Effects of rough walls on sheared annular centrifugal Rayleigh-Bénard convection

Abstract

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