Harker Blaine M, Gee Kent L, Neilsen Tracianne B, Wall Alan T, James Michael M
Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, USA.
Battlespace Acoustics Branch, Air Force Research Laboratory, Wright-Patterson AFB, Ohio 45433, USA.
J Acoust Soc Am. 2019 Jul;146(1):665. doi: 10.1121/1.5118239.
Application of phased-array algorithms to acoustic measurements in the vicinity of a high-performance military aircraft yields equivalent source reconstructions over a range of engine conditions. Beamforming techniques for aeroacoustics applications have undergone significant advances over the past decade to account for difficulties that arise when traditional methods are applied to distributed sources such as those found in jet noise. The hybrid method, an inverse method approached via beamforming, is applied to jet noise measured along a 50 element, 30 m linear array to obtain equivalent source distributions. The source distribution extent decreases with increasing frequency or with a decrease in engine condition. A source coherence analysis along the axial dimension of the jet plume reveals that the source coherence lengths scale inversely with increasing engine condition. In addition, a method for extending the array bandwidth to frequencies beyond the spatial Nyquist frequency limit is also implemented. A directivity analysis of the beamforming results reveals that sources near the nozzle radiate to the sideline from a relatively stationary point irrespective of frequency, while the noise source origin of downstream radiating noise varies significantly with frequency.
将相控阵算法应用于高性能军用飞机附近的声学测量，可在一系列发动机工况下实现等效声源重构。在过去十年中，用于航空声学应用的波束形成技术取得了重大进展，以解决将传统方法应用于分布式声源（如喷气噪声中的声源）时出现的困难。混合方法是一种通过波束形成实现的反演方法，应用于沿50个单元、30米线性阵列测量的喷气噪声，以获得等效声源分布。声源分布范围随频率增加或发动机工况降低而减小。沿喷气羽流轴向维度的声源相干分析表明，声源相干长度与发动机工况增加成反比。此外，还实现了一种将阵列带宽扩展到超出空间奈奎斯特频率极限的频率的方法。波束形成结果的指向性分析表明，喷嘴附近的声源无论频率如何，都从相对固定的点向边线辐射，而下游辐射噪声的声源起源随频率变化显著。
