Thermal convective instability of a horizontal saturated porous layer with a segment of inhomogeneity

Convective stability is studied for an infinite horizontal porous layer containing a vertical porous segment of different properties. The critical Rayleigh number depends on the aspect ratio of the nonhomogeneous region and the ratios of permeability, thermal conductivity, and thermal diffusivity of the matrix. Incipient streamlines may be either symmetric or antisymmetric.