The main purpose of this study is to survey numerically comparison of two- phase and single phase of heat transfer and flow field of copper-water nanofluid in a wavy channel. The computational fluid dynamics （CFD） p...The main purpose of this study is to survey numerically comparison of two- phase and single phase of heat transfer and flow field of copper-water nanofluid in a wavy channel. The computational fluid dynamics （CFD） prediction is used for heat transfer and flow prediction of the single phase and three different two-phase models （mixture, volume of fluid （VOF）, and Eulerian）. The heat transfer coefficient, temperature, and velocity distributions are investigated. The results show that the differences between the temperature fie].d in the single phase and two-phase models are greater than those in the hydrodynamic tleld. Also, it is found that the heat transfer coefficient predicted by the single phase model is enhanced by increasing the volume fraction of nanoparticles for all Reynolds numbers; while for the two-phase models, when the Reynolds number is low, increasing the volume fraction of nanoparticles will enhance the heat transfer coefficient in the front and the middle of the wavy channel, but gradually decrease along the wavy channel.展开更多
This work investigates the flow of a third grade fluid in a rotating frame of reference. The fluid is incompressible and magnetohydrodynamic （MHD）. The flow is bounded between two porous plates, the lower of which i...This work investigates the flow of a third grade fluid in a rotating frame of reference. The fluid is incompressible and magnetohydrodynamic （MHD）. The flow is bounded between two porous plates, the lower of which is shrinking linearly. Mathematical modelling of the considered flow leads to a nonlinear problem. The solution of this nonlinear problem is computed by the homotopy analysis method （HAM）. Graphs are presented to demonstrate the effect of several emerging parameters, which clearly describe the flow characteristics.展开更多
The effects of axisymmetric flow of a Powell-Eyring fluid over an impermeable radially stretching surface are presented. Characteristics of the heat transfer process are analyzed with a more realistic condition named ...The effects of axisymmetric flow of a Powell-Eyring fluid over an impermeable radially stretching surface are presented. Characteristics of the heat transfer process are analyzed with a more realistic condition named the convective boundary condition. Governing equations for the flow problem are derived by the boundary layer approximations. The modeled highly coupled partial differential system is converted into a system of ordinary differential equations with acceptable similarity transformations. The convergent series solutions for the resulting system are constructed and analyzed. Optimal values are obtained and presented in a numerical form using an optimal homotopy analysis method （OHAM）. The rheological characteristics of different parameters of the velocity and temperature profiles are presented graphically. Tabular variations of the skin friction coefficient and the Nusselt number are also calculated. It is observed that the temperature distribution shows opposite behavior for Prandtl and Biot numbers. Furthermore, the rate of heating/cooling is higher for both the Prandtl and Biot numbers.展开更多
In this paper Williamson ?uid is taken into account to study its peristaltic ?ow with heat effects. The study is carried out in a wave frame of reference for symmetric channel. Analysis of heat transfer is accomplishe...In this paper Williamson ?uid is taken into account to study its peristaltic ?ow with heat effects. The study is carried out in a wave frame of reference for symmetric channel. Analysis of heat transfer is accomplished by accounting the effects of non-constant thermal conductivity and viscosity and viscous dissipation. Modeling of fundamental equations is followed by the construction of closed form solutions for pressure gradient, stream function and temperature while assuming Reynold's number to be very low and wavelength to be very long. Double perturbation technique is employed, considering Weissenberg number and variable ?uid property parameter to be very small. The effects of emerging parameters on pumping, trapping, axial pressure gradient, heat transfer coe?cient, pressure rise,velocity pro?le and temperature are analyzed through the graphical representation. A direct relation is observed between temperature and thermal conductivity whereas the indirect proportionality with viscosity. The heat transfer coe?cient is lower for a ?uid with variable thermal conductivity and variable viscosity as compared to the ?uid with constant thermal conductivity and constant viscosity.展开更多
In this article,heat and mass transfer with Joule heating on magnetohydrodynamic(MHD)peristaltic blood under the influence of Hall effect is examined.Mathematical modelling is based on momentum,energy and concentratio...In this article,heat and mass transfer with Joule heating on magnetohydrodynamic(MHD)peristaltic blood under the influence of Hall effect is examined.Mathematical modelling is based on momentum,energy and concentration which are taken into account using ohms law.The governing partial differential equations are further simplified by neglecting the inertial forces and long wavelength approximations.Exact solutions have been presented for velocity,temperature and concentration profile.The influence of all the physical pertinent parameters is taken into account with the help graphs.It is found that Hartmann number and Hall parameter shows opposite behaviour on velocity,temperature and concentration profile.It is worth mentioning that pressure rise also depicts opposite behaviour for Hartmann number and Hall parameter.The present analysis is also presented for Newtonian fluid(α→0)as a special case for our study.It is observed that Hall Effect and magnetic field shows opposite behaviour on velocity and temperature profile.Temperature profile increases due to the increment in Prandtl number and Eckert number.Numerical comparison is also presented between the existing published results by takingα=0;M=0 as a special case of our study.展开更多
