Effects of Applied Acoustic Fields on Attached Jet Flows

Abstract

The effects of application of sound of a spectrum of frequencies and amplitudes to bounded attached jets of a range of Reynolds numbers flowing over surfaces of various radii of curvature have been examined using hot-wire anemometry, smoke visualization, and tuft-deflection techniques. Frequencies of sound to which the jet is sensitive, results of changes in sound amplitude at a given frequency, and the growth of the effects of applied sound with arc length from the nozzle exit were investigated to provide some qualitative design criteria for controlling the sensitivity of flueric elements to externally applied sound. Frequencies of sound which are related to the jet nozzle resonance characteristics have the most severe effect on the attached jet. For a given applied frequency, the flow field of the jet can be altered for a much wider range of jet Reynolds number at higher amplitudes of applied sound than at relatively low amplitudes of applied sound. Four Reynolds numbers regimes can be established to describe the behavior of the attached jet with applied sound, Frequency- and amplitude-dependent jumps in angle of detachment of the jet are attainable in the first two regimes, and deflections of the jet proportional to the applied frequency and amplitude are attainable in the third and fourth regimes.