TURBULENT BOUNDARY LAYER FLOW OVER CIRCULAR CAVITIES

摘要

Increasingly stringent emission standards for commercial aircraft engines will require a greater focus on airframe drag and noise reduction techniques. One source of drag that may be reduced is that due to the presence of cavities on aircraft surfaces such as rivet depressions and landing gear wheel wells. In order to gain a greater understanding of the causes of the drag related to such cavities, turbulent flow over circular cavities has been experimentally investigated in a subsonic wind tunnel. Velocity measurements acquired in the cavity wake, using hot-wire anemometry, together with pressure measurements on the cavity surfaces show a link between the flow in the cavity and that in its wake.. Oscillations in the pressure and velocity time series for a cavity depth to diameter ratio (h/D) ≈ 0.5 demonstrated a consistent peak at a frequency expected for the cavity feedback resonance mechanism. Since this peak was not observed at other depth configurations, cavity feedback resonance may be a cause for the high level of flow asymmetry and cavity drag observed for h/D ≈ 0.5. Good agreement was noted between the present experimental results and those from previous investigations.