Investigation of filtration convection in a near-critical Van-der-Waals gas for substantial temperature differences

The qualitative mechanisms of stationary filtration convection in a near-critical Van-der-Waals gas with substantial temperature variations are investigated. The object of the study is a thin porous ring in a vertical heat-conducting plane, saturated with the gas. An adequate mathematical model, based on the averaging of the two-dimensional equations over the ring thickness, is proposed. The dependence of natural-convection characteristics on the non-Boussinesq parameters (compressibility criteria, temperature difference, and proximity to the critical point) is found. The limits of applicability of the previously known regularities related to the conditions of onset and the properties of stationary convection are discussed.