Porous media saturated with substances with the parameters near the thermodynamical critical point known as near- or supercritical fluids are considered. As they approach the critical point, the specific heat at constant pressure and the compressibility grow unboundedly, leading to significant peculiarities in hydrodynamic and thermal behavior. Numerical simulation of dynamics and heat transfer in a horizontal porous layer heated from below is carried out. A near-critical fluid is modeled as van der Waals gas. Initially, conditions are isothermal, a fluid phase is at rest and stratified in the gravity field, so that the density profile is non- linear. When heating starts, a fluid phase becomes moving. Non-Boussinesq effects in development of Rayleigh-Darcy convection are investigated.
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