Pressure Oscillations in a Subsonic Cavity at Yaw

Abstract

An experimental investigation was undertaken to examine the effect of yaw angle on flow oscillations that occur in an open cavity placed within a subsonic boundary layer. A rectangular cavity with a length-to-depth ratio of unity and a planform aspect ratio of 8.7 was placed within a thick turbulent boundary layer with a corresponding Reynolds number based on the momentum thickness of 10.5 × 10 3 . Pressure time histories were acquired at 15 separate yaw angles using microphone-type pressure transducers. The spectral character of these signals was analyzed, and the pressure levels and dominant frequencies were determined. This study indicates that large changes in the pressure level occur as the yaw angle is changed from 0 to 70 deg. A state of resonance was observed at an angle of 60 deg. Relative sound pressure level calculations indicate that the energy within the cavity increased more than seven times at this orientation. Evidence suggesting a critical angle of approximately 60 deg, as well as mode switching from a fluid dynamic mode to a fluid acoustic mode, is also presented.