Turbulent rotating convection at high Rayleigh and Taylor numbers

Abstract

We report heat transport measurements in a cylindrical convection apparatus rotating about the vertical axis. The aspect ratio was 1/2. The working fluid was cryogenic helium gas and the following parameter ranges applied: the Rayleigh number, Ra , varied in the range 10 11 < Ra < 4.3 × 10 15 , the Taylor number, Ta , varied in the range 10 11 < Ta < 3 × 10 15 , the convective Rossby number, Ro , varied in the range 0.4 < Ro < 1.6 and the Prandtl number, Pr , varied in the range 0.7 < Pr < 5.9. Boussinesq conditions applied quite closely. The heat transport for steady rotation, under all conditions of the present experiments, was smaller than that for the non-rotating case. When the rotation rate varied periodically in time, a sharp transition to a state of significantly enhanced heat transport was observed for modulation Taylor numbers Ta * ≳ 10 14 , where Ta * is based on the peak value of the modulation angular velocity.