On the influence of centrifugal buoyancy on rotating convection

Abstract

Centrifugal buoyancy forces in a container rotating about an axis aligned with gravity lead to mean flows that interact with rotating convection. A model of the interactions between these flows and the thermal instabilities that occur in weakly nonlinear rapidly rotating convection is used to estimate when, in terms of external parameters, centrifugal buoyancy has a substantial influence on thermal convective instability. The significant physical effects include the direct action of centrifugal buoyancy on the eddies themselves, the upwards advection of basic-state vertical shear by the perturbation rolls, and the alteration of the mean thermal stratification upon which eddies grow by the basic centrifugally induced circulation. It is shown that the first effect is the most important for common laboratory settings, and can lead to destabilization of the system at outer radii. Other manifestations of centrifugal buoyancy include the generation of a positive offset of the mean temperature at the centre of the cell, and a reduction of this offset by heat fluxes arising from the centrifugally modified finite-amplitude convective eddies.