Journal of Applied and Computational Sciences in Mechanics | Ferdowsi University of Mashhad (original) (raw)

Papers by Journal of Applied and Computational Sciences in Mechanics

Journal of Applied and Computational Sciences in Mechanics, 2024

Today, liver cancer ranks sixth among cancers and ranks fourth among the causes of death. Examini... more Today, liver cancer ranks sixth among cancers and ranks fourth among the causes of death. Examining the condition of the body and early recognition of this disease can be effective in its control and treatment. Examining the mechanical properties of the liver tissue and studying its Young's modulus will identify the health status of the tissue and the patient. In this research, Young's modulus has been theoretically calculated using slab friction models, reset integration, and Bleiman and Sorin models. Also, using atomic force microscope, this modulus has been extracted experimentally. Comparison of theoretical and experimental modules obtained will have similar results. According to the examination of texture and relationships at the nano level, the second model of Billman and Sorin is more accurate due to the smaller range of changes and the more complex equation. Therefore, it is suggested to use the second model of Billman and Sorin in future researches.

Journal of Applied and Computational Sciences in Mechanics, 2024

In this study, the effect of using vortex generators in the form of semicircular plates with diff... more In this study, the effect of using vortex generators in the form of semicircular plates with different angles and at different longitudinal distances in the chimney of a laboratory furnace with natural gas fuel on the hydrodynamics of the flow and the rate of heat transfer from combustion products has been investigated experimentally and numerically. The investigated parameters were angles for blades and the number of blades. The results show that vortex generators with reducing the speed in the central area of the chimney and increasing the residence time of the combustion products and also by directing the flow towards the boundary layer adjacent to the wall, increases the heat transfer to the chimney. The angle of 55º and the number of blades 7 was the optimum condition that prevents the flow of exhaust gases from returning, and in this case, by changing the gas flow rate in the range of 0.5 to 0.75 m3/hr, the heat transfer to the chimney wall increases by 21% on average.

Journal of Applied and Computational Sciences in Mechanics, 2024

Nowadays, liquid cooling channels are used for cooling of electronic equipment. These channels ha... more Nowadays, liquid cooling channels are used for cooling of electronic equipment. These channels have to change the cross-section to pass over elements, so they undergo sudden contractions or expansions. These changes create areas that are unfavorable for heat transfer. Various methods have been proposed to improve heat transfer in these areas. In the present study, the possibility of using a nonuniform magnetic field to improve heat transfer in a millichannel including two sudden contractions has been discussed. In this study, it is assumed that a ferrofluid (EMG-805-a commercial brand) flows in the channel with a laminar regime, fully developed and steady state conditions. The walls of the channel are adiabatic, while the walls of the steps, which are in the vicinity of the electronic element, have a constant heat flux. The effects of different parameters, including locations of dipoles on the bottom and top walls, the number of dipoles, the Reynolds number, and the strength of the magnetic field on the improvement of heat transfer have been investigated. The obtained results show that the increase in Reynolds number and the strength of the magnetic field cause an increase in local Nusselt. The results show that applying a magnetic dipole on the bottom wall and just after the steps results in a significant increase in the local Nusselt number and an increase of 164.05% in the average Nusselt number compared to the case without a magnetic field.

Journal of Applied and Computational Sciences in Mechanics, 2024

Total hip joint replacement has problems, one of the most important of which is the stress shield... more Total hip joint replacement has problems, one of the most important of which is the stress shield phenomenon and weak bone growth. When the modulus of elasticity of the prosthesis is higher than that of the bone, most of the physiological load is transferred to the implant and the bone deteriorates. The solution to minimize it and strengthen bone growth is to use materials with elasticity modulus close to bone for prosthesis, and functionally graded materials (FGM) with porosity have shown better results than other materials. In this article, the model of cylinder and prosthesis based on ISO 7206-4 and the model of prosthesis and bone are used, and the results of applied stresses, stiffness of prostheses, and micromovements between prosthesis and bone are analyzed by the finite element method. The superiority of this study compared to previous studies is the use of prosthetic and cylinder models for different geometries and the investigation of micromovements and its effect on bone growth. The results show that the use of porous FGM prostheses for each different prosthesis geometry is effective in reducing the stress shield and bone growth.

Journal of Applied and Computational Sciences in Mechanics, 2024

The present study investigated mechanical properties such as Young's modulus and tensile strength... more The present study investigated mechanical properties such as Young's modulus and tensile strength of aluminum nanocomposite reinforced with defective graphene with vacancy and hole defects under uniaxial tension using molecular dynamics simulation. Also, the effect of the number of graphene layers in a constant volume ratio on the mechanical behavior of the nanocomposite has also been obtained. This simulation was done with the help of the LAMMPS open-source package by modeling a periodic system with NVE and NPT ensembles. The AIREBO and MEAM potentials were used to describe the interaction of carbon and aluminum atoms, respectively, and Lennard Jones potential was used for the interaction between these atoms. The obtained results show that adding a single layer of graphene to the structure of pure aluminum has improved Young's modulus and tensile strength of pure aluminum by 220 and 320%, respectively. In addition, it is observed that the effect of pinhole and vacancy defects on Young's modulus and tensile strength is non-linear and has a decreasing trend.

