Topological Differences in Mean Wakes of Circular and Square Cantilevered Cylinders

The turbulent quasi-periodic wake of a circular and a square cross-section cantilevered finite aspect ratio cylinder protruding a thin laminar boundary layer is investigated experimentally. The mean wake vortical structure and flow topology are found to be more complex for the square than the circular geometry. The differences arise from interactions involving periodically shed Karman-like vortices. For the square cylinder, the circulation of the shed vortices is significantly stronger, giving rise to more complex interactions between shed vortices and the redeveloping boundary layer. The strength of the shed vortices is related to the rate vorticity, generated on the obstacle faces, is transported along the separated shear layers. The obstacle surface topology thus plays an important role by modifying the separation process.