Pressure oscillations in a subsonic cavity at yaw

An experimental investigation was undertaken to examine the effect of yaw a ngle on flow oscillations that occur in an open cavity placed within a subs onic boundary layer. A rectangular cavity with a length-to-depth ratio of u nity 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 x 10(3). pressure time histories were acquired at 15 sepa rate yaw angles using microphone-type pressure transducers. The spectral ch aracter of these signals was analyzed, and the pressure levels and dominant frequencies were determined. This study indicates that large changes in th e pressure level occur as the yaw angle is changed from 0 to 70 deg. A stat e of resonance was observed at an angle of 60 deg. Relative sound pressure level calculations indicate that the energy within the cavity increased mor e than seven times at this orientation. Evidence suggesting a critical angl e of approximately 60 deg, as well as mode switching from a fluid dynamic m ode to a fluid acoustic mode, is also presented.