Journal of Applied and Computational Sciences in Mechanics | Ferdowsi University of Mashhad (original) (raw)
Papers by Journal of Applied and Computational Sciences in Mechanics
The Journal of Applied and Computational Sciences in Mechanics, 2013
Improving mechanical properties of composites based on strength-to-weight ratio has been gained m... more Improving mechanical properties of composites based on strength-to-weight ratio has been gained much attention in various applications. Having the most resistant and at the same time the lightest and the most economical structure is believed as an aim in these applications. These three factors are usually opposed to each other. So, applying optimization algorithms for improving mechanical properties of composites is very important. Particle swarm optimization (PSO) is used in balanced symmetric hybrid laminated composites for accessing the lowest weight and cost based on the first natural frequency. In this research, the objective function is a combination of the weight and cost which are both functions of the numbers and material of layers, while the natural frequency, in addition to the above factors, is a function of the fibers angle and the stacking sequenc, too. The results obtained from PSO algorithm (including optimized stacking sequences and the number of plies reinforced by either glass or graphite fibers) are compared with obtained results from genetic algorithm (GA) and ant colony optimization (ACO). The results confirme the advantages of hybrid composites and reveale that PSO provide the same results and in some cases even better sequences relative to the mentioned algorithms. This algorithm is so useful and competitive with respect to other heuristic algorithms.
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The Journal of Applied and Computational Sciences in Mechanics, 2013
In this work, Harmony Search Meta-Heuristic Optimization Algorithm has been developed for aerodyn... more In this work, Harmony Search Meta-Heuristic Optimization Algorithm has been developed for aerodynamic shape optimization problem for the first time. The aerodynamic shape, which has been investigated, is an airfoil with Parces method for its shape parameterization. The problem was minimization of aerodynamic objective function using inverse design method and the objective function has been the deviation of pressure distribution between investigated airfoil and the target airfoil. The 2-Dimensional compressible Navier-Stokes equations have been considered for simulation of flow using Spalart-Almaras turbulence model. A global improvement has been carried out to enhance the efficiency of Harmony Search Algorithm. In improved Harmony Search Algorithm one obtains the optimum design values and target airfoil by changing the airfoil shape design variables. To do this, algorithm starts from NACA0012 airfoil and reconstructs the target airfoil (RAE2822) by making pressure distribution closer to the target airfoil pressure distribution. For more accurate investigation and to make sure about the accuracy of algorithm, this optimization process has also been done in inverse direction. It means that, NACA0012 airfoil has been reconstructed starting from RAE2822 airfoil. The obtained results show that the utilization of Harmony Search Algorithm allows us to obtain an efficient and powerful tool for Aerodynamic Shape Optimization.
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The Journal of Applied and Computational Sciences in Mechanics, 2013
In this paper, the transient inertial viscoelastic flow around a circular cylinder is investigate... more In this paper, the transient inertial viscoelastic flow around a circular cylinder is investigated numerically. A second order finite-volume method is used to increase the numerical accuracy. Here, the Giesekus model is used as the constitutive equation. This nonlinear model has prominent ability in describing normal stress differences and viscosity in power-law regions. The impacts of the elasticity and Reynolds number on the shedding frequency are discussed. Also, drag reduction phenomenon in the viscoelastic flow is studied by extracting pressure distribution on the cylinder surface. The obtained results are in good agreement with recent experimental and numerical investigations reported in the literature for Newtonian fluids.
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The Journal of Applied and Computational Sciences in Mechanics, 2013
Laminar counterflow diffusion flames provide useful information about basic properties of non-pre... more Laminar counterflow diffusion flames provide useful information about basic properties of non-premixed combustion. A lot of studies have been performed on H2/O2 counterflow. Most of previous studies include undiluted or diluted systems of hydrogen (with CO2 or N2) against an air flow under a variety of conditions such as strain rates, inlet temperature and pressure. The main purpose of this research is to investigate the extinction limits and also to see how the temperature changes against the strain rate. The effect of Ar and He gases as diluents on combustion and extinction limits of H2/O2 is also investigated. Numerical simulations have been done with the OPPDIF code from CHEMKIN software. The obtained numerical results are compared with the others results and show the accuracy of numerical solution. Increasing the diluent percent causes decreasing of the maximum temperature and also the maximum mole fraction of active radicals of H and OH. Decreasing of producing H radical causes the fuel be slightly influenced by this species and thus the fuel diffuses more to oxide side. Increasing the diluent percent also causes decreasing of blow off and quenching limits in hydrogen combustion and accordingly narrows the flammability; But the increasing of inlet temperature flows and ambient pressure extend the flammability limits.
