Visualization of impingement of broken-down vortex on tail

The impingement of a streamwise vortex on a fin is investigated experimentally with high-image-density particle image velocimetry (PIV) and dynamic pressure transducers in order to relate the structure of vortex breakdown to the spectra of surface pressure along the fin. The instantaneous and ensemble-averaged distributions of vorticity from PIV show strong concentrations of vorticity along the edges of the breakdown region. Correspondingly, the amplitude response of the pressure spectra is the strongest when the fin is located near the edge of vortex breakdown. The dominant frequency of the surface pressure is insensitive to cross-stream displacements of the vortex axis relative to the leading edge of the fin. Spectra of surface pressure at crucial locations on the fin are related to these features of the instantaneous and averaged flow structure.