Magnetohydrodynamic Mixed Convection Flow Research Articles

Unsteady MHD Mixed Convection Flow in Hybrid Nanofluid at Three-Dimensional Stagnation Point

There has been significant interest in exploring a stagnation point flow due to its numerous potential uses in engineering applications such as cooling of nuclear reactors. Hence, this study proposed a numerical analysis on the unsteady magnetohydrodynamic (MHD) mixed convection at three-dimensional stagnation point flow in Al2O3–Cu/H2O hybrid nanofluid over a permeable sheet. The ordinary differential equations are accomplished by simplifying the governing partial differential equations through suitable similarity transformation. The numerical computation is established by the MATLAB system software using the bvp4c technique. The bvp4c procedure is excellent in providing more than one solution once sufficient predictions are visible. The influence of certain functioning parameters is inspected, and notable results exposed that the rate of heat transfer is exaggerated along with the skin friction coefficient while the suction/injection and magnetic parameters are intensified. The results also signified that the rise in the volume fraction of the nanoparticle and the decline of the unsteadiness parameter demonstrates a downward attribution towards the heat transfer performance and skin friction coefficient. Conclusively, the observations are confirmed to have multiple solutions, which eventually contribute to an investigation of the analysis of the solution stability, thereby justifying the viability of the first solution.

Analytical study of MHD mixed convection flow for Maxwell nanofluid with variable thermal conductivity and Soret and Dufour effects

The key purpose of this article is to discuss the magnetohydrodynamic mixed convection flow for a Maxwell nanofluid past a stretching and permeable sheet. Variable thermal conductivity and Dufour and Soret effects are also taken into consideration. The modeled equations are transformed into a set of non-linear ordinary differential equations by employing similar transformable variables. The renovated system of equations is interpreted by Homotopy Analysis Method (HAM). The results determined by HAM have been compared with numerical solutions, and a good agreement has been noticed in both solutions. The main outcomes of this investigation are that velocity slows down with augmentation in Maxwell and magnetic parameters, temperature increases with radiation and thermophoretic parameters and reduces with growing values of Prandtl number and Brownian motion parameters, and furthermore, the motile micro-organism is a dropping function of Peclect and bio-convection Lewis numbers and bio-convection concentration difference parameters.

Irreversibility characterization in nanoliquid flow with velocity slip and dissipation by a stretchable cylinder

Here we scrutinize magnetohydrodynamic mixed convection flow of viscous nanoliquid by a stretching cylinder. Heat flux, Joule heating and dissipation effect are examined in heat equation. Thermophoresis and Brownian diffusion behaviors are accounted. Entropy generation investigation is addressed. A first order chemical reaction is also accounted. Nonlinear PDEs are converted to ordinary differential system employing similarity variables. To develop a convergent solution we implemented ND-solve method. Variation of various sundry variables on Bejan number, velocity, entropy rate, concentration and temperature are graphically deliberated. Variation of various influential variables on Nusselt and Sherwood numbers are graphically examined. Larger slip parameter reduces the velocity field. Temperature is improved against the larger radiation variable. Concentration has a reverse trend against thermophoresis and Brownian motion variables. Radiation and magnetic variables have similar behavior on entropy optimization. Bejan number is reduced versus larger Brinkman number.

Entropy Generation for MHD Maxwell Nanofluid Flow Past a Porous and Stretching Surface with Dufour and Soret Effects

In this study, the entropy generation for magnetohydrodynamic (MHD) mixed convection and Maxwell nanofluid flow is discussed. The flow is considered over a stretching and penetrable surface. The thermal conductivity, velocity slip condition, and thermal radiation are also considered for the flow system. The entropy generation and irreversibility analysis have been considered and the impact of the physical parameters has been observed. The modeled equations are converted into a set of non-linear ODEs with the help of similar transformable variables. The sophisticated homotopy analysis method (HAM) is used to obtain analytic approximations for the resulting system of non-linear differential equations. Among the many outputs of the study, it is found that the velocity distribution is a decreasing function of Maxwell, magnetic parameters, and an increasing function of mixed convection factor within the boundary layer. Temperature profile upsurges with a consistent expansion in radiation thermophoretic and Dufour parameters. The Bejan number increases with an increase in the Brinkman number and radiation parameter. The concentration profile increases with an augmentation of the Soret number and decreases with increasing values of the Schmidt number.

