Turbulence in rotating Rayleigh-Bénard convection in low-Prandtl-number fluids

Abstract

The heat flux in rotating Rayleigh-Bénard convection in a fluid of Prandtl number Pr=0.1 enclosed between free-slip top and bottom boundaries is investigated using direct numerical simulation in a wide range of Rayleigh numbers (10(4)≤Ra≤10(8)) and Taylor numbers (0≤Ta≤10(8)). The Nusselt number Nu scales with the Rayleigh number Ra as Ra(β) with β=2/7 for values of Nu greater than a critical value Nu(c), which occurs for Ta/Ra∼1. The exponent β is not universal for Nu<Nu(c) (for Ta/Ra>1) but a function of Ta showing a minimum for some intermediate value of Ta. The critical Nusselt number Nu(c) and the corresponding critical Rossby number Ro(c) scale with Ta as Ta(0.277±0.001) and Ta(-0.015±0.003), respectively.