Journal of Applied and Computational Mechanics
https://jacm.scu.ac.ir/
Journal of Applied and Computational Mechanicsendaily1Fri, 01 Apr 2022 00:00:00 +0430Fri, 01 Apr 2022 00:00:00 +0430Topology 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.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.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.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.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.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.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.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.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.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;.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.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.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.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.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.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.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.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.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.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.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;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.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.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.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.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;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.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;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 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.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.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.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.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 evaluates 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 is found that, despite the simplicity of the SLAU scheme in the absence of tuning variables, it provides reasonable predictions for different turbine blades in point of location and strength of the shocks. The SLAU scheme could converge at a much higher rate, leading to very much lower values of residuals. The SLAU scheme causes about 30% and 20% improvements over the prediction of the shock-induced losses in supersonic and subsonic outlet flows, respectively.Theoretical Study on Poiseuille Flow of Herschel-Bulkley Fluid in Porous Media
https://jacm.scu.ac.ir/article_16840.html
This theoretical study analyses the effects of geometrical and fluid parameters on the flow metrics in the Hagen-Poiseuille and plane-Poiseuille flows of Herschel-Bulkley fluid through porous medium which is considered as (i) single pipe/single channel and (ii) multi&ndash;pipes/multi-channels when the distribution of pores size in the flow medium are represented by each one of the four probability density functions: (i) Uniform distribution, (ii) Linear distribution of Type-I, (iii) Linear distribution of Type-II and (iv) Quadratic distribution. It is found that in Hagen-Poiseuille and plane-Poiseuille flows, Buckingham-Reiner function increases linearly when the pressure gradient increases in the range 1 - 2.5 and then it ascends slowly with the raise of pressure gradient in the range 2.5 - 5.In all of the four kinds of pores size distribution, the fluid&rsquo;s mean velocity, flow medium&rsquo;s porosity and permeability are substantially higher in Hagen-Poiseuille fluid rheology than in plane-Poiseuille fluid rheology and, these flow quantitiesascend considerably with the raise of pipe radius/channel width and a reverse characteristic is noted for these rheological measures when the power law index parameter increases.The flow medium&rsquo;s porosity decreases rapidly when the period of the pipes/channels distribution rises from 1 to 2 and it drops very slowly when the period of the pipes/channels rises from 2 to 11.A Deep Learning Approach to Predict the Flow Field and Thermal Patterns of Nonencapsulated Phase Change Materials Suspensions in an Enclosure
https://jacm.scu.ac.ir/article_16903.html
The flow and heat transfer of a novel type of functional phase change nanofluids, nano-&lrm;encapsulated phase change suspensions, is investigated in the present study using a deep neural &lrm;networks framework. A deep neural network was used to learn the natural convection flow and &lrm;heat transfer of the phase change nanofluid in an enclosure. A dataset of flow and heat transfer &lrm;samples containing 3290 samples of the flow field and temperature distributions was used to &lrm;train the deep neural network. The design variables were fusion temperature of nanoparticles, &lrm;Stefan number, and Rayleigh number. The results showed that the proposed combination of a &lrm;feed-forward neural network and a convolutional neural network as a deep neural network could &lrm;robustly learn the complex physics of flow and heat transfer of phase change nanofluids. The &lrm;trained neural network could estimate the flow and heat transfer without iterative and costly &lrm;numerical computations. The present neural network framework is a promising tool for the design &lrm;and prediction of complex physical systems&lrm;.Theoretical Study of Convective Heat Transfer in Ternary Nanofluid Flowing past a Stretching Sheet
