Experimental Cavity Pressure Measurements at Subsonic and Transonic Speeds Static-Pressure Results

Abstract

An experimental investigation was conducted to determine cavity flow characteristics at subsonic and transonic speeds. A rectangular box cavity was tested in the Langley 8-Foot Transonic Pressure Tunnel at Mach numbers from 0.20 to 0.95 at a unit Reynolds number of approximately 3 times 10 super 6 per foot. The boundary layer approaching the cavity was turbulent. Cavities were tested over a range of length-to-depth ratios l/h of 1 to 17.5 for cavity width-to-depth ratios of 1, 4, 8, and 16. Fluctuating- and static-pressure data in the cavity were obtained; however, only static-pressure data is analyzed in the report. The boundaries between the flow regimes based on cavity length-to-depth ratio were determined. The change to transitional flow from open flow occurs at l/h approx 6--8 however, the change from transitional- to closed-cavity flow occurred over a wide range of l/h and was dependent on Mach number and cavity configuration. The change from closed to open flow was found to occur gradually. The effect of changing cavity dimensions showed that if the value of l/h was kept fixed but the cavity width was decreased or cavity height was increased, the cavity pressure distribution tended more toward a more closed flow distribution. The supplement is also available from: ftp://techreports.larc.nasa.gov/pub/techreports/larc/93/tp3358supplement.ps .Z