Hossein Afshar | East Tehran Branch, Islamic Azad Uni. (original) (raw)

Papers by Hossein Afshar

Research paper thumbnail of Heat and mass transfer for MHD nanofluid flow on a porous stretching sheet with prescribed boundary conditions

Case Studies in Thermal Engineering, 2023

A theoretical study is conducted in order to scrutinize the thermodynamic first law of the MHD na... more A theoretical study is conducted in order to scrutinize the thermodynamic first law of the MHD nanofluid flow with an inclined magnetic field, radiation, heat source/sink, viscous dissipation, Joule heating, concentration power-law exponent, and the chemical reaction on a porous stretching surface immersed within a permeable Darcian medium. Cobalt ferrite nanoparticles (CoFe 2 O 4) have been combined with pure water to form a nanofluid called CoFe 2 O 4 /H 2 O. The controlling mathematical equations for MHD nanofluid flow are transformed through similarity transformation into non-dimensional equations. The exact solutions for the energy and mass transfer equations are provided in terms of confluent hypergeometric function. The effects of controlling parameters on the velocity, temperature, and concentration profiles are discussed and illustrated with figures and tables. According to the results, increasing the concentration powerlaw exponent yields a rise in the Sherwood number (PSC) magnitude and the wall concentration (PMF). Furthermore, the 3-D plots showed that the skin friction coefficient is directly related to the Hartmann number, suction parameter, and nanoparticle volume fraction parameter.

Research paper thumbnail of Optimization of the SMX static mixer types thermal and hydraulic performance by coupling CFD-Genetic Algorithm

The thermo-fluid performance of static mixers was evaluated by numerical simulation of the flow f... more The thermo-fluid performance of static mixers was evaluated by numerical simulation of the flow field and heat transfer in turbulent flows. Four types of mixers_ namely: twisted tape turbulator, LPD, SMX, and KSM_ were studied at different Reynolds numbers. The validation of numerical results confirmed their agreement with the experimental results in the literature. According to results, twisted tape and SMX had the lowest and highest effects on enhancing heat transfer rate, respectively. However, SMX showed a higher pressure drop than other mixers. Therefore, Genetic Algorithm (GA) was used to optimize its configuration. Design parameters were considered to be number of mixers, Reynolds number and installation angle of plates. Design of Experiments (DoE) method was used to select the design points. In addition, Response Surface Methodology (RSM) and GA were used to conduct optimization process. Maximum heat transfer rate and minimum pressure drop were defined as objective functions. Sensitivity analysis showed that the objective functions represent maximum sensitivity to Reynolds number. GA derived optimum point at the following conditions: Reynolds number = 96,500, number of mixers = 5, central plate's angle = 45 o and lateral plates' angle = 49 o. The prediction accuracy of optimization algorithm was assessed by simulation and it was proved that it could predict the thermofluid performance of the studied mixers with an acceptable accuracy (prediction error < 3%). The thermo-fluid performance of the optimized mixer (SMX-Optimized) showed that it increases heat transfer rate by 1.78 folds compared to bare pipe.

Research paper thumbnail of MHD flow and conductive heat transfer on a permeable stretching cylinder: Benchmark solutions

Case Studies in Thermal Engineering, 2023

Research is conducted on parametric heat transfer and fluid flow solutions under the influencing ... more Research is conducted on parametric heat transfer and fluid flow solutions under the influencing factors of the porous stretching cylinder, magnetic field, curvature, permeable media, radiation, Joule heating, viscous dissipation, and heat generation/absorption. High non-linear coupled PDEs are solved and result in high non-linear coupled ODEs. The confluent hypergeometric function solves the energy equation with the PHF (prescribed heat flux) boundary condition. An analysis of physical parameters’ effects is presented as tables and figures. According to the results, the variation of radiation parameters and Eckert numbers for the local Nusselt number in the injection area is negligible, while the variation of the heat source/sink parameters is considerable. The suction/injection and curvature parameters directly affect the local skin friction coefficient and Nusselt number. The porous stretching cylinder has a higher skin friction coefficient and heat transfer rate when compared to the porous stretching sheet.