https://jacm.scu.ac.ir/article_16910.html
A new theoretical tri-hybrid nanofluid model for enhancing the heat transfer is presented in this article. This model explains the method to obtain a better heat conductor than the hybrid nanofluid. The tri-hybrid nanofluid is formed by suspending three types of nanoparticles with different physical and chemical bonds into a base fluid. In this study, the nanoparticles TiO2, Al2O3 and SiO2 are suspended into water thus forming the combination TiO2-SiO2-Al2O3-H2O. This combination helps in decomposing harmful substances, environmental purification and other appliances that requires cooling. The properties of tri-hybrid nanofluid such as Density, Viscosity, Thermal Conductivity, Electrical Conductivity and Specific Heat capacitance are defined mathematically in this article. The system of equations that governs the flow and temperature of the fluid are converted to ordinary differential equations and are solved using RKF-45 method. The results are discussed through graphs and it is observed that the tri-hybrid nanofluid has a better thermal conductivity than the hybrid nanofluid.A Modified Couple Stress-Based Model for the Nonlinear Vibrational Analysis of Nano-Disks Using Multiple Scales Method
https://jacm.scu.ac.ir/article_16935.html
In this article, the nonlinear vibrational behavior of a nano-disk was analyzed using the multiple scales method (MSM). The modified couple stress theory was used to consider the small-scale effect via the application of nonlocal parameter. Employing Hamilton's principle, two coupled nonlinear differential equations were derived based on the nonlinear von-K&aacute;rm&aacute;n strain-displacement relation and the classical plate theory. The Galerkin-based procedure was utilized to obtain a Duffing-type nonlinear ordinary differential equation with a cubic nonlinear term and solved by the application of MSM. The effects of nonlocal parameter, aspect ratio, different boundary conditions, and the nonlinear shift frequencies, were obtained on the overall behavior of the nano-disk. Results indicate that increasing the central dimensionless amplitude of the nano-disk, the nonlinear frequency, and the shift index exhibit an increasing behavior, while the increase in the non-dimensional nonlocal parameter, causes a decrease in the nonlinear frequency ratios and the shift index. Additionally, the increase in h/r increases the effect of dimensionless central amplitude on the nonlinear frequencies ratios. Additionally, comparison of the current results with those previously published in the literature shows good agreements. This indicates that the MSM can ease up the solution, and hence, can be applied to the solution of nonlinear nano-disks with high accuracy.Numerical Study on the Ferrofluid Droplet Splitting in a T-junction with Branches of Unequal Widths using Asymmetric Magnetic Field
https://jacm.scu.ac.ir/article_16956.html
Research on the microdroplet splitting phenomenon has intensified in recent years. Microdroplet splitting has numerous applications in chemical synthesis, biology, and separation processes. The current paper covers the numerical study of ferrofluid microdroplet splitting at various lengths and velocities inside the T-junction with branches of unequal widths under asymmetric magnetic fields. Microdroplet splitting can be controlled by using an asymmetric magnetic field and the asymmetry in the width of T-junctions branches. Three geometrical models of the T-junction with different widths ratio (0.7, 0.85, and 1), along with a magnetic field with various intensities are studied. This magnetic field is generated by a line dipole. In this study, the distance between the dipole and origin is kept constant. The splitting ratio of ferrofluid microdroplets at different velocities (different capillary numbers), different non-dimensional lengths and different magnetic force (different magnetic Bond numbers) at the center of T-junction are calculated for each amount of branch width. The results are verified with previous works and their correctness is proved. The splitting ratio is defined as the volumetric ratio of the larger daughter droplet to the mother droplet. The results indicate that generally, the stronger the asymmetric magnetic force is, the more asymmetric the splitting will become, with the splitting ratio becoming closer to 1. Also, as asymmetry increases between the widths of the two branches of the T-junction, the splitting ratio approaches 1.The Direct Impact Method for Studying Dynamic Behavior of Viscoplastic Materials
https://jacm.scu.ac.ir/article_17187.html
