Supercritical convective motions in a short horizontal cylinder

As a result of the breakdown of mechanical equilibrium in a fluid in a closed cavity heated from below a monotonic convective motion arises, its spectrum being determined by the shape of the cavity. With increasing Rayleigh number, the stationary motion becomes unstable, and periodic convective oscillations arise in the fluid; with increasing super-criticality, these are replaced by irregular fluctuations. In some cases, the irregular oscillations are established directly after the monotonic motion. The investigation of the time characteristics of these oscillations, which occupy an intermediate position between ordered motion and developed turbulence, is of interest for understanding the nature of turbulence.