Study on Active Suppression of Jet Noise

实现环境友好型、高效的超音速喷气推进系统需要降低射流噪声。为了阐明微射流对超音速射流噪声的影响及其降噪机理，本文进行了实验和数值研究。进行了远场声学测量，发现整体声压级降低了10dB。流场可视化和CFD分析表明，微射流注入改变了激波池结构，抑制了射流剪切层的大波动。并尝试了一种利用压电致动器降低射流噪声的新方法。

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.