Research paper thumbnail of MHD heat and mass transfer nanofluid flow on a porous cylinder with chemical reaction and viscous dissipation effects: Benchmark solutions

Case Studies in Thermal Engineering, 2022

The present study deals with a parametric study of heat and mass transfer of a steady, laminar, a... more The present study deals with a parametric study of heat and mass transfer of a steady, laminar, and 2D nanofluid flow under the influence of an inclined magnetic field, curvature, permeable medium, thermal radiation, electrical resistance heating, viscous dissipation, heat source/sink, chemical reaction, and concentration power-law exponent effects. Similarity transformations are employed to convert highly nonlinear PDEs to highly nonlinear ODEs. The Frobenius method was used to obtain the heat and mass transfer solutions in terms of hypergeometric function. Iron Oxide Black and water are used as the nanoparticles and base fluid, respectively. Heat and mass transfer boundary conditions are classified as PST (Prescribed surface temperature) and PSC (Prescribed surface concentration), respectively. The effects of nanoparticle volume fraction and curvature parameters on the local skin friction coefficient have been presented. The Box-Behnken design (BBD) is employed to demonstrate the effects of nanoparticle volume fraction parameter, Darcy number, and chemical reaction parameter on the local Sherwood number. Results show that the curvature parameter directly affects the local skin friction coefficient and velocity. In addition, with a rising concentration power-law exponent parameter, the thickness of the concentration boundary layer becomes thinner.

Research paper thumbnail of Therapeutic Nanostructures: Application of Mechanical Engineering in Drug Delivery

Nanoarchitectonics for Smart Delivery and Drug Targeting, 2016

The purpose of this chapter is to discuss the application of lasers and metal nanoparticles for t... more The purpose of this chapter is to discuss the application of lasers and metal nanoparticles for the treatment of cancers with epithelial origin. The combination of laser therapy and nanoparticles in cancer treatment includes four major sections: (1) Cancer (2) Principals of nanotechnology (3) Principles of laser (4) Combination of laser and nanoparticles for treatment of cancers with epithelial origin. Disadvantages of lasers and nanoparticles combined therapy include high cost and difficulty of finding identical particles. Besides, it requires complicated and advanced technology, which may not be easily obtained. It can be concluded that laser and nanoparticles together are novel classes of cancer therapy and diagnosis. More studies should be done to rule out the most effective nanoparticles and laser wavelength. Also, more animal studies and clinical trials need to be completed, as there has always been a lack of perfect studies in the field. These methods and mechanisms can be used as a treatment modality to aid in the cure of cancers in the future.

Research paper thumbnail of Effect of Dispersed Nanoparticles on Thermophysical Properties of Nanofluid and Heat Transfer Coefficients

Journal of Applied Fluid Mechanics, 2016

Research paper thumbnail of 3D Numerical Simulation of Propeller and its Aerodynamic Interference Effects on Tail of a Flying Boat

Journal of Applied Sciences, 2015

Research paper thumbnail of Two Phase Analysis of Heat Transfer and Dispersion of Nano Particles in a Microchannel

Heat Transfer: Volume 2, 2008

The effect of different parameters on dispersion of nanoparticles in a microchannel in slip flow ... more The effect of different parameters on dispersion of nanoparticles in a microchannel in slip flow regime is studied. The equations of particle motion and energy balance are solved numerically and the effect of particle diameter, starting position of particles in microchannel, and slip coefficient on dispersion of particles is discussed. Radiative heat flux in energy equation and drag force, Saffman lift force, Brownian force and gravitational force in momentum equation are included. The results show that the Brownian force has considerable effect on particle motion in microchannel. Particles temperature at the outlet can be controlled by variation of their diameter and starting position in microchannel.

Research paper thumbnail of Developing an optimal valve closing rule curve for real-time pressure control in pipes

Journal of Mechanical Science and Technology, 2013

Research paper thumbnail of A Study of Winglet and Aerodynamic Interferences in 3-D Viscous Flow around a Flying-Boat in Ground Effect

Journal of Applied Sciences, 2009

Research paper thumbnail of Microchannel heat transfer and dispersion of nanoparticles in slip flow regime with constant heat flux

International Communications in Heat and Mass Transfer, 2009

If the hydrodynamic diameter of a channel is comparable with the mean free path of the gas molecu... more If the hydrodynamic diameter of a channel is comparable with the mean free path of the gas molecules moving inside the channel, the fluid can no longer be considered to be in thermodynamic equilibrium and a variety of non-continuum or rarefaction effects can occur. To avoid enormous complexity and extensive numerical cost encountered in modeling of nonlinear Boltzmann equations, the

