Vortex breakdown-edge interaction: Consequence of edge oscillations

High-image-density particle image velocimetry is employed to determine the instantaneous and averaged features of distortion of vortex breakdown incid ent on a stationary and an oscillating leading edge. It is demonstrated tha t the onset of vortex breakdown can be advanced or retarded substantially, depending on the period of the edge oscillation relative to the inherent fr equency of vortex breakdown. These features are interpreted with the aid of global representations of averaged and rms distributions of velocity, vort icity, and Reynolds stress, as well as a cinema sequence of instantaneous p atterns of velocity and vorticity. Moreover, instantaneous, whole-field ima ges in a cinema sequence allow evaluation of global representations of spec tra and cross spectra, providing further insight into the central mechanism s that dictate the surface loading of the edge.