Coherent oscillations of turbulent Rayleigh-Bénard convection in a thin vertical disk.

A well-defined oscillation is observed in the power spectrum of several fluctuating signals in turbulent Rayleigh-Bénard convection occurring in a thin vertical disk filled with water. The experiment reveals that the coherent oscillations are produced by periodic emission of thermal plumes, which gives rise to periodic pulses of forcing, resulting in a pulsed large-scale circulation in the thin cell. The experimental results agree well with the theoretical predictions made from two coupled nonlinear delayed equations.