Research paper thumbnail of Two-Phase Study of Fluid Flow and Heat Transfer in Gas-Solid Flows (Nanofluids)

Applied Mechanics and Materials, 2011

In this paper, two phase heat transfer of a mixture of nanopaticles in air flow as a type of nano... more In this paper, two phase heat transfer of a mixture of nanopaticles in air flow as a type of nanofluid is studied. Volume fraction of the dispersed phase is very low (less than 1%). Nanoparticles travel in the base fluid due to drag, brownian and gravity forces and are tracked according to lagrangian approach. Effect of reduced specific heat of nanofluid on heat transfer is considered. The results show an increase in heat transfer rate which is very much more than that predicted by the Maxwell model.

Research paper thumbnail of Developing a Closing Rule Curve for Valves in Pipelines to Control the Water Hammer Impacts: Application of the NSGA-II Optimization Model

Pipelines 2008, 2008

ABSTRACT Water hammer is known as a phenomenon that has adverse effects on pipelines. Closing rat... more ABSTRACT Water hammer is known as a phenomenon that has adverse effects on pipelines. Closing rate of valves plays an important role in controlling this phenomenon. In the water hammer process, the water pressure rise and water discharge are inversely correlated. Therefore, a tradeoff curve (Pareto front) between water pressure rise and water discharge can be developed. Developing these Pareto front using traditional multiple-objective optimization models is always time consuming. Therefore, in recent years, several multiple-objective evolutionary optimization models have been proposed which can provide the Pareto-front with an acceptable computational time. In this paper, the Non-dominated Sorting Genetic Algorithms II (NSGA II) is used for developing the Pareto front. To predict the pressure rise and pipe discharge for a valve closing scenario, a simulation model is also developed using the Characteristic Method. The simulation model is then linked to the NSGA II optimization model. After developing the trade-off curve between the water pressure rise and the discharge, a valve operating rule is developed for each non-inferior point on the trade-off curve. The results show that the proposed methodology can be effectively used for reducing the adverse effects of the water hammer in pipelines.

Research paper thumbnail of Effect of Dispersed Nanoparticles on Thermophysical Properties of Nanofluid and Heat Transfer Coefficients

Journal of Applied Fluid Mechanics, 2016

In this investigation, effects of dispersed Cu nanoparticles in water on heat transfer coefficien... more In this investigation, effects of dispersed Cu nanoparticles in water on heat transfer coefficients are studied using Eulerian-Lagranigian approach. Nanoparticles disperse in the fluid due to drag, weight and Brownian forces acting on them. A new particle search algorithm is used to trace the particles in every time step. Thermal coupling between dispersed and carrier phases is done and also thermal and momentum interaction between particles and solid walls are taken onto account to obtain velocity and temperature fields. The specific heat of nanofluid is obtained using conventional models. The results show that regarding thermophysical properties of particles and base fluid, and also other conditions like mass flow rate and particle size, degradation or intensification of heat transfer coefficients can occur.

Research paper thumbnail of The Effects of Changes in Height on the Aerodynamic Performance of Automobiles

In this study, the fluid flow around a Pride vehicle was solved in a two-dimensional design using... more In this study, the fluid flow around a Pride vehicle was solved in a two-dimensional design using numerical methods. To do so, a two-dimensional figure of a Pride was modeled and gridded, and different surfaces were introduced. Then, governing equations the fluid flow was solved for the standard K-ε model and the appropriate boundary conditions. Areas that increased lift and drag forces were specified through studying the results and observing flow lines, pressure distribution, and vortices created around the automobile. In this way, the ideal height for different speeds was determined through examining the changes in those forces at different heights. In this study, the Pride was examined at different heights 80, 120, 160 (standard), 200, and 250 mm for the speeds 10, 20, 33, and 40 m/s. The results showed that lift and drag forces depended on the height of the automobile and changed at different heights

Research paper thumbnail of Experimental and 3-D Numerical Simulation of Flow over a Rectangular Broad-Crested Weir

