Effect of fluid injection on turbulence and noise reduction of a supersonic jet
Effect of fluid injection on turbulence and noise reduction of a supersonic jet
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流体喷射对超音速喷气机湍流和降噪的影响
DOI：
10.1098/rsta.2019.0082
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
P. Morris
中科院分区：
文献类型：
--
作者：
Chitrarth Prasad;P. Morris
由于大尺度湍流结构和喷流中激波单元的存在，超音速喷气（如用于高性能军用飞机的超音速喷气）具有下游和上游噪声分量。流体插入技术是一种降噪方法，已被证明可以有效地降低这两种噪声分量。本文分析了与不同的流体插入配置相关的非定常流动变化，目的是帮助理解详细的降噪机制。使用近场数据与远场麦克风信号的直接互相关，发现即使使用单个喷射器作为流体插入物也有助于打破流动的大尺度结构。然而，一个更方位角分布吹需要减少上游宽带冲击相关噪声（BBSAN）。在每个方位角位置处添加上游喷射器进一步增强BBSAN减少。射流流场分解成流体动力学和声学模式表明，流体插入喷嘴降低了最高降噪平面中相干声模式的振幅和对流速度。这篇文章是“航空声学研究前沿：理论，计算和实验”主题的一部分。
Supersonic jets, such as the ones used in high-performance military aircraft, have both downstream and upstream noise components due to the large-scale turbulent structures and the presence of shock cells in the jet plume. The fluid insert technology is a noise reduction method that has been shown to effectively reduce both these noise components. This paper analyses the unsteady flow changes associated with different fluid insert configurations with a goal of helping to understand the detailed noise reduction mechanisms. Using direct cross-correlations of the near-field data with the far-field microphone signals, it is found that even the use of a single injector as a fluid insert helps break up the large-scale structures of the flow. However, a more azimuthally distributed blowing is required to reduce the upstream broadband shock-associated noise (BBSAN). Addition of upstream injectors at each azimuthal location further enhances the BBSAN reduction. Decomposition of the jet flow-field into hydrodynamic and acoustic modes shows that fluid insert nozzles reduce the amplitude and convection speed of the coherent acoustic mode in the plane of highest noise reduction. This article is part of the theme issue ‘Frontiers of aeroacoustics research: theory, computation and experiment’.