The damping behaviour is studied in the frequency domain (constant damping ratio model vs. Kelvin-Voigt/ beta damping model) and time-domain (proposed modified hysteresis model vs. Kelvin-Voigt/ beta damping model). In the frequency domain, it was found that the Kelvin-Voigt model essentially damps out the displacement response of the modes more than the constant damping ratio model does. In the transient analysis, the Kelvin-Voigt model likewise produced unnaturally rapid damping of the oscillations for both the single- and bi-metal beam, compared to the modified hysteretic damping model, which produced a damping behaviour closer to actual metal behaviour. This was consistent with results obtained in the frequency domain.Potential of Semi-Empirical Heat Transfer Models in Predicting the Effects of Equivalence Ratio on Low Temperature Reaction and High Temperature Reaction Heat Release of an HCCI Engine
https://jacm.scu.ac.ir/article_16712.html
In this paper, the influence of equivalence ratio on the low-temperature reaction heat release (LTR-HR) and high-temperature reaction heat release (HTR-HR) of homogeneous charge compression ignition engine has been experimentally and numerically examined. The numerical study was performed using zero-dimensional (0D) single-zone model by considering the chemical kinetic of fuel combustion. Annand, Woschni, Hohenberg, Chang (Assanis), and Hensel semi-empirical heat transfer models were employed in the 0D single-zone simulations. In this study, the in-cylinder pressure, rate of heat release, LTR-HR and HTR-HR were investigated. The Hensel heat transfer model was the only model that predicted the combustion in all of the operating conditions. The Hohenberg model properly recognized the effects of equivalence ratio changes on the HTR-HR.Stress Mode Superposition for a Priori Detection of Highly Stressed Areas: Mode Normalisation and Loading Influence
https://jacm.scu.ac.ir/article_16742.html
From the economic and technical point of view, the reduction of development periods and required resources represent a considerable benefit. For the reduction of numerical effort and processed data in numerical stress analysis, the present paper is focused onto the investigation of an efficient method for the a priori detection of a structural component&rsquo;s highly stressed areas. Based on the theory of stress mode superposition and the frequency domain solution of the decoupled equations of motion, an analytically consistent approach for a priori mode superposition is presented. In this context, the influence of multiaxial loading and mode normalisation is investigated. Validation is performed on a simplified industrial model of a twist-beam rear axle.A Novel Flexible Lane Changing (FLC) Method in Complicated Dynamic Environment for Automated Vehicles
https://jacm.scu.ac.ir/article_16757.html
Decision making and path planning in case of highly transient dynamics of the surrounding as well as the effect of road condition are the issues that are not completely solved in the previous researches. The goal is to perform a safe and comfortable lane change that includes flexible re-planning capabilities. In this paper, a novel structure for path planning and decision making part of a vehicle automatic lane change has been introduced which comprehensively considers both longitudinal and lateral dynamics of the vehicle. The presented method is able to perform re-planning even in the middle of a lane change maneuver according to new traffic condition. Inclusion of the dynamics of all involved vehicles and providing online performance are the other advantages of the proposed system. The algorithm is simulated and various scenarios are constructed to evaluate the efficiency of the system. The results show that the system has completely acceptable performance.The Dynamics of the Working Body of the Tubular Conveyor with the Chain Drive
https://jacm.scu.ac.ir/article_16759.html
The theoretical calculations of the dynamics of the conveyor drive chain oscillations for different speeds of bulk material movement as a result of motion internal perturbations have been presented in the article. Resonant oscillations have been studied. It has been established that the amplitude of the transition through the resonance is greater for higher speeds of the conveyor drive chain and the maximum dynamic tension in the chain increases with increasing speed of transportation of bulk material. The dependences of the natural frequency of the system "drive chain of the conveyor line - grain" on the parameters of the system and the amplitude, as well as the amplitude of the resonant oscillations of the system on the speed of grain movement have been obtained. The dependence of the resonance amplitude of the system "conveyor chain drive - grain mass" on the speed of the drive chain at certain parameters has been determined. Taking into account the obtained theoretical data, an improved construction of a tubular chain conveyor with various working bodies and stand equipment using the Altivar 71 frequency converter for complex tasks of the electric drive from 0.75 to 630 kW has been developed. The experimental researches have been carried out and the dependences for definition of productivity and a rotation moment at transportation by the tubular scraper conveyor on curvilinear routes for loose material (wheat and peas) have been received.Alternative Integration Approaches in the Weight Function Method for Crack Problems
https://jacm.scu.ac.ir/article_16772.html
This study proposes two alternative approaches to complement existing integration strategies used in the weight function method for linear elastic crack problems. The first approach is based on an interpolation type integration scheme and the second approach is based on Gauss quadrature. The proposed approaches enable a computationally efficient numerical integration for computing stress intensity factors in 2D fracture problems. The efficiency is gained through a comparatively low number of integration points facilitated by higher-order approximation. The integration weights only need to be computed once for a given crack length-to-width ratio and can be applied to arbitrary continuous and smooth stress distributions. The proposed approaches show excellent accuracy. In particular, the Gauss quadrature approach exhibits several orders of magnitude more accuracy compared to the most commonly used trapezoidal integration.Performance Investigation of Simple Low-dissipation AUSM (SLAU) Scheme in Modeling of 2-D Inviscid Flow in Steam Turbine Cascade Blades.
https://jacm.scu.ac.ir/article_16773.html
This study evaluated the performance of the SLAU, AUSM+UP upwind schemes, and CUSP artificial dissipation scheme for the flow through the convergent-divergent nozzles and turbine stator blades under different pressure ratios by developing an in-house code. By comparing the results with analytical and experimental results, it was found that, despite the simplicity of the SLAU scheme in the absence of tuning variables, it provided reasonable predictions for different turbine blades in point of location and strength of the shocks. Moreover, the SLAU scheme could converge at a much higher rate, leading to very much lower values of residuals. The SLAU scheme caused about 30% and 20% improvements over the prediction of the shock-induced losses in supersonic and subsonic outlet flows, respectively.