214 AbstractA broad-crested weir is a flat-crested structure with alarge crest length compared to... more 214 AbstractA broad-crested weir is a flat-crested structure with alarge crest length compared to the flow thickness which is widely used in open channels, rivers, irrigation and drainage systems. New experiments were conducted on a rectangular broad-crested weir with a rounded corner. In this study, Computational Fluid Dynamics (CFD) model together with laboratory model were used in order to determining the free-surface profile of rectangular broad-crested weir. Simulations were performed using the volume of fluid (VOF) free surface model and three turbulence models of the RNG k–ε, standard k–ε and the large eddy simulation (LES) to find the water level profile and streamlines.The structured mesh with high concentration near the solid regions was used in te numerical procedure. The computational results showed a close agreement with experimental data obtained in the laboratory. Also, results indicate that RNG model has the minimum level.

Research paper thumbnail of Optimization of the SMX static mixer types thermal and hydraulic performance by coupling CFD-Genetic Algorithm

International Communications in Heat and Mass Transfer, 2021

The thermo-fluid performance of static mixers was evaluated by numerical simulation of the flow f... more The thermo-fluid performance of static mixers was evaluated by numerical simulation of the flow field and heat transfer in turbulent flows. Four types of mixers_ namely: twisted tape turbulator, LPD, SMX, and KSM_ were studied at different Reynolds numbers. The validation of numerical results confirmed their agreement with the experimental results in the literature. According to results, twisted tape and SMX had the lowest and highest effects on enhancing heat transfer rate, respectively. However, SMX showed a higher pressure drop than other mixers. Therefore, Genetic Algorithm (GA) was used to optimize its configuration. Design parameters were considered to be number of mixers, Reynolds number and installation angle of plates. Design of Experiments (DoE) method was used to select the design points. In addition, Response Surface Methodology (RSM) and GA were used to conduct optimization process. Maximum heat transfer rate and minimum pressure drop were defined as objective functions...

Research paper thumbnail of Flow Over a Broad-Crested Weir in Subcritical Flow Conditions, Physical Study

Research paper thumbnail of Using a Porous Environment In Catalytic Gas Heaters to Optimize Energy Consumption and Reduce Pollution in Heating the Furnaces

Waste of energy in furnaces and cost fluctuations, especially the ascending trend of oil price wh... more Waste of energy in furnaces and cost fluctuations, especially the ascending trend of oil price which controls the energy market, have made the developing countries consider the processes to optimize energy consumption and improve industrial processes to decrease the production costs, and this approach has gradually been taken by semi-industrial countries as well. Nowadays, the modifications in consumption pattern and the ways of using energy have vital impacts on economic developments of the countries. Moreover, the hazardous influences of nitrogen oxides on environmental pollution have forced the designers of energy generator machines to think of procedures to lower the harmful gases as they often try to recognize the problematic sections inside combustion and control the temperature conditions in each section to restrain the production of harmful gases.

Research paper thumbnail of Analytical solution of MHD micropolar nanofluid flow and forced convection heat transfer with entropy generation analysis past a linearly stretching sheet

This perusal attempts to model and interpret the entropy generation analysis and the flow field o... more This perusal attempts to model and interpret the entropy generation analysis and the flow field of 2-D, steady, viscous, incompressible and laminar boundary layer and forced convection heat transport of micropolar ferrofluid past a stretching sheet including suction and normal magnetic field effects. The porous sheet’s velocity and temperature are presumed to change linearly. Exact explicit solutions of the velocity, angular velocity and temperature distributions have been derived. The impacts of physical parameters on the local skin friction coefficient, the local Nusselt number, the entropy generation number further the velocities and temperature distributions are analyzed by tables and graphs. The angular velocity has more value than velocity for the least value of the magnetic and material parameters. The entropy generation number has a direct relation with material parameter and Brinkman either Reynolds numbers. Moreover, an inverse relation with the Prandtl number.

