Natural convection across a vertical layered porous cavity

Numerical studies are reported for steady-state natural convection in a two-dimensional layered porous cavity heated from the side wall. Emphasis is placed on the effects caused by the sublayer thickness ratio, permeability contrast and non-uniform conductivity in a system comprising two sublayers. Calculations have covered a wide range of these parameters. It has been observed that the flow and temperature fields for a layered structure with K₁/K₂ < 1 are completely different from those of K₁/K₂ > 1. When the thermal properties are uniform, the average Nusselt number for a layered system of K₁/K₂ < 1 is always greater than that of a homogeneous system, and it increases with Rayleigh number, but decreases with the sublayer thickness ratio. For systems of K₁/K₂ > 1, the average Nusselt number is always less than that of a homogeneous system, and it increases with both Rayleigh number and the thickness ratio. When there exists a difference in the thermal conductivity of the two sublayers, a second recirculating cell is generated in the less permeable layer for K₁/K₂ > 1. The average Nusselt number is found to increase with the conductivity ratio for K₁/K₂ > 1, and decrease for K₁/K₂ > 1. Heat transfer results including streamline and isotherm patterns, temperature and velocity profiles, and the Nusselt vs Rayleigh number relation in terms of these parameters, are presented.