Amirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Numerical Investigation of Vortex-Induced Vibrations of an elastically-mounted
Circular Cylinder Beneath a Free Surface: Modes & FrequenciesNumerical Investigation of Vortex-Induced Vibrations of an elastically-mounted
Circular Cylinder Beneath a Free Surface: Modes & Frequencies11691186276510.22060/mej.2017.13236.5578FASeyed MostafaHosseinalipoorIran University of Science and TechnologyNavidHaji Ghafoori BoukaniIran University of Science and TechnologyJournal Article20170805In this paper, a two-dimensional numerical simulation is applied to study the Vortex[1]Induced Vibrations (VIV) of an elastically mounted rigid circular cylinder beneath a free surface of fluid. The effect of free surface in laminar flow (60 < Re < 130) with Fr=0.2 is investigated with considering two Gap-Ratios of 2.5, 1.5. The natural structural frequency of oscillator is assumed to match the vortex shedding frequency for a stationary cylinder at Re=100. Simulations of VIV and Free Surface of fluid flow have separately shown good agreement with previous results. User Defined Function (UDF) hooked in the Software is given to couple the motion of cylinder to flow motion. For simulation of free surface, Volume of fluid (VOF) method is used. This paper is the second part of an investigation about effects of Free Surface of fluid on VIV phenomena. The effects of Free Surface is investigated with using a comparison of vortex shedding modes and non-dimensional frequency diagrams for the two Gap-Ratios. With approaching cylinder to free surface, results shows changing type of vortex shedding modes, abatement in lock-in region, increasing Strouhal number and non[1]dimensional frequency ratio.In this paper, a two-dimensional numerical simulation is applied to study the Vortex[1]Induced Vibrations (VIV) of an elastically mounted rigid circular cylinder beneath a free surface of fluid. The effect of free surface in laminar flow (60 < Re < 130) with Fr=0.2 is investigated with considering two Gap-Ratios of 2.5, 1.5. The natural structural frequency of oscillator is assumed to match the vortex shedding frequency for a stationary cylinder at Re=100. Simulations of VIV and Free Surface of fluid flow have separately shown good agreement with previous results. User Defined Function (UDF) hooked in the Software is given to couple the motion of cylinder to flow motion. For simulation of free surface, Volume of fluid (VOF) method is used. This paper is the second part of an investigation about effects of Free Surface of fluid on VIV phenomena. The effects of Free Surface is investigated with using a comparison of vortex shedding modes and non-dimensional frequency diagrams for the two Gap-Ratios. With approaching cylinder to free surface, results shows changing type of vortex shedding modes, abatement in lock-in region, increasing Strouhal number and non[1]dimensional frequency ratio.https://mej.aut.ac.ir/article_2765_370bfb31abd222b582245b977ea5f25a.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Investigating the Influence of Geometry on Performance Characteristics of Mounted
Cushions in Hydraulic CylindersInvestigating the Influence of Geometry on Performance Characteristics of Mounted
Cushions in Hydraulic Cylinders11871200287210.22060/mej.2018.13391.5617FAMoeinMajnouni MehrdarSari agricultural sciences and natural resourcesDavoudKalantaribiosystem mechanics, agricultural engineering, Sari university of agricultural sciences and natural resources,Seyed RezaMousavi SeyedySari agricultural sciences and natural resourcesJournal Article20170907In this research, design, fabrication and evaluation of 5 different hydraulic cushions have been considered in order to optimize the stopping mechanism of pistons at the end of the course. The comparison of 5 cushion spears including Cylindrical, Conical, Sagittal, Double conical and Parabolic cushion have been studied with reviewing the motion behavior of piston and measuring displacement, speed, acceleration, flow rate and hydraulic pressure in an one way hydraulic cylinder. Results showed that the sagittal cushion with maximum pressure increasing of 1.98% for 200 kg load and 0.35% for 350 kg load had the lowest percentage of hydraulic pressure rise and cylindrical cushion with maximum pressure increasing of 11.98% for 200 kg load and 3.92% for 350 kg load had highest percentage of hydraulic pressure rise. Also operational time of sagittal cushion in experiments with 350 kg load was respectively 33.8 and 63.9 percent lower than that of conical and cylindrical cushion. Also double conical cushion has the nearest performance to the sagittal cushion. As a concluding result with tacking into account the low response time, steady speed reduction and steady rate of hydraulic oil discharge, sagittal cushion is recommended to be used in industries.In this research, design, fabrication and evaluation of 5 different hydraulic cushions have been considered in order to optimize the stopping mechanism of pistons at the end of the course. The comparison of 5 cushion spears including Cylindrical, Conical, Sagittal, Double conical and Parabolic cushion have been studied with reviewing the motion behavior of piston and measuring displacement, speed, acceleration, flow rate and hydraulic pressure in an one way hydraulic cylinder. Results showed that the sagittal cushion with maximum pressure increasing of 1.98% for 200 kg load and 0.35% for 350 kg load had the lowest percentage of hydraulic pressure rise and cylindrical cushion with maximum pressure increasing of 11.98% for 200 kg load and 3.92% for 350 kg load had highest percentage of hydraulic pressure rise. Also operational time of sagittal cushion in experiments with 350 kg load was respectively 33.8 and 63.9 percent lower than that of conical and cylindrical cushion. Also double conical cushion has the nearest performance to the sagittal cushion. As a concluding result with tacking into account the low response time, steady speed reduction and steady rate of hydraulic oil discharge, sagittal cushion is recommended to be used in industries.https://mej.aut.ac.ir/article_2872_7e0a0209b929d097bd3e8ef30567a5c1.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Experimental Comparison of Breakup and Flow Characteristics of Rectangular and
Elliptical Water JetsExperimental Comparison of Breakup and Flow Characteristics of Rectangular and
Elliptical Water Jets12011216289210.22060/mej.2018.13828.5725FAAminJaberiDepartment of Aerospace Engineering, Amirkabir University of Technology0000-0001-7629-2626MehranTadjfarDepartment of Aerospace Engineering, Amirkabir University of Technology0000-0002-7381-1491ArminSheidaniDepartment of Aerospace Engineering, Amirkabir University of TechnologyJournal Article20171213The flow characteristics of water jets issuing from rectangular and elliptical injectors into quiescent air were experimentally investigated. Injectors were of the same cross-sectional area and a circular injector was also employed as the reference case. Digital images taken by a diffused backlight technique were processed to extract the main characteristics of the jet column at different jet velocities. The measurements were carried out for mass flow rates varying from 2 L/h to 120 L/h with small enough steps at low speeds to capture Rayleigh regime. Aside from the qualitative description of the jet flows, stability curve was plotted to make a comparison between different jets. The comparison revealed that the ellipse jet is the first one to reach the critical Weber number, while the circular jet remains laminar at higher velocities than the other two jets. Moreover, axis-switching phenomenon was carefully studied as the common characteristic of rectangular and elliptical jets. The wavelength and maximum amplitude of axis-switching were measured at