MHD Mixed Convection Flow and Heat Transfer of a Dual Stratified Micropolar Fluid Over a Vertical Stretching/ Shrinking Sheet With Suction, Chemical Reaction and Heat Source

The purpose of this study was to investigate the magnetohydrodynamic (MHD) mixed convection flow and heat transfer of a dual stratified micropolar fluid over a vertical permeable stretching/ shrinking sheet with chemical reaction and heat source. The governing nonlinear partial differential equations are reduced into a system of nonlinear ordinary differential equations using an appropriate similarity transformation. Then, the obtained ordinary differential equations are solved numerically using the boundary value problem solver (bvp4c) in MATLAB software. The numerical results are tabulated and plotted for the heat transfer characteristics, namely, the skin friction coefficient, the local Nusselt number, the local Sherwood number as well as the velocity, temperature and concentration profiles for some values of the governing parameters. The present numerical results also have been compared with the previous reported results for a particular case and the comparisons are found to be in an excellent agreement. The results indicate that the skin friction coefficient and the local Nusselt number increase with chemical reaction and heat source. The magnitude of the local Sherwood number increases with the increasing of chemical reaction parameter. However, the magnitude of the local Sherwood number decreases with heat source effect.

Effects of symmetry on magnetohydrodynamic mixed convection flow in a vertical duct

Magnetohydrodynamic convection in a downward flow of liquid metal in a vertical duct is investigated experimentally and numerically. It is known from earlier studies that in a certain range of parameters, the flow exhibits high-amplitude pulsations of temperature in the form of isolated bursts or quasi-regular fluctuations. This study extends the analysis while focusing on the effects of symmetry introduced by two-sided rather than one-sided wall heating. It is found that the temperature pulsations are robust physical phenomena appearing for both types of heating and various inlet conditions. At the same time, the properties, typical amplitude, and range of existence in the parametric space are very different at the symmetric and asymmetric heating. The obtained data show good agreement between computations and experiments and allow us to explain the physical mechanisms causing the pulsation behavior.

MHD mixed convective radiative flow of Eyring‐Powell fluid over an oscillatory stretching sheet using bivariate spectral method on overlapping grids

AbstractThe bivariate spectral quasilinearization method (BSQLM) on overlapping grids is presented and applied in the analysis of unsteady magnetohydrodynamic mixed convection flow of Eyring‐Powell fluid over an oscillatory stretching sheet embedded in a non‐Darcy porous medium with nonlinear radiative heat flux and variable thermophysical properties. The fluid properties, namely the fluid viscosity, thermal conductivity, and mass diffusivity, are assumed to vary with temperature. It is assumed that the first‐order chemical reaction with heat generation/absorption takes place in the flow. The flow domain is subject to uniform transverse magnetic field perpendicular to the stretching surface. The transformed flow equations are solved numerically using BSQLM on overlapping grids. The convergence properties and accuracy of the method are assessed. The proposed method is computationally efficient, and it gives stable and highly accurate results after few iterations and using few grid points in each subinterval. The improved accuracy rests upon the use of the overlapping grid, which produces sparse coefficient matrices that are easy to invert and have small condition numbers. The effects of physical parameters on the flow fields, local skin friction, the Nusselt number, and the Sherwood number are exhibited through graphs and tables. Amongst other findings, we found that the amplitude of the fluid flow along with flow characteristics may efficiently improve through the utilization of variable fluid viscosity. Heat and mass transportation processes enhance with the inclusion of nonlinear radiative heat flux, temperature‐dependent thermal conductivity, and mass diffusion coefficient, whereas they diminish with the increase in the local inertia coefficient. The current flow analysis can be useful in various engineering applications including paper production, polymer solution, glass blowing, extrusion of thermal system manufacturing process, and heat transportation enhancement.

Magnetohydrodynamic Mixed Convection and Entropy Analysis of Nanofluid in Gamma-Shaped Porous Cavity

The entropy generation due to magnetohydrodynamic mixed convection flow and heat transfer in a Gamma-shaped porous cavity is explored in this research by the finite volume technique. There exists an internal heating generation inside the cavity and the top and bottom walls are moving by constant velocities to induce forced convection. The cavity is filled with copper/water nanofluid and subjected to an inclined uniform magnetic field. A numerical simulation is performed to study the effects of several key parameters such as the Hartmann number, nanoparticle volume fraction, and the length and location of a heat source inside the Gamma-shaped cavity on the heat transfer performance. The numerical results are presented graphically in the forms of isotherm, streamline contour plots and changing Nusselt numbers and entropy generation. The increase of the Nusselt number with the volume fraction is more pronounced for the smallest heat source, a heat source placed at the lowest height from the bottom side, the lowest volumetric heat generation, the lowest imposed magnetic field, the lowest Darcy number, and for a porous media with the lowest solid to fluid thermal conductivity ratio. Increasing the nanoparticle volume fraction has a higher impact on the production of entropy than the enhancement in the heat transfer rate.