Journal of Applied and Computational Sciences in Mechanics, 2024

Heat transfer in boiler with supercritical fluid is asymmetrical. Also, in this type of boilers, ... more Heat transfer in boiler with supercritical fluid is asymmetrical. Also, in this type of boilers, pipes are installed both horizontally and inclined. But usually in the previous works, heat transfer is considered symmetrically or the pipes are horizontal or vertical. Therefore, in the present paper, heat transfer in a boiler tube with supercritical fluid in which there are both horizontal and inclined parts is studied and analyzed. The heat flux of the pipe is considered asymmetric. Numerical simulation has been done using Fluent software. Also, the REFPROP database has been used to apply the supercritical fluid properties of water. In order to model the turbulence, the RNG k-ε model based on Reynolds-averaged Navier-Stokes has been used. The results show that the highest and lowest internal tube temperature reach near the pseudocritical temperature range (380 Celsius) at a height of 10 m and 15.5 m, respectively. The highest temperature of the tube wall changes from the beginning to the end of the tube between 603 o C and 666 o C. Also, the Nusselt number increases with the increase of the tube height and its value increases significantly near the pseudocritical temperature. In this range, the value of the Nusselt number reaches 6800, which is 3.6 times its value at the entrance of the tube.

Journal of Applied and Computational Sciences in Mechanics, 2024

This paper considers a three-dimensional micropump based on a piezoelectric actuator. COMSOL soft... more This paper considers a three-dimensional micropump based on a piezoelectric actuator. COMSOL software version 6.5 is used to simulate the performance of the micropump. At first, a reference micropump is defined, which works at a frequency of 60 Hz and a voltage of 1500 V that is capable of pumping a maximum flow rate of 0.038 ml/s. The influence of frequency, voltage, the axial position of input and output of micropump, dimensions of piezoelectric actuator and membrane, and shape of the actuator on the fluid output flow rate and pumped fluid volume is investigated. The results demonstrate that the frequency, voltage, dimensions of the piezoelectric actuator and the membrane has a direct effect on the output flow rate and the pumped fluid volume so that the output flow rate of the fluid and the volume of the pumped fluid increase with the increase of these parameters. For example, the output flow rate of the micropump at 100 and 20 Hz frequency is 0.065 and 0.011 ml/s, respectively. By increasing the voltage from 1500 to 1875 V, the micropump output flow rate increases to 0.047 ml/s. The results show that the rectangular piezoelectric actuator has a lower efficiency than the circular one.

Journal of Applied and Computational Sciences in Mechanics, 2010

In this paper the performance of a Savonius wind turbine has been studied both experimentally and... more In this paper the performance of a Savonius wind turbine has been studied both experimentally and theoretically using the FloEFD software. Two different types of vertical axis Savonius rotor, namely, conventional and advanced rotors, have been compared. It is shown that the coefficient of static moment for an advanced Savonius rotor is about 11% more than that for a conventional one. A study has also been conducted to investigate the variation of the power coefficient for the advanced Savonius rotor installed in MERC and recommendations have been presented to enhance its performance.

Journal of Applied and Computational Sciences in Mechanics, 2010

In this paper,variable confinement parameters were successfully developed for compressible vortic... more In this paper,variable confinement parameters were successfully developed for compressible vorticity confinement. Three variable confinement parameters that have velocity dimension were defined based on three artificial dissipation schemes. The resulting confinement parameters are functions of spectral radii of the Jacobian matrices and the Jacobian matrices themselves. Therefore, the confinement parameters implicitly contain the grid size and the other local fluid properties. The ability of the new confinement parameters for 3-D supersonic flows over a blunt-nose-cylinder at high angles of attack with massive separation in the presence of an adverse pressure gradient condition was considered. Effect of various dissipation schemes on the solution was studied. Results showed that the new confinement parameters allow the capture of vortical layers. Vorticity confinement prevents the diffusion of the secondary vortex at leeside plane on coarse grid. As the grid size increases, improvement of the results (especially, confinement results of CUSP confinement parameter) is seen. When variable confinement parameters are used, the tuning constant is equal to or larger than the equivalent value of the constant confinement [Hu et al.][8]. This means that this value is closer to the unity than constant confinement, especially for CUSP confinement parameter.

