Inertial Modes in a Rotating Horizontal Annulus with Boundaries of Different Temperatures and Their Effect on the Averaged Convection

Time-averaged thermal convection in a rotating horizontal annulus with a higher temperature at its inner boundary is studied. The centrifugal force plays a stabilizing role, while thermal convection is determined by the “thermovibrational mechanism”. Convective flow is excited due to oscillations of a non-isothermal rotating fluid. Thermal vibrational convection manifests in the form of two-dimensional vortices elongated along the axis of rotation, which develop in a threshold manner with an increase in the amplitude of fluid oscillations. The objective of the present study is to clarify the nature of another phenomenon, i.e., three-dimensional convective vortices observed in the experiments both before the excitation of the convection described above and in the supercritical region. The experimental study of the oscillatory and the time-averaged flow fields by particle image velocimetry is accompanied by the theoretical research of inertial waves. It is found that three-dimensional fluid flows owe their origin to inertial waves. This is confirmed by a high degree of agreement between the experimental and theoretical results. Experiments with cavities of different lengths indicate that the vortices are clearly seen in cavities that meet the conditions of resonant excitation of inertial modes. Furthermore, the length of the cavity has no effect on heat transfer, which is explained by the comparatively low intensity of the wave-induced flows. The main contribution to heat transfer is due to vortices elongated along the axis of rotation. The novel results are of significant practical importance in various fields.