Structure of Karman vortex shedding from a yawed cylinder in a uniform flow.

In order to investigate the effect of yaw angle of Karman vortex shedding from a circular cylinder in a uniform flow, the flow pattern was observed by the smoke wire method. The pressure distribution, secondary flow in the wake along the cylinder and the velocity fluctuation, u, at a point where Karman vortex shedding was clearly observed in the u-signal, were measured. The yaw angle produced a pressure gradient along the cylinder in the dead water region behind it. Secondary flow due to this pressure gradient made the formation of Karman vortex 3-dimensional. The frequency and the regularity of the vortex shedding reduced with increasing yaw angle. When a pair of parallel thin plates was set in the wake to interrupt the secondary flow, the above effects of yaw angle were effectively reduced in the area between them.