Non-Boussinesq simulations of Rayleigh-Benard convection in a perfect gas

摘要: We present direct numerical simulations of Boussinesq and non-Boussinesq Rayleigh–Benard convection in a rigid box containing perfect gas. For small stratifications, which includes fluids, the first instability after steady rolls was an oscillatory (a Hopf bifurcation). The resulting characterized by two hot cold blobs circulating each convective roll. same sign thermal perturbations (blobs) are at diametrically opposite points on circular rolls, i.e., they symmetric about roll center. time for (or cold) blob to circulate between three turnover times. When stratification sufficient strength, there dramatic change nature bifurcation. became antisymmetric with respect center, blob. In this case, or circulated around one time. stratified layer, Rayleigh number varies height. found that bifurcation, base closest value. appeared be related increase speed Mach number) rolls. It did not seem affected transport property variation temperature. If along aspect ratio less than 2 walls perpendicular axis periodic, then only could found. describe how our results might reproduced laboratory experiment cryogenic helium