Generalization of the theory of convection and numerical simulations with an all-regime and well-balanced finite volume scheme. Application to thermo-compositional diabatic convection in brown-dwarf and Earth atmosphere

Séminaire IPAG de Pascal Tremblin (CEA/MdS), jeudi 27 mai 2021, 11h00, IPAG seminar room

We present a new conservative finite volume numerical scheme for the study of stratified hydrodynamics that is able to capture both low-Mach and high-Mach flows (all-regime) and hydrostatic equilibrium at machine precision (well-balanced). The scheme is based on a splitting strategy between the acoustic and transport part of the Euler system and can be implemented in a implicit-explicit approach to get rid of the restrictive sound-speed CFL condition while being fully conservative. This new scheme has been implemented using the Kokkos library enabling performance portable across different HPC architectures (CPU, GPU, Manycore).

Using this new solver, we perform numerical simulations of different convective instabilities and show that the presence of source terms are leading to a new family of unstable systems. By generalizing the theory of convection to any type of thermal and compositional source terms (diabatic processes), we show that thermohaline convection in Earth oceans, fingering convection in stellar atmospheres, moist convection in Earth atmosphere, and two-phase convective flows in the cooling systems of nuclear power plants are all deriving from the same general diabatic convective instability. We also show that convection triggered by CO/CH4 chemical transition with radiative transfer in the atmosphere of brown dwarfs and (or other chemical transition in exoplanet atmospheres) is an exact analog of Earth moist convective system.