Research paper thumbnail of Heat and mass transfer for MHD nanofluid flow on a porous stretching sheet with prescribed boundary conditions

Case Studies in Thermal Engineering, 2023

A theoretical study is conducted in order to scrutinize the thermodynamic first law of the MHD na... more A theoretical study is conducted in order to scrutinize the thermodynamic first law of the MHD nanofluid flow with an inclined magnetic field, radiation, heat source/sink, viscous dissipation, Joule heating, concentration power-law exponent, and the chemical reaction on a porous stretching surface immersed within a permeable Darcian medium. Cobalt ferrite nanoparticles (CoFe 2 O 4) have been combined with pure water to form a nanofluid called CoFe 2 O 4 /H 2 O. The controlling mathematical equations for MHD nanofluid flow are transformed through similarity transformation into non-dimensional equations. The exact solutions for the energy and mass transfer equations are provided in terms of confluent hypergeometric function. The effects of controlling parameters on the velocity, temperature, and concentration profiles are discussed and illustrated with figures and tables. According to the results, increasing the concentration powerlaw exponent yields a rise in the Sherwood number (PSC) magnitude and the wall concentration (PMF). Furthermore, the 3-D plots showed that the skin friction coefficient is directly related to the Hartmann number, suction parameter, and nanoparticle volume fraction parameter.

Research paper thumbnail of Optimization of the SMX static mixer types thermal and hydraulic performance by coupling CFD-Genetic Algorithm

The thermo-fluid performance of static mixers was evaluated by numerical simulation of the flow f... more The thermo-fluid performance of static mixers was evaluated by numerical simulation of the flow field and heat transfer in turbulent flows. Four types of mixers_ namely: twisted tape turbulator, LPD, SMX, and KSM_ were studied at different Reynolds numbers. The validation of numerical results confirmed their agreement with the experimental results in the literature. According to results, twisted tape and SMX had the lowest and highest effects on enhancing heat transfer rate, respectively. However, SMX showed a higher pressure drop than other mixers. Therefore, Genetic Algorithm (GA) was used to optimize its configuration. Design parameters were considered to be number of mixers, Reynolds number and installation angle of plates. Design of Experiments (DoE) method was used to select the design points. In addition, Response Surface Methodology (RSM) and GA were used to conduct optimization process. Maximum heat transfer rate and minimum pressure drop were defined as objective functions. Sensitivity analysis showed that the objective functions represent maximum sensitivity to Reynolds number. GA derived optimum point at the following conditions: Reynolds number = 96,500, number of mixers = 5, central plate's angle = 45 o and lateral plates' angle = 49 o. The prediction accuracy of optimization algorithm was assessed by simulation and it was proved that it could predict the thermofluid performance of the studied mixers with an acceptable accuracy (prediction error < 3%). The thermo-fluid performance of the optimized mixer (SMX-Optimized) showed that it increases heat transfer rate by 1.78 folds compared to bare pipe.

Research paper thumbnail of MHD flow and conductive heat transfer on a permeable stretching cylinder: Benchmark solutions

Case Studies in Thermal Engineering, 2023

Research is conducted on parametric heat transfer and fluid flow solutions under the influencing ... more Research is conducted on parametric heat transfer and fluid flow solutions under the influencing factors of the porous stretching cylinder, magnetic field, curvature, permeable media, radiation, Joule heating, viscous dissipation, and heat generation/absorption. High non-linear coupled PDEs are solved and result in high non-linear coupled ODEs. The confluent hypergeometric function solves the energy equation with the PHF (prescribed heat flux) boundary condition. An analysis of physical parameters’ effects is presented as tables and figures. According to the results, the variation of radiation parameters and Eckert numbers for the local Nusselt number in the injection area is negligible, while the variation of the heat source/sink parameters is considerable. The suction/injection and curvature parameters directly affect the local skin friction coefficient and Nusselt number. The porous stretching cylinder has a higher skin friction coefficient and heat transfer rate when compared to the porous stretching sheet.

Research paper thumbnail of MHD heat and mass transfer nanofluid flow on a porous cylinder with chemical reaction and viscous dissipation effects: Benchmark solutions

Case Studies in Thermal Engineering, 2022

The present study deals with a parametric study of heat and mass transfer of a steady, laminar, a... more The present study deals with a parametric study of heat and mass transfer of a steady, laminar, and 2D nanofluid flow under the influence of an inclined magnetic field, curvature, permeable medium, thermal radiation, electrical resistance heating, viscous dissipation, heat source/sink, chemical reaction, and concentration power-law exponent effects. Similarity transformations are employed to convert highly nonlinear PDEs to highly nonlinear ODEs. The Frobenius method was used to obtain the heat and mass transfer solutions in terms of hypergeometric function. Iron Oxide Black and water are used as the nanoparticles and base fluid, respectively. Heat and mass transfer boundary conditions are classified as PST (Prescribed surface temperature) and PSC (Prescribed surface concentration), respectively. The effects of nanoparticle volume fraction and curvature parameters on the local skin friction coefficient have been presented. The Box-Behnken design (BBD) is employed to demonstrate the effects of nanoparticle volume fraction parameter, Darcy number, and chemical reaction parameter on the local Sherwood number. Results show that the curvature parameter directly affects the local skin friction coefficient and velocity. In addition, with a rising concentration power-law exponent parameter, the thickness of the concentration boundary layer becomes thinner.

