EFFECT OF L/D AND YAW ANGLE ON FLOW OSCILLATIONS IN SUBSONIC RECTANGULAR CAVITIES

by BAI, XINWEN

An experimental investigation was undertaken to examine the effect of cavity depth and yaw angle on flow oscillations that occur in an open cavity placed within a subsonic boundary layer. A rectangular cavity was placed within a thick turbulent boundary layer with a corresponding Reynolds number based on the cavity length of 61,935. Pressure time histories were acquired at five separate cavity depths (or L/D values) at each yaw angle from 5 degree to 90 degree using microphone-type pressure transducers. The spectral character of these signals was analyzed, and pressure level and dominant frequencies were determined. This study indicates that large changes in the pressure level occur as L/D varies from 0.5 to 2.1 and as the yaw angle varies from 5 to 90 deg. Relative sound pressure level calculations indicate that the energy within the cavity compared with that of the boundary layer was observed to increase by approximately 22 percent at L/D=2.1 and 2.2 times at yaw angle=60 deg.