Fluid dynamics of a mixed convective/stably stratified system-A review of some recent works

Numerous fluid systems organise into a turbulent layer adjacent to a stably stratified one, for instance, planetary atmospheres and stellar interiors. Capturing the coupled dynamics of such systems and understanding the exchanges of energy and momentum at the interface between the two layers are challenging, because of the large range of involved time- and length-scales: indeed, the rapid small-scale turbulence excites waves at intermediate scale, which propagate and interact non-linearly to generate large-scale circulations, whose most famous example is the quasi-biennial oscillation of the Earth's atmosphere. We review here some recent progress on the wave characterisation and on the non-linear mean flow generation, based on the combined experimental and numerical study of a model laboratory system. Applications in climate and stellar modelling are also briefly discussed.