Mhd Mixed Convection in Copper-Water Nanofluid Filled Lid-Driven Square Cavity Containing Multiple Adiabatic Obstacles with Discrete Heating

The objective of the present work is to investigate the influence of nanoparticles of copper within the base fluid (water) on magneto-hydrodynamic mixed-convection flow in a square cavity with internal generation. A control finite volume method and SIMPLER algorithm are used in the numerical calculations. The geometry is a lid-driven square cavity with four interior square adiabatic obstacles. A uniform heat source is located in a part of the left wall and a part of the right wall of the enclosure is maintained at cooler temperature while the remaining parts of the two walls are thermally insulated. Both the upper and bottom walls of the cavity are considered to be adiabatic. A comparison with previously published works shows a very good agreement. It is observed that the Richardson number, Ri, significantly alters the behavior of streamlines when increased from <i>0.1</i> to <i>100.0</i>. Also, the heat source position parameter, <i>D</i>, significantly changes the pattern of isotherms and its strength shifted when <i>D</i> moves from <i>0.3</i> to <i>0.7</i>.

MHD mixed convection stagnation point flow of a hybrid nanofluid past a vertical flat plate with convective boundary condition

The steady magnetohydrodynamics (MHD) mixed convection stagnation point flow of a hybrid nanofluid past a vertical flat plate with convective boundary condition is investigated in this study. By choosing appropriate similarity variables, the partial differential equations are transformed into a system of linear equations which are solved afterwards by using the boundary value problem solver, namely bvp4c in Matlab software. The solutions of the ordinary differential equations are proven to have two branches which are upper and lower solutions in a certain range of the mixed convection parameter. This leads to the execution of a stability analysis that verifies the achievable solution of the upper branch which is considered stable while the lower branch is unstable. The findings exposed that the fluid velocity increases with the increasing value of the magnetic parameter while the fluid temperature is decreased contradictory.

Second law analysis with effects of Arrhenius activation energy and binary chemical reaction on nanofluid flow

The Arrhenius activation energy and binary chemical reaction are taken into account to consider the magnetohydrodynamic mixed convection second grade nanofluid flow through a porous medium in the presence of thermal radiation, heat absorption/generation, buoyancy effects and entropy generation. The items composing of the governing systems are degenerated to nonlinear ordinary differential equations by adopting the appropriate similarity transformations which are computed through Runge-Kutta-Fehlberg (RKF) numerical technique along with Shooting method. The solution is manifested through graphs which provides a detailed explanations of each profile in terms of involved parameters effects. The compared results maintain outstanding approach to the previous papers.

Thermal Radiation and MHD Effects in the Mixed Convection Flow of Fe3O4–Water Ferrofluid towards a Nonlinearly Moving Surface

This paper investigated the magnetohydrodynamic (MHD) mixed convection flow of Fe3O4-water ferrofluid over a nonlinearly moving surface. The present work focused on how the state of suction on the surface of the moving sheet and the effects of thermal radiation influence the fluid flow and heat transfer characteristics within the stagnation region. As such, a similarity solution is engaged to transform the governing partial differential equations to the ordinary differential equations. A collocation method, namely the bvp4c function in the MATLAB software solves the reduced system, numerically. Two different numerical solutions were identified for the cases of assisting and opposing flows. The stability analysis was conducted to test the stability of the non-uniqueness solutions. The increment of the thermal radiation effect affects the rate of heat transfer to decrease. The stability analysis conveyed that the upper branch solution is stable and vice versa for the other solution.