This work is devoted to the direct impact method for determining the deformation diagrams of viscoplastic materials at high strain rates. As the conventional Split Hopkinson Pressure Bar method, the direct impact method is based on the measuring bar technique. The description of the experimental scheme and the traditional experimental data proceeding method are given. The description and the results of numerical analysis of the direct impact scheme are presented. A modified procedure for processing experimental information is proposed which allows to expand the area of correct calculation of strains in the specimen according to the experimental data obtained by the direct impact method. As an illustration the deformation diagrams of copper S101 and aluminum alloy D16T in the strain rate range from 1000 to 10000 s-1 have been obtained using the Split Hopkinson Pressure Bar method and the direct impact method. The use of the direct impact method made it possible to obtain deformation curves at strain rates an order of magnitude higher than the conventional SHPB method. The range of studied plastic deformations is increased by 4 times for the case of copper and 3 times for aluminum alloy.Direct Transcription Approach to Dynamic Optimization Problems in Engineering
https://jacm.scu.ac.ir/article_17192.html
The direct transcription method that employs global collocation at Legendre-Gauss-Radau points is addressed and applied to infinite-dimensional dynamic optimization problems in engineering. The formulation of these latter is considered referring to a Bolza-type performance index. A reduced unconstrained form of it is particularly studied in the pseudospectral domain and the continuous-to-discrete conversion is thoroughly discussed. An equivalent finite-dimension nonlinear programming problem is therefore obtained and hints on its numerical implementation are given. Eventually, a few benchmark historical problems in engineering are revisited, stated, numerically solved and compared to literature.A Stress Tensor-based Failure Criterion for Ordinary State-based Peridynamic Models
https://jacm.scu.ac.ir/article_17214.html
Peridynamics is a recent nonlocal theory of continuum mechanics that is suitable to describe fracture problems in solid mechanics. In this paper, a new failure criterion based on the stress field is developed by adopting the damage correspondence model in the ordinary state-based peridynamic theory. The proposed stress tensor-based failure criterion is capable of predicting more accurately crack propagation in the mixed mode I-II fracture problems different from other failure criteria in peridynamics. The effectiveness of the proposed model is demonstrated by performing several examples of mixed-mode dynamic fracture in brittle materials.Lamb Wave Analysis in Anisotropic Multilayer Piezoelectric-piezomagnetic Material
https://jacm.scu.ac.ir/article_17215.html
The dynamic response of an anisotropic multilayer magneto-electro-elastic (MEE) plate due to an external excitation is investigated in this work, using the stiffness matrix approach. A parametric study is performed by varying the stacking sequence, polarization direction, boundary conditions, and interlayer thickness. The proposed method yields the numerical estimation of the dispersion curve and the free vibration of the Lamb waves for different crystallographic orientations and magneto-electric boundary conditions. It is demonstrated that the anisotropy highly affects the dispersion curve and the non-dimensional frequency, and also decreases the interlayer thickness of the magneto-electro-elastic multilayer and raises the phase velocity of the fundamental symmetric Lamb mode vibration. The key outcomes of this research can serve as a reference in the design and analysis of new smart magneto-electro-elastic structures.Spectral Methods Application in Problems of the Thin-walled Structures Deformation
https://jacm.scu.ac.ir/article_17220.html
The spectral method (p-FEM) is used to solve the problem of a thin-walled structure deformation, such as a stiffened panel. The problem of the continuous conjugation of the membrane function from H1 and the deflection function from H2 was solved by modifying the &ldquo;boundary&rdquo; functions. Basis systems were constructed that satisfy not only the essential but also the natural boundary conditions, which made it possible to increase the rate of convergence of the approximate solution. The veracity of the results is confirmed by comparing the obtained spectral solution with the solution obtained by the h-FEM. It has been shown that the exponential rate of convergence characteristic of spectral methods is preserved if the Gibbs phenomenon is avoided. The constructed basis systems can be effectively used for solving various problems of mechanics.Flow Regimes Characteristics of Water-crude Oil in a Rectangular Y-microchannel
https://jacm.scu.ac.ir/article_17236.html
