Boundary layers in rotating weakly turbulent Rayleigh-Benard convection

TL;DR

This paper investigates how rotation affects boundary layers in weakly turbulent Rayleigh-Benard convection at low Rayleigh numbers, revealing a smooth transition in heat transfer enhancement and proposing a model based on the Grossmann-Lohse theory.

Contribution

It introduces a detailed analysis of boundary layer behavior under rotation at low Rayleigh numbers and develops a model to describe heat transfer enhancement in this regime.

Findings

Smooth onset of heat transfer enhancement with increasing rotation rate.

Agreement of boundary layer behavior with laminar BL theory.

Proposed model based on Grossmann-Lohse theory for low Ra regime.

Abstract

The effect of rotation on the boundary layers (BLs) in a Rayleigh-Benard (RB) system at a relatively low Rayleigh number, i.e. $Ra = 4\times10^7$, is studied for different Pr by direct numerical simulations and the results are compared with laminar BL theory. In this regime we find a smooth onset of the heat transfer enhancement as function of increasing rotation rate. We study this regime in detail and introduce a model based on the Grossmann-Lohse theory to describe the heat transfer enhancement as function of the rotation rate for this relatively low Ra number regime and weak background rotation $Ro\gtrsim 1$. The smooth onset of heat transfer enhancement observed here is in contrast to the sharp onset observed at larger $Ra \gtrsim 10^8$ by Stevens {\it{et al.}} [Phys. Rev. Lett. {\bf{103}}, 024503, 2009], although only a small shift in the Ra-Ro-Pr phase space is involved.