Measurements in the tip vortex roll-up region of an oscillating wing

The tip vortex roll-up phenomena behind an oscillating rectangular wing was examined. Phase-averaged mean axial and tangential velocity profiles in the near field of the trailing vortex behind the oscillating wing were obtained. These velocity profiles demonstrate the hysteretic behavior of the wake. To adequately describe the change of circulation during a cycle of oscillation, the phase lag of the measurement signal was taken into account.