On the thermal offset in turbulent rotating convection

Abstract

A simple mechanistic model to explain the thermal offset observed in highly turbulent rotating convectionexperiments is presented. The experiments indicate that for sufficiently high Taylor number the system develops an asymmetry that is counter to the expected behavior of a Boussinesq fluid: The temperature at the midplane of the experiment is higher than the average of the top and bottom isothermal boundaries. The magnitude of this bias increases with the basic rotation and with the density difference between the top and bottom boundaries. Our model considers this to be a result of a mean circulation induced by centrifugal buoyancy. An analytical calculation of this motion field, postulated to be a laminar perturbation to the turbulence-induced mean stratification, generates a reasonably accurate description of the observed thermal offset.