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The Journal of Applied and Computational Sciences in Mechanics, 2013
Natural convection heat transfer from a vertical heated plate in a saturated porous medium is ana... more Natural convection heat transfer from a vertical heated plate in a saturated porous medium is analyzed under thermal non-equilibrium assumptions. The plate is maintained at a non uniform temperature and the fluid is considered to be with internal heat generation. The coupled momentum and energy equations for fluid and solid phases are transformed to a similarity format, and solved numerically. The resulting velocity and temperature distributions are shown for different values of the problem parameters. Also the values of the local Nusselt numbers for both solid and fluid phases are shown. The effect of suction/injection on the free convection boundary layer is also studied. The obtained results are compared with those presented in the literature in the case of thermal equilibrium model.
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The Journal of Applied and Computational Sciences in Mechanics, 2013
In this paper, an analytical study of the forced vibrations of hexapod table is studied. Consider... more In this paper, an analytical study of the forced vibrations of hexapod table is studied. Considering external force as a time sinusoid force, forced vibrations of the platform are investigated. Resonance frequencies and vibrations of the moving platform are also calculated in different directions. The results of the analytical approach are verified using FEM simulation. Modelling the harmonic milling forces, a careful examination of the forced vibration are carried out in different cutting conditions and different configurations. Resonance frequencies and the range of vibrations are then calculated. Finally, knowing the resonance frequencies and the vibrations of hexapod table, different configurations of the table, which results in dynamic instability, are investigated
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The Journal of Applied and Computational Sciences in Mechanics, 2013
In high-pressure axial turbines, when the fluid mass flow is low, the supersonic blades are being... more In high-pressure axial turbines, when the fluid mass flow is low, the supersonic blades are being used to obtain a high specific work output. To prevent losses due to low blade aspect ratio, the turbine is used in partial admission conditions. The turbine stator is a group of convergence-divergence nozzles that provides the supersonic flow. The design of these nozzles is important, because there is a direct relationship between the degree of partial admission and nozzle design parameters. The turbine efficiency is highly dependent on partial admission degree. To assess, in first step, an evaluation was carried out using an appropriate turbine efficiency correlation; then, a three-dimensional numerical analysis was implemented, and finally a series of experimental tests were carried out to validate the above assessments. The experimental results showed a good agreement with 1D and 3D numerical predicted results of turbine performance. The results showed that even small changes in the nozzle geometric parameters and partial admission degree, have a significant impact on the turbine performance and the flow distribution in the axial gap.
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The Journal of Applied and Computational Sciences in Mechanics, 2013
Drilling is one of the main machining processes carried out in the assembly stage of automobile m... more Drilling is one of the main machining processes carried out in the assembly stage of automobile manufacturing and aerospace components. Generally, delamination is considered as a major problem during drilling of composite materials. In this paper, the effects of feed rate, cutting speed and drill point angle on thrust force and delamination factor have been studied by using full factorial design. According to the results, feed rate has the most significant effect on thrust force followed by drill point angle. Moreover, the Half-Normal plot was used to identify which experiment factors have significant effects on the delamination factor; According to the results, feed rate has the most important effect. Acoustic emission signals and wavelet analysis were employed to monitor drilling process and discriminate frequency distributions of different cutting mechanisms. After time-frequency analyzing of AE signals, component 2 (EPC2) with frequency range of 62.5-125 kHz was attributed to matrix cracking and component 5 (EPC5) with frequency range of 250-312.5 kHz and average energy of 32% was attributed to fiber cutting.