Research paper thumbnail of Therapeutic Nanostructures: Application of Mechanical Engineering in Drug Delivery

Nanoarchitectonics for Smart Delivery and Drug Targeting, 2016

The purpose of this chapter is to discuss the application of lasers and metal nanoparticles for t... more The purpose of this chapter is to discuss the application of lasers and metal nanoparticles for the treatment of cancers with epithelial origin. The combination of laser therapy and nanoparticles in cancer treatment includes four major sections: (1) Cancer (2) Principals of nanotechnology (3) Principles of laser (4) Combination of laser and nanoparticles for treatment of cancers with epithelial origin. Disadvantages of lasers and nanoparticles combined therapy include high cost and difficulty of finding identical particles. Besides, it requires complicated and advanced technology, which may not be easily obtained. It can be concluded that laser and nanoparticles together are novel classes of cancer therapy and diagnosis. More studies should be done to rule out the most effective nanoparticles and laser wavelength. Also, more animal studies and clinical trials need to be completed, as there has always been a lack of perfect studies in the field. These methods and mechanisms can be used as a treatment modality to aid in the cure of cancers in the future.

Research paper thumbnail of Effect of Dispersed Nanoparticles on Thermophysical Properties of Nanofluid and Heat Transfer Coefficients

Journal of Applied Fluid Mechanics, 2016

Research paper thumbnail of 3D Numerical Simulation of Propeller and its Aerodynamic Interference Effects on Tail of a Flying Boat

Journal of Applied Sciences, 2015

Research paper thumbnail of Two Phase Analysis of Heat Transfer and Dispersion of Nano Particles in a Microchannel

Heat Transfer: Volume 2, 2008

The effect of different parameters on dispersion of nanoparticles in a microchannel in slip flow ... more The effect of different parameters on dispersion of nanoparticles in a microchannel in slip flow regime is studied. The equations of particle motion and energy balance are solved numerically and the effect of particle diameter, starting position of particles in microchannel, and slip coefficient on dispersion of particles is discussed. Radiative heat flux in energy equation and drag force, Saffman lift force, Brownian force and gravitational force in momentum equation are included. The results show that the Brownian force has considerable effect on particle motion in microchannel. Particles temperature at the outlet can be controlled by variation of their diameter and starting position in microchannel.

Research paper thumbnail of Developing an optimal valve closing rule curve for real-time pressure control in pipes

Journal of Mechanical Science and Technology, 2013

Research paper thumbnail of A Study of Winglet and Aerodynamic Interferences in 3-D Viscous Flow around a Flying-Boat in Ground Effect

Journal of Applied Sciences, 2009

Research paper thumbnail of Microchannel heat transfer and dispersion of nanoparticles in slip flow regime with constant heat flux

International Communications in Heat and Mass Transfer, 2009

If the hydrodynamic diameter of a channel is comparable with the mean free path of the gas molecu... more If the hydrodynamic diameter of a channel is comparable with the mean free path of the gas molecules moving inside the channel, the fluid can no longer be considered to be in thermodynamic equilibrium and a variety of non-continuum or rarefaction effects can occur. To avoid enormous complexity and extensive numerical cost encountered in modeling of nonlinear Boltzmann equations, the

Research paper thumbnail of Two-Phase Study of Fluid Flow and Heat Transfer in Gas-Solid Flows (Nanofluids)

Applied Mechanics and Materials, 2011

In this paper, two phase heat transfer of a mixture of nanopaticles in air flow as a type of nano... more In this paper, two phase heat transfer of a mixture of nanopaticles in air flow as a type of nanofluid is studied. Volume fraction of the dispersed phase is very low (less than 1%). Nanoparticles travel in the base fluid due to drag, brownian and gravity forces and are tracked according to lagrangian approach. Effect of reduced specific heat of nanofluid on heat transfer is considered. The results show an increase in heat transfer rate which is very much more than that predicted by the Maxwell model.

