Second order closure for stratified convection: bulk region and overshooting

TL;DR

This paper introduces a second order closure model for stratified convection that effectively captures both bulk turbulence and overshooting regions, validated against high-resolution simulations up to Rayleigh number 10^9.

Contribution

The paper presents a novel second order closure model capable of simultaneously representing bulk and boundary layer regions in stratified convection systems.

Findings

Model accurately reproduces simulation data in stratified convection.

Effective in high Rayleigh number regimes up to 10^9.

Captures complex interactions between turbulent boundary layers and stable flows.

Abstract

The parameterization of small-scale turbulent fluctuations in convective systems and in the presence of strong stratification is a key issue for many applied problems in oceanography, atmospheric science and planetology. In the presence of stratification, one needs to cope with bulk turbulent fluctuations and with inversion regions, where temperature, density -or both- develop highly non-linear mean profiles due to the interactions between the turbulent boundary layer and the unmixed -stable- flow above/below it. We present a second order closure able to cope simultaneously with both bulk and boundary layer regions, and we test it against high-resolution state-of-the-art 2D numerical simulations in a convective and stratified belt for values of the Rayleigh number, up to Ra = 10^9. Data are taken from a Rayleigh-Taylor system confined by the existence of an adiabatic gradient.