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The Journal of Applied and Computational Sciences in Mechanics, 2013
As the science of Mechanics has been improved in recent years, different standards have been crea... more As the science of Mechanics has been improved in recent years, different standards have been created in designing structures such as pressure vessels. Most of these standards have been developed by means of experience and examination. Today, most of researches, proceed the numerical analysis of the different elements of the pressure vessels and somehow they have put some questions on the previous standards. In this paper, offering an applicable model, it is shown that heuristic optimization methods such as genetic algorithm, particle swarm optimization and especially imperialist competitive algorithm can be used as a simple and fast method for designing the vessels without breaking any of the engineering conditions and criteria. Due to the present results of this research, these methods are caused a noticeable decrease of the vessel’s weight, with a high convergence speed, in a short time, compare to the design carried out in handbooks. You may observe that the Imperialist Competitive Algorithm has a better performance and convergence than the two other methods.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
In according to the simplicity of the lattice Boltzmann method’s(LBM) algorithm and its benefits,... more In according to the simplicity of the lattice Boltzmann method’s(LBM) algorithm and its benefits, it has been used as a successful method in computational fluid dynamics in the last decades. In this paper, LBM was used to simulate the flow over a cylinder. To analyze the application of LBM in simulation curved surface, different methods to compute drag coefficient were used. These methods are: momentum exchange, momentum exchange on the wall, stress integration, computing stress by velocity components. The result shows the ability of Lattice Boltzmann method to simulate curved surface.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
One of the cooling systems that has received considerable attentions in recent years is the adsor... more One of the cooling systems that has received considerable attentions in recent years is the adsorption chiller, which works based on the adsorption and desorption of a working fluid in a solid porous bed. Different parameters such as fin height directly affect the bed heat and mass transfer processes, and therefore, the performance of the adsorption chillers. In the present study a numerical model has been introduced to optimize the fin height in a RD silica gel bed with water as the working fluid. A control volume approach has been employed to determine the temperature distributions in the heat transfer fluid, metal tube, and fins, while the simultaneous solutions of the heat and mass transfer equations should be carried out in a three dimensional coordinate system for the adsorption bed. It was found that the coefficient of performance increases and specific cooling power decreases as the fin height of the bed increases.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
In the present study the effect of curvature ratio and coil pitch for TiO2/water nanofluid lamina... more In the present study the effect of curvature ratio and coil pitch for TiO2/water nanofluid laminar flow on heat transfer behavior and pressure drop through helical coils with different geometries was investigated experimentally. The TiO2/water nanofluids at 0.25% to 2% particle volume concentrations have been prepared by using a two-step method. The experiments were performed for coils with curvature ratio of 10 and 20 and coil pitch of 24 and 42. Based on the experimental data, it is found that the Nusselt number as well as Reynolds number improves while increasing particle volume concentration. This enhancement is due to the higher effective thermal conductivity of nanofluid and also intensification of nanoparticles. Besides, increase in density and viscosity of nanofluid compared to the base fluid leads to a pressure drop increment for flow through helical coiled tube. Furthermore, the heat transfer rate improves with the increase of pitch coils and decrease of curvature ratio. Additionally, curvature ratio shows more significant effect on Nusselt number and pressure drop than pitch spacing. 42.1% enhancement on Nusselt number is obtained for the nanofluid with 2% volume concentarion in comparison to the base fluid. Finally, it is shown that the experimental results and predicted results of Nusselt number and pressure drop for nanofluid flow through helical coils hold reasonable agreement.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
In this study, the effect of suction and the parameters such as suction amplitude, suction coeffi... more In this study, the effect of suction and the parameters such as suction amplitude, suction coefficient and suction jet length on NACA0012 was evaluated. The turbulence employed model was the RSM model. Suction jet is located in 10% of the chord length. The range of suction jet entrance velocity was selected from 0.1 to 0.5 of freestream velocity. The maximum increase in lift to drag ratio was seen at suction amplitude of 0.5. In addition, lift to drag ratio elevated when suction jet length increased and reached to its maximum value at 2.5% of the chord length.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
In the present study, turbulent flow in channels of a plate heat exchanger with corrugated Chevro... more In the present study, turbulent flow in channels of a plate heat exchanger with corrugated Chevron plates has been simulated numerically using the commercial CFD package, FLUENT. Unstructured mesh is used for discretizing the computational domain and SIMPLE algorithm is utilized to solve the pressure and velocity equations. There is a wide selection of different plate heat exchangers within the industry; therefore, 3D models of common corrugated Chevron plates with Chevron angles of 45-45 and 60-60 have been simulated to obtain and analyze temperature, pressure, and velocity fields of flow. The results show that geometrical parameters of the plates such as Chevron angle have indisputable effects on flow pattern and heat transfer of the heat exchanger. Finally, the effects of Chevron angle and Reynolds number (4000≤Re≤20000) on friction factor and Nusselt number of the flow were studied and compared with former experimental results. The numerical results show a good agreement with the experimental data. In addition, it was seen that increasing the Chevron angles would lead to increasing the friction factor and Nusselt number simultaneously.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