Journal of Applied and Computational Sciences in Mechanics, 2010

Exergy analysis is a method that can calculate thermodynamic losses by means of second law of the... more Exergy analysis is a method that can calculate thermodynamic losses by means of second law of thermodynamic. In this study, exergy analysis has been performed for the silencer of OM314 diesel engine. Irreversibility due to heat transfer from silencer to environment, silencer's internal irreversibility and total irreversibility for different conditions of engine operation have been measured and calculated. For finding out the relation between irreversibility and exit sound intensity, simultaneously, exit sound intensity from the silencer has been measured. Results illustrate that by tripling of silencer irreversibility, exit sound intensity increases only 10 percent. Also the results shows that the irreversibility due to heat transfers have the most contribution in total irreversibility of silencer. So from the view point of second law of thermodynamics, it seems that cooling the silencer can be an effective method for sound reduction. Also results illustrate that, sound intensity of silencer is basically dependent to engine speed.

Journal of Applied and Computational Sciences in Mechanics, 2010

The aim of this article is analyzing heat and mass transfer in counter current open cooling tower... more The aim of this article is analyzing heat and mass transfer in counter current open cooling towers. After reviewing preceding researches and rewriting the governing equations, a method is proposed which is independent of Lewis number variations in solving the problem, has been introduced. Also, the effect of Lewis number variations has been compared with this method. This method has been presented in Design and Rating situations which is more comprehensive than the preceding researches. Finally, the results of present method have been analyzed and investigated using the performance data of an industrial cooling tower.

Journal of Applied and Computational Sciences in Mechanics, 2010

In recent years, the hydroforming has attracted the attention of the automotive industry due to r... more In recent years, the hydroforming has attracted the attention of the automotive industry due to reduction in weight and increase in strength of automotive parts. Thus, the knowledge of the process to produce parts with desired quality and accuracy has been growing. One of the effective methods in improving the formability in the hydroforming is known as pulsating hydroforming. However, the reason of improvement of the formability in pulsating hydroforming is still unclear for the closed-die hydroforming of tubes. In this study, the pulsating hydroforming of tube with box die was simulated by the finite element method to examine the effect of pulsating pressure on improvement of formability. In addition, the calculated results are compared with experimental results and it is shown that the improvement of the formability occurs before contact of the tube and die in expansion zone of the tube. Thus, it can be obtained from the results, that the main reason of improvement of the formability is due to the deformation behavior before start of contact of the tube and die. Flat bulging appears for the pulsating pressure in the former stage, whereas round bulging and wrinkling occur for the high and low non-pulsating pressures, respectively.

Journal of Applied and Computational Sciences in Mechanics, 2010

Engine cooling system plays a major role in performance of vehicle engine, in which the radiator ... more Engine cooling system plays a major role in performance of vehicle engine, in which the radiator and the fan are the main components. In this article, the performance of two fans with different characteristics has been appraised within an engine cooling system. For this purpose, performance characteristics curves of both fans, including, static pressure and total pressure against flow rate have been generated. Then a test rig, similar to that of an engine's cooling system, was set up for the fan and the radiator. Subsequently the air flow rate and Radiator's inlet flow distribution have been measured precisely under working conditions using hot wire anemometer. also, the inlet airflow pattern was analyzed. Results reveal that intersection point of the system resistance curve and static pressure curve of the fans, do not represent the actual and true values of flow rate of the fans. However the actual flow rate is less than those anticipated. Then, some modifications were made to the entrance of one of the fans and it's shroud, and similar tests have been performed. Although the test results after modification showed more uniformity in the flow towards the radiator, the increase of flow rate was minimal in the cooling system. Also, road tests of the vehicle did not represent much improvement on the performance of the cooling system.

Journal of Applied and Computational Sciences in Mechanics, 2010

Light wells are extensively used in high-rise buildings as an integrated part of the building for... more Light wells are extensively used in high-rise buildings as an integrated part of the building for daylighting. Since the solar illuminance is usually higher on horizontal surfaces than the vertical ones, roof skylights transmit more daylight than vertical windows. For proper design of daylighting, a parametric study on the effective parameters in daylighting is required. In this study, the effects of these parameters are investigated for a four-story building. Attenuation of the daylight in the floors, effects of reflectivity of the surfaces of the light well, as well as effects of the reflectivities of light well floor and room walls, effects of the dimensions of the skylight, and the slope of skylight to horizon have been studied,. The daylight factor for the three situations of the lightwell: four-sided, three-sided, and in the corner of the building have been obtained. The radiosity method or point by point algorithm has been used for daylighting calculations. Results of the present study can be used in improving the daylighting of the buildings.

