ABSTRACT

This study deals with natural convection driven by combined thermal and solutal buoyancy forces in a binary fluid. The particular configuration analyzed here is a confined enclosure partially filled with a vertical layer of a porous medium. The analysis is relevant to heat and mass transfer in the mushy zone during solidification processes. The mathematical description of the problem makes use of a one-domain formulation of the conservation equations. The presented numerical results quantitatively show the significant influence of the presence of a relatively thin porous layer on the flow structure and on heat and species transfer in the enclosure.
The paper is dedicated to the analysis of the influence of the main governing parameters on the heat and species transfer as a function of the permeability of the porous layer. The emphasis is put on the parameters characterizing the double diffusive mechanisms: the thermal Rayleigh number, the Lewis number and the buoyancy ratio. The results show a specific behaviour of the Nusselt number in the "double diffusive" regime.