The paper deals with the investigation of the flow regimes of water and crude oil in a Y-microchannel. Systematic experiments allow distinguishing four different types of water-oil flow regimes in studied microchannel, namely, plug regime, droplet regime, parallel regime, and the first-revealed chaotic regime, as well as defining the ranges of parameters corresponding to these regimes. The dependences of the water plug length and frequency of their formation in crude oil on various parameters are obtained, and universal correlations are derived. It was demonstrated that when determining the dimensionless plug lengths and the Strouhal number corresponding to droplet detachment, it is necessary to take into account not only the ratio of the dispersed and carrier phase flow rates but also the capillary number. The systematic numerical simulation of the considered flows is conducted using the VOF method. The conducted comparison of the computation and experimental results has shown that the numerical simulation qualitatively correctly predicts the characteristics of water and oil flows in the Y-type channel under consideration.Impact-enhanced Electrostatic Vibration Energy Harvester
https://jacm.scu.ac.ir/article_17239.html
An influence of mechanical impacts between variable capacitor electrodes on the electrostatic vibration energy harvester (e-VEH) operation is studied theoretically. The analysis is carried out for two conditioning circuits with parallel and serial load connection. A relationship between e-VEH parameters and external mechanical force characteristics enabling to assess the possibility of operation in a periodic impact mode is obtained. Dependences of the average power generated by the impact-enhanced e-VEH versus the number of collisions between the electrodes and the load resistor value are calculated. The operation of the harvester for two circuits in impact and non-impact modes is compared and analyzed. It is shown that the average power generated by the e-VEH for the impact mode can exceed the power for the non-impact mode by 1&ndash;2 orders of magnitude along with a significant decrease of the harvester optimal load resistance.Generation of a Quadrilateral Mesh based on NURBS for Gyroids of Variable Thickness and Porosity
https://jacm.scu.ac.ir/article_17242.html
The Gyroid is a periodic minimal surface explored in different applications, such as architecture and nanotechnology. The general topology is suitable for the construction of porous structures. This paper presents a non-iterative, novel methodology for the generation of a NURBS-based Gyroid volume. The Gyroid fundamental patch is defined with the Weierstrass parameterization. Furthermore, the geometry is manipulated to generate a structured mesh, allowing better element quality for FEM and IGA simulations. The re-parametrization is carried out by a Least-Squares approximation with a parametric NURBS surface, enabling a better definition of the mid-surface normals for the generation of the complete Gyroid volume. Different cases of variational thickness and porosity are presented to validate the versatility of our method.Research into the Properties of Selected Single Speed Two-Carrier Planetary Gear Trains
https://jacm.scu.ac.ir/article_17257.html
A two-carrier planetary gear train (PGT) configuration, named S13WN, was developed for a specific application with a negative transmission ratio in the interval between -20 and -21. 72 valid combinations of component PGTs ideal torque ratios have been developed for this configuration, from which kinematically feasible combinations providing minimal dimensions and maximum efficiency within the required interval have been selected. The minimal dimensions of the PGT were achieved with a cylindrical case shape, i.e., with the ratio of the ring gears reference diameters close to unity. Nine other PGT configurations have been synthesized for the same transmission ratio, and their design parameters optimized. The two solutions that offer the most improvements over S13WN have been developed into design concepts.Effect of Porosity and Hygrothermal Environment on FGP Hollow Spheres under Electromechanical Loads
https://jacm.scu.ac.ir/article_17256.html
Semi-analytical studies for the porosity action of a hollow sphere made of functionally graded piezoelectric material are presented. A semi-analytical technique for radial displacement is presented. A combination of internal and external pressures, temperature distribution, uniform hygrothermal distribution, and an electric potential variation has been discussed between the inner and outer surfaces of the sphere. The material physical properties for the present porous hollow sphere are varying through the thickness due to the power functions of the radius. Numerical outcomes are validated for radial displacement, electric potential, and stresses for the perfect and porous functionally graded hollow sphere. The effect of different mechanical, piezoelectric, and hygrothermal are investigated.Strength of Steel Shell Cylindrical Panels Reinforced with an Orthogonal Grid of Stiffeners
https://jacm.scu.ac.ir/article_17283.html