Journal of Applied and Computational Sciences in Mechanics, 2010

In this paper, Fluent software is used to study the flow behavior of methane and air in a CNG-air... more In this paper, Fluent software is used to study the flow behavior of methane and air in a CNG-air mixer. Analyses were carried out on various designs to investigate the effect of engine speed on the λ. The design was optimized for throat size, number and size of the holes at the throat circumference. The prototypes were manufactured based on optimized dimensions that were obtained from CFD analyses. The experiments have been done on the prototypes in order to verify the results obtained from CFD analyses. The results show that the performance of the optimized design was good and the decrease of engine power was about 10% and the pollutants such as CO and HC in the gas mode in comparison with the gasoline mode were decreased 100% and 79% respectively.

Journal of Applied and Computational Sciences in Mechanics, 2010

In this paper, an analytical solution is presented to consider the effect of electromechanical co... more In this paper, an analytical solution is presented to consider the effect of electromechanical coupling on the interlaminar stresses at the free-edge of an angle-ply piezoelectric laminated plate. To this end, a variational approach is used to investigate the free-edge effect in a long laminated piezoelectric plate under uniform axial strain. A comparison of coupled and uncoupled piezoelectric analysis is performed using the second-order shear deformation plate theory. The analytical solutions are discussed and compared with numerical results available in the literature. It is found that the interlaminar stresses at the free-edge are significantly higher in the coupled case for cross-ply laminates, whereas the coupling effect for the symmetric angle-ply laminate is of minor significance.

Journal of Applied and Computational Sciences in Mechanics, 2010

In this paper, Oseen differential equation and continuity equations are solved for viscous flow a... more In this paper, Oseen differential equation and continuity equations are solved for viscous flow around a stationary sphere using Lamb relations for velocity and pressure components. It is assumed that the tangential stress is proportional to the slip velocity on the surface. Slip considerably affects the tangential and radial velocity profiles such that increasing slip at a given Reynolds number delays flow separation and inflect point creation in velocity profiles. Slip effects on total drag coefficient at lower Reynolds number are relatively limited. Increasing slip on the surface decreases the shear drag coefficient, while the radial drag coefficient increases. At full-slip conditions, shear drag coefficient is basically zero and radial drag coefficient reaches its maximum value. Therefore, it is concluded that flow around the spherical nano particle at full-slip condition is not equal to potential flow around the spherical particle.

Journal of Applied and Computational Sciences in Mechanics, 2010

The fuller die, which is used for elongated components, is a type of perform die employed in the ... more The fuller die, which is used for elongated components, is a type of perform die employed in the closed-die forging process. In this research, using the finite-element method and the model test technique, both the required load and material flow are studied for the four-blow fullering operation. The experiments are conducted using lead as the model material and steel tools. Comparison of the numerical predictions and experimental results show a good agreement between them. For the extension of various process variables, FEM simulations are performed using ANSYS commercial software. Then, by means of linear regression and based on the finite-element results, some useful relationships are proposed for prediction of elongation, sideways spread and the required load for the four-blow fullering process. The designers can use the results of this investigation for prediction of elongation, sideways spread and fullering load instead of time consuming and expensive experiments.

Journal of Applied and Computational Sciences in Mechanics, 2010

Seamless tubular components with various cross sections, such as cylindrical, conical, and square... more Seamless tubular components with various cross sections, such as cylindrical, conical, and square cross section stepped tubes, are mainly produced in a tube hydroforming process. In forming those parts with this process, achieving shapes with sharp corners, requires an increase in the internal pressure. This may cause local thinning and bursting at the tube corners. The authors propose a new hydroforming die set in which the die corner filling is improved for cylindrical stepped tubes. In the new die, the forming of tube consists of two steps of bulging and final forming. In this paper, the effect of pressure path on thickness distribution and geometry of stepped tubes are studied by finite element simulation and experiment. The results in this paper illustrate that the bulging pressure and the pressure-axial feeding of the final forming stage influence the desired final geometry and that the proper selection of these parameters affects on the deformed part geometry. It is also shown that in the new die set it is possible to produce a sound part with uniform thickness distribution along the wall side.

Journal of Applied and Computational Sciences in Mechanics, 2010

Successful development, evaluation, and qualification of propulsion systems such as turbojet and ... more Successful development, evaluation, and qualification of propulsion systems such as turbojet and turbofan engines and rocket motors require the measurement of the performance and reliability of these systems. Thrust stands or testers are instruments for solid and liquid motors test. In this paper, a method for calculation of solid motors random vibrations effects on a thrust stand structure is developed. At first some Power Spectral Density (PSD) of three kinds of solid motors has been calculated by MATLAB codes. Then a typical thrust stand which has been designed based on special dynamics principles, has been modeled in Solidworks and transferred to ANSYS. In ANSYS, the modal and spectral analysis of the structure has been done. Then each motor's PSD has been applied on structure separately and maximum stress has been determined by ANSYS codes. Followed by structure fatigue life has been estimated by a formula derived from compound of Miner's cumulative fatigue damage ratio equation and Gaussian distribution curve. The results show that the amount of PSD at first frequencies has significant effect on structure fatigue life and it is not possible to reach to a conclusion about the vibrations effect, just based on maximum motor thrust.

