EFFECT OF AN AEROELASTIC FILM ON CONFINED SUBSONIC CAVITY RESONANCE by Melissa Carter B.S., Mechanical Engineering, University of New Mexico, 2001 M.S., Mechanical Engineering, University of New Mexico, 2011 ABSTRACT Two shallow three-dimensional cavities were used to study the effect on cavity resonance of an aeroelastic film placed on the wall opposite the cavity in confined (duct) flow. Flow speeds were very low subsonic with Mach number varying from 0.05 to 0.10. The cavities have length-to-depth ratios of 2.5 and 1.5, with identical depths. It was expected that the aeroelastic film in flutter would interact with acoustic signals from the cavity to enhance or inhibit cavity pressure oscillations. Two different film tensions were applied to the film to affect flutter conditions. However, the film support mechanism design did not allow flutter, and each film experienced static displacement caused by outside air pressure. Cavity sound data recorded by a microphone was compared for tests with and without the film. The effects of film tension were insignificant, primarily because the film was not in flutter. The longer cavity exhibited higher sound pressure levels over the entire range of frequencies with an aeroelastic film present. The shorter cavity showed smaller differences, perhaps because the film is longer than the cavity. The presence of an aeroelastic film did affect the shear-layer frequencies in the cavities. For Cavity 2, higher amplitude peaks in the range of estimated resonance frequencies were observed with the film present. The results for the longer cavity indicate that a film on the opposite wall will interact with cavity pressure oscillations to affect sound pressure levels in resonance
