Rayleigh-Benard convection with phase changes in a Galerkin model

TL;DR

This paper investigates the transition to turbulence in moist Rayleigh-Benard convection using a three-dimensional Galerkin model, analyzing how phase changes influence convective patterns and stability in a conditionally unstable regime.

Contribution

It introduces a comprehensive phase space analysis of moist convection with phase changes, highlighting the conditions for self-sustained convective regimes and regime transitions.

Findings

Localized moist convection in steady, oscillating, or turbulent states

Parameter ranges for self-sustained convection in subcritical conditions

Similarity of moist convection transitions to shear flow turbulence

Abstract

The transition to turbulence in Rayleigh-Benard convection with phase changes and the resulting convective patterns are studied in a three-dimensional Galerkin model. Our study is focused to the conditionally unstable regime of moist convection in which the stratification is stable for unsaturated air parcels and unstable for saturated parcels. We perform a comprehensive statistical analysis of the transition to convection that samples the dependence of attractors (or fixed points) in the phase space of the model on the dimensionless parameters. Conditionally unstable convection can be initiated either from a fully unsaturated linearly stable equilibrium or a fully saturated linearly unstable equilibrium. Highly localized moist convection can be found in steady state, in oscillating recharge-discharge regime or turbulent in dependence on the aspect ratio and the degree of stable stratification of the unsaturated air. Our phase space analysis predicts parameter ranges for which self-sustained convective regimes in the case of subcritical conditional instability can be observed. The observed regime transitions for moist convection bear some similarities to transitions to turbulence in simple shear flows.