different flow conditions and the results were compared. Though the axis-switching wavelength of both jets demonstrated a linear increment with Weber number, the rectangular jet was found to increase with a higher slope.The flow characteristics of water jets issuing from rectangular and elliptical injectors into quiescent air were experimentally investigated. Injectors were of the same cross-sectional area and a circular injector was also employed as the reference case. Digital images taken by a diffused backlight technique were processed to extract the main characteristics of the jet column at different jet velocities. The measurements were carried out for mass flow rates varying from 2 L/h to 120 L/h with small enough steps at low speeds to capture Rayleigh regime. Aside from the qualitative description of the jet flows, stability curve was plotted to make a comparison between different jets. The comparison revealed that the ellipse jet is the first one to reach the critical Weber number, while the circular jet remains laminar at higher velocities than the other two jets. Moreover, axis-switching phenomenon was carefully studied as the common characteristic of rectangular and elliptical jets. The wavelength and maximum amplitude of axis-switching were measured at different flow conditions and the results were compared. Though the axis-switching wavelength of both jets demonstrated a linear increment with Weber number, the rectangular jet was found to increase with a higher slope.https://mej.aut.ac.ir/article_2892_6fe131632103526e3a6e8114c78eb1e1.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Experimental Analysis of Operating Modes Effect of Open-end and Dead-end on
Water Management in H2/O2 Proton-Exchange Membrane Fuel Cells StackExperimental Analysis of Operating Modes Effect of Open-end and Dead-end on
Water Management in H2/O2 Proton-Exchange Membrane Fuel Cells Stack12171234300710.22060/mej.2018.13945.5759FAMazaherRahimi EsboeeFuel Cell Technology Research Laboratory, Malek Ashtar University of Technology, Fereydounkenar, Iran.EbrahimAlizadehFuel Cell Technology Research Laboratory, Malek Ashtar University of Technology, Freydounkenar, Iran.Ali AkbarRanjbarDepartment of Mechanical Engineering, Babol “Noshiravani” University of Technology, IranSeyed MajidRahgoshayFuel Cell Technology Research Laboratory, Malek Ashtar University of Technology, Fereydounkenar, Iran.Sayed HosseinMasrouri SaadatFuel Cell Technology Research Laboratory, Malek Ashtar University of Technology0000-0002-2869-4935MajidKhorshidianFuel Cell Technology Research Laboratory, Malek Ashtar University of Technology, Fereydounkenar, Iran.Journal Article20180110The management of consumption the reactive gas in proton-exchange membrane fuel cells is classified into three types: open-end, recirculation and dead-end. In dead-end mode, reactant gasses due to accumulating of water and inert gas should be purged alternatively. In this paper a protonexchange membrane fuel cells stack with transparent end plates and a unique design for investigation of water management is designed, manufactured and fabricated. In this paper, for the first time, the discussion of water management in a dead-end anode and cathode proton-exchange membrane fuel cells stack with details of form and remove of water has been investigated. The results have shown that at the current density of lower than 200 mA/cm2, the produced water is in the form of separate droplets and there is no film flow and slug flow of water in the channel. Also, as expected, the accumulation of droplets and film flow in the lower half was more than the upper half and therefore the reduction of the number of channels to increase gas speed and effective water removal in this part was essential. The results have shown that for steady-state operation, the maximum time possible for closing the output valves is 5 seconds and the minimum time required to open it is 5 seconds.The management of consumption the reactive gas in proton-exchange membrane fuel cells is classified into three types: open-end, recirculation and dead-end. In dead-end mode, reactant gasses due to accumulating of water and inert gas should be purged alternatively. In this paper a protonexchange membrane fuel cells stack with transparent end plates and a unique design for investigation of water management is designed, manufactured and fabricated. In this paper, for the first time, the discussion of water management in a dead-end anode and cathode proton-exchange membrane fuel cells stack with details of form and remove of water has been investigated. The results have shown that at the current density of lower than 200 mA/cm2, the produced water is in the form of separate droplets and there is no film flow and slug flow of water in the channel. Also, as expected, the accumulation of droplets and film flow in the lower half was more than the upper half and therefore the reduction of the number of channels to increase gas speed and effective water removal in this part was essential. The results have shown that for steady-state operation, the maximum time possible for closing the output valves is 5 seconds and the minimum time required to open it is 5 seconds.https://mej.aut.ac.ir/article_3007_a724b9124acc7b5058ed75a31a9c2919.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Numerical Study of Lock Exchange Turbidity Current Depositional Behavior in Stratified EnvironmentNumerical Study of Lock Exchange Turbidity Current Depositional Behavior in Stratified Environment12351252292510.22060/mej.2018.14062.5789FASabaTeymouriDepartment of Mechanical Engineering, University Of Zanjan, Zanjan, Iran.EhsanKhavasiMechanical engineering department, University of ZanjanHamidYousefiDepartment of Mechanical Engineering, University Of Zanjan, Zanjan, Iran.Journal Article20180208In this paper, three-dimensional numerical simulation was conducted to study the lock exchange turbidity current depositional behavior in a stratified environment. Simulations are carried out using Large Eddy Simulation method. The obtained results in stratified case are in good agreement with experimental data. Also, the presence of stratified environment reduces the current velocity, so that the front location is reduced by 57%, but does not have any significant effect on the sedimentation pattern. In addition, the results showed that increasing the slope to 12 degrees increases the sedimentation rate by 15 and 40 percent compared to the slopes 9 and 6 degrees. It was also observed that increasing the particle diameter reduced the momentum and the current sedimentation increases 0.75 and 3.7 times higher. For more accurate representation of the particle interaction, the particle settling velocity also varies with concentration. The results of this analysis indicate that assuming the variable settling velocity in the early stages of the current progression leads to insignificant change in the front velocity, but when the current propagates more, the faster front velocity will be predicted. In variable velocity case, the current separation location increases by 22%..In this paper, three-dimensional numerical simulation was conducted to study the lock exchange turbidity current depositional behavior in a stratified environment. Simulations are carried out using Large Eddy Simulation method. The obtained results in stratified case are in good agreement with experimental data. Also, the presence of stratified environment reduces the current velocity, so that the front location is reduced by 57%, but does not have any significant effect on the sedimentation pattern. In addition, the results showed that increasing the slope to 12 degrees increases the sedimentation rate by 15 and 40 percent compared to the slopes 9 and 6 degrees. It was also observed that increasing the particle diameter reduced the momentum and the current sedimentation increases 0.75 and 3.7 times higher. For more accurate representation of the particle interaction, the particle settling velocity also varies with concentration. The results of this analysis indicate that assuming the variable settling velocity in the early stages of the current progression leads to insignificant change in the front velocity, but when the current propagates more, the faster front velocity will be predicted. In variable velocity case, the current separation location increases by 22%..https://mej.aut.ac.ir/article_2925_ac34ae1fda29b8fe781ac8d6d32a6bc7.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Semi-empirical Investigation of Trailing Edge Noise by Measuring Unsteady Surface