Forming limit curve (FLC) is an important tool for evaluation of formability of sheet metals subj... more Forming limit curve (FLC) is an important tool for evaluation of formability of sheet metals subjected to different loading. Free bulge of aluminume tubes has been investigated numerically to obtain FLC. To verify the numerical results one experimental setup has been manufactured which has the ability of controlling the internal pressure and axial feed. In this study, time and zone of bursting in tube hydroforming is predicted using seven ductile fracture criteria. For calibration of these criteria, the uniaxial tension is simulated in Abaqus/Explicit. Different loading curves are applied on tube to obtain the different points of FLC. Predicted FLCs by ductile fracture criteria have been compared with experimental results. The FLC which is predicted by Ayada' s criterion has best match to experimental one. Results show that Prediction of all criteria are the same in strain position which is similar to uniaxial tension. Based on the results, criteria which apply the effect of average stress in prediction of dutile fracture are more appropriate for tube hydroforming process.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
Forming limit curve (FLC) is an important tool for evaluation of formability of sheet metals subj... more Forming limit curve (FLC) is an important tool for evaluation of formability of sheet metals subjected to different loading. Free bulge of aluminume tubes has been investigated numerically to obtain FLC. To verify the numerical results one experimental setup has been manufactured which has the ability of controlling the internal pressure and axial feed. In this study, time and zone of bursting in tube hydroforming is predicted using seven ductile fracture criteria. For calibration of these criteria, the uniaxial tension is simulated in Abaqus/Explicit. Different loading curves are applied on tube to obtain the different points of FLC. Predicted FLCs by ductile fracture criteria have been compared with experimental results. The FLC which is predicted by Ayada' s criterion has best match to experimental one. Results show that Prediction of all criteria are the same in strain position which is similar to uniaxial tension. Based on the results, criteria which apply the effect of average stress in prediction of dutile fracture are more appropriate for tube hydroforming process.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
In this research, the steady-state flow filed around a 3D body and rotor configuration of the ROB... more In this research, the steady-state flow filed around a 3D body and rotor configuration of the ROBIN helicopter is simulated. The rotor is modeled by an actuator disk. For this purpose, an annular computational domain replaces the rotor and some modeled source terms are added to the momentum equations. This modeling of rotor considerably speed up computational time. The flow field over this helicopter fuselage is simulated for six cases of different advance ratios and thrust coefficients. The accuracy of using uniform, linear and BET distributions for the rotor in the source term is investigated. With the BET and some corrections to pitch angles, pressure coefficients and variation of thrust and power of rotor are predicted in agreement with experimental data. For the nominal thrust coefficient of 0.06, different loading methods on rotor using experimental results are compared for two advance ratio of 0.05 and 0.23. In the advance ratio of 0.23 for the upper surface of helicopter, no considerable difference among the different employed methods is observed. However, for the advance ratio of 0.05 and for the side that helicopter blades get closer to the body (Starboard side), the results with the modified methods are better than BET method. The presence of strut in the computational domain has important effects in high speeds and causes reduction of pressure coefficients over body especially in downstream of the strut.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
In this paper, the capabilities of modeling linear viscoelasticty in a finite element method soft... more In this paper, the capabilities of modeling linear viscoelasticty in a finite element method software package (COMSOL Multiphysics) are investigated. The governing equations of linear viscoelasticity have been developed for 2D cases of plane stress and plane strain. These equations have been verified by solving a related engineering example. Since the developed equations are suitable for modeling of multiphysics mechanisms, the presented model can also be used for modeling of the linear viscoleasticity coupled with other multiphysics phenomena.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
In this paper, two API X70 steel pipes (with spiral seam weld) of 56 inch outside diameter and 0.... more In this paper, two API X70 steel pipes (with spiral seam weld) of 56 inch outside diameter and 0.780 inch wall thickness were girth welded first. Next, hole drilling tests were conducted for strain measurement on the surfaces of the pipes. The values of residual stresses on the internal and external surfaces of the pipe were determined, from strain data using ASTM 837 standard. The experimental data showed that the maximum tensile residual stress (318MPa) was located on the centre line of the weld gap on the pipe outer surface alongside with the pipe hoop direction. Moreover, the maximum compressive (hoop and axial) residual stresses (137MPa) occurred on the pipe inner surface at 30mm from the centre line of the weld gap.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
In this paper, numerical investigation of a flat passive micromixer with heterogeneous surface pr... more In this paper, numerical investigation of a flat passive micromixer with heterogeneous surface properties that the flow through it, is driven by the electroosmotic flow have been presented. The governing equations, which consist of a Laplace equation for the distribution of external electric potential, a Poisson equation for the distribution of electric double layer potential, modified Navier-Stokes equations for the flow field, the Nernst-Planck equation for the distribution of ions concentration have been solved numerically for an incompressible steady flow of a Newtonian fluid using the finite-volume method. The key features of an ideal electro-osmotic flow with uniform zeta potential has been compared with analytical solutions for the ionic concentration and velocity fields for the validation of the numerical scheme. Results show that the arrangement of the heterogeneous surface properties has a significant impact on the efficiency of mixing. Maximum mixing efficiency is related to the condition that the asymmetry in the wall of the heterogeneous arrangement loads increase. The increase in intensity of the electric charge with constant power load of the electroosmotic micropump enhances the efficiency of mixing.
