Heat transport scaling and transition in geostrophic rotating convection with varying aspect ratio

TL;DR

This study investigates how heat transport in geostrophic rotating convection varies with aspect ratio and rotation rate, revealing a transition from buoyancy to geostrophic dominance and providing new insights into heat-transport scaling laws.

Contribution

It offers high-precision experimental and numerical analysis of heat transport scaling in geostrophic convection across different aspect ratios and Ekman numbers, clarifying transition behaviors.

Findings

Transition from buoyancy to geostrophic convection depends on Ekman number

Heat transport enhancement occurs in the geostrophic regime

Scaling exponent decreases with smaller aspect ratios

Abstract

We present high-precision experimental and numerical studies of the Nusselt number $Nu$ as functions of the Rayleigh number $Ra$ in geostrophic rotating convection with domain aspect ratio ${\Gamma}$ varying from 0.4 to 3.8 and the Ekman number Ek from $2.0{\times}10^{-7}$ to $2.7{\times}10^{-5}$. The heat-transport data $Nu(Ra)$ reveal a gradual transition from buoyancy-dominated to geostrophic convection at large $Ek$, whereas the transition becomes sharp with decreasing $Ek$. We determine the power-law scaling of $Nu{\sim}Ra^{\gamma}$, and show that the boundary flows give rise to pronounced enhancement of $Nu$ in a broad range of the geostrophic regime, leading to reduction of the scaling exponent ${\gamma}$ in small ${\Gamma}$ cells. The present work provides new insight into the heat-transport scaling in geostrophic convection and may explain the discrepancies observed in previous studies.