Differential Rotation Driven by Convection in a Rapidly Rotating Annulus

The generation of a mean zonal flow by centrifugally driven thermal convection in a rotating annulus heated from the outside and cooled from within is investigated theoretically as well as experimentally. It is shown that the direction of the mean flow depends on the curvature of the conical surfaces bounding the fluid in the axial direction. Convex conical boundaries give rise to a prograde mean flow in the outer part and a retrograde mean flow in the inner part of the fluid annulus. The directions are reversed for concave conical boundaries. Although the parameter regime for which the theoretical results have been derived could not be realized in the experiment, semi-quantitative agreement between theoretical predictions and observations has been found.