LATTICE BOLTZMANN SIMULATIONS OF DOUBLE-DIFFUSIVE CONVECTION IN LID-DRIVEN COMPOSITE CAVITY

The lattice Boltzmann method was adopted to investigate double-diffusive mixed convection in a lid-driven composite cavity at the pore scale. The cavity was composed of a layer of disordered random porous media and two free spaces filled with pure fluid. A numerical study based on the coupled lattice Bhatnagar-Gross-Krook model and the concentration distribution function was conducted to illustrate the influence of Lewis number Le (2.0 <= Le <= 50), Richardson number Ri (10(-3) <= Ri <= 10(3)), and porous medium layer porosity (epsilon = 0.6/0.7/0.8) on the double-diffusive mixed convection keeping the buoyancy ratio N = 1.0 and Prandtl number Pr = 0.7. The isotherms, isoconcentrations, and streamlines were analyzed, as well as the local and average Nusselt and Sherwood numbers along the left high temperature and concentration wall. Results showed that the porosity had a considerable influence on the temperature, concentration, and flow fields. The larger the porosity and Le, the larger the average Nusselt (Nu(av)) and (average Sherwood) Sh(av) at Ri = 1.0. Nu(av) and Sh(av) of the left wall decreased with an increase in Ri with fixed porosity in the composite cavities.