The influence of surface mass flux on mixed convection over horizontal plates in saturated porous media

Abstract

THE FIRST attempts to study mixed convection in a porous layer were those of Wooding [I], Prats [2], Sutton [3]. and Homsy and Sherwood 141. The emohases in these studies. however, were on the stability of-the flow field and the establishment of the criterion for the onset of convection. Experimental results were very limited and were reported only by Combamous and Bia [5]. By using a boundarylayer formulation and the similarity method, Cheng [6, 71 conducted a series of investigations to study mixed convection over vertical, inclined and horizontal plates in porous media. Recently, numerical results of mixed convection in vertical and horizontal porous layers with non-uniform heating on the boundary have been reported [8, 91, while experimental results have been reported only for the latter case [IO, 111. As a continuing effort toward a complete understanding of transport phenomena in porous media, we consider in this note the influence of surface mass transfer on mixed convection over horizontal plates in saturated porous media. The approach follows that used by Cheng and co-workers [12, 131 for the study of free convection. Similarity solutions are obtained for the special case where the surface temperature, free stream velocity and injection, or withdrawal, velocity are a prescribed power function of distance. The limiting cases of free and forced convection are also examined.