Active control of shallow cavity acoustic resonance

Shallow cavity (weapons bay) resonance can be characterized by a standing waveshear layer feedback loop, with sound pressure levels of up to 160 dB occurring in the cavity. Resonance of this magnitude can cause destruction of internal bay instrumentation and degrade weapon performance. Previous cavity resonance control techniques have focused on static methods for specific flight conditions. The current study investigates active cavity resonance suppression techniques, based on manipulation of the cavity shear layer and disruption of the resonance feedback loop. An active leading edge oscillating flap and High Frequency Tone Generator (HFTG) are tested for a range of subsonic to supersonic Mach numbers for various shallow cavity configurations. Parametric changes for the active flap, such as oscillation amplitude and frequency, are studied. Maximum control across a range of Mach numbers occurs for various oscillating flap configurations and oscillation frequencies, indicating the necessity for active control. Reductions in sound pressure levels of up to 30 dB were obtained using the High Frequency Tone Generator (non-optimized).