The paper presents an approach to the strength analysis in steel cylindrical panels reinforced from the concave side with an orthogonal grid of stiffeners. A mathematical model of the Timoshenko (Mindlin &ndash; Reissner) type is used. Transverse shears and geometric nonlinearity are taken into account. The stiffeners are introduced in two ways: using the method of refined discrete introduction (proposed by author) and the method of structural anisotropy. Computational algorithm based on the Ritz method and the best parameter continuation method. For strength analysis von Mises criterion is used. The values of the maximum permissible strength loss loads are shown for several variants of structures made of steel S345. The extension of areas of non-fulfillment of strength conditions according to the Mises criterion for the stiffened and unstiffened structures are shown.Analysis of Possibilities to Use Predictive Mathematical Models for Studying the Dam Deformation State
https://jacm.scu.ac.ir/article_17288.html
Long-term monitoring of the safety and reliability of large dams operation has been attracting increasing attention of researchers. Moreover, special consideration is given to the study of dam displacements that characterize its global behavior. The article discusses specifics of constructing predictive mathematical models for studying the deformation process associated with displacements of the high-head dam crest. The authors present the most successfully designed predictive mathematical models for various combinations of input effective factors, including the results of field observations and the calculated values of the component displacements. These models allow forecasting the control points of the dam body for various time stages of its operation. The advantages of using a mathematical model with separate introduction of the main effective factors into the model are shown, thereby eliminating the effect of their multicollinearity. Using the example of the Sayano-Shushenskaya hydro power plant for certain time stages of the dam operation and structures with different temperature conditions (average, warm and cold in respect to annual temperatures), the authors present the results of forecasting the dam displacements.Insight into Stability Analysis on Modified Magnetic Field of Radiative Non-Newtonian Reiner–Philippoff Fluid Model
https://jacm.scu.ac.ir/article_17289.html
The field of magnetohydrodynamics (MHD) encompasses a wide range of physical objects due to their stabilising effects. Thus, this study concerns the numerical investigation of the radiative non-Newtonian fluid flow past a shrinking sheet in the presence of an aligned magnetic field. By adopting proper similarity transformations, the governing partial derivatives of multivariable differential equations are converted to similarity equations of a particular form. The numerical results are obtained by using the bvp4c technique. According to the findings, increases in the suction parameter resulted in higher values of the skin friction and heat transfer rate. The same pattern emerges as the aligned angle and magnetic parameter are considered. On the other hand, the inclusion of the Bingham number, the Reiner&ndash;Philippoff fluid, and the thermal radiation parameters deteriorate the heat transfer performance, evidently. The dual solutions are established, which results in a stability analysis that upholds the validity of the first solution.A Study of Curved Louver Fin Configuration for Heat Transfer Enhancement
https://jacm.scu.ac.ir/article_17292.html
Herein, the heat transfer performance of the curved surface of a louvered fin heat exchanger using computational fluid dynamics (CFD) is examined. Four new models are used with curved surfaces in different locations. The air inlet velocity is 1&ndash;9 m/s. The air and fin wall temperature remain constant at 300 and 353 K, respectively. The result of the reference flat fin is confirmed with experimental results. The results demonstrate that curved fins changed the airflow path and created vortices. The air tends to flow between louver fins, improving its velocity and enhancing heat transfer. The result from the case that individual fin is close to the middle fin demonstrated that louver fin provides a 15% increase compared to that of the reference. However, when the air inlet velocity is high, the performance evaluation criteria from the case that individual fin is close to the first fin, is the highest, which results in a 1% increase from that of the reference. Therefore, increasing heat transfer can compensate the effect of pressure drop because of vortices in the louver fin domain. This study can be applied to the air conditioning system to increase its efficiency and cut the operation cost down.Application of Newmark Average Acceleration and Ritz Methods on Dynamical Analysis of Composite Beams under a Moving Load
https://jacm.scu.ac.ir/article_17296.html
