On the effectiveness of variable properties and thermophoresis on steady MHD heat and mass transfer over a porous flat surface

Purpose - The purpose of this paper is to examine the effects of thermophoresis and magnetic field on steady two-dimensional laminar hydrodynamic flow with heat and mass transfer over a semi-infinite permeable flat surface in the presence of viscous dissipation and thermal radiation effects. The fluid viscosity and thermal conductivity are assumed to vary as a function of temperature. Design/methodology/approach - The boundary layer equations are transformed to non-linear ordinary differential equations using scaling group of transformations and these equations are solved numerically by using the fourth order Runge-Kutta method with shooting technique for some values of physical parameters. Findings Some of the results obtained for a special case of the problem are compared to the results published in previous work and are found to be in excellent agreement. Many results are obtained and a representative set is displayed graphically to illustrate the influence of the physical parameters involved in the problem on the velocity, temperature and concentration profiles, as well as the local skin-friction coefficient, the wall heat transfer and the particle deposition rate. Research limitations/implications - One valuable, important observation is that the effect of the variable viscosity parameter is to increase the effect of all studied parameters in the boundary-layer's flow field. Also, the skin-friction coefficient, wall heat transfer and wall deposition flux in a fluid of uniform viscosity are higher than in a fluid of non-uniform viscosity when the surface is permeable. Originality/value - The paper presents a numerical solution for two-dimensional boundary-layer flow with heat and mass transfer over a semi-infinite permeable flat surface. Numerical results indicate that the combining effects of magnetic field and radiation strongly controls flow and mass transfer characteristics for the thermophoretic hydrodynamic flow. This problem is interesting from the physical point of view and also for its applications in engineering sciences.