Research paper thumbnail of Developing a Closing Rule Curve for Valves in Pipelines to Control the Water Hammer Impacts: Application of the NSGA-II Optimization Model

Pipelines 2008, 2008

ABSTRACT Water hammer is known as a phenomenon that has adverse effects on pipelines. Closing rat... more ABSTRACT Water hammer is known as a phenomenon that has adverse effects on pipelines. Closing rate of valves plays an important role in controlling this phenomenon. In the water hammer process, the water pressure rise and water discharge are inversely correlated. Therefore, a tradeoff curve (Pareto front) between water pressure rise and water discharge can be developed. Developing these Pareto front using traditional multiple-objective optimization models is always time consuming. Therefore, in recent years, several multiple-objective evolutionary optimization models have been proposed which can provide the Pareto-front with an acceptable computational time. In this paper, the Non-dominated Sorting Genetic Algorithms II (NSGA II) is used for developing the Pareto front. To predict the pressure rise and pipe discharge for a valve closing scenario, a simulation model is also developed using the Characteristic Method. The simulation model is then linked to the NSGA II optimization model. After developing the trade-off curve between the water pressure rise and the discharge, a valve operating rule is developed for each non-inferior point on the trade-off curve. The results show that the proposed methodology can be effectively used for reducing the adverse effects of the water hammer in pipelines.

Research paper thumbnail of Effect of Dispersed Nanoparticles on Thermophysical Properties of Nanofluid and Heat Transfer Coefficients

Journal of Applied Fluid Mechanics, 2016

In this investigation, effects of dispersed Cu nanoparticles in water on heat transfer coefficien... more In this investigation, effects of dispersed Cu nanoparticles in water on heat transfer coefficients are studied using Eulerian-Lagranigian approach. Nanoparticles disperse in the fluid due to drag, weight and Brownian forces acting on them. A new particle search algorithm is used to trace the particles in every time step. Thermal coupling between dispersed and carrier phases is done and also thermal and momentum interaction between particles and solid walls are taken onto account to obtain velocity and temperature fields. The specific heat of nanofluid is obtained using conventional models. The results show that regarding thermophysical properties of particles and base fluid, and also other conditions like mass flow rate and particle size, degradation or intensification of heat transfer coefficients can occur.

Research paper thumbnail of The Effects of Changes in Height on the Aerodynamic Performance of Automobiles

In this study, the fluid flow around a Pride vehicle was solved in a two-dimensional design using... more In this study, the fluid flow around a Pride vehicle was solved in a two-dimensional design using numerical methods. To do so, a two-dimensional figure of a Pride was modeled and gridded, and different surfaces were introduced. Then, governing equations the fluid flow was solved for the standard K-ε model and the appropriate boundary conditions. Areas that increased lift and drag forces were specified through studying the results and observing flow lines, pressure distribution, and vortices created around the automobile. In this way, the ideal height for different speeds was determined through examining the changes in those forces at different heights. In this study, the Pride was examined at different heights 80, 120, 160 (standard), 200, and 250 mm for the speeds 10, 20, 33, and 40 m/s. The results showed that lift and drag forces depended on the height of the automobile and changed at different heights

Research paper thumbnail of Experimental and 3-D Numerical Simulation of Flow over a Rectangular Broad-Crested Weir

214 AbstractA broad-crested weir is a flat-crested structure with alarge crest length compared to... more 214 AbstractA broad-crested weir is a flat-crested structure with alarge crest length compared to the flow thickness which is widely used in open channels, rivers, irrigation and drainage systems. New experiments were conducted on a rectangular broad-crested weir with a rounded corner. In this study, Computational Fluid Dynamics (CFD) model together with laboratory model were used in order to determining the free-surface profile of rectangular broad-crested weir. Simulations were performed using the volume of fluid (VOF) free surface model and three turbulence models of the RNG k–ε, standard k–ε and the large eddy simulation (LES) to find the water level profile and streamlines.The structured mesh with high concentration near the solid regions was used in te numerical procedure. The computational results showed a close agreement with experimental data obtained in the laboratory. Also, results indicate that RNG model has the minimum level.