Computational analysis of magnetohydrodynamic mixed convection flow along vertical cylinder in the presence of aligned magnetic field

The magnetohydrodynamic mixed convection boundary layer flow in the presence of aligned magnetic field along a vertical cylinder is considered. Particular attention is paid to investigate how the buoyancy effects of thermal diffusion combine with joule heating affect the two dimensional flow. Effects of the mixed convection parameter λ, magnetic force parameter S, magnetic Prandtl number Pm and Prandtl number Pr on the velocity, temperature distribution, magnetic flux, skin friction, rate of heat transfer and magnetic intensity are studied. Further, the conservation equations are approximated by using finite difference method with a second order central difference scheme for entire regime, and extended series solution at the surface of cylinder. The obtained results show that the skin friction, rate of heat transfer, magnetic intensity, magnetic flux and temperature distribution can be enhanced or reduced by proper choice of parameters involved in the convective fluid flow problem and presented graphically. The increase in magnetic force parameter S enhances the momentum boundary layer while the thermal boundary layer and magnetic flux at the surface of the cylinder is reduced. The obtained results are compared by both methods and found to be in good agreement.

Finite Element Analysis of Magnetohydrodynamic Mixed Convection in a Lid-Driven Trapezoidal Enclosure Having Heated Triangular Block

A numerical research on magnetohydrodynamic mixed convection flow in a lid-driven trapezoidal enclosure at non-uniform heating of bottom wall has been studied numerically. The enclosure consists of insulated top wall and cold side walls, too. It also contains a heated triangular block (Rot = 0° - 90°) located somewhere inside the enclosure. The boundary top wall of the enclosure is moving through uniform speed U0. The geometry of the model has been represented mathematically by coupled governing equations in accordance with proper boundary conditions and then a two-dimensional Galerkin finite element based numerical approach has been adopted to solve this paper. The numerical computations have been carried out for the wide range of parameters Prandtl number (0.5 ≤ Pr ≤ 2), Reynolds number (60 ≤ Re ≤ 120), Rayleigh number (Ra = 103) and Hartmann number (Ha = 20) taking with different rotations of heated triangular block. The results have been shown in the form of streamlines, temperature patterns or isotherms, average Nusselt number and average bulk temperature of the fluid in the enclosure at non-uniform heating of bottom wall. It is also indicated that both the streamlines, isotherm patterns strongly depend on the aforesaid governing parameters and location of the triangular block but the thermal conductivity of the triangular block has a noteworthy role on the isotherm pattern lines. Moreover, the variation of Nuav of hot bottom wall and θav in the enclosure is demonstrated here to show the characteristics of heat transfer in the enclosure.

Homotopy solution for MHD mixed convective unsteady flow of a Powell-Eyring fluid in a vertical porous space with oscillating wall temperature

In this paper, unsteady magnetohydrodynamic (MHD) flow of Powell-Eyring fluid in a vertical channel with diffusion thermo and thermal diffusion effects in the presence of heat source have been studied. The governing nonlinear, coupled partial differential equations are reduced to ODEs using oscillating parameter and then solved by homotopy analysis method (HAM). The influence of emerging parameters on heat and mass transfer characteristics of the flow are studied. It is found that the velocity of a Non-Newtonian fluid is found to decrease in comparison with Newtonian fluid. Also, it is observed that thermal parameters and Soret number are lead to promote the temperature of the fluid significantly. Increasing magnetic parameter tends to produce oscillating behaviour on volume flow rate whereas uniform depreciation can be noticed with increasing Schmidt number.

Homotopy solution for MHD mixed convective unsteady flow of a Powell-Eyring fluid in a vertical porous space with oscillating wall temperature

In this paper, unsteady magnetohydrodynamic (MHD) flow of Powell-Eyring fluid in a vertical channel with diffusion thermo and thermal diffusion effects in the presence of heat source have been studied. The governing nonlinear, coupled partial differential equations are reduced to ODEs using oscillating parameter and then solved by homotopy analysis method (HAM). The influence of emerging parameters on heat and mass transfer characteristics of the flow are studied. It is found that the velocity of a Non-Newtonian fluid is found to decrease in comparison with Newtonian fluid. Also, it is observed that thermal parameters and Soret number are lead to promote the temperature of the fluid significantly. Increasing magnetic parameter tends to produce oscillating behaviour on volume flow rate whereas uniform depreciation can be noticed with increasing Schmidt number.

Thermo-Diffusion and Multislip Effects on MHD Mixed Convection Unsteady Flow of Micropolar Nanofluid over a Shrinking/Stretching Sheet with Radiation in the Presence of Heat Source

The main purpose of this study is to investigate the multislip effects on the magneto-hydrodynamic (MHD) mixed convection unsteady flow of micropolar nano-fluids over a stretching/shrinking sheet along with radiation in the presence of a heat source. The consequences of multislip and buoyancy conditions have been integrated. By using the suitable similarity variables are used to solve the governing non-linear partial differential equations into a system of coupled non-linear ordinary differential equations. The transformed equations are solved numerically by using Runge–Kutta fourth-order method with shooting technique. The impacts of the several parameters on the velocity, temperature, micro-rotation, and concentration profiles as well as on the skin friction coefficient, Sherwood number, and Nusselt number are discussed with the help of graphs and tables.

