Correspondence between flow structures and heat transfer in regime transitions in turbulent rotating thermal convection

Abstract

We present an experimental study of the properties of heat transport and flow structures in rotating thermal convection. The heat-transfer efficiency is found to exhibit a scaling transition at a transitional Ekman number Ekt, at which sharp transitions of the dynamical and geometrical properties of the columnar structures also occur. This precise correspondence implies that the behaviors of heat-transfer efficiency are intimately related to the changes in the coherent structures in the bulk flow. The sharp transition at Ekt provides the first unambiguous experimental evidence for the regime transition from convective Taylor column regime to plume regime, at which the columns break down due to the increased inertial effect. Compared to the heat-transport behaviors, the transitions of the flow-field statistics are much sharper, which suggests that in further investigations of regime transitions, flow-field measurements may be used to provide a more definitive criterion.