Ali J. Chamkha

Unsteady MHD convective heat and mass transfer past a semi-infinite vertical permeable moving plate with heat absorption

The problem of unsteady, two-dimensional, laminar, boundary-layer flow of a viscous, incompressible, electrically conducting and heat-absorbing fluid along a semi-infinite vertical permeable moving plate in the presence of a uniform transverse magnetic field and thermal and concentration buoyancy effects is considered. The plate is assumed to move with a constant velocity in the direction of fluid flow while the free stream velocity is assumed to follow the exponentially increasing small perturbation law. Time-dependent wall suction is assumed to occur at the permeable surface. The dimensionless governing equations for this investigation are solved analytically using two-term harmonic and non-harmonic functions. The obtained analytical results reduce to previously published results on a special case of the problem. Numerical evaluation of the analytical results is performed and some graphical results for the velocity, temperature and concentration profiles within the boundary layer and tabulated results for the skin-friction coefficient, Nusselt number and the Sherwood number are presented and discussed.

Mixed convection flow in a lid-driven enclosure filled with a fluid-saturated porous medium

Abstract Volume averaged equations governing unsteady, laminar, mixed convection flow in an enclosure filled with a Darcian fluid-saturated uniform porous medium in the presence of internal heat generation is formulated. The two vertical walls of the enclosure are insulated while the horizontal walls are kept at constant temperatures with the top surface is moving at a constant speed. The developed equations are nondimensionalized and then solved numerically subject the appropriate initial and boundary conditions by the finite-volume approach along with the Alternating Direct Implicit (ADI) procedure. Comparisons with previously published work are performed and found to be in excellent agreement. A parametric study is conducted and a set of graphical results is presented and discussed to elucidate interesting features of the solution.

HYDROMAGNETIC COMBINED CONVECTION FLOW IN A VERTICAL LID-DRIVEN CAVITY WITH INTERNAL HEAT GENERATION OR ABSORPTION

The problem of unsteady, laminar, combined forced-free convection flow in a square cavity in the presence of internal heat generation or absorption and a magnetic field is formulated. Both the top and bottom horizontal walls of the cavity are insulated while the left and right vertical walls are kept at constant and different temperatures. The left vertical wall is moving in its own plane at a constant speed while all other walls are fixed. A uniform magnetic field is applied in the horizontal direction normal to the moving wall. A temperature-dependent heat source or sink is assumed to exist within the cavity. The governing equations and conditions are solved numerically by the finite-volume approach along with the alternating direct implicit (ADI) procedure. Two cases of thermal boundary conditions corresponding to aiding and opposing flows are considered. Comparisons with previously published work are performed and the results are found to be in excellent agreement. A parametric study is conducted and a set of representative graphical results is presented and discussed to illustrate the influence of the physical parameters on the solution.

Flow and convective heat transfer of a ferro-nanofluid in a double-sided lid-driven cavity with a wavy wall in the presence of a variable magnetic field

ABSTRACT In this work, the effect of a variable spatial magnetic field on ferro-nanofluid flow and heat transfer in a double-sided lid-driven enclosure with a sinusoidal hot wall is investigated. The working fluid is a mixture of iron oxide (Fe3O4) nanoparticles and water and is referred to as a ferro-nanofluid. The control volume-based finite element method (CVFEM) is used to solve the governing equations in the stream function–vorticity formulation. In deriving the governing equations for this investigation, the effect of both ferro-hydrodynamics and magneto-hydrodynamics is taken into account. The numerical calculations are performed for different governing parameters namely; the Reynolds number, nanoparticle volume fraction, magnetic number (arising from Ferrohydrodynamics (FHD) consideration), and the Hartmann number (arising from Magnetohydrodynamics (MHD) consideration). The results show that an enhancement in heat transfer has a direct relationship with the Reynolds number and the Hartmann number, but it has an inverse relationship with the magnetic number. Also, it can be concluded that the Nusselt number increases with the increase of the nanoparticle volume fraction, magnetic number, and the Reynolds number while the opposite trend is observed for the Hartmann number.

