Effects of radius ratio on annular centrifugal Rayleigh-B\'{e}nard convection

TL;DR

This study uses 3D simulations to explore how the radius ratio affects flow structures and heat transfer in annular centrifugal Rayleigh-Bénard convection, revealing asymmetric plume movement, zonal flow formation, and efficiency variations.

Contribution

It provides new insights into the impact of radius ratio on flow asymmetry, zonal flow development, and heat transport in ACRBC through detailed numerical simulations.

Findings

Zonal flow weakens as radius ratio increases.

Heat transport efficiency increases with radius ratio.

Bulk temperature deviation from mean increases as radius ratio decreases.

Abstract

We report on a three-dimensional direct numerical simulation study of flow structure and heat transport in the annular centrifugal Rayleigh-B\'{e}nard convection (ACRBC) system, with cold inner and hot outer cylinders corotating axially, for the Rayleigh number range Ra $ \in [{10^6},{10^8}]$ and radius ratio range $\eta = {R_i}/{R_o} \in [0.3,0.9]$. This study focuses on the dependence of flow properties on the radius ratio $\eta$. The temperature and velocity fields reveal that different curvatures of the inner and outer cylinders of the ACRBC system lead to asymmetric movements of hot and cold plumes under the action of Coriolis force, resulting in the formation of zonal flow. The physical mechanism of zonal flow is verified by the dependence of the drift frequency of the large-scale circulation rolls and the space- and time-averaged azimuthal velocity on $\eta$. We find that the larger $\eta$ is, the weaker the zonal flow becomes. We show that the heat transport efficiency increases with $\eta$. It is also found that the bulk temperature deviates from the arithmetic mean temperature and the deviation increases as $\eta$ decreases. This effect can be explained by a simple model that accounts for the curvature effects and the radially-dependent centrifugal force in ACRBC.