Transient Convection Flow in Super-Imposed Fluid and Porous Layers 2000-01-2322
This paper is aimed at investigating the effects of combined Marangoni and Rayleigh convections in a porous layer, underlain by a fluid layer. The two-dimensional transient numerical model represents a dual rectangular cavity system in which the porous cavity is located below the fluid cavity. Both cavities are saturated with hexane. The problem consists of studying the combined Marangoni and Rayleigh effects on the flow. The interaction between the Marangoni and the Rayleigh convection is investigated in detail. The porous cavity is heated at the bottom while the top liquid cavity has a free surface and is maintained at a room temperature. In addition, the role of the aspect ratio of the porous layer over the fluid layer in determining the convection pattern was studied. Results indicate that the Marangoni convection enhances the flow in the porous layer for high aspect ratio while the Rayleigh number suppresses the Marangoni convection at the free surface for a low aspect ratio.. At a critical aspect ratio above 3, the Marangoni convection becomes dominant over the Rayleigh convection in the liquid layer.