Experimental results on edge-tone oscillations in high-speed subsonic jets

Abstract

A well-controlle d investigation of the feedback phenomenon that occurs when a probe is inserted into a jet potential core was carried out for a subsonic jet. The recently incorporated capability of conditional sampling into the Lockheed laser velocimeter was used for this type of investigation . The major aspects investigated were the path of the feedback loop and the effect of the edge tone on the jet fluid dynamics. The analysis of the experimental results indicates that for our particular experimental arrangement the feedback loop is completed within the jet itself and not by sound traveling outside the main jet. Furthermore, it was found that the potentialcore region between the nozzle exit and the probe acts similar to a wave guide, and hydrodynamic standing waves are set up in this region.