In this paper, dynamic results of carbon nanotube (CNT)-reinforced composite beams under a moving load are presented. The constitutive equations in motion are obtained by the Lagrange procedure according to Timoshenko beam theory and then solved by using the Ritz method. In the solution of the moving load problem, the Newmark average acceleration method is used in the time history. In the numerical results, the effects of CNTs&rsquo; volume fraction, patterns of CNTs, and the velocity of moving load on the dynamic responses of CNT-reinforced composite beam are investigated in detail. It is observed that the reinforcement patterns and volume fraction of CNTs are very effective on the behavior of the moving load. Also, it is found that X-Beam and O-Beam have the biggest and lowest rigidities in all models, respectively.Size Effect on the Axisymmetric Vibrational Response of Functionally Graded Circular Nano-Plate Based on the Nonlocal Stress-Driven Method
https://jacm.scu.ac.ir/article_17033.html
In this work, the axisymmetric-vibrational behavior of a size-dependent circular nano-plate with functionally graded material with different types of boundary conditions was investigated. The analysis was performed based on the Stress-driven model (SDM) and Strain-gradient theory (SGT) in conjunction with classical plate theory. The governing equations of motion and their corresponding equations for boundary conditions were obtained based on Hamilton&rsquo;s principle and solved using the generalized differential quadrature rule. Results show that this method is applicable to the vibrational analysis of such structures with a fast convergence rate; as N approaches 6 for the first mode, and 10 for the second as well as the third and fourth modes, regardless of the type of boundary condition. In both models, the influences of various parameters such as size-effect parameter Lc, material heterogeneity index n, and types of boundary conditions were obtained on the first four modes and compared with each other. Results indicate that the natural frequencies in these modes increase with an increase in the heterogeneity index n, and size-effect parameter Lc. Additionally, these parameters appear to have a stiffening effect on the nano-plate vibrational behavior. However, for a nano-plate resting on a knife or simply supported edge, in the first mode, the SDM shows a more stiffening effect on the plate behavior as compared with the SGT. Nonetheless, for the clamped and free edge boundary conditions, both models predicted the same behavior. The SGT showed a higher-stiffening effect only in the fourth mode, for all types of considered boundary conditions.Magnetized Bi-convective Nanofluid Flow and Entropy Production Using Temperature-sensitive Base Fluid Properties: A Unique Approach
https://jacm.scu.ac.ir/article_17080.html
The flow mechanism and entropy production of a bi-convective, magnetized, radiative nano-liquid flow for an inverted cone considering temperature-sensitive water properties is accomplished numerically. The functional nanomaterial comprises Copper, Alumina in the base liquid, water. The mathematical equations representing the system's physical characteristics are solved numerically by adopting a robust numerical approach for indulgencing non-similar solutions to understand numerous parameters' effect on temperature, velocity, salient gradients, and entropy production. The investigation summarizes that buoyancy force and injection heighten the velocity, and suction, particle percentage, radiation elevate the heat transfer. At the same time, the radiation and Brinkman number enhance the entropy generation. It is also detected from this investigation that the magnetic effect shows dual behaviour in entropy generation.Calculation of Backscattered Ultrasonic Waves Field from a Copper-clad Steel Rod Immersing in Water and Effect of Clad Corrosion and Interfacial Disbond between Clad and Rod Defects on this Field using the Finite Element Method
https://jacm.scu.ac.ir/article_17135.html
Inspection and specificity of the intactness of multi-layer and small-size parts like copper-clad steel rod is a hard task and requires high accuracy. The intactness of these parts is crucial due to their importance. One of the inspection methods for these parts is using ultrasonic waves. The scattering phenomenon occurs when these waves impact curved shape bodies under a special condition. The ultrasonic scattering waves contain a lot of information from the physical conditions and mechanical properties of the part. However, using these waves requires high accuracy and attention due to their complexity. One result of the ultrasonic scattering waves is the far-field backscattered frequency spectrum, form function. For the first time in this research, the form function of a copper-clad steel rod that is immersed in water is calculated using the finite element method (FEM) available in the commercial ABAQUS software. For validating the proposed model, the simulation results are compared with analytical and experimental results in the normalized frequency range of 4 &pound; Ka &pound; 10. A good agreement is observed between the three methods at the resonance frequencies, and in the overall form of obtained form function. Furthermore, the effects of the two most common defects in these rods, i.e., the corrosion and interfacial disbond between the clad and steel rod, is studied. Results show that this method can properly specify the corrosion percentage and location, and also the length and location of the interfacial disbond defect.&nbsp;Magneto Casson-Carreau Fluid Flow through a Circular Porous Cylinder with Partial Slip
