Effect of vibrations on thermal convection in thick rotating annulus

Abstract

The effect of transverse vibrations on thermal convection in a rotating thick cylindrical fluid layer is investigated experimentally. The layer rotates about the horizontal axis of symmetry. The temperatures of the layer boundaries are different (the outer boundary is cold) and maintained constant. The study is limited to the case of fast rotation. The centrifugal force of inertia plays a stabilizing role, bringing the fluid into a state of a stable mechanical equilibrium. The vibrations affect the equilibrium of the layer in a narrow frequency range close to the rotation frequency. The structure of the convective flows is studied using PIV-method. It is found that when the frequencies of vibrations and rotation definitely coincide, the convective flow has a form of the couple of symmetric two-dimensional vortices, the position of which is stationary in the cavity reference frame. The convection occurs under the action of an induced inertial force field (superposition of vibrational and centrifugal inertial force fields). With a frequency mismatch, the induced force field rotates in the cavity reference frame. The maximum heat transport corresponds to a resonant excitation of the azimuthal two-dimensional inertial oscillations of the non-isothermal fluid layer. The convective heat transport in this case is much higher than in the case of the frequencies coincidence. The dependence of heat transport, both under resonance conditions and with equal frequencies, on vibration parameters is studied. It is shown that the centrifugal and vibrational mechanisms play a key role in the development of the convection.