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The Journal of Applied and Computational Sciences in Mechanics, 2013
Improving mechanical properties of composites based on strength-to-weight ratio has been gained m... more Improving mechanical properties of composites based on strength-to-weight ratio has been gained much attention in various applications. Having the most resistant and at the same time the lightest and the most economical structure is believed as an aim in these applications. These three factors are usually opposed to each other. So, applying optimization algorithms for improving mechanical properties of composites is very important. Particle swarm optimization (PSO) is used in balanced symmetric hybrid laminated composites for accessing the lowest weight and cost based on the first natural frequency. In this research, the objective function is a combination of the weight and cost which are both functions of the numbers and material of layers, while the natural frequency, in addition to the above factors, is a function of the fibers angle and the stacking sequenc, too. The results obtained from PSO algorithm (including optimized stacking sequences and the number of plies reinforced by either glass or graphite fibers) are compared with obtained results from genetic algorithm (GA) and ant colony optimization (ACO). The results confirme the advantages of hybrid composites and reveale that PSO provide the same results and in some cases even better sequences relative to the mentioned algorithms. This algorithm is so useful and competitive with respect to other heuristic algorithms.
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The Journal of Applied and Computational Sciences in Mechanics, 2013
In this work, Harmony Search Meta-Heuristic Optimization Algorithm has been developed for aerodyn... more In this work, Harmony Search Meta-Heuristic Optimization Algorithm has been developed for aerodynamic shape optimization problem for the first time. The aerodynamic shape, which has been investigated, is an airfoil with Parces method for its shape parameterization. The problem was minimization of aerodynamic objective function using inverse design method and the objective function has been the deviation of pressure distribution between investigated airfoil and the target airfoil. The 2-Dimensional compressible Navier-Stokes equations have been considered for simulation of flow using Spalart-Almaras turbulence model. A global improvement has been carried out to enhance the efficiency of Harmony Search Algorithm. In improved Harmony Search Algorithm one obtains the optimum design values and target airfoil by changing the airfoil shape design variables. To do this, algorithm starts from NACA0012 airfoil and reconstructs the target airfoil (RAE2822) by making pressure distribution closer to the target airfoil pressure distribution. For more accurate investigation and to make sure about the accuracy of algorithm, this optimization process has also been done in inverse direction. It means that, NACA0012 airfoil has been reconstructed starting from RAE2822 airfoil. The obtained results show that the utilization of Harmony Search Algorithm allows us to obtain an efficient and powerful tool for Aerodynamic Shape Optimization.
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The Journal of Applied and Computational Sciences in Mechanics, 2013
In this paper, the transient inertial viscoelastic flow around a circular cylinder is investigate... more In this paper, the transient inertial viscoelastic flow around a circular cylinder is investigated numerically. A second order finite-volume method is used to increase the numerical accuracy. Here, the Giesekus model is used as the constitutive equation. This nonlinear model has prominent ability in describing normal stress differences and viscosity in power-law regions. The impacts of the elasticity and Reynolds number on the shedding frequency are discussed. Also, drag reduction phenomenon in the viscoelastic flow is studied by extracting pressure distribution on the cylinder surface. The obtained results are in good agreement with recent experimental and numerical investigations reported in the literature for Newtonian fluids.
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The Journal of Applied and Computational Sciences in Mechanics, 2013
Laminar counterflow diffusion flames provide useful information about basic properties of non-pre... more Laminar counterflow diffusion flames provide useful information about basic properties of non-premixed combustion. A lot of studies have been performed on H2/O2 counterflow. Most of previous studies include undiluted or diluted systems of hydrogen (with CO2 or N2) against an air flow under a variety of conditions such as strain rates, inlet temperature and pressure. The main purpose of this research is to investigate the extinction limits and also to see how the temperature changes against the strain rate. The effect of Ar and He gases as diluents on combustion and extinction limits of H2/O2 is also investigated. Numerical simulations have been done with the OPPDIF code from CHEMKIN software. The obtained numerical results are compared with the others results and show the accuracy of numerical solution. Increasing the diluent percent causes decreasing of the maximum temperature and also the maximum mole fraction of active radicals of H and OH. Decreasing of producing H radical causes the fuel be slightly influenced by this species and thus the fuel diffuses more to oxide side. Increasing the diluent percent also causes decreasing of blow off and quenching limits in hydrogen combustion and accordingly narrows the flammability; But the increasing of inlet temperature flows and ambient pressure extend the flammability limits.
