VORTICES IN SPHERE WAKES

Abstract

The formation and structure of vortices characteristic of sphere wakes corresponding to a range of Reynolds numbers extending from 200 to 500 have been examined. The manner in which vorticity is released to the free stream has been deduced from the photographic evidence. It has been found that, over the entire range of Reynolds numbers considered, at least part of the vorticity generated in the boundary layer is transferred to the stream by means of an involved sheet. This sheet is distorted continuously by the backflowing fluid and reappears as the demarcating surface of the vortex elements of the wake. The spiraling path was found to be associated with the asymmetry relative to the upstream–downstream axis of the sphere.