Experimental investigations on indeterminate-origin V- and A-notched jets

Abstract

Experimental studies on aspect ratio of 1.5 indeterminate-origin V- and A-notched nozzles using flow visualization and hot-wire anemometry techniques are reported here. Time-sequenced flow visualization images of forced water jets at Reynolds number of 2000 show that the general vortex dynamics of the two nozzle types are largely similar despite the differences in the peak and trough configurations. In addition to vortex lines emanating from both nozzles which result in streamwise vortex pairs forming along both peak and trough locations, consistent bending of the large-stale ring vortices is also observed at some downstream distances away from both nozzle exits, which suggests some limited form of axis-switching behavior. Velocity measurements for unforced air jets issuing from these nozzle types at Reynolds number of 20,500 show that there exist subtle yet discernible quantitative flow differences depending on whether the peak and trough contours are smooth or sharp. Sharp peaks and smooth troughs result in wider jet widths over smooth peaks and sharp troughs, respectively, although the differences become smaller with increasing downstream distance. Jet-width comparisons also reveal crossover locations and hence distortions to the jet cross sections, which further supports the notion of axis-switching behavior observed during flow visualizations. Two axis-switching locations have been found for each of the two nozzle types with the gross general flow behavior similar to those observed earlier for free elliptic jets. Copyright © 2007 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.