Numerical study of MHD mixed convection flow over a diamond-shaped obstacle using OpenFOAM

The development of the flow structure with assisting the buoyancy in the liquid metal flow over the diamond-shaped obstacle and the influence of the presence of magnetic field on the vorticity and heat dissipation from the hot surface is investigated numerically at fixed Reynolds number of Re = 1000. The computation is performed by the in-house developed magnetohydrodynamics (MHD) based flow solver using open source CFD tool OpenFOAM. The liquid metal with a Prandtl number of Pr = 0.02 is considered as working fluid and is assumed to be electrically conducting in nature. The strength of the buoyancy in the flow is varied in the range of four different Richardson number of Ri = 0, 0.5, 1, and 5. The consequence of the rising buoyancy in the flow on the vorticity and time-averaged Nusselt number over the hot surface is observed. The unsteadiness in the flow due to the rise in the buoyancy is further controlled and regulated by the application of a magnetic field. The intensity of the magnetic field is governed by non-dimensional Hartmann number (Ha) varies in the range of Ha = 0–50. It is observed from the results that the Lorentz force in the flow opposes the Kármán vortex street and the buoyancy in the flow degenerates the vortex. The undulation in the heat transfer due to rise in the buoyancy is suppressed by the presence of Lorentz force without sacrificing the Nusselt number at low Hartmann number. The study of isotherms, streamlines, time-averaged Nussselt number, vorticity is discussed in detail.

Transport phenomena in MHD mixed convective nanofluid flow

Purpose This study aims to investigate the unsteady magnetohydrodynamic mixed convective nanofluid flow by using Buongiorno two-phase model to achieve an appropriate mechanism to improve the efficiency of solar energy systems by mitigating the energy losses. Design/methodology/approach The transport phenomena occurring in this physical problem are modelled using nonlinear partial differential equations and are non-dimensionalised by using non-similar transformations. The quasilinearisation technique is used to solve the resulting system with the help of a finite difference scheme. Findings The study reveals that the effect of the applied transverse magnetic parameter is to increase the temperature profile and to reduce the wall heat transfer rate. The Brownian diffusion and thermophoresis parameters that characterise the nanofluids contribute to the reduction in wall heat transfer rate. The presence of nanoparticles in the fluid gives rise to critical values for the thermophoresis parameter describing the behaviour of the wall heat and mass transfer rates. Wall heating and cooling are analysed by considering the percentage increase or percentage decrease in the heat and mass transfer rates in the presence of nanoparticles in the fluid. Research limitations/implications The investigation on wall cooling/heating leads to the analysis of control parameters applicable to the industrial design of thermal systems for energy storage, energy harvesting and cooling applications. Practical implications The analysis of the control parameters is of practical value to the solar industry. Social implications In countries, such as South Africa, daily power cuts are a reality. Any research into improving the quality of energy obtained from alternate sources is a national necessity. Originality/value From the literature survey in the present study, it is found that no similar work has been reported in the open literature that analyses the time-dependent mixed convection flow along the exponentially stretching surface in the presence of the effects of a magnetic field, nanoparticles and non-similar solutions.

Steady incompressible magnetohydrodynamics Casson boundary layer flow past a permeable vertical and exponentially shrinking sheet: A stability analysis

AbstractSteady incompressible magnetohydrodynamic mixed convection boundary layer flow of a Casson fluid on an exponentially vertical shrinking sheet using the non‐Newtonian heating equation is investigated in this paper. There are three main objectives of this study, namely, to develop a new mathematical model, to obtain multiple solutions, and to perform stability analysis. The governing partial differential equations have been changed into nonlinear ordinary differential equations. The resultant equations of boundary value problems are then converted into the equivalent initial value problems using the shooting method before they can be solved using Runge‐Kutta of order four. The numerical results are obtained and found to be in good agreement with the published literature. The results also indicate that the velocity boundary layer becomes thinner as the magnetic, slip, and Casson parameters increase. Dual solutions for temperature and velocity distributions are obtained. Furthermore, the results suggest that the presence of the force of buoyancy (opposing flow case) would cause the occurrence of dual solutions. However, based on the stability analysis, only the first solution is stable.