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The Journal of Applied and Computational Sciences in Mechanics, 2013
Natural convection heat transfer from a vertical heated plate in a saturated porous medium is ana... more Natural convection heat transfer from a vertical heated plate in a saturated porous medium is analyzed under thermal non-equilibrium assumptions. The plate is maintained at a non uniform temperature and the fluid is considered to be with internal heat generation. The coupled momentum and energy equations for fluid and solid phases are transformed to a similarity format, and solved numerically. The resulting velocity and temperature distributions are shown for different values of the problem parameters. Also the values of the local Nusselt numbers for both solid and fluid phases are shown. The effect of suction/injection on the free convection boundary layer is also studied. The obtained results are compared with those presented in the literature in the case of thermal equilibrium model.
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The Journal of Applied and Computational Sciences in Mechanics, 2013
In this paper, an analytical study of the forced vibrations of hexapod table is studied. Consider... more In this paper, an analytical study of the forced vibrations of hexapod table is studied. Considering external force as a time sinusoid force, forced vibrations of the platform are investigated. Resonance frequencies and vibrations of the moving platform are also calculated in different directions. The results of the analytical approach are verified using FEM simulation. Modelling the harmonic milling forces, a careful examination of the forced vibration are carried out in different cutting conditions and different configurations. Resonance frequencies and the range of vibrations are then calculated. Finally, knowing the resonance frequencies and the vibrations of hexapod table, different configurations of the table, which results in dynamic instability, are investigated
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The Journal of Applied and Computational Sciences in Mechanics, 2013
In high-pressure axial turbines, when the fluid mass flow is low, the supersonic blades are being... more In high-pressure axial turbines, when the fluid mass flow is low, the supersonic blades are being used to obtain a high specific work output. To prevent losses due to low blade aspect ratio, the turbine is used in partial admission conditions. The turbine stator is a group of convergence-divergence nozzles that provides the supersonic flow. The design of these nozzles is important, because there is a direct relationship between the degree of partial admission and nozzle design parameters. The turbine efficiency is highly dependent on partial admission degree. To assess, in first step, an evaluation was carried out using an appropriate turbine efficiency correlation; then, a three-dimensional numerical analysis was implemented, and finally a series of experimental tests were carried out to validate the above assessments. The experimental results showed a good agreement with 1D and 3D numerical predicted results of turbine performance. The results showed that even small changes in the nozzle geometric parameters and partial admission degree, have a significant impact on the turbine performance and the flow distribution in the axial gap.
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The Journal of Applied and Computational Sciences in Mechanics, 2013
Drilling is one of the main machining processes carried out in the assembly stage of automobile m... more Drilling is one of the main machining processes carried out in the assembly stage of automobile manufacturing and aerospace components. Generally, delamination is considered as a major problem during drilling of composite materials. In this paper, the effects of feed rate, cutting speed and drill point angle on thrust force and delamination factor have been studied by using full factorial design. According to the results, feed rate has the most significant effect on thrust force followed by drill point angle. Moreover, the Half-Normal plot was used to identify which experiment factors have significant effects on the delamination factor; According to the results, feed rate has the most important effect. Acoustic emission signals and wavelet analysis were employed to monitor drilling process and discriminate frequency distributions of different cutting mechanisms. After time-frequency analyzing of AE signals, component 2 (EPC2) with frequency range of 62.5-125 kHz was attributed to matrix cracking and component 5 (EPC5) with frequency range of 250-312.5 kHz and average energy of 32% was attributed to fiber cutting.
Bookmarks Related papers MentionsView impact
The Journal of Applied and Computational Sciences in Mechanics, 2013
As the science of Mechanics has been improved in recent years, different standards have been crea... more As the science of Mechanics has been improved in recent years, different standards have been created in designing structures such as pressure vessels. Most of these standards have been developed by means of experience and examination. Today, most of researches, proceed the numerical analysis of the different elements of the pressure vessels and somehow they have put some questions on the previous standards. In this paper, offering an applicable model, it is shown that heuristic optimization methods such as genetic algorithm, particle swarm optimization and especially imperialist competitive algorithm can be used as a simple and fast method for designing the vessels without breaking any of the engineering conditions and criteria. Due to the present results of this research, these methods are caused a noticeable decrease of the vessel’s weight, with a high convergence speed, in a short time, compare to the design carried out in handbooks. You may observe that the Imperialist Competitive Algorithm has a better performance and convergence than the two other methods.
Bookmarks Related papers MentionsView impact
The Journal of Applied and Computational Sciences in Mechanics, 2014
In according to the simplicity of the lattice Boltzmann method’s(LBM) algorithm and its benefits,... more In according to the simplicity of the lattice Boltzmann method’s(LBM) algorithm and its benefits, it has been used as a successful method in computational fluid dynamics in the last decades. In this paper, LBM was used to simulate the flow over a cylinder. To analyze the application of LBM in simulation curved surface, different methods to compute drag coefficient were used. These methods are: momentum exchange, momentum exchange on the wall, stress integration, computing stress by velocity components. The result shows the ability of Lattice Boltzmann method to simulate curved surface.
