Heat transfer in porous media Rayleigh–Bénard convection at various Prandtl numbers

We perform two-dimensional direct numerical simulations to study the effect of porous media on global transport properties and flow structures in Rayleigh–Bénard (RB) convection at different Prandtl numbers. The are carried out a square RB cell with uniformly placed circular obstacles, where porosity spans between ϕ=1 ϕ=0.75 Rayleigh number Ra fixed 108, two high numbers (10,4.3) low (0.03,0.1). It is found that Nusselt Nu varies non-monotonically decreasing porosity, first increased then suppressed both high-Pr low-Pr cases, while transition points greatly advanced Pr. Though trends similar Pr, we point physical mechanisms behind them different. At enhance heat transfer by increasing coherence inhibit impeding passage plume bulk region porosity. However, viscous weakened mainly through large-scale circulation (LSC). As decreases, LSC enhanced laminarized, inhibiting shedding from boundary layer. Moreover, further explore structure under random distribution obstacles find some similarities evolution structure. discovery new mechanism for Pr advances understanding natural may provide implications industrial designs.