Transitions between turbulent states in rotating Rayleigh-Benard convection

TL;DR

This study investigates how increasing rotation affects heat transfer in turbulent Rayleigh-Benard convection, revealing an abrupt transition to a state with enhanced heat transfer due to vortex interactions.

Contribution

It provides experimental and numerical evidence of a critical rotation rate where heat transfer behavior abruptly changes in rotating turbulent convection.

Findings

Critical inverse Rossby number $1/Ro_c \,\simeq 0.4$ marks transition point.

Heat transfer is enhanced beyond $1/Ro_c$ due to Ekman vortices.

Large-scale convection rolls are suppressed at high rotation rates.

Abstract

Weakly-rotating turbulent Rayleigh-Benard convection was studied experimentally and numerically. With increasing rotation and large enough Rayleigh number an abrupt transition from a turbulent state with nearly rotation-independent heat transport to another turbulent state with enhanced heat transfer is observed at a critical inverse Rossby number $1/Ro_c \simeq 0.4$. Whereas for $1/Ro < 1/Ro_c$ the strength of the large-scale convection-roll is either enhanced or essentially unmodified depending on parameters, its strength is increasingly diminished beyond $1/Ro_c$ where it competes with Ekman vortices that cause vertical fluid transport and thus heat-transfer enhancement.