Experimental Study of Thermal Convection and Heat Transfer in Rotating Horizontal Annulus

A genuine technological issue–the thermal convection of liquid in a rotating cavity–is investigated experimentally. The experiments are conducted within a horizontal annulus with isothermal boundaries. The inner boundary of the annulus has a higher temperature, thus exerting a stabilising influence on the system. It is shown that when the layer rotation velocity diminishes, two-dimensional azimuthally periodic convective rolls, rotating together with the cavity, emerge in a threshold manner. The development of convection is accompanied by a significant intensification of heat transfer through the layer. It is shown that the averaged thermal convection excitation in the form of a system of two-dimensional rolls occurs against the background of oscillations of a non-isothermal fluid in the cavity reference frame caused by the gravity field. The excitation threshold and the structure of convective rolls are consistent with the results of the earlier theoretical studies by the authors performed using the equations of “vibrational” convection obtained by the averaging method. Furthermore, the experiments have revealed a new type of averaged flow in the form of a spatially periodic system of toroidal vortices. It is shown that a steady streaming, excited by the inertial oscillations of the fluid, is responsible for the generation of the toroidal vortices. These flows develop in a non-threshold manner and are most clearly manifested in a case of resonant excitation of one of the inertial modes.