Noise and Flowfield Characteristics of a Supersonic Jet Impinging on a Porous Surface

Abstract

Control of the highly resonant flowfield associated with supersonic impinging jet has been experimentally investigated. Measurements were made in the supersonic impinging jet facility at AAPL for a Mach 1.5 ideally expanded jet. Measurements included unsteady pressures on the lift plate, acoustic measurements in the nearfield and beneath the impingement plane and velocity measurements using PIV. Results show that both passive control using porous surface and active control with high momentum microjet injection are effective in reducing nearfield noise and flow unsteadiness over a range of geometrical parameters, however, the type of noise reduction achieved by the two control techniques is different. The passive control reduces broadband noise whereas microjet injection attenuates high amplitude impinging tones. The hybrid control, a combination of two control methods reduces both broadband and high amplitude impinging tones and surprisingly its effectiveness is more that the additive affect of the two control techniques.