Convection in a horizontal, doubly layered porous medium has been investigated numerically. A two-dimensional, time-dependent model has been developed to compute heat transfer in a saturated porous medium that is locally heated from either above or below. The primary objective is to ascertain how these modes of heating can be differentiated via an examination of the heat transfer results. Natural and mixed convection are considered. For mixed convection in which a uniform horizontal flow is assumed to enter the domain, the qualitative relation between the Rayleigh and Peclet numbers is obtained over a large range for each. The effect of the length of the heating zone on the flow structure is also examined. The permeability ratio and the ratio of the thermal conductivity of the two layers is allowed to vary. This gives the computed Nusselt numbers a broad range of applicability in geophysical and engineered systems.
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