MULTIPLE SOLUTIONS FOR DOUBLE-DIFFUSIVE CONVECTION IN A VERTICAL POROUS ENCLOSURE

A numerical study is made of double-diffusive natural convection in a rectangular fluid-saturated vertical porous enclosure. The flows are d riven by conditions of uniform heat and mass fluxes imposed along the two vertical side walls of the cavity where the two buoyancy effects c an either augment or counteract each other. An extensive series of num erical simulations is conducted in the range 1 less than or equal to R (T) less than or equal to 165, 1 less than or equal to Le less than or equal to 10(3), -20 less than or equal to N less than or equal to 20 and, A = 1, where R(T), Le, Nand A are the Darcy-modified Rayleigh num ber, Lewis number, buoyancy ratio and aspect ratio of the enclosure, r espectively. For aiding flows (N > 0) the behaviour of the resulting d ouble-diffusive convection is in qualitative agreement with the availa ble numerical results. For opposing flows (N < 0) the existence of mul tiple steady states is demonstrated. It is determined that, for a give n value of N, both Lewis and Rayleigh numbers have an influence on the domain of existence of these multiple steady states. Comprehensive Nu sselt and Sherwood number data are presented as functions of the gover ning parameters mentioned above. The effects of the buoyancy ratio are found to be rather significant on the flow pattern and heat and mass transfer, especially for the opposing flows.