Measurements in rollup region of the tip vortex from a rectangular wing

The rollup region of the tip vortex from a rectangular wing of NACA 0015 profile was measured using a laser Doppler velocimetry to study the time-averaged flow structure in highly three-dimensional near-wake region. The vortex core was found to be predominantly due to axial vorticity that is concentrated at the center and approaches a zero value at the outer portion of the vortex. The length and velocity scales of the vortex were also demonstrated to originate from the near wake, with the inner part of the vortex easily reaching a universal state.