Double diffusive convection in a vertical enclosure inserted with two saturated porous layers confining a fluid layer

Abstract Thermosolutal natural convection in an enclosure filled with fluid and inserted with isotropic or anisotropic porous layers is analyzed numerically. Identical porous layers are attached to the vertical walls, and the walls are held at constant temperatures and concentrations. The horizontal walls of the enclosure are assumed to be adiabatic and impermeable. The aspect ratio of the cavity is equal to two and the saturating fluid is air ( Pr =0.71). The analysis is performed for thermal Grashof numbers 10 6 and 10 7 , Schmidt number of 7.1 and for different Darcy number, porous layer thickness and permeability ratio. The results are presented for thermally driven flow, N =0, and for concentration driven flow, N =10. The effect of hydraulic anisotropy on the rate of heat and mass transfer is discussed. It is found that the rate of heat transfer and the rate of mass transfer are weak functions of the Darcy number for high and low permeability regimes. For a certain range of the parameters, the rate of heat transfer decreases when the flow penetrates into the porous layer. Hence, there is an optimum (minimum) value of Nusselt number, which is a function of the anisotropy parameter. Correlation for heat and mass transfer are presented.