https://jacm.scu.ac.ir/article_17140.html
In the current study, a comparative analysis of two-dimensional heat transfer by the free convective flow of non-Newtonian Casson and Carreau fluid in electro-conductive polymer on the outside surface of a horizontal circular cylinder under slip and radial magnetic field effects is regarded. The Casson and Carreau fluid model formulation were first developed for the problem of the boundary layer of the horizontal circular cylinder and by using non-similarity transformations, the combined governing partial differential equations are translated into ordinary differential equations. The differential equations obtained are resolved by the Keller Box Method (KBM). The impact of the key parameters, the rate of heat transfer and skin friction is evaluated through graphs and tables. The result reveals that an increase in magnetic number decreases the velocity field of both Casson and Carreau fluid also Casson fluid is higher values when compared to Carreau fluid in variation of magnetic number.Numerical Simulation of Fuzzy Volterra Integro-differential Equation using Improved Runge-Kutta Method
https://jacm.scu.ac.ir/article_17145.html
In this research, fourth-order Improved Runge-Kutta method with three stages for solving fuzzy Volterra integro-differential (FVID) equations of the second kind under the concept of generalized Hukuhara differentiability is proposed. The advantage of the proposed method in this study compared with the same order classic Runge-Kutta method is, Improved Runge-Kutta (IRK) method uses a fewer number of stages in each step which causes less computational cost in total. Here, the integral part is approximated by applying the combination of Lagrange interpolation polynomials and Simpson&rsquo;s rule. The numerical results are compared with some existing methods such as the fourth-order Runge-Kutta (RK) method, variational iteration method (VIM), and homotopy perturbation method (HPM) to prove the efficiency of IRK method. Based on the obtained results, it is clear that the fourth-order Improved Runge-Kutta method with higher accuracy and less number of stages which leads the less computational cost is more efficient than other existing methods for solving FVID equations.Pull-in Phenomenon in the Electrostatically Micro-switch Suspended between Two Conductive Plates using the Artificial Neural Network
https://jacm.scu.ac.ir/article_17147.html
Artificial Neural Networks (ANN) are designed to evaluate the pull-in voltage of MEMS switches. The mathematical model of a micro-switch subjected to electrostatic force is preliminarily illustrated to get the relevant equations providing static deflection and pull-in voltage. Adopting the Step-by-Step Linearization Method together with a Galerkin-based reduced order model, numerical results in terms of pull-in voltage are obtained to be employed in the training process of ANN. Then, feed forward back propagation ANNs are designed and a learning process based on the Levenberg-Marquardt method is performed. The ability of designed neural networks to determine pull-in voltage have been compared with previous results presented in experimental and theoretical studies and it has been shown that the presented method has a good ability to approximate the threshold voltage of micro switch. Furthermore, the geometric and physical effect of the micro-switch on the pull-in voltage was also examined using these designed networks and relevant findings were provided.Numerical Simulations of Spoiler’s Effect on a Hatchback and a Sedan Car Exposed to Crosswind Effect
https://jacm.scu.ac.ir/article_17193.html
Numerical simulations of the airflow around a hatchback and a sedan vehicle without and with spoilers are carried out, besides, its effect on drag and lift coefficients are investigated with and without crosswinds. The effects of crosswind on aerodynamic forces are considered and its results are compared with the case without considering the effects of crosswind. For this purpose, the steady-state three-dimensional Navier-Stokes equations are solved by the Simple Method. Moreover, for turbulence modeling, the Realizable k-e model is implemented. The spoiler angle and its length are changed for both car models; furthermore, the effects of two spoilers on drag and lift coefficients are investigated in detail. All cases are simulated with and without crosswind. The results show that the impact of the spoiler for without crosswind conditions to decrease the lift coefficient in both models is significant; in addition, the drag coefficients are reduced for some cares. It can be concluded that the increase of spoiler length for both sedan and hatchback vehicles can increase the downward force and vehicle stability.Economic Evaluation of Supplying Commercial Thermal Load by a New CPVT System: A Case Study in Iran
