Shigeo Kida
Kyoto University, Japan

Super-Rotation Flow in a Precessing Spherical Cavity

The flow inside a precessing spherical cavity exhibits a variety of states, either steady, periodic, or chaotic, depending on the spin and precession angular velocities.
Here we present our recent numerical study on the stability characteristics and structure of the flow in a precessing spherical cavity whose spin and precession axes are orthogonal to each other. After discussing the stability boundary of the steady states and the toral structure of streamlines, we concentrate our attention on the super-rotation flow. When both the Reynolds number and the Poincare number are large, two different flow regions appear in the cavity, i.e. the thin boundary layer and the inner region. The majority of the cavity volume is occupied by the latter, and the flow there is almost uniform along the precession axis (the Taylor-Proudman theorem holds) and swirls around it nearly as a solid-body rotation. Interestingly enough, this swirl flow is faster than the precession rotation. We consider the generation mechanism of this super-rotation flow.