Effects of rotation on Rayleigh-Bénard convection

Turbulent rotating convection in a cylinder is investigated both numerically and experimentally. The focus of this work is on two topics: the convective heat transfer through the fluid layer, expressed as the Nusselt number, and the domain-filling structure typical for confined convection, the so-called large-scale circulation (LSC). The presence of the LSC is addressed for several rotation rates. For sufficiently strong rotation, characterized by Rossby numbers Ro . 0.72 no LSC is found. For larger Rossby numbers, i.e., slower rotation, a precession of the LSC in anticyclonic direction (counter to the background rotation) is appreciated. It is shown that the heat transfer has a maximal value at Ro = 0.18 of about 20% larger than in the non-rotating case Ro = 8. Since the LSC is no longer present at this Rossby value we conclude that it can play no role in the observed enhancement of the heat transfer. This indicates that important extensions of existing scaling theory are needed to account for heat-transfer in rotating Rayleigh-B´enard convection