Study on Active Suppression of Jet Noise

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Jet noise reduction is required for the realization of environmentally-friendly and highly-efficient supersonic jet propulsion system. In the present study, experimental and numerical investigations were performed in order to clarify the effects of microjet injection on supersonic jet noise and the mechanism of the noise reduction. Far field acoustic measurements were executed and the reduction of the overall sound pressure level up to 10dB was found. Flow field visualization and CFD analysis clarified that shock cell structure was changed and large fluctuation of jet shear layers was suppressed by microjet injection. A new approach with Piezo-electric actuator was tried to reduce the jet noise as well.