Mixed convection in a double lid-driven cubic cavity

To study the intricate three-dimensional flow structures and the companion heat transfer rates in double lid-driven cubic cavity heated from the top and cooled from below, a numerical methodology based on the finite volume method and a full multigrid acceleration is utilized in this paper. The four remaining walls forming the cubic cavity are adiabatic. The working fluid is air so that the Prandtl number equates to 0.71. Numerical solutions are generated for representative combinations of the controlling Reynolds number inside 100⩽Re⩽1000 and the Richardson numbers inside 0.001⩽Ri⩽10. Typical sets of streamlines and isotherms are presented to analyze the tortuous circulatory flow patterns set up by the competition between the forced flow created by the double driven walls and the buoyancy force of the fluid. For extreme combinations of high Ri and low Re, the heat transfer is essentially dominated by conduction. On the other hand, for extreme combinations of small Ri and high Re, the heat transfer becomes convective dominating. Numerical values of the overall Nusselt number in harmony with the Re- and Ri-intervals are presented and they are compared afterward against the standard case of a single lid driven cavity. It is discovered that a remarkable heat transfer improvement of up to 76% can be reached for the particular combination of Re=400 and Ri=1.