PressuresSemi-empirical Investigation of Trailing Edge Noise by Measuring Unsteady Surface
Pressures12531270100510.22060/mej.2017.12480.5352FAAbbasAfshariphd student / yazd universityAli AkbarDehghanMohammadFarmaniphd student/ yazd universityJournal Article20170204Turbulent boundary layer trailing edge noise is one of the main sources of aerodynamic noise and extensive studies have been devoted to trailing edge noise identification during the past decades. In the present study, for measuring the main parameters affecting the trailing edge noise including the surface pressure spectra, the spanwise length scale of the surface pressure fluctuations and eddy convection velocity in the trailing edge region, a flat-plate model equipped with several streamwise and spanwise surface pressure transducers is designed and built. The spanwise length scale and eddy convection velocity are calculated by simultaneously measuring of unsteady surface pressure in both streamwise and spanwise directions. The results show that the best collapses in the surface pressure spectra at low frequency and mid to high frequencies can be obtained by using outer and inner layer scales respectively. Furthermore, the longitudinal and lateral coherences can provide adequate information about the lifespan of the turbulent eddies and their physical size. Finally, the far-field trailing edge noise induced by the turbulent flow over the flat plate has been predicted by using the Amit-Roger model and results show the effectiveness of this model for prediction of far-field turbulent boundary layer trailing edge noise.Turbulent boundary layer trailing edge noise is one of the main sources of aerodynamic noise and extensive studies have been devoted to trailing edge noise identification during the past decades. In the present study, for measuring the main parameters affecting the trailing edge noise including the surface pressure spectra, the spanwise length scale of the surface pressure fluctuations and eddy convection velocity in the trailing edge region, a flat-plate model equipped with several streamwise and spanwise surface pressure transducers is designed and built. The spanwise length scale and eddy convection velocity are calculated by simultaneously measuring of unsteady surface pressure in both streamwise and spanwise directions. The results show that the best collapses in the surface pressure spectra at low frequency and mid to high frequencies can be obtained by using outer and inner layer scales respectively. Furthermore, the longitudinal and lateral coherences can provide adequate information about the lifespan of the turbulent eddies and their physical size. Finally, the far-field trailing edge noise induced by the turbulent flow over the flat plate has been predicted by using the Amit-Roger model and results show the effectiveness of this model for prediction of far-field turbulent boundary layer trailing edge noise.https://mej.aut.ac.ir/article_1005_2387337ba1e0b0249ba90f55b2ba2521.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Computational Investigation of the Effect of Adhesion between Cancer Cells and
Vessel Walls on the Movement of the Cells in Blood VesselsComputational Investigation of the Effect of Adhesion between Cancer Cells and
Vessel Walls on the Movement of the Cells in Blood Vessels12711288288210.22060/mej.2018.11903.5569FAAsgharKhorramMSc/University of TehranBahmanVahidiAssistant professor/University of Tehran0000-0001-5597-3748ZahraMollahoseiniMSc student/University of TehranJournal Article20170729Cancer is a disease that causes mortality in the world. Despite of improvements in medicine, there is not still sufficient knowledge of cancer. Therefore, there is a strong need for engineering modeling to understand it. The motion and adhesion of cancer cells in a blood vessel during metastasis is a complex mechanism that occurs in body. A two[1]dimensional model of the movement of cancer cells has been developed that is solved in two different modes in a straight line in a blood vessel. These modes are related to presence and absence of adhesion between cancer cell and blood vessel wall in presence of adhesion between cancer cell and white blood cell. The analysis is performed using FEM and FSI equations. It is assumed that the properties of blood and cells are homogeneous and fluid is incompressible and Newtonian. Cancer cell is modeled as a rigid body and white blood cell is assumed as linear elastic. The analysis shows that the influence of adhesion between the cell and the vessel wall is more important from cell-cell adhesion. Through consideration in the adhesion charts along with medical issues such as drug delivery to patients can affect the treatment or prevention of metastasis.Cancer is a disease that causes mortality in the world. Despite of improvements in medicine, there is not still sufficient knowledge of cancer. Therefore, there is a strong need for engineering modeling to understand it. The motion and adhesion of cancer cells in a blood vessel during metastasis is a complex mechanism that occurs in body. A two[1]dimensional model of the movement of cancer cells has been developed that is solved in two different modes in a straight line in a blood vessel. These modes are related to presence and absence of adhesion between cancer cell and blood vessel wall in presence of adhesion between cancer cell and white blood cell. The analysis is performed using FEM and FSI equations. It is assumed that the properties of blood and cells are homogeneous and fluid is incompressible and Newtonian. Cancer cell is modeled as a rigid body and white blood cell is assumed as linear elastic. The analysis shows that the influence of adhesion between the cell and the vessel wall is more important from cell-cell adhesion. Through consideration in the adhesion charts along with medical issues such as drug delivery to patients can affect the treatment or prevention of metastasis.https://mej.aut.ac.ir/article_2882_2ef35a8b78b572a47f56846acbeef5d3.