Direct Numerical Simulations of Supergravitational Thermal Convection: From Gravitational to Centrifugal Buoyancy Dominance*

We report our DNS results on supergravitational thermal convection in an annular container heated at the outer sidewall and cooled at the inner wall, all subjected to a constant rotation around a vertical axis (as in the ACRBC facility in Chao Sun's Lab at Tsinghua University). For a fixed Rayleigh number Ra (thermal driving) and increasing Froude number Fr from 0 (no-rotation) to 100 (strong centrifugal buoyancy), we observe an evolution of the global flow structure and heat transport scaling properties from those typical for vertical convection, where the imposed temperature gradient is orthogonal to the driving force (gravitational buoyancy), to those typical for Rayleigh-Benard convection, where the temperature gradient is parallel to the force (centrifugal buoyancy). With the centrifugal buoyancy dominating, the flow undergoes a transition from a 3D global flow structure to a quasi-2D one with a suppressed mixing in the vertical direction, where larger Ra-values require larger Fr-values for the transition.