A new instability for finite Prandtl number rotating convection with free-slip boundary conditions

TL;DR

This paper reveals a new type of instability in finite Prandtl number rotating convection with free-slip boundaries, driven by horizontal mean flow and affecting roll stability at all rotation rates.

Contribution

It introduces a novel instability mechanism in rotating convection, analyzed through a specialized singular perturbation approach, expanding understanding of flow stability under free-slip conditions.

Findings

Rolls are unstable to small angle perturbations at all rotation rates.

The instability is driven by horizontal mean flow.

A singular perturbation analysis is used to estimate the mean flow.

Abstract

Rolls in finite Prandtl number rotating convection with free-slip top and bottom boundary conditions are shown to be unstable with respect to small angle perturbations for any value of the rotation rate. This instability is driven by the horizontal mean flow whose estimation requires a special singular perturbation analysis.