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Simultaneous Simulation of Gas Diffusion Layer and Air Channel in a Polymer Electrolyte Membrane Fuel Cell: Pore-Scale Modeling of Water FloodingSimultaneous Simulation of Gas Diffusion Layer and Air Channel in a Polymer Electrolyte Membrane Fuel Cell: Pore-Scale Modeling of Water Flooding1289130487510.22060/mej.2016.875FAMohsenNazariJournal Article20160812In this study, Lattice Boltzmann method is used to investigate liquid water transport in a carbon paper gas diffusion layer and gas channel of polymer electrolyte membrane fuel cells. The effects of gas diffusion layer wettability on the removal process and liquid water distribution are investigated. In addition, liquid water dynamic behaviors and liquid water saturation within the gas diffusion layer in two case of steady and transient are explored. This study focuses on the effects of surface wettability on the number of effective clusters, merging of clusters, and the required time for reaching the steady-state water distribution. The results show that the wettability of surface affects on the saturation of liquid water in the gas diffusion layer and in 100lu<Y<160lu, this effect is noticeable. The steady- water distribution is observed at time step of 1590000 and 1500000 (lattice unit) for the contact angles of 115° and 145°, respectively. Thus the simulation results show that by increasing the contact angle of fibers in gas diffusion layer, the required time to obtain a steady state water distribution is reduced. Therefore, if the solid surface becomes more hydrophobic, water management will be improved in the gas diffusion layer.In this study, Lattice Boltzmann method is used to investigate liquid water transport in a carbon paper gas diffusion layer and gas channel of polymer electrolyte membrane fuel cells. The effects of gas diffusion layer wettability on the removal process and liquid water distribution are investigated. In addition, liquid water dynamic behaviors and liquid water saturation within the gas diffusion layer in two case of steady and transient are explored. This study focuses on the effects of surface wettability on the number of effective clusters, merging of clusters, and the required time for reaching the steady-state water distribution. The results show that the wettability of surface affects on the saturation of liquid water in the gas diffusion layer and in 100lu<Y<160lu, this effect is noticeable. The steady- water distribution is observed at time step of 1590000 and 1500000 (lattice unit) for the contact angles of 115° and 145°, respectively. Thus the simulation results show that by increasing the contact angle of fibers in gas diffusion layer, the required time to obtain a steady state water distribution is reduced. Therefore, if the solid surface becomes more hydrophobic, water management will be improved in the gas diffusion layer.https://mej.aut.ac.ir/article_875_4b0a59ddf11c58e7446c9df0da541a84.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Droplet Deformation Between Two Moving Parallel PlatesDroplet Deformation Between Two Moving Parallel Plates13051324288510.22060/mej.2018.13067.5525FAMahdiSalami HosseiniPolymer Engineering Department, Sahand University of TechnologyMohammad AliMoeenisahand university studentMirkarimRazavi Aghjehfaculty memberMahdiMostafaianLeibniz Institute for Polymer Research, Dresden University of TechnologyJournal Article20170629One of the most important and challenging subjects for scientists is the numerical simulation of the transport phenomena in heterogeneous media. The discontinuity in the properties causes computational errors leading to incorrect estimation of the exact values. The extended finite element method is one of the powerful tools to predict the behavior of heterogenic materials and phenomena. In the present study, we attempted to adapt the extended finite element method to study the flow of a two phase system and investigate the effect of different material and operational parameters such as Capillary number on the drop deformation process in Newtonian/Newtonian and non-Newtonian/ Newtonian systems. The results showed a good agreement with the experimental ones and complete compliance with other methods in benchmark studies. The results indicated that increasing the initial radius of the droplet would increase the steady-state deformation parameter. Moreover, it was shown that increasing viscosity ratio suppressed the droplet deformation. The effect of non-Newtonian fluid behavior was also investigated for a Carreau fluid. Furthermore, the distribution of shear rate around the droplet was discussed.One of the most important and challenging subjects for scientists is the numerical simulation of the transport phenomena in heterogeneous media. The discontinuity in the properties causes computational errors leading to incorrect estimation of the exact values. The extended finite element method is one of the powerful tools to predict the behavior of heterogenic materials and phenomena. In the present study, we attempted to adapt the extended finite element method to study the flow of a two phase system and investigate the effect of different material and operational parameters such as Capillary number on the drop deformation process in Newtonian/Newtonian and non-Newtonian/ Newtonian systems. The results showed a good agreement with the experimental ones and complete compliance with other methods in benchmark studies. The results indicated that increasing the initial radius of the droplet would increase the steady-state deformation parameter. Moreover, it was shown that increasing viscosity ratio suppressed the droplet deformation. The effect of non-Newtonian fluid behavior was also investigated for a Carreau fluid. Furthermore, the distribution of shear rate around the droplet was discussed.https://mej.aut.ac.ir/article_2885_e98741479a7b998f88b8f8c9f0b6b6f1.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Numerical Study of the Hemodynamic Parameters of Y-Bypass Graft at Rest and
Exercise StateNumerical Study of the Hemodynamic Parameters of Y-Bypass Graft at Rest and
Exercise State13251338276410.22060/mej.2017.12944.5479FAGhassemHeidarinejadHamidrezaBabakhanitmuAlirezaRostamiArakJournal Article20170530The simulation of blood flow in bypass grafts can help medical evaluation. Numerical simulation of blood flow in Configurations recommended by the surgeon Such as the configurations of Y is the aim of this study in order to predict hemodynamic parameters of this configuration in a patient with double stenosis 65 and 50 percent is examined at rest and during exercise. The computational domain was created from CT images from the human cardiac. In this study, blood is assumed homogeneous, non-Newtonian and pulsatile. For real modeling of flow and blood pressure, lumped model is used in outlet at rest and exercise states.The results indicate using this configuration is compensated the pressure drop and flow and time average wall shear stress has reduced in stenosis region and oscillatory shear index and relative residence time range has reduced in area pre and post-stenosis.Y bypass grafting investigation indicates time average wall shear is low at the bifurcation graft and There is possibility of creating restenosis in these areas, but These parameters are in the ideal range at the exercise state.The simulation of blood flow in bypass grafts can help medical evaluation. Numerical simulation of blood flow in Configurations recommended by the surgeon Such as the configurations of Y is the aim of this study in order to predict hemodynamic parameters of this configuration in a patient with double stenosis 65 and 50 percent is examined at rest and during exercise. The computational domain was created from CT images from the human cardiac. In this study, blood is assumed homogeneous, non-Newtonian and pulsatile. For real modeling of flow and blood pressure, lumped model is used in outlet at rest and exercise states.The results indicate using this configuration is compensated the pressure drop and flow and time average wall shear stress has reduced in stenosis region and oscillatory shear index and relative residence time range has reduced in area pre and post-stenosis.Y bypass grafting investigation indicates time average wall shear is low at the bifurcation graft and There is possibility of creating restenosis in these areas, but These parameters are in the ideal range at the exercise state.https://mej.aut.ac.ir/article_2764_98d8a23fd60826a2a474c5b4f5811707.