THE FOCUS of the present study is on the fundamentals of the flow in a porous medium confined between two vertical walls maintained at different temperatures and different concentrations of a certain chemical species (Fig. 1)buoyancy effects In the study of natural convection through porous media, the bulk of the research effort has been devoted to the flow caused by a single buoyancy effect, namely, the effect of temperature variations.The interest in this class of flows has been stimulated by heat transfer engineering applications such as geothermal energy conversion and thermal insulation design , hence the two main configurations in which these heat-transfer-driven flows have been studied :(i) heat transfer across a horizontal porous layer with horizontal walls at different temperatures(ii) heat transfer through a layer with different vertical wall temperatures and adiabatic horizontal wal