Research paper thumbnail of Optimization of the SMX static mixer types thermal and hydraulic performance by coupling CFD-Genetic Algorithm

International Communications in Heat and Mass Transfer, 2021

The thermo-fluid performance of static mixers was evaluated by numerical simulation of the flow f... more The thermo-fluid performance of static mixers was evaluated by numerical simulation of the flow field and heat transfer in turbulent flows. Four types of mixers_ namely: twisted tape turbulator, LPD, SMX, and KSM_ were studied at different Reynolds numbers. The validation of numerical results confirmed their agreement with the experimental results in the literature. According to results, twisted tape and SMX had the lowest and highest effects on enhancing heat transfer rate, respectively. However, SMX showed a higher pressure drop than other mixers. Therefore, Genetic Algorithm (GA) was used to optimize its configuration. Design parameters were considered to be number of mixers, Reynolds number and installation angle of plates. Design of Experiments (DoE) method was used to select the design points. In addition, Response Surface Methodology (RSM) and GA were used to conduct optimization process. Maximum heat transfer rate and minimum pressure drop were defined as objective functions...

Research paper thumbnail of Flow Over a Broad-Crested Weir in Subcritical Flow Conditions, Physical Study

Research paper thumbnail of Using a Porous Environment In Catalytic Gas Heaters to Optimize Energy Consumption and Reduce Pollution in Heating the Furnaces

Waste of energy in furnaces and cost fluctuations, especially the ascending trend of oil price wh... more Waste of energy in furnaces and cost fluctuations, especially the ascending trend of oil price which controls the energy market, have made the developing countries consider the processes to optimize energy consumption and improve industrial processes to decrease the production costs, and this approach has gradually been taken by semi-industrial countries as well. Nowadays, the modifications in consumption pattern and the ways of using energy have vital impacts on economic developments of the countries. Moreover, the hazardous influences of nitrogen oxides on environmental pollution have forced the designers of energy generator machines to think of procedures to lower the harmful gases as they often try to recognize the problematic sections inside combustion and control the temperature conditions in each section to restrain the production of harmful gases.

Research paper thumbnail of Analytical solution of MHD micropolar nanofluid flow and forced convection heat transfer with entropy generation analysis past a linearly stretching sheet

This perusal attempts to model and interpret the entropy generation analysis and the flow field o... more This perusal attempts to model and interpret the entropy generation analysis and the flow field of 2-D, steady, viscous, incompressible and laminar boundary layer and forced convection heat transport of micropolar ferrofluid past a stretching sheet including suction and normal magnetic field effects. The porous sheet’s velocity and temperature are presumed to change linearly. Exact explicit solutions of the velocity, angular velocity and temperature distributions have been derived. The impacts of physical parameters on the local skin friction coefficient, the local Nusselt number, the entropy generation number further the velocities and temperature distributions are analyzed by tables and graphs. The angular velocity has more value than velocity for the least value of the magnetic and material parameters. The entropy generation number has a direct relation with material parameter and Brinkman either Reynolds numbers. Moreover, an inverse relation with the Prandtl number.

Research paper thumbnail of Developing a closing rule curve for valves in pipelines to control the water hammer impacts: Application of the NSGA-II optimization model

Water hammer is known as a phenomenon that has adverse effects on pipelines. Closing rate of valv... more Water hammer is known as a phenomenon that has adverse effects on pipelines. Closing rate of valves plays an important role in controlling this phenomenon. In the water hammer process, the water pressure rise and water discharge are inversely correlated. Therefore, a tradeoff curve (Pareto front) between water pressure rise and water discharge can be developed. Developing these Pareto front using traditional multiple-objective optimization models is always time consuming. Therefore, in recent years, several multiple-objective evolutionary optimization models have been proposed which can provide the Pareto-front with an acceptable computational time. In this paper, the Non-dominated Sorting Genetic Algorithms II (NSGA II) is used for developing the Pareto front. To predict the pressure rise and pipe discharge for a valve closing scenario, a simulation model is also developed using the Characteristic Method. The simulation model is then linked to the NSGA II optimization model. After developing the trade-off curve between the water pressure rise and the discharge, a valve operating rule is developed for each non-inferior point on the trade-off curve. The results show that the proposed methodology can be effectively used for reducing the adverse effects of the water hammer in pipelines.