Bookmarks Related papers MentionsView impact
The Journal of Applied and Computational Sciences in Mechanics, 2014
One of the cooling systems that has received considerable attentions in recent years is the adsor... more One of the cooling systems that has received considerable attentions in recent years is the adsorption chiller, which works based on the adsorption and desorption of a working fluid in a solid porous bed. Different parameters such as fin height directly affect the bed heat and mass transfer processes, and therefore, the performance of the adsorption chillers. In the present study a numerical model has been introduced to optimize the fin height in a RD silica gel bed with water as the working fluid. A control volume approach has been employed to determine the temperature distributions in the heat transfer fluid, metal tube, and fins, while the simultaneous solutions of the heat and mass transfer equations should be carried out in a three dimensional coordinate system for the adsorption bed. It was found that the coefficient of performance increases and specific cooling power decreases as the fin height of the bed increases.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
In the present study the effect of curvature ratio and coil pitch for TiO2/water nanofluid lamina... more In the present study the effect of curvature ratio and coil pitch for TiO2/water nanofluid laminar flow on heat transfer behavior and pressure drop through helical coils with different geometries was investigated experimentally. The TiO2/water nanofluids at 0.25% to 2% particle volume concentrations have been prepared by using a two-step method. The experiments were performed for coils with curvature ratio of 10 and 20 and coil pitch of 24 and 42. Based on the experimental data, it is found that the Nusselt number as well as Reynolds number improves while increasing particle volume concentration. This enhancement is due to the higher effective thermal conductivity of nanofluid and also intensification of nanoparticles. Besides, increase in density and viscosity of nanofluid compared to the base fluid leads to a pressure drop increment for flow through helical coiled tube. Furthermore, the heat transfer rate improves with the increase of pitch coils and decrease of curvature ratio. Additionally, curvature ratio shows more significant effect on Nusselt number and pressure drop than pitch spacing. 42.1% enhancement on Nusselt number is obtained for the nanofluid with 2% volume concentarion in comparison to the base fluid. Finally, it is shown that the experimental results and predicted results of Nusselt number and pressure drop for nanofluid flow through helical coils hold reasonable agreement.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
In this study, the effect of suction and the parameters such as suction amplitude, suction coeffi... more In this study, the effect of suction and the parameters such as suction amplitude, suction coefficient and suction jet length on NACA0012 was evaluated. The turbulence employed model was the RSM model. Suction jet is located in 10% of the chord length. The range of suction jet entrance velocity was selected from 0.1 to 0.5 of freestream velocity. The maximum increase in lift to drag ratio was seen at suction amplitude of 0.5. In addition, lift to drag ratio elevated when suction jet length increased and reached to its maximum value at 2.5% of the chord length.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
In the present study, turbulent flow in channels of a plate heat exchanger with corrugated Chevro... more In the present study, turbulent flow in channels of a plate heat exchanger with corrugated Chevron plates has been simulated numerically using the commercial CFD package, FLUENT. Unstructured mesh is used for discretizing the computational domain and SIMPLE algorithm is utilized to solve the pressure and velocity equations. There is a wide selection of different plate heat exchangers within the industry; therefore, 3D models of common corrugated Chevron plates with Chevron angles of 45-45 and 60-60 have been simulated to obtain and analyze temperature, pressure, and velocity fields of flow. The results show that geometrical parameters of the plates such as Chevron angle have indisputable effects on flow pattern and heat transfer of the heat exchanger. Finally, the effects of Chevron angle and Reynolds number (4000≤Re≤20000) on friction factor and Nusselt number of the flow were studied and compared with former experimental results. The numerical results show a good agreement with the experimental data. In addition, it was seen that increasing the Chevron angles would lead to increasing the friction factor and Nusselt number simultaneously.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
Forming limit curve (FLC) is an important tool for evaluation of formability of sheet metals subj... more Forming limit curve (FLC) is an important tool for evaluation of formability of sheet metals subjected to different loading. Free bulge of aluminume tubes has been investigated numerically to obtain FLC. To verify the numerical results one experimental setup has been manufactured which has the ability of controlling the internal pressure and axial feed. In this study, time and zone of bursting in tube hydroforming is predicted using seven ductile fracture criteria. For calibration of these criteria, the uniaxial tension is simulated in Abaqus/Explicit. Different loading curves are applied on tube to obtain the different points of FLC. Predicted FLCs by ductile fracture criteria have been compared with experimental results. The FLC which is predicted by Ayada' s criterion has best match to experimental one. Results show that Prediction of all criteria are the same in strain position which is similar to uniaxial tension. Based on the results, criteria which apply the effect of average stress in prediction of dutile fracture are more appropriate for tube hydroforming process.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