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Numerical and Experimental Analysis for Fluid Flow Inside Corrugated Tube quipped with Twisted TapesNumerical and Experimental Analysis for Fluid Flow Inside Corrugated Tube quipped with Twisted Tapes13391362305810.22060/mej.2018.14398.5847FAHosseinGhalyanchi LangeroudiPhD student of Department of Mechanical Engineering, ,University Campus 2, University of Guilan, Rasht, Iran,KouroshJavaherdehInstructor of Department of Mechanical Engineering, Faculty of Engineering, University of Guilan0000-0002-1570-011XJournal Article20180501The aim of present paper is to study numerical simulation by using finite volume method for Newtonian and non-Newtonian fluid flow inside corrugated tube equipped with typical twisted tape and V-cut twisted tape at constant heat flux. For validation of this simulation, this results compared with empirical correlations of researchers. In this analysis water was as Newtonian fluid and 0.2 wt % carboxymethyle cellulse in water was as a non-Newtonian fluid, the range of Reynolds number for Newtonian and non-Newtonian fluid varied 5300 to 25700 and 2400 to 6800 respectively. In this analysis, the effects of using different turbulence models, variable heat flux and creating V-cut on Nusselt number and friction factor is investigated. The obtained results showed that standard κ -ω model of turbulence for Newtonian fluid is a proper model rather than the other models and it had good agreements between experimental data, and the average differences for Nusselt number in typical and V-cut twisted tapes were less than 15.2% and 14.4% respectively. On other hand, in identical condition for non-Newtonian fluid, using of standard κ - ε model of turbulence is a proper model rather than the other models and the average differences on Nusselt number for typical twisted tape were less than 18%..The aim of present paper is to study numerical simulation by using finite volume method for Newtonian and non-Newtonian fluid flow inside corrugated tube equipped with typical twisted tape and V-cut twisted tape at constant heat flux. For validation of this simulation, this results compared with empirical correlations of researchers. In this analysis water was as Newtonian fluid and 0.2 wt % carboxymethyle cellulse in water was as a non-Newtonian fluid, the range of Reynolds number for Newtonian and non-Newtonian fluid varied 5300 to 25700 and 2400 to 6800 respectively. In this analysis, the effects of using different turbulence models, variable heat flux and creating V-cut on Nusselt number and friction factor is investigated. The obtained results showed that standard κ -ω model of turbulence for Newtonian fluid is a proper model rather than the other models and it had good agreements between experimental data, and the average differences for Nusselt number in typical and V-cut twisted tapes were less than 15.2% and 14.4% respectively. On other hand, in identical condition for non-Newtonian fluid, using of standard κ - ε model of turbulence is a proper model rather than the other models and the average differences on Nusselt number for typical twisted tape were less than 18%..https://mej.aut.ac.ir/article_3058_3f5ee243547dee91fbd053c1c4a845aa.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Numerical and Experimental Investigation of Non-Newtonian High Viscosity Flow
Field in Multi Materials Extrusion ProcessNumerical and Experimental Investigation of Non-Newtonian High Viscosity Flow
Field in Multi Materials Extrusion Process13631380300910.22060/mej.2018.13960.5763FASeyed MohammadJavadiQuchan university of technologyAli MohammadNaserian-NikDepartment of mechanical engineering, Faculty of engineering, Quchan university of technologyJournal Article20180114Predicting and reducing of the rubber cross-section dimensions after exiting die channel are of great importance in the design process of extrusion die. In this research, the effect of velocity distribution at the die exit on the rubber dimensions is experimentally and numerically studied with the aid of finite volume method. Three-dimensional simulation of non-Newtonian high-viscosity flow was performed to predict the distribution of velocity and pressure in the die channels. Recognizing the soft and hard materials boundaries in the multi-material cross-sections, the two-phase volume of fluid method is employed. The viscosity of melted rubber flow in the die is calculated by interpolating the experimental data obtained from Rubber Process Analyzer apparatus based on least squares method. A comparison between primary (with nonuniform profile) and modified dies shows more precise dimensions of the modified die. In the narrow portions of the profile in the vicinity of wide regions, because of the impossibility of achieving a uniform velocity distribution, the produced cross-section is smaller than the design value. In addition, optimizing channel geometries by the employed numerical method reduces the pressure loss in the modified die by 40% in comparison with that of the primary designed die.Predicting and reducing of the rubber cross-section dimensions after exiting die channel are of great importance in the design process of extrusion die. In this research, the effect of velocity distribution at the die exit on the rubber dimensions is experimentally and numerically studied with the aid of finite volume method. Three-dimensional simulation of non-Newtonian high-viscosity flow was performed to predict the distribution of velocity and pressure in the die channels. Recognizing the soft and hard materials boundaries in the multi-material cross-sections, the two-phase volume of fluid method is employed. The viscosity of melted rubber flow in the die is calculated by interpolating the experimental data obtained from Rubber Process Analyzer apparatus based on least squares method. A comparison between primary (with nonuniform profile) and modified dies shows more precise dimensions of the modified die. In the narrow portions of the profile in the vicinity of wide regions, because of the impossibility of achieving a uniform velocity distribution, the produced cross-section is smaller than the design value. In addition, optimizing channel geometries by the employed numerical method reduces the pressure loss in the modified die by 40% in comparison with that of the primary designed die.https://mej.aut.ac.ir/article_3009_ee16fa83c0f151ef85e617f5aa3867a6.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220A New Approach for Uncertainty Analysis of the Numerical Data Using Genetic Algorithm Based on Grid RefinementA New Approach for Uncertainty Analysis of the Numerical Data Using Genetic Algorithm Based on Grid Refinement13811394282910.22060/mej.2018.13246.5581FAMahnazDehghanScience andResearch Branch, Azad UniversityM.Dehghan, M.MAlek Ashtar UniversityAli R.DavariDepartment of MEchanical and Aerospace Eng., Schience and Research Branch, Azad University0000-0003-0101-7069Journal Article20170808A new approach using the genetic algorithms has been presented to estimate the uncertainties in numerical pressure calculation on a 3D wing. The amount of error in this method has been estimated in the form of power series as a function of the element size. The error tensor is expressed as the sum of squares and has been used as the fitness function in the genetic algorithm. The conventional method for error minimization has been differentiation which is replaced by the genetic algorithm in this paper. The error analysis along with a safety factor has been introduced as the uncertainties in numerical calculations. According to the results, refining the grids down to 25% of the initial size, reduced the error by an amount of 50%. The total uncertainty calculated in this paper was 0.03. This value determines a confidence level of 97.6%. The reliability of the results on three baselines higher than 97% approves the high accuracy of the present calculations. The highest and the lowest reliability in the present calculations was 99.16% and 97.6%, respectivelyA new approach using the genetic algorithms has been presented to estimate the uncertainties in numerical pressure calculation on a 3D wing. The amount of error in this method has been estimated in the form of power series as a function of the element size. The error tensor is expressed as the sum of squares and has been used as the fitness function in the genetic algorithm. The conventional method for error minimization has been differentiation which is replaced by the genetic algorithm in this paper. The error analysis along with a safety factor has been introduced as the uncertainties in numerical calculations. According to the results, refining the grids down to 25% of the initial size, reduced the error by an amount of 50%. The total uncertainty calculated in this paper was 0.03. This value determines a confidence level of 97.6%. The reliability of the results on three baselines higher than 97% approves the high accuracy of the present calculations. The highest and the lowest reliability in the present calculations was 99.16% and 97.6%, respectivelyhttps://mej.aut.ac.ir/article_2829_46b2644cbdf489fac0e2d192212d206d.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Design of a Pelton Turbine Installed on Centrifugal Pump in Reverse Osmosis System
