On the thermal effect of porous material in porous media Rayleigh-Benard convection

We perform a two-dimensional numerical study on the thermal effect of porous media on global heat transport and flow structure in Rayleigh-B & eacute;nard (RB) convection, focusing on the role of thermal conductivity ? of porous media, which ranges from 0.1 to 50 relative to the fluid. The simulation is carried out in a square RB cell with the Rayleigh number Ra ranging from 107 to 109 and the Prandtl number Pr fixed at 4.3. The porosity of the system is fixed at F = 0.812, with the porous media modelled by a set of randomly displayed circular obstacles. For a fixed Ra, the increase of conductivity shows a small effect on the total heat transfer, slightly depressing the Nusselt number. The limited influence comes from the small number of obstacles contacting with thermal plumes in the system as well as the counteraction of the increased plume area and the depressed plume strength. The study shows that the global heat transfer is insensitive to the conduction effect of separated porous media in the bulk region, which may have implications for industrial designs.