Aspect ratio effect on the near wake of a free-ended circular cylinder in a cross-flow

The free-end effect of a finite circular cylinder in a cross flow on the near wake characteristics has been investigated experimentally. Three finite cylinders having aspect ratio(L/D) of 6, 10 and 13 were mounted on a flat plate. Hot-wire anemometer was employed to measure the wake velocity at the Reynolds number of 20,000. Mean pressure distributions on the cylinder surface were measured and flow near the free-end was visualized to see the flow structure qualitatively. The three dimensionality of the FC wake becomes dominant with decreasing the FC aspect ratio, i.e., the free-end effect is remarkable at smaller aspect ratio. The three dimensionality of the FC wake maybe attributed to the strong entrainment of irrotational fluids caused by the downwash flow at very near the free end.