Journal of Applied and Computational Sciences in Mechanics, 2024

Today, liver cancer ranks sixth among cancers and ranks fourth among the causes of death. Examini... more Today, liver cancer ranks sixth among cancers and ranks fourth among the causes of death. Examining the condition of the body and early recognition of this disease can be effective in its control and treatment. Examining the mechanical properties of the liver tissue and studying its Young's modulus will identify the health status of the tissue and the patient. In this research, Young's modulus has been theoretically calculated using slab friction models, reset integration, and Bleiman and Sorin models. Also, using atomic force microscope, this modulus has been extracted experimentally. Comparison of theoretical and experimental modules obtained will have similar results. According to the examination of texture and relationships at the nano level, the second model of Billman and Sorin is more accurate due to the smaller range of changes and the more complex equation. Therefore, it is suggested to use the second model of Billman and Sorin in future researches.

Journal of Applied and Computational Sciences in Mechanics, 2024

In this study, the effect of using vortex generators in the form of semicircular plates with diff... more In this study, the effect of using vortex generators in the form of semicircular plates with different angles and at different longitudinal distances in the chimney of a laboratory furnace with natural gas fuel on the hydrodynamics of the flow and the rate of heat transfer from combustion products has been investigated experimentally and numerically. The investigated parameters were angles for blades and the number of blades. The results show that vortex generators with reducing the speed in the central area of the chimney and increasing the residence time of the combustion products and also by directing the flow towards the boundary layer adjacent to the wall, increases the heat transfer to the chimney. The angle of 55º and the number of blades 7 was the optimum condition that prevents the flow of exhaust gases from returning, and in this case, by changing the gas flow rate in the range of 0.5 to 0.75 m3/hr, the heat transfer to the chimney wall increases by 21% on average.

Journal of Applied and Computational Sciences in Mechanics, 2024

Nowadays, liquid cooling channels are used for cooling of electronic equipment. These channels ha... more Nowadays, liquid cooling channels are used for cooling of electronic equipment. These channels have to change the cross-section to pass over elements, so they undergo sudden contractions or expansions. These changes create areas that are unfavorable for heat transfer. Various methods have been proposed to improve heat transfer in these areas. In the present study, the possibility of using a nonuniform magnetic field to improve heat transfer in a millichannel including two sudden contractions has been discussed. In this study, it is assumed that a ferrofluid (EMG-805-a commercial brand) flows in the channel with a laminar regime, fully developed and steady state conditions. The walls of the channel are adiabatic, while the walls of the steps, which are in the vicinity of the electronic element, have a constant heat flux. The effects of different parameters, including locations of dipoles on the bottom and top walls, the number of dipoles, the Reynolds number, and the strength of the magnetic field on the improvement of heat transfer have been investigated. The obtained results show that the increase in Reynolds number and the strength of the magnetic field cause an increase in local Nusselt. The results show that applying a magnetic dipole on the bottom wall and just after the steps results in a significant increase in the local Nusselt number and an increase of 164.05% in the average Nusselt number compared to the case without a magnetic field.

Journal of Applied and Computational Sciences in Mechanics, 2024

Total hip joint replacement has problems, one of the most important of which is the stress shield... more Total hip joint replacement has problems, one of the most important of which is the stress shield phenomenon and weak bone growth. When the modulus of elasticity of the prosthesis is higher than that of the bone, most of the physiological load is transferred to the implant and the bone deteriorates. The solution to minimize it and strengthen bone growth is to use materials with elasticity modulus close to bone for prosthesis, and functionally graded materials (FGM) with porosity have shown better results than other materials. In this article, the model of cylinder and prosthesis based on ISO 7206-4 and the model of prosthesis and bone are used, and the results of applied stresses, stiffness of prostheses, and micromovements between prosthesis and bone are analyzed by the finite element method. The superiority of this study compared to previous studies is the use of prosthetic and cylinder models for different geometries and the investigation of micromovements and its effect on bone growth. The results show that the use of porous FGM prostheses for each different prosthesis geometry is effective in reducing the stress shield and bone growth.

Journal of Applied and Computational Sciences in Mechanics, 2024

The present study investigated mechanical properties such as Young's modulus and tensile strength... more The present study investigated mechanical properties such as Young's modulus and tensile strength of aluminum nanocomposite reinforced with defective graphene with vacancy and hole defects under uniaxial tension using molecular dynamics simulation. Also, the effect of the number of graphene layers in a constant volume ratio on the mechanical behavior of the nanocomposite has also been obtained. This simulation was done with the help of the LAMMPS open-source package by modeling a periodic system with NVE and NPT ensembles. The AIREBO and MEAM potentials were used to describe the interaction of carbon and aluminum atoms, respectively, and Lennard Jones potential was used for the interaction between these atoms. The obtained results show that adding a single layer of graphene to the structure of pure aluminum has improved Young's modulus and tensile strength of pure aluminum by 220 and 320%, respectively. In addition, it is observed that the effect of pinhole and vacancy defects on Young's modulus and tensile strength is non-linear and has a decreasing trend.

