Viscous flows and instabilities near rotating bodies

This study is a survey of experiments on the flow near rotating bodies. The bodies discussed are bodies of revolution, such as spheres, disks, cylinders and cones. The flow and the instabilities around, between and within these rotating bodies and combinations of them are investigated. Special emphasis is placed on the first onset and the further development of instabilities. Depending on the geometry and the boundary condition spiral vortices, Görtler-type vortices and counter-rotating Taylor vortices are obtained in the unstable flow regime. Their behaviour and appearance for different initial and boundary conditions are analysed in detail and the development to transition to turbulence is described. The non-uniqueness of the flow in the supercritical Reynolds number regime results in different vortex configurations depending on the flow's history. The instabilities may occur in steady and unsteady form or in a combination of both types. The experimental results are compared with available theoretical results. These are mostly obtained numerically because of difficulties with closed form solutions of the governing equations. Some of the vortices in the unstable flow regime for different geometries show similar flow patterns. It is, therefore, a main purpose of this contribution to draw attention to their common properties as well as their differences.