Reversals of Large-Scale Circulation in Turbulent Convection in Rectangular Cavities

The behavior of large-scale circulation appearing against the background of Rayleigh-Benard turbulent convection in rectangular cavities of various geometries (from a thin layer to a cubic cell) has been experimentally investigated. It has been shown that the regimes of large-scale circulation with spontaneous reversals separated by long periods of quasistationary circulation appear both in a limited range of the Rayleigh number and in a limited range of the aspect ratio, which determines the ratio of the thickness of a cell to the side in the circulation plane. A regime without reversals is established in a thick layer, whereas a regime characterized by numerous changes in the direction of circulation, which are not separated by intervals with the stable direction of the large-scale flow, arises in a thin layer. The spectra of oscillations of the amplitude of large-scale circulation have been analyzed. It has been shown that a dominant frequency appears in the spectrum of oscillations of the cubic cell.