Journal of Applied and Computational Sciences in Mechanics, 2024

Heat transfer in boiler with supercritical fluid is asymmetrical. Also, in this type of boilers, ... more Heat transfer in boiler with supercritical fluid is asymmetrical. Also, in this type of boilers, pipes are installed both horizontally and inclined. But usually in the previous works, heat transfer is considered symmetrically or the pipes are horizontal or vertical. Therefore, in the present paper, heat transfer in a boiler tube with supercritical fluid in which there are both horizontal and inclined parts is studied and analyzed. The heat flux of the pipe is considered asymmetric. Numerical simulation has been done using Fluent software. Also, the REFPROP database has been used to apply the supercritical fluid properties of water. In order to model the turbulence, the RNG k-ε model based on Reynolds-averaged Navier-Stokes has been used. The results show that the highest and lowest internal tube temperature reach near the pseudocritical temperature range (380 Celsius) at a height of 10 m and 15.5 m, respectively. The highest temperature of the tube wall changes from the beginning to the end of the tube between 603 o C and 666 o C. Also, the Nusselt number increases with the increase of the tube height and its value increases significantly near the pseudocritical temperature. In this range, the value of the Nusselt number reaches 6800, which is 3.6 times its value at the entrance of the tube.

Journal of Applied and Computational Sciences in Mechanics, 2024

This paper considers a three-dimensional micropump based on a piezoelectric actuator. COMSOL soft... more This paper considers a three-dimensional micropump based on a piezoelectric actuator. COMSOL software version 6.5 is used to simulate the performance of the micropump. At first, a reference micropump is defined, which works at a frequency of 60 Hz and a voltage of 1500 V that is capable of pumping a maximum flow rate of 0.038 ml/s. The influence of frequency, voltage, the axial position of input and output of micropump, dimensions of piezoelectric actuator and membrane, and shape of the actuator on the fluid output flow rate and pumped fluid volume is investigated. The results demonstrate that the frequency, voltage, dimensions of the piezoelectric actuator and the membrane has a direct effect on the output flow rate and the pumped fluid volume so that the output flow rate of the fluid and the volume of the pumped fluid increase with the increase of these parameters. For example, the output flow rate of the micropump at 100 and 20 Hz frequency is 0.065 and 0.011 ml/s, respectively. By increasing the voltage from 1500 to 1875 V, the micropump output flow rate increases to 0.047 ml/s. The results show that the rectangular piezoelectric actuator has a lower efficiency than the circular one.

Journal of Applied and Computational Sciences in Mechanics, 2010

In this paper the performance of a Savonius wind turbine has been studied both experimentally and... more In this paper the performance of a Savonius wind turbine has been studied both experimentally and theoretically using the FloEFD software. Two different types of vertical axis Savonius rotor, namely, conventional and advanced rotors, have been compared. It is shown that the coefficient of static moment for an advanced Savonius rotor is about 11% more than that for a conventional one. A study has also been conducted to investigate the variation of the power coefficient for the advanced Savonius rotor installed in MERC and recommendations have been presented to enhance its performance.

Journal of Applied and Computational Sciences in Mechanics, 2010

In this paper,variable confinement parameters were successfully developed for compressible vortic... more In this paper,variable confinement parameters were successfully developed for compressible vorticity confinement. Three variable confinement parameters that have velocity dimension were defined based on three artificial dissipation schemes. The resulting confinement parameters are functions of spectral radii of the Jacobian matrices and the Jacobian matrices themselves. Therefore, the confinement parameters implicitly contain the grid size and the other local fluid properties. The ability of the new confinement parameters for 3-D supersonic flows over a blunt-nose-cylinder at high angles of attack with massive separation in the presence of an adverse pressure gradient condition was considered. Effect of various dissipation schemes on the solution was studied. Results showed that the new confinement parameters allow the capture of vortical layers. Vorticity confinement prevents the diffusion of the secondary vortex at leeside plane on coarse grid. As the grid size increases, improvement of the results (especially, confinement results of CUSP confinement parameter) is seen. When variable confinement parameters are used, the tuning constant is equal to or larger than the equivalent value of the constant confinement [Hu et al.][8]. This means that this value is closer to the unity than constant confinement, especially for CUSP confinement parameter.

