Effects of rough walls on sheared annular centrifugal Rayleigh-B\'enard convection

TL;DR

This study uses numerical simulations to explore how wall roughness and shear influence heat transfer in an annular centrifugal Rayleigh-Bénard convection system, revealing regime-dependent effects of shear on heat transfer.

Contribution

It introduces a detailed analysis of the coupling effects of wall roughness and shear in ACRBC, highlighting how shear influences heat transfer across different regimes.

Findings

Increased shear enhances heat transfer in buoyancy-dominant regime.

Heat transfer sharply decreases at transitional shear levels.

Beyond a critical shear, heat transfer stabilizes despite further increases.

Abstract

In this study, we investigate the coupling effects of roughness and wall shear in an annular centrifugal Rayleigh-B\'enard convection (ACRBC) system, where two cylinders rotate with different angular velocities. Two-dimensional direct numerical simulations are conducted within a Rayleigh number range of $10^{6} \leq Ra \leq 10^{8}$, and the non-dimensional angular velocity difference ($\varOmega$), representing wall shear, varied from 0 to 1. The Prandtl number is fixed at $Pr = 4.3$, the inverse Rossby number at $Ro^{-1} = 20$, and the radius ratio at $\eta = 0.5$. The interaction between wall shear and roughness leads to distinct heat transfer behavior in different regimes. In the buoyancy-dominant regime, an increase in the non-dimensional angular velocity difference ($\varOmega$) significantly enhances heat transfer. However, as $\varOmega$ continues to rise, a sharp reduction in heat transfer is observed in the transitional regime. Beyond a critical value of $\varOmega$, the flow enters a shear-dominant regime, where heat transfer remains unchanged despite further increases in $\varOmega$.