Vorticity distribution of vortex street in the wake of a circular cylinder.

The vorticity distributions in the vortex street behind a circular cylinder were measured by using the hot-wire technique in a low-speed wind tunnel. At intermediate distances from the cylinder, the vorticity distribution of a vortex in the vortex street was similar to that of an isolated viscous vortex which had a Gaussian distribution. The equivorticity lines in a cross section of a vortex were nearly concentric circles. Farther downstream, the vorticities wcich were concentrated around a vortex center diffused into the surroundings. Hovever, the vorticity distribution around the vortex center was still similar to that of the isolated viscous vortex. The circulation of a vortex in the vortex street was decreased as the distance from the cylinder increased. Farther downstream, when two consecutive vortices in the primary vortex street merged, the resultant circulation corresponded approximately to twice the basic vortex.