Journal of Applied and Computational Sciences in Mechanics, 2010

Exergy analysis is a method that can calculate thermodynamic losses by means of second law of the... more Exergy analysis is a method that can calculate thermodynamic losses by means of second law of thermodynamic. In this study, exergy analysis has been performed for the silencer of OM314 diesel engine. Irreversibility due to heat transfer from silencer to environment, silencer's internal irreversibility and total irreversibility for different conditions of engine operation have been measured and calculated. For finding out the relation between irreversibility and exit sound intensity, simultaneously, exit sound intensity from the silencer has been measured. Results illustrate that by tripling of silencer irreversibility, exit sound intensity increases only 10 percent. Also the results shows that the irreversibility due to heat transfers have the most contribution in total irreversibility of silencer. So from the view point of second law of thermodynamics, it seems that cooling the silencer can be an effective method for sound reduction. Also results illustrate that, sound intensity of silencer is basically dependent to engine speed.

Journal of Applied and Computational Sciences in Mechanics, 2010

The aim of this article is analyzing heat and mass transfer in counter current open cooling tower... more The aim of this article is analyzing heat and mass transfer in counter current open cooling towers. After reviewing preceding researches and rewriting the governing equations, a method is proposed which is independent of Lewis number variations in solving the problem, has been introduced. Also, the effect of Lewis number variations has been compared with this method. This method has been presented in Design and Rating situations which is more comprehensive than the preceding researches. Finally, the results of present method have been analyzed and investigated using the performance data of an industrial cooling tower.

Journal of Applied and Computational Sciences in Mechanics, 2010

In recent years, the hydroforming has attracted the attention of the automotive industry due to r... more In recent years, the hydroforming has attracted the attention of the automotive industry due to reduction in weight and increase in strength of automotive parts. Thus, the knowledge of the process to produce parts with desired quality and accuracy has been growing. One of the effective methods in improving the formability in the hydroforming is known as pulsating hydroforming. However, the reason of improvement of the formability in pulsating hydroforming is still unclear for the closed-die hydroforming of tubes. In this study, the pulsating hydroforming of tube with box die was simulated by the finite element method to examine the effect of pulsating pressure on improvement of formability. In addition, the calculated results are compared with experimental results and it is shown that the improvement of the formability occurs before contact of the tube and die in expansion zone of the tube. Thus, it can be obtained from the results, that the main reason of improvement of the formability is due to the deformation behavior before start of contact of the tube and die. Flat bulging appears for the pulsating pressure in the former stage, whereas round bulging and wrinkling occur for the high and low non-pulsating pressures, respectively.

Journal of Applied and Computational Sciences in Mechanics, 2010

Engine cooling system plays a major role in performance of vehicle engine, in which the radiator ... more Engine cooling system plays a major role in performance of vehicle engine, in which the radiator and the fan are the main components. In this article, the performance of two fans with different characteristics has been appraised within an engine cooling system. For this purpose, performance characteristics curves of both fans, including, static pressure and total pressure against flow rate have been generated. Then a test rig, similar to that of an engine's cooling system, was set up for the fan and the radiator. Subsequently the air flow rate and Radiator's inlet flow distribution have been measured precisely under working conditions using hot wire anemometer. also, the inlet airflow pattern was analyzed. Results reveal that intersection point of the system resistance curve and static pressure curve of the fans, do not represent the actual and true values of flow rate of the fans. However the actual flow rate is less than those anticipated. Then, some modifications were made to the entrance of one of the fans and it's shroud, and similar tests have been performed. Although the test results after modification showed more uniformity in the flow towards the radiator, the increase of flow rate was minimal in the cooling system. Also, road tests of the vehicle did not represent much improvement on the performance of the cooling system.

Journal of Applied and Computational Sciences in Mechanics, 2010

Light wells are extensively used in high-rise buildings as an integrated part of the building for... more Light wells are extensively used in high-rise buildings as an integrated part of the building for daylighting. Since the solar illuminance is usually higher on horizontal surfaces than the vertical ones, roof skylights transmit more daylight than vertical windows. For proper design of daylighting, a parametric study on the effective parameters in daylighting is required. In this study, the effects of these parameters are investigated for a four-story building. Attenuation of the daylight in the floors, effects of reflectivity of the surfaces of the light well, as well as effects of the reflectivities of light well floor and room walls, effects of the dimensions of the skylight, and the slope of skylight to horizon have been studied,. The daylight factor for the three situations of the lightwell: four-sided, three-sided, and in the corner of the building have been obtained. The radiosity method or point by point algorithm has been used for daylighting calculations. Results of the present study can be used in improving the daylighting of the buildings.

Journal of Applied and Computational Sciences in Mechanics, 2010

In this paper, Fluent software is used to study the flow behavior of methane and air in a CNG-air... more In this paper, Fluent software is used to study the flow behavior of methane and air in a CNG-air mixer. Analyses were carried out on various designs to investigate the effect of engine speed on the λ. The design was optimized for throat size, number and size of the holes at the throat circumference. The prototypes were manufactured based on optimized dimensions that were obtained from CFD analyses. The experiments have been done on the prototypes in order to verify the results obtained from CFD analyses. The results show that the performance of the optimized design was good and the decrease of engine power was about 10% and the pollutants such as CO and HC in the gas mode in comparison with the gasoline mode were decreased 100% and 79% respectively.

