Weakly rotating turbulent Rayleigh-Bénard convection was studied experimentally and numerically. With increasing rotation and large enough Rayleigh number a supercritical bifurcation from a turbulent state with nearly rotation-independent heat transport to another with enhanced heat transfer is observed at a critical inverse Rossby number 1/Ro_c≃0.4. The strength of the large-scale convection roll is either enhanced or essentially unmodified depending on parameters for 1/Ro < 1/Ro_c, but the strength increasingly diminishes beyond 1/Ro_c where it competes with Ekman vortices that cause vertical fluid transport and thus heat-transfer enhancement.
Stevens, R. J. A. M., Zhong, J-Q., Clercx, H. J. H., Ahlers, G., & Lohse, D. (2009). Transitions between turbulent states in rotating Rayleigh-Bénard convection. Physical review letters, 103(2), 024503. [10.1103/PhysRevLett.103.024503]. https://doi.org/10.1103/PhysRevLett.103.024503