Water droplets cause corrosion and erosion,condensation loss,and thermal efficiency reduction in low-pressure steam turbines.In this study,multi-objective optimization was carried out using the black-box method throug...Water droplets cause corrosion and erosion,condensation loss,and thermal efficiency reduction in low-pressure steam turbines.In this study,multi-objective optimization was carried out using the black-box method through the automatic linking of a genetic algorithm(GA)and a computational fluid dynamics(CFD)code to find the optimal values of two design variables(inlet stagnation temperature and cascade pressure ratio)to reduce wetness in the last stages of turbines.The wet steam flow numerical model was used to calculate the optimization parameters,including wetness fraction rate,mean droplet radius,erosion rate,condensation loss rate,kinetic energy rate,and mass flow rate.Examining the validation results showed a good agreement between the experimental data and the numerical outcomes.According to the optimization results,the inlet stagnation temperature and the cascade pressure ratio were proposed to be 388.67(K)and 0.55(-),respectively.In particular,the suggested optimaltemperature and pressure ratio improved the liquid mass fraction and mean droplet radius by about 32%and 29%,respectively.Also,in the identified optimal operating state,the ratios of erosion,condensation loss,and kinetic energy fell by 76%,32.7%,and 15.85%,respectively,while the mass flow rate ratio rose by 0.68%.展开更多
The present paper attempts to solve equations in the initial stage and the two-phase flow regime of fuel spray penetration using the HPM-Padétechnique,which is a combination of the homotopy perturbation method(HP...The present paper attempts to solve equations in the initial stage and the two-phase flow regime of fuel spray penetration using the HPM-Padétechnique,which is a combination of the homotopy perturbation method(HPM)and Padéapproximation.At the initial stage,the effects of the droplet drag and the air entrainment were explained while in the two-phase flow stage,the spray droplets had the same velocities as the entrained air.The results for various injection pressures and ambient densities are presented graphically and then discussed upon.The obtained results for these two stages show a good agreement with previously obtained expressions via successive approximations in the available literature.The numerical result indicates that the proposed method is straight forward to implement,efficient and accurate for solving nonlinear equations of fuel spray.展开更多
In this investigation,a semi-numerical method based on Bernstein polynomials for solving off-centered stagnation flow towards a rotating disc is introduced.This method expands the desired solutions in terms of a set o...In this investigation,a semi-numerical method based on Bernstein polynomials for solving off-centered stagnation flow towards a rotating disc is introduced.This method expands the desired solutions in terms of a set of Bernstein polynomials over a closed interval and then makes use of the tau method to determine the expansion coefficients to construct approximate solutions.This method can satisfy boundary conditions at infinity.The properties of Bernstein polynomials are presented and are utilized to reduce the solution of governing nonlinear equations and their associated boundary conditions to the solution of algebraic equations.Graphical results are presented to investigate the influence of the rotation ratioαon the radial velocity,azimuthal velocity and the induced velocities.A comparative study with the previous results of viscous fluid flow in the literature is made.展开更多
文摘The main purpose of this study is to survey numerically comparison of two- phase and single phase of heat transfer and flow field of copper-water nanofluid in a wavy channel. The computational fluid dynamics （CFD） prediction is used for heat transfer and flow prediction of the single phase and three different two-phase models （mixture, volume of fluid （VOF）, and Eulerian）. The heat transfer coefficient, temperature, and velocity distributions are investigated. The results show that the differences between the temperature fie].d in the single phase and two-phase models are greater than those in the hydrodynamic tleld. Also, it is found that the heat transfer coefficient predicted by the single phase model is enhanced by increasing the volume fraction of nanoparticles for all Reynolds numbers; while for the two-phase models, when the Reynolds number is low, increasing the volume fraction of nanoparticles will enhance the heat transfer coefficient in the front and the middle of the wavy channel, but gradually decrease along the wavy channel.
文摘This work investigates the flow of a third grade fluid in a rotating frame of reference. The fluid is incompressible and magnetohydrodynamic （MHD）. The flow is bounded between two porous plates, the lower of which is shrinking linearly. Mathematical modelling of the considered flow leads to a nonlinear problem. The solution of this nonlinear problem is computed by the homotopy analysis method （HAM）. Graphs are presented to demonstrate the effect of several emerging parameters, which clearly describe the flow characteristics.
文摘The effects of axisymmetric flow of a Powell-Eyring fluid over an impermeable radially stretching surface are presented. Characteristics of the heat transfer process are analyzed with a more realistic condition named the convective boundary condition. Governing equations for the flow problem are derived by the boundary layer approximations. The modeled highly coupled partial differential system is converted into a system of ordinary differential equations with acceptable similarity transformations. The convergent series solutions for the resulting system are constructed and analyzed. Optimal values are obtained and presented in a numerical form using an optimal homotopy analysis method （OHAM）. The rheological characteristics of different parameters of the velocity and temperature profiles are presented graphically. Tabular variations of the skin friction coefficient and the Nusselt number are also calculated. It is observed that the temperature distribution shows opposite behavior for Prandtl and Biot numbers. Furthermore, the rate of heating/cooling is higher for both the Prandtl and Biot numbers.
