Oil flow patterns of separated flow on a hemispherical cylinder at incidence

The structure of the flow in the separated region on a hemispherical cylinder at incidence was studied with flow visualization. Skin-friction patterns developing in dependence upon flow parameters were examined. Using the manifold of skin-friction patterns, simple basic structures are identified, from which the most complicated ones found in the tests can be derived. In the unstable laminar flow range, closed separated regions with the features of two-dimensional separation bubbles are observed. In stable laminar flow the spatial vortex structure of the separated region was also visualized. It shows that the vorticity, convected from the surface, concentrates along different axes, which leads to steady and unsteady vortex motions depending on the direction of the vortex axes with respect to the mean flow.