for Energy RecoveryDesign of a Pelton Turbine Installed on Centrifugal Pump in Reverse Osmosis System
for Energy Recovery13951410296210.22060/mej.2018.13874.5735FAAbdollahEskandariPayame Noor University - Faculty of Engineering0000-0003-4441-6473Journal Article20171227In this work, injector regulating valve and Pelton turbine impeller has been numerically and analytically designed and simulated. The impeller of the Pelton turbine added on the shaft of a high pressure multistage pump which is used in sea water reverse osmosis package to recover a part of input power from rejected flow return back after filter unit. Using ANSYS CFX, flow through the regulating valve for many outlet injector diameters has been numerically simulated to obtain head loss. For the point of operation, dimension of turbine impeller calculated using turbomachinery relations and some experimental data in order to synchronize as much as possible with the pump. The exact point of operation for the pump, turbine and injector obtained by intersecting performance curves of pump and turbine. In order to investigate the results, the full-scale Pelton turbine and regulating valve manufactured with the material of duplex and installed on the pump. Performance test on the site shown about 26% decrease in input power. Because of the affinity relation for turbomachinery, the results can be validated for other point of operation due to change in pump speed.In this work, injector regulating valve and Pelton turbine impeller has been numerically and analytically designed and simulated. The impeller of the Pelton turbine added on the shaft of a high pressure multistage pump which is used in sea water reverse osmosis package to recover a part of input power from rejected flow return back after filter unit. Using ANSYS CFX, flow through the regulating valve for many outlet injector diameters has been numerically simulated to obtain head loss. For the point of operation, dimension of turbine impeller calculated using turbomachinery relations and some experimental data in order to synchronize as much as possible with the pump. The exact point of operation for the pump, turbine and injector obtained by intersecting performance curves of pump and turbine. In order to investigate the results, the full-scale Pelton turbine and regulating valve manufactured with the material of duplex and installed on the pump. Performance test on the site shown about 26% decrease in input power. Because of the affinity relation for turbomachinery, the results can be validated for other point of operation due to change in pump speed.https://mej.aut.ac.ir/article_2962_3b2d8f129ae2f408f2153cd9ce663043.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Numerical Investigation of Flow Behavior Around Chordwise Morphing NACA 0012Numerical Investigation of Flow Behavior Around Chordwise Morphing NACA 001214111426281510.22060/mej.2018.13708.5699FASeyed EsmailRazaviProfessor at University of TabrizMir HosseinNegahbanM.Sc. Graduate Student of University of TabrizJournal Article20171117In the present study, numerical simulation of transonic flow around chordwise morphing airfoil has been accessed. Fluid-Structure interaction for analyzing flow field behavior in conjunction with morphing airfoil is used. In this regard, a two-dimensional finite element model is established and the arbitrary Lagrangian-Eulerian formulation (ALE), in the flow field and structure configuration is applied to accommodate the deforming boundaries and due to the good conformation of flow filed and deforming boundaries in this formulation, the distortion of computational grid is diminished after the deformation. The procedure incorporates the one-equation Spalart-Allmaras turbulence model which is a suitable model for aerodynamics. In this study, the preferable Mach number for the transonic regime is 0.7. Chordwise elastic deformability by uniformly varying extended parabolic load on both leading and trailing edges is considered for morphing purposes. The model is validated against conventional rigid airfoil for various angles of attack, and the comparisons show considerable improvement in the aerodynamic performance and prove the efficiency of elastic morphing airfoil. Moreover, the ultimate results indicate that chordwise morphing contributes to the best flight conditions for cruise flight which contains a wide flight endurance. All the simulations are steady-state and are carried out by COMSOL Multiphysics software.In the present study, numerical simulation of transonic flow around chordwise morphing airfoil has been accessed. Fluid-Structure interaction for analyzing flow field behavior in conjunction with morphing airfoil is used. In this regard, a two-dimensional finite element model is established and the arbitrary Lagrangian-Eulerian formulation (ALE), in the flow field and structure configuration is applied to accommodate the deforming boundaries and due to the good conformation of flow filed and deforming boundaries in this formulation, the distortion of computational grid is diminished after the deformation. The procedure incorporates the one-equation Spalart-Allmaras turbulence model which is a suitable model for aerodynamics. In this study, the preferable Mach number for the transonic regime is 0.7. Chordwise elastic deformability by uniformly varying extended parabolic load on both leading and trailing edges is considered for morphing purposes. The model is validated against conventional rigid airfoil for various angles of attack, and the comparisons show considerable improvement in the aerodynamic performance and prove the efficiency of elastic morphing airfoil. Moreover, the ultimate results indicate that chordwise morphing contributes to the best flight conditions for cruise flight which contains a wide flight endurance. All the simulations are steady-state and are carried out by COMSOL Multiphysics software.https://mej.aut.ac.ir/article_2815_f5b1b89d98b7286673128a5fb112cb9a.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Numerical Study of Water Droplet Impact on a Surface Using a Sharp Approach for
Interface ModelingNumerical Study of Water Droplet Impact on a Surface Using a Sharp Approach for
