Vortical flow over the free end surface of a finite circular cylinder mounted on a flat plate

A flow visualization study using the oil streak-line method and the smoke-laser light sheet arrangement was carried out to investigate the three-dimensional separated flow pattern over the free end surface region of a finite circular cylinder (aspect ratios of 1.25 and 4.25) mounted on a flat plate. The experiment was performed for the cases of two Reynolds numbers: 5.92x10(3) and 1.48x10(5). An owl-faced configuration of various kinds of singular points on the free end surface was disclosed from the oil surface flow visualization. In order to aid understanding of the oil streak-line pattern, the smoke-laser light sheet visualization clearly demonstrated that a pair of tornado-like vortices evolving from the eyes of the owl face marched along the downstream distance over the free end surface together with a pair of side tip vortices. A topological sketch to characterize the surface flow and the vortical structure emanating from the top surface is included.