Forming limit curve (FLC) is an important tool for evaluation of formability of sheet metals subj... more Forming limit curve (FLC) is an important tool for evaluation of formability of sheet metals subjected to different loading. Free bulge of aluminume tubes has been investigated numerically to obtain FLC. To verify the numerical results one experimental setup has been manufactured which has the ability of controlling the internal pressure and axial feed. In this study, time and zone of bursting in tube hydroforming is predicted using seven ductile fracture criteria. For calibration of these criteria, the uniaxial tension is simulated in Abaqus/Explicit. Different loading curves are applied on tube to obtain the different points of FLC. Predicted FLCs by ductile fracture criteria have been compared with experimental results. The FLC which is predicted by Ayada' s criterion has best match to experimental one. Results show that Prediction of all criteria are the same in strain position which is similar to uniaxial tension. Based on the results, criteria which apply the effect of average stress in prediction of dutile fracture are more appropriate for tube hydroforming process.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
In this research, the steady-state flow filed around a 3D body and rotor configuration of the ROB... more In this research, the steady-state flow filed around a 3D body and rotor configuration of the ROBIN helicopter is simulated. The rotor is modeled by an actuator disk. For this purpose, an annular computational domain replaces the rotor and some modeled source terms are added to the momentum equations. This modeling of rotor considerably speed up computational time. The flow field over this helicopter fuselage is simulated for six cases of different advance ratios and thrust coefficients. The accuracy of using uniform, linear and BET distributions for the rotor in the source term is investigated. With the BET and some corrections to pitch angles, pressure coefficients and variation of thrust and power of rotor are predicted in agreement with experimental data. For the nominal thrust coefficient of 0.06, different loading methods on rotor using experimental results are compared for two advance ratio of 0.05 and 0.23. In the advance ratio of 0.23 for the upper surface of helicopter, no considerable difference among the different employed methods is observed. However, for the advance ratio of 0.05 and for the side that helicopter blades get closer to the body (Starboard side), the results with the modified methods are better than BET method. The presence of strut in the computational domain has important effects in high speeds and causes reduction of pressure coefficients over body especially in downstream of the strut.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
In this paper, the capabilities of modeling linear viscoelasticty in a finite element method soft... more In this paper, the capabilities of modeling linear viscoelasticty in a finite element method software package (COMSOL Multiphysics) are investigated. The governing equations of linear viscoelasticity have been developed for 2D cases of plane stress and plane strain. These equations have been verified by solving a related engineering example. Since the developed equations are suitable for modeling of multiphysics mechanisms, the presented model can also be used for modeling of the linear viscoleasticity coupled with other multiphysics phenomena.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
In this paper, two API X70 steel pipes (with spiral seam weld) of 56 inch outside diameter and 0.... more In this paper, two API X70 steel pipes (with spiral seam weld) of 56 inch outside diameter and 0.780 inch wall thickness were girth welded first. Next, hole drilling tests were conducted for strain measurement on the surfaces of the pipes. The values of residual stresses on the internal and external surfaces of the pipe were determined, from strain data using ASTM 837 standard. The experimental data showed that the maximum tensile residual stress (318MPa) was located on the centre line of the weld gap on the pipe outer surface alongside with the pipe hoop direction. Moreover, the maximum compressive (hoop and axial) residual stresses (137MPa) occurred on the pipe inner surface at 30mm from the centre line of the weld gap.
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The Journal of Applied and Computational Sciences in Mechanics, 2014
In this paper, numerical investigation of a flat passive micromixer with heterogeneous surface pr... more In this paper, numerical investigation of a flat passive micromixer with heterogeneous surface properties that the flow through it, is driven by the electroosmotic flow have been presented. The governing equations, which consist of a Laplace equation for the distribution of external electric potential, a Poisson equation for the distribution of electric double layer potential, modified Navier-Stokes equations for the flow field, the Nernst-Planck equation for the distribution of ions concentration have been solved numerically for an incompressible steady flow of a Newtonian fluid using the finite-volume method. The key features of an ideal electro-osmotic flow with uniform zeta potential has been compared with analytical solutions for the ionic concentration and velocity fields for the validation of the numerical scheme. Results show that the arrangement of the heterogeneous surface properties has a significant impact on the efficiency of mixing. Maximum mixing efficiency is related to the condition that the asymmetry in the wall of the heterogeneous arrangement loads increase. The increase in intensity of the electric charge with constant power load of the electroosmotic micropump enhances the efficiency of mixing.
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