Abstract
The determination procedure of the vortex core region in the vortex ring attached to the shear layer in a pulatile jet flow was studied experimentally with PIV under the condition of a distance to the wall L^* =1.15 and 2.26 to measure the circulation of vortex ring. It was obtained that the distribution of the vorticity ζ^* and the circumferential velocity V_0 around the vortex center were compared with the Oseen vortex solution, and both were in good agreement with the Oseen vortex independent of the L^*. The threshold level of the vorticity defined at the maximum point of the V_0 to decide the vortex core region in the vortex ring. The vortex core region, similar to the forced vortex flow in the Rankine-Vortex, is defined as the region where the vorticity is higher than the threshold level. The circulation of the vortex ring is then estimated by the integrated the vorticity in the vortex core region.