MHD FLOW OF A UNIFORMLY STRETCHED VERTICAL PERMEABLE SURFACE IN THE PRESENCE OF HEAT GENERATION/ABSORPTION AND A CHEMICAL REACTION

Analytical solutions for heat and mass transfer by laminar flow of a Newtonian, viscous, electrically conducting and heat generating/absorbing fluid on a continuously moving vertical permeable surface in the presence of a magnetic field and a first-order chemical reaction are reported. The solutions are obtained for all heat absorption conditions and restricted heat generation conditions. In the absence of heat generation/absorption and magnetic field effects are consistent with those previously reported in the literature. A parametric study is conducted and the results are presented and discussed

Electrohydrodynamic free convection heat transfer of a nanofluid in a semi-annulus enclosure with a sinusoidal wall

ABSTRACT Natural convection heat transfer of a nanofluid in the presence of an electric field is investigated. The control volume finite element method (CVFEM) is utilized to simulate this problem. A Fe3O4–ethylene glycol nanofluid is used as the working fluid. The effect of the electric field on nanofluid viscosity is taken into account. Numerical investigation is conducted for several values of Rayleigh number, nanoparticle volume fraction, and the voltage supplied. The numerical results show that the voltage used can change the flow shape. The Coulomb force causes the isotherms to become denser near the bottom wall. Heat transfer rises with increase in the voltage supplied and Rayleigh number. The effect of electric field on heat transfer is more pronounced at low Rayleigh numbers due to the predomination of the conduction mechanism.

Flow and mass transfer on a stretching sheet with a magnetic field and chemically reactive species

An analysis has been carried out to obtain the flow and mass transfer characteristics of a viscous electrically conducting fluid on a continuously stretching surface with non-zero slot velocity. The motion is caused solely by the stretching surface which introduces non-similarity in the velocity and concentration fields. The partial differential equations governing the boundary layer flow and mass transfer are solved by using an implicit finite-difference scheme. The magnetic field significantly increases the surface skin friction, but slightly reduces the surface mass transfer. The surface mass transfer strongly depends on the Schmidt number and the reaction rate and it increases with their increasing values. The surface mass transfer for the first-order reaction is more than that for the second- or-third-order reaction.

Hydromagnetic three-dimensional free convection on a vertical stretching surface with heat generation or absorption

Abstract The problem of steady, laminar, free convection flow over a vertical porous surface in the presence of a magnetic field and heat generation or absorption is considered. The governing three-dimensional partial differential equations for this investigation are transformed into ordinary differential equations using three-dimensional similarity variables. The resulting equations are solved numerically by an accurate, implicit, iterative finite-difference methodology and the obtained results are compared favorably with previously published work. A parametric study is performed to illustrate the influence of the Prandtl number, Hartmann number, heat generation/absorption coefficient, and the surface mass transfer coefficient on the profiles of the velocity components and temperature. Numerical data for the skin-friction coefficient and the Nusselt number functions have been tabulated for various parametric conditions.

MHD FREE CONVECTION FLOW OF A NANOFLUID PAST A VERTICAL PLATE IN THE PRESENCE OF HEAT GENERATION OR ABSORPTION EFFECTS

This work is focused on the numerical solution of steady natural convection boundary-layer flow of a nanofluid consisting of a pure fluid with nanoparticles along a permeable vertical plate in the presence of magnetic field, heat generation or absorption, and suction or injection effects. The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis. The governing boundary-layer equations of the problem are formulated and transformed into a non-similar form. The obtained equations are then solved numerically by an efficient, iterative, tri-diagonal, implicit finite-difference method. Comparisons with previously published work are performed and are found to be in excellent agreement. Representative results for the longitudinal velocity, temperature, and nanoparticle volume fraction profiles as well as the local heat transfer rates for various values of the physical parameters are displayed in both graphical and tabular forms.

Thermal radiation and buoyancy effects on hydromagnetic flow over an accelerating permeable surface with heat source or sink

Abstract Similarity equations governing steady hydromagnetic boundary-layer flow over an accelerating permeable surface in the presence of such effects as thermal radiation, thermal buoyancy, and heat generation or absorption effects are obtained. These equations are solved numerically by an implicit finite-difference method. Favorable comparisons with previously published work are obtained. The effects of the various parameters on the velocity and temperature profiles as well as the skin-friction coefficient and wall heat transfer are presented graphically and in tabulated form.