https://jacm.scu.ac.ir/article_17234.html
This paper aims to provide a concentrated photovoltaic thermal (CPVT) system regarding the high potential of receiving solar energy in Iran. Generated thermal energy of the system supplies the average thermal load of a commercial building and also its generated electricity is sold to the grid according to Iran's feed-in tariff (FiT). In order to calculate the system profitability, an economic evaluation is done in 20 years that is regarded as a novel approach. Furthermore, sensitivity analyses are performed to develop the results to the other locations with different economic conditions and various potential of energy resources, and also to present an appropriate financial outlook. The results demonstrate that the system is highly profitable given net present value (NPV) of 551.55 k$, internal rate of return (IRR) of 150.79%, benefit to cost ratio (BCR) of 10.32, payback time (PBT) of 0.51 years, and levelized cost of energy (LCOE) of 0.1293 $/MWh. Moreover, sensitivity analyses show that the system profitability is greatly appropriate even regarding the variety of unpredictable parameters. For instance, if the generated energy decreases by 20%, IRR and PBT will equal 120.63% and 0.63 years respectively, and the system can still maintain its high profitability. Moreover, it has been revealed that the enhancement of FiT can increase the system's economic efficiency. According to the results, it is noticeably profitable to use the CPVT systems to produce electrical and thermal power in countries with a high potential of receiving solar energy (especially middle-eastern countries).Electrochemical and Mechanical Properties of Ni/g-C3N4 Nanocomposite Coatings with Enhanced Corrosion Protective Properties: A Case Study for Modeling the Corrosion Resistance by ANN and ANFIS Models
https://jacm.scu.ac.ir/article_17241.html
This work investigates the effect of electrolysis bath parameters on the corrosion, micro-hardness, and wear behavior of Ni coatings. The characterization of synthesized Graphitic carbon nitride (g-C3N4) was done by Fourier transform infrared, Raman spectroscopy, and transmission electron microscope. The surface morphology of coated samples with various amounts of current density was studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The corrosion prevention effect of Ni/g-C3N4 nanocomposite coatings was investigated by EIS and polarization techniques. The experimental outcome demonstrates that an electrolysis bath of 0.3 g/L g-C3N4 and 0.1 A.cm-2 presents a Ni coating with the highest corrosion protection, wear resistance, and microhardness. The corrosion current densities of Ni/g-C3N4 coatings obtained by electrochemical tests were used for training two machine learning techniques (Artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS)) based on current density, g-C3N4 concentration, and plating time as an input. Various statistical criteria showed that the ANFIS model (R2= 0.99) could forecast corrosion current density more accurately than ANN with R2= 0.91. Finally, due to the robust performance of ANFIS in modeling the corrosion behavior of Ni/g-C3N4 nanocomposite coating, the effect of each parameter was studied.Temperature Effect on Moving Water Droplets at the Channel of PEMFC by Multi-component Multiphase Lattice Boltzmann Method
https://jacm.scu.ac.ir/article_17253.html
In this paper, a multi-component multiphase pseudopotential Lattice Boltzmann method with multi relaxation time (MRT) collision operator is presented to examine the dynamic behavior of liquid droplets movement and coalescence process in the gas channel of PEMFC. In the numerical method, the forcing term is improved to achieve a high-density ratio and thermodynamic consistency. First, the density ratio, Laplace law, and contact angle are validated with previous studies. Then, different parameters, such as operating temperature, pressure difference, surface contact angle, the radius of droplets, and distance between two droplets on the droplet movement and coalescence process are studied. The results revealed by rising temperature from 30 to 80 degrees, the speed of drop increases around 6 percent. The simulation results indicated that the rising of pressure gradient increases the gas flow velocity on the channel and leads to increasing the shear force and eventually faster movement of the droplet on the gas channel. Also, investigation of various contact angles shows that a hydrophilic surface causes a resistance force between the droplet and the wall and delays the removal of droplets. Moreover, droplet coalescence is useful for droplet movement because of increasing the velocity gradient on top of the droplet; consequently, the shear force on the droplet is raised during coalescence.