Journal of Applied and Computational Sciences in Mechanics, 2010

In this paper, an analytical solution is presented to consider the effect of electromechanical co... more In this paper, an analytical solution is presented to consider the effect of electromechanical coupling on the interlaminar stresses at the free-edge of an angle-ply piezoelectric laminated plate. To this end, a variational approach is used to investigate the free-edge effect in a long laminated piezoelectric plate under uniform axial strain. A comparison of coupled and uncoupled piezoelectric analysis is performed using the second-order shear deformation plate theory. The analytical solutions are discussed and compared with numerical results available in the literature. It is found that the interlaminar stresses at the free-edge are significantly higher in the coupled case for cross-ply laminates, whereas the coupling effect for the symmetric angle-ply laminate is of minor significance.

Journal of Applied and Computational Sciences in Mechanics, 2010

In this paper, Oseen differential equation and continuity equations are solved for viscous flow a... more In this paper, Oseen differential equation and continuity equations are solved for viscous flow around a stationary sphere using Lamb relations for velocity and pressure components. It is assumed that the tangential stress is proportional to the slip velocity on the surface. Slip considerably affects the tangential and radial velocity profiles such that increasing slip at a given Reynolds number delays flow separation and inflect point creation in velocity profiles. Slip effects on total drag coefficient at lower Reynolds number are relatively limited. Increasing slip on the surface decreases the shear drag coefficient, while the radial drag coefficient increases. At full-slip conditions, shear drag coefficient is basically zero and radial drag coefficient reaches its maximum value. Therefore, it is concluded that flow around the spherical nano particle at full-slip condition is not equal to potential flow around the spherical particle.

Journal of Applied and Computational Sciences in Mechanics, 2010

The fuller die, which is used for elongated components, is a type of perform die employed in the ... more The fuller die, which is used for elongated components, is a type of perform die employed in the closed-die forging process. In this research, using the finite-element method and the model test technique, both the required load and material flow are studied for the four-blow fullering operation. The experiments are conducted using lead as the model material and steel tools. Comparison of the numerical predictions and experimental results show a good agreement between them. For the extension of various process variables, FEM simulations are performed using ANSYS commercial software. Then, by means of linear regression and based on the finite-element results, some useful relationships are proposed for prediction of elongation, sideways spread and the required load for the four-blow fullering process. The designers can use the results of this investigation for prediction of elongation, sideways spread and fullering load instead of time consuming and expensive experiments.

Journal of Applied and Computational Sciences in Mechanics, 2010

Seamless tubular components with various cross sections, such as cylindrical, conical, and square... more Seamless tubular components with various cross sections, such as cylindrical, conical, and square cross section stepped tubes, are mainly produced in a tube hydroforming process. In forming those parts with this process, achieving shapes with sharp corners, requires an increase in the internal pressure. This may cause local thinning and bursting at the tube corners. The authors propose a new hydroforming die set in which the die corner filling is improved for cylindrical stepped tubes. In the new die, the forming of tube consists of two steps of bulging and final forming. In this paper, the effect of pressure path on thickness distribution and geometry of stepped tubes are studied by finite element simulation and experiment. The results in this paper illustrate that the bulging pressure and the pressure-axial feeding of the final forming stage influence the desired final geometry and that the proper selection of these parameters affects on the deformed part geometry. It is also shown that in the new die set it is possible to produce a sound part with uniform thickness distribution along the wall side.

Journal of Applied and Computational Sciences in Mechanics, 2010

Successful development, evaluation, and qualification of propulsion systems such as turbojet and ... more Successful development, evaluation, and qualification of propulsion systems such as turbojet and turbofan engines and rocket motors require the measurement of the performance and reliability of these systems. Thrust stands or testers are instruments for solid and liquid motors test. In this paper, a method for calculation of solid motors random vibrations effects on a thrust stand structure is developed. At first some Power Spectral Density (PSD) of three kinds of solid motors has been calculated by MATLAB codes. Then a typical thrust stand which has been designed based on special dynamics principles, has been modeled in Solidworks and transferred to ANSYS. In ANSYS, the modal and spectral analysis of the structure has been done. Then each motor's PSD has been applied on structure separately and maximum stress has been determined by ANSYS codes. Followed by structure fatigue life has been estimated by a formula derived from compound of Miner's cumulative fatigue damage ratio equation and Gaussian distribution curve. The results show that the amount of PSD at first frequencies has significant effect on structure fatigue life and it is not possible to reach to a conclusion about the vibrations effect, just based on maximum motor thrust.