Boundary Zonal Flow in Rotating Turbulent Rayleigh-B\'enard Convection

TL;DR

This study investigates boundary zonal flows in rapidly rotating turbulent Rayleigh-Bénard convection, revealing their structure, scaling laws, and impact on heat transport near the side wall in a cylindrical cell.

Contribution

It identifies and characterizes the boundary zonal flow in rotating convection, providing new insights into its structure, dynamics, and scaling behavior compared to classical large-scale circulation.

Findings

Boundary zonal flow replaces classical large-scale circulation.

BZF enhances heat transport near the side wall.

BZF width scales as Ra^{1/4} Ek^{2/3}.

Abstract

For rapidly rotating turbulent Rayleigh--B\'enard convection in a slender cylindrical cell, experiments and direct numerical simulations reveal a boundary zonal flow (BZF) that replaces the classical large-scale circulation. The BZF is located near the vertical side wall and enables enhanced heat transport there. Although the azimuthal velocity of the BZF is cyclonic (in the rotating frame), the temperature is an anticyclonic traveling wave of mode one whose signature is a bimodal temperature distribution near the radial boundary. The BZF width is found to scale like $Ra^{1/4}Ek^{2/3}$ where the Ekman number $Ek$ decreases with increasing rotation rate.