Model for the dynamics of the large-scale circulations in two-layer turbulent convection

A physically motivated low-dimensional model describes properly the interaction of two vertically-aligned large-scale circulations (LSC) in two-layer turbulent convection, and predicts their preferred flow states of thermal and viscous coupling. The model reveals that flow reversals can be achieved when turbulent fluctuations drive the LSC azimuthal diffusion into a flow state such that the two LSC planes are orthogonal to each other, the strength of the LSC in the high Rayleigh number fluid layer then reduces to zero deterministically. The model provides satisfactory interpretation for the high occurrence frequency of flow reversals observed in two-layer turbulent convection.