Flow external to a rotating torus (or a sphere)

Dr. Sophie Calabretto (Department of Mathematics,Macquarie University)
Title: Flow external to a rotating torus (or a sphere)
Abstract: The unsteady flow generated due to the impulsive motion of a torus or sphere is a paradigm for the study of many temporally developing boundary layers. The boundary layer is known to exhibit a finite-time singularity at the equator. We present results of a study that focuses upon the behaviour of the flow after the onset of this singularity. Our computational results demonstrate that the singularity in the boundary layer manifests as the ejection of a radial jet. This radial jet is preceded by a toroidal starting vortex pair, which detaches and propagates away from the sphere. The radial jet subsequently develops an absolute instability, which propagates upstream towards the sphere surface.

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