Interface Modeling14271442102410.22060/mej.2017.12679.5395FAMohammadEmdadiYasouj University, Yasouj, IranJournal Article20170319In this research, water droplet impact process on a solid surface is simulated using a sharp approach for interface modeling. This approach is based on the solving momentum and continuity equations and imposing appropriate jump conditions at the interface. The level set method is used for interface tracking and the ghost fluid method is used to impose jump conditions at the interface accurately. In this way, smearing of quantities across interface is prevented and discontinuities are preserved at interface. The accuracy of numerical procedure is approved via comparison of simulation results with experimental and numerical data. Simulation results show that the used numerical method in comparison with the volume of fluid method represents more accurate prediction of droplet behavior during impact process. The effect of contact angle between water droplet and surface on the impact process is investigated. For contact angles less than 90°, water droplet spreads on the surface after impact. But, for contact angles greater than 90°, droplet starts to recoil after spreading. In this case, it is possible that droplet rebound from surface after recoiling. Maximum spreading radius of droplet decreases by an increase in contact angle.In this research, water droplet impact process on a solid surface is simulated using a sharp approach for interface modeling. This approach is based on the solving momentum and continuity equations and imposing appropriate jump conditions at the interface. The level set method is used for interface tracking and the ghost fluid method is used to impose jump conditions at the interface accurately. In this way, smearing of quantities across interface is prevented and discontinuities are preserved at interface. The accuracy of numerical procedure is approved via comparison of simulation results with experimental and numerical data. Simulation results show that the used numerical method in comparison with the volume of fluid method represents more accurate prediction of droplet behavior during impact process. The effect of contact angle between water droplet and surface on the impact process is investigated. For contact angles less than 90°, water droplet spreads on the surface after impact. But, for contact angles greater than 90°, droplet starts to recoil after spreading. In this case, it is possible that droplet rebound from surface after recoiling. Maximum spreading radius of droplet decreases by an increase in contact angle.https://mej.aut.ac.ir/article_1024_021bbc7ee20b71134d53e20206bd6feb.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Performance Investigation of Hybrid Darrieus-Savonius Wind Turbine Compared to
Straight-Bladed Darrieus Turbine by Three-Dimensional Numerical SimulationPerformance Investigation of Hybrid Darrieus-Savonius Wind Turbine Compared to
Straight-Bladed Darrieus Turbine by Three-Dimensional Numerical Simulation14431454282010.22060/mej.2018.13505.5651FANozarAkbariAbolfazlAbdolahifarAerodynamics,Aerospace Faculty,AmirKabir University of Technology(Tehran Polytechnic),Tehran,IranJournal Article20171008The purpose of this research is to investigate the performance of hybrid Darrieus- Savonius wind turbines to achieve a model with high starting moment and suitable performance conditions. Straight-bladed Darrieus wind turbines have high-amplitude fluctuations in moment and, at some angles, this moment is not enough to start the turbine motion. The hybrid turbine is compared with two equivalent models of straight-bladed Darrieus wind turbines. The first model has equal available power and the second model has equal height with the hybrid turbine. Three-dimensional simulation is performed using computational fluid dynamics and solving unsteady Reynolds averaged Navier-Stokes equations with finite volume method, using turbulence model and rotating mesh for rotation of the turbine. According to the results, at the self-starting, the hybrid turbine possesses 22.24% and 17.5% less standard deviation and 69.8% and 56.9% more average moment, respectively, compared to the first and second equivalent turbines. In operational mode, the hybrid turbine at the rotational speed of 30 RPM possesses 16.1% and 27.3% less standard deviation and 19.1% and 1.03% more average moment, respectively. Therefore, the hybrid turbine at the self-starting, as well as at low rotational speeds, possesses more average moment and less fluctuations compared to equivalent Darrieus turbines.The purpose of this research is to investigate the performance of hybrid Darrieus- Savonius wind turbines to achieve a model with high starting moment and suitable performance conditions. Straight-bladed Darrieus wind turbines have high-amplitude fluctuations in moment and, at some angles, this moment is not enough to start the turbine motion. The hybrid turbine is compared with two equivalent models of straight-bladed Darrieus wind turbines. The first model has equal available power and the second model has equal height with the hybrid turbine. Three-dimensional simulation is performed using computational fluid dynamics and solving unsteady Reynolds averaged Navier-Stokes equations with finite volume method, using turbulence model and rotating mesh for rotation of the turbine. According to the results, at the self-starting, the hybrid turbine possesses 22.24% and 17.5% less standard deviation and 69.8% and 56.9% more average moment, respectively, compared to the first and second equivalent turbines. In operational mode, the hybrid turbine at the rotational speed of 30 RPM possesses 16.1% and 27.3% less standard deviation and 19.1% and 1.03% more average moment, respectively. Therefore, the hybrid turbine at the self-starting, as well as at low rotational speeds, possesses more average moment and less fluctuations compared to equivalent Darrieus turbines.https://mej.aut.ac.ir/article_2820_aee92f16efd522b9326c25cc3237ac15.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Numerical Investigation of a Pulse-Jet Filter Cleaning System PerformanceNumerical Investigation of a Pulse-Jet Filter Cleaning System Performance14551468289110.22060/mej.2018.12920.5469FAAmirArefianDepartment of Mechanical Engineering, Amirkabir University of Technology, Tehran, IranNavidZehtabiyan-RezaieDepartment of Mechanical Engineering, Amirkabir University of Technology, Tehran, Iran0000-0003-1189-0507RezaHosseini AbardehDepartment of Mechanical Engineering, Amirkabir University of Technology, Tehran, IranJournal Article20170521In this study, numerical simulation of a pulse-jet filter cleaning system is conducted and its performance is investigated under pre-defined conditions. In the first step, 3D simulation of the system from a high pressure tank to the filter inlet is performed and the output is used as the input of second step. In the second step, simulation is performed for filters with inlet mass flow rates calculated from the previous step. To validate the model, the results are compared to experimental data showing acceptable agreement. The results show that regardless of the valve type, the cleaning pulse generates after 0.5 s and suddenly decreases afterward. No shock or choking is observed in the system. Another interesting result is the induced flow, generated after the nozzles, which increases the filter inlet mass flow rate. In addition, the axial distribution of the filter outlet flow is not uniform, degrading from inlet to outlet. Finally, a complete parametric study is performed to investigate the effect of the tank pressure on the pressure difference in the filter which is an important index in the cleaning performance analysis.In this study, numerical simulation of a pulse-jet filter cleaning system is conducted and its performance is investigated under pre-defined conditions. In the first step, 3D simulation of the system from a high pressure tank to the filter inlet is performed and the output is used as the input of second step. In the second step, simulation is performed for filters with inlet mass flow rates calculated from the previous step. To validate the model, the results are compared to experimental data showing acceptable agreement. The results show that regardless of the valve type, the cleaning pulse generates after 0.5 s and suddenly decreases afterward. No shock or choking is observed in the system. Another interesting result is the induced flow, generated after the nozzles, which increases the filter inlet mass flow rate. In addition, the axial distribution of the filter outlet flow is not uniform, degrading from inlet to outlet. Finally, a complete parametric study is performed to investigate the effect of the tank pressure on the pressure difference in the filter which is an important index in the cleaning performance analysis.https://mej.aut.ac.ir/article_2891_7a006957be65e608e863301eb98e1808.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Steady Simulation of the Flow inside the Internal Combustion Engine Turbocharger’s
