Flow Control for Vehicle Populsion/Weapons Integration

An internal aircraft weapons bay, when exposed to freestream flow, experiences an intense aeroacoustic environment and varied suppression concepts have been tested for attenuating flow-induced oscillations. Recent tests with open-loop, high-frequencyexcitation have shown great promise in providing broadband attenuation and elimination of tones. High frequency actuation apparently alters the dynamics of the turbulent energy cascade and accelerates the transfer of energy from low frequency, large scaleeddies to high frequency, small-scale eddies, where it finally gets dissipated as heat. The proposed program is focused on using a Hartmann-Sprenger resonance tube as a high frequency actuator for cavity acoustic attenuation. Large Eddy Simulation (LES)will be complemented by Phase-averaged Schlieren and by Particle Image Velocimetry (PIV) measurements in miniature and sub-scale cavities. These diagnostics will provide insight into turbulence-acoustic interactions. Testing at varied scales will providevalidation of scaling laws for high frequency actuation physics. CFD simulations will provide guidance for the design of the high frequency actuator. These investigations will provide the foundation for designing a prototype High Frequency AcousticSuppression (HFAS) system for eventual flight-testing on a RAAF F-111. The HFAS prototype will be based on a modification of the full-scale Active Separation Control (ASC) flight demonstration model.