Mechanism of spontaneous large-scale-circulation reversals

Establish the physical mechanism that triggers the spontaneous halts and reversals of the direction of the large-scale circulation in Rayleigh–Bénard convection.

Background

The paper situates two-dimensional annular Rayleigh–Bénard convection within the broader study of buoyancy-driven flows, whose long-term dynamics include coherent plumes and large-scale circulation patterns. Although these structures have been extensively investigated in Eulerian settings, the authors identify the spontaneous stopping and reversal of the circulation as an unresolved physical phenomenon.

This problem is distinct from the paper’s central Lagrangian analysis of coherent structures in annular convection: the authors mention it as an existing open question motivating the broader relevance of understanding convection, rather than claiming to resolve it through their finite-time diagnostics.