Compressible turbulent convection in highly stratified adiabatic background

Buoyancy-driven turbulent convection leads to a fully compressible flow with a prominent top-down asymmetry of first-and second-order statistics when the adiabatic equilibrium profiles of temperature, density and pressure change very strongly across the convection layer. The growth of this asymmetry and the formation of an increasingly thicker stabilized sublayer with a slightly negative mean convective heat flux J(c)(z) at the top of the convection zone is reported here by a series of highly resolved three-dimensional direct numerical simulations beyond the Oberbeck-Boussinesq and anelastic limits for dimensionless dissipation numbers, 0.1 <= D <= 0.8, at fixed Rayleigh number Ra = 10(6) and superadiabaticity epsilon = 0.1. The highly stratified compressible convection regime appears for D > D-crit approximate to 0.65, when density fluctuations collapse to those of pressure; it is characterized by an up to nearly 50 % reduced global turbulent heat transfer and a sparse network of focused thin and sheet-like thermal plumes falling through the top sublayer deep into the bulk.

Automated summary

Buoyancy-driven turbulent convection exhibits a top-down asymmetry when the adiabatic equilibrium profiles of temperature, density, and pressure change strongly across the convection layer. This asymmetry grows and leads to the formation of a thickened stabilized sublayer at the top of the convection zone. The highly stratified compressible convection regime shows a significant reduction in global turbulent heat transfer and the presence of sparse thermal plumes falling through the top sublayer.