An experimental investigation of turbulent boundary layer flow over surface-mounted circular cavities

Abstract

Turbulent boundary layer flow over cavities of circular planform has been measured experimentally by examining pressures at the cavity surfaces and velocity and turbulence in the cavity wake for cavity depths ( h) of 0.20, 0.47, and 0.70 D (cavity diameter). Tests were conducted at a constant Mach number of 0.08 resulting in Re X = 7.3 × 106 and ReD = 1.3 × 105. Velocity measurements acquired in the cavity wake, using hot-wire anemometry, suggest the existence of an asymmetric trailing vortex for h/D ≍ 0.5. The increased amplitude of broadband low-frequency pressure oscillations observed at h/ D ≍ 0.5 may be a result of the high level of flow asymmetry and cavity drag observed for this depth and not for other depths tested. Also, a faint peak is seen in the power spectrum for this depth at a Strouhal number related in previous work to cavity feedback resonance. Contours of fluctuation pressures at the cavity surfaces are also presented. Details of a flow-switching control mechanism for the asymmetric trailing vortex noted for h/D ≍ 0.5 are also presented herein. Good agreement was noted between the present results and those from previous investigations.