Laboratory Exploration of Heat Transfer Regimes in Rapidly Rotating Turbulent Convection

TL;DR

This study experimentally investigates heat transfer in rapidly rotating turbulent convection at extremely high Rayleigh numbers and low Ekman numbers, revealing a new rotationally-influenced turbulence regime with distinct scaling laws.

Contribution

It provides the first laboratory evidence of a novel turbulence regime in rapidly rotating convection, characterized by specific temperature gradient scaling and a critical Rossby number.

Findings

Identification of a new rotationally-influenced turbulence regime.

Temperature gradients scale as Ra^{-0.2} in this regime.

A critical Rossby number Ro^*=0.06 distinguishes this regime from other convection types.

Abstract

We report heat transfer and temperature profile measurements in laboratory experiments of rapidly rotating convection in water under intense thermal forcing (Rayleigh number $Ra$ as high as $\sim 10^{13}$) and unprecedentedly strong rotational influence (Ekman numbers $E$ as low as $10^{-8}$). Measurements of the mid-height vertical temperature gradient connect quantitatively to predictions from numerical models of asymptotically rapidly rotating convection, separating various flow phenomenologies. Past the limit of validity of the asymptotically-reduced models, we find novel behaviors in a regime we refer to as rotationally-influenced turbulence, where rotation is important but not as dominant as in the known geostrophic turbulence regime. The temperature gradients collapse to a Rayleigh-number scaling as $Ra^{-0.2}$ in this new regime. It is bounded from above by a critical convective Rossby number $Ro^*=0.06$ independent of domain aspect ratio $\Gamma$, clearly distinguishing it from well-studied rotation-affected convection.