文摘In this paper Williamson ?uid is taken into account to study its peristaltic ?ow with heat effects. The study is carried out in a wave frame of reference for symmetric channel. Analysis of heat transfer is accomplished by accounting the effects of non-constant thermal conductivity and viscosity and viscous dissipation. Modeling of fundamental equations is followed by the construction of closed form solutions for pressure gradient, stream function and temperature while assuming Reynold's number to be very low and wavelength to be very long. Double perturbation technique is employed, considering Weissenberg number and variable ?uid property parameter to be very small. The effects of emerging parameters on pumping, trapping, axial pressure gradient, heat transfer coe?cient, pressure rise,velocity pro?le and temperature are analyzed through the graphical representation. A direct relation is observed between temperature and thermal conductivity whereas the indirect proportionality with viscosity. The heat transfer coe?cient is lower for a ?uid with variable thermal conductivity and variable viscosity as compared to the ?uid with constant thermal conductivity and constant viscosity.
文摘In this article,heat and mass transfer with Joule heating on magnetohydrodynamic(MHD)peristaltic blood under the influence of Hall effect is examined.Mathematical modelling is based on momentum,energy and concentration which are taken into account using ohms law.The governing partial differential equations are further simplified by neglecting the inertial forces and long wavelength approximations.Exact solutions have been presented for velocity,temperature and concentration profile.The influence of all the physical pertinent parameters is taken into account with the help graphs.It is found that Hartmann number and Hall parameter shows opposite behaviour on velocity,temperature and concentration profile.It is worth mentioning that pressure rise also depicts opposite behaviour for Hartmann number and Hall parameter.The present analysis is also presented for Newtonian fluid(α→0)as a special case for our study.It is observed that Hall Effect and magnetic field shows opposite behaviour on velocity and temperature profile.Temperature profile increases due to the increment in Prandtl number and Eckert number.Numerical comparison is also presented between the existing published results by takingα=0;M=0 as a special case of our study.
基金This research was supported by Brain Pool program funded by the Ministry of Science and ICT through the National Research Foundation of Korea.(NRF-2022H1D3A2A02090885).
文摘Water droplets cause corrosion and erosion,condensation loss,and thermal efficiency reduction in low-pressure steam turbines.In this study,multi-objective optimization was carried out using the black-box method through the automatic linking of a genetic algorithm(GA)and a computational fluid dynamics(CFD)code to find the optimal values of two design variables(inlet stagnation temperature and cascade pressure ratio)to reduce wetness in the last stages of turbines.The wet steam flow numerical model was used to calculate the optimization parameters,including wetness fraction rate,mean droplet radius,erosion rate,condensation loss rate,kinetic energy rate,and mass flow rate.Examining the validation results showed a good agreement between the experimental data and the numerical outcomes.According to the optimization results,the inlet stagnation temperature and the cascade pressure ratio were proposed to be 388.67(K)and 0.55(-),respectively.In particular,the suggested optimaltemperature and pressure ratio improved the liquid mass fraction and mean droplet radius by about 32%and 29%,respectively.Also,in the identified optimal operating state,the ratios of erosion,condensation loss,and kinetic energy fell by 76%,32.7%,and 15.85%,respectively,while the mass flow rate ratio rose by 0.68%.
文摘The present paper attempts to solve equations in the initial stage and the two-phase flow regime of fuel spray penetration using the HPM-Padétechnique,which is a combination of the homotopy perturbation method(HPM)and Padéapproximation.At the initial stage,the effects of the droplet drag and the air entrainment were explained while in the two-phase flow stage,the spray droplets had the same velocities as the entrained air.The results for various injection pressures and ambient densities are presented graphically and then discussed upon.The obtained results for these two stages show a good agreement with previously obtained expressions via successive approximations in the available literature.The numerical result indicates that the proposed method is straight forward to implement,efficient and accurate for solving nonlinear equations of fuel spray.
文摘In this investigation,a semi-numerical method based on Bernstein polynomials for solving off-centered stagnation flow towards a rotating disc is introduced.This method expands the desired solutions in terms of a set of Bernstein polynomials over a closed interval and then makes use of the tau method to determine the expansion coefficients to construct approximate solutions.This method can satisfy boundary conditions at infinity.The properties of Bernstein polynomials are presented and are utilized to reduce the solution of governing nonlinear equations and their associated boundary conditions to the solution of algebraic equations.Graphical results are presented to investigate the influence of the rotation ratioαon the radial velocity,azimuthal velocity and the induced velocities.A comparative study with the previous results of viscous fluid flow in the literature is made.