TurbineSteady Simulation of the Flow inside the Internal Combustion Engine Turbocharger’s
Turbine14691486299810.22060/mej.2018.14098.5810FAMojtabaFarajpoor KhanaposhtaniMechanical Engineering Department, AmirKabir University of Technology.S.MostafaAgha MirsalimMechanical Engineering Department of Amirkabir University, Iran, TehranSeyyed ShahaboldinAlaviounExpert of Designing Department of Iran Khodro's Research Institute (IPCO Company)Journal Article20180303Turbocharger systems, can increase volumetric efficiency and decrease fuel consumption and emissions of an engine due to compressing the entering air to the engine. Flow characteristic inside turbine is sophisticated and several phenomena like flow separation and high turbulent flow can occur inside turbine. Determining exact performance behavior of turbine can alter the matching process of the turbocharger with the engine. The main goal of this research is 3D and steady simulation of the flow inside turbocharger’s turbine and analysis of the performance behavior of turbine under different working conditions. To this end, 3D flow inside turbine including volute, rotor, diffuser and wastegate passage is investigated steadily. Validating simulation results by experimental results shows that there exist 3 to 9 percent of error between these. In order to control the rotational speed of turbine, turbocharger is equipped with wastegate. By measuring the exact amount of wastegate opening in different working conditions of turbine on a test cell, flow simulation inside turbine is accomplished in different wastegate openings and the effect of wastegate opening on the turbine performance and isentropic efficiency is investigated. The results shows that opening of wastegate can reduce isentropic efficiency and power produced by the turbine significantly.Turbocharger systems, can increase volumetric efficiency and decrease fuel consumption and emissions of an engine due to compressing the entering air to the engine. Flow characteristic inside turbine is sophisticated and several phenomena like flow separation and high turbulent flow can occur inside turbine. Determining exact performance behavior of turbine can alter the matching process of the turbocharger with the engine. The main goal of this research is 3D and steady simulation of the flow inside turbocharger’s turbine and analysis of the performance behavior of turbine under different working conditions. To this end, 3D flow inside turbine including volute, rotor, diffuser and wastegate passage is investigated steadily. Validating simulation results by experimental results shows that there exist 3 to 9 percent of error between these. In order to control the rotational speed of turbine, turbocharger is equipped with wastegate. By measuring the exact amount of wastegate opening in different working conditions of turbine on a test cell, flow simulation inside turbine is accomplished in different wastegate openings and the effect of wastegate opening on the turbine performance and isentropic efficiency is investigated. The results shows that opening of wastegate can reduce isentropic efficiency and power produced by the turbine significantly.https://mej.aut.ac.ir/article_2998_71887f62f073a78511cbac56f8cab53f.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603251620200220Experimental Study of Hydrodynamic Behavior and Breakup of Liquid Jet with/
without the Electric FieldExperimental Study of Hydrodynamic Behavior and Breakup of Liquid Jet with/
without the Electric Field14871498279510.22060/mej.2018.13591.5679FARezaGharraei KhosroshahiMechanical Engineering Department, Azarbaijan Shahid Madani UniversityMahdiTavanaMechanical Engineering Department, Azarbaijan Shahid Madani University, Tabriz, IranSimaBaheri IslamiAssociate Professor/ University of TabrizJournal Article20171025In this study, the hydrodynamic behavior of fluid jet with/without application of electric field is studied and intensity and direction of the electrical field are investigated experimentally on instability and jet breakup. The study of the shape and size of produced droplets after the fluid jet breakup are another cases in this study. Results show that fluid jet characteristics depend on Reynolds number in jets which are only based on gravity. Jet mean diameter and its breakup length in this type of jets are directly related to Reynolds number. Studies show that jet mean diameter is increased and breakup length is decreased by applying electrical field. According to investigations, increasing of electrical field intensity leads to decreasing in jet breakup length and direct field has a significant effect in comparison with reverse one on it. Studies show that jet mean diameter and breakup length are decreased by applying electrical field. Increasing of electrical field intensity leads to decreasing in jet breakup length and direct field has a significant effect in comparison with reverse one on it. By applying a 6 kV electric field, the upper jet breakup length can be reduced by 27% in comparison with non-field state. The standard deviation of produced droplets in non-filed state and reverse electrical field with 2kV intensity is equal to 1.3 and 1.1, respectively which indicates a more uniform droplet in presence of reverse electric field. The investigation of produced droplets in term of roundness showed that electrical field leads to producing circular droplets and reducing the frequency of irregular droplets.In this study, the hydrodynamic behavior of fluid jet with/without application of electric field is studied and intensity and direction of the electrical field are investigated experimentally on instability and jet breakup. The study of the shape and size of produced droplets after the fluid jet breakup are another cases in this study. Results show that fluid jet characteristics depend on Reynolds number in jets which are only based on gravity. Jet mean diameter and its breakup length in this type of jets are directly related to Reynolds number. Studies show that jet mean diameter is increased and breakup length is decreased by applying electrical field. According to investigations, increasing of electrical field intensity leads to decreasing in jet breakup length and direct field has a significant effect in comparison with reverse one on it. Studies show that jet mean diameter and breakup length are decreased by applying electrical field. Increasing of electrical field intensity leads to decreasing in jet breakup length and direct field has a significant effect in comparison with reverse one on it. By applying a 6 kV electric field, the upper jet breakup length can be reduced by 27% in comparison with non-field state. The standard deviation of produced droplets in non-filed state and reverse electrical field with 2kV intensity is equal to 1.3 and 1.1, respectively which indicates a more uniform droplet in presence of reverse electric field. The investigation of produced droplets in term of roundness showed that electrical field leads to producing circular droplets and reducing the frequency of irregular droplets.https://mej.aut.ac.ir/article_2795_a7f592cef8b130a6967a90617db5681b.pdf