Visualization of Vortex-Fin Interaction

Quantitative Interpretation of Flow Structure

Abstract

The interaction of a streamwise vortex with a fin is investigated experimentally using high-image-density particle image velocimetry, which allows determination of the instantaneous distributions of vorticity over entire planes of the flow. The vortex distortion past the fin is described in terms of averaged patterns of velocity field and instantaneous vorticity contours at two different locations of the fin. The instantaneous structure of the broken-down vortex upstream of the leading-edge of the fin exhibits the classical staggered pattern of alternating positive and negative concentrations of vorticity. Along the leading-edge of the fin, however, including the edge of the tip, positive concentrations of vorticity dominate. Averaging of these instantaneous vorticity concentrations shows that a time-averaged, positive vorticity layer exists along the leading-edge and tip of the fin. Over the surface of the fin, the averaged levels of vorticity are significantly lower than those on the edge.