About the ambiguity of noise source localization based on the causality correlation technique

About the ambiguity of noise source localization based on the causality correlation technique
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关于基于因果相关技术的噪声源定位模糊性

DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
A. Schröder
A. Schröder
中科院分区：
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文献类型：
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作者：
A. Henning;Björn Wrede;A. Schröder

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同步PIV和声学测量的典型因果关系相关结果样本 提出了一种杆-翼型构型和一种冷喷流。解释由此产生的相关性的困难 示出了湍流流量与远场压力波动之间的系数。方法 的时空分辨系数矩阵的解释是证明，特别注意， 流动拓扑中相干结构的影响。相干结构的两种简化模型 在亚音速射流进行了分析，以有助于理解和有意义的解释， 因果关系的结果。第一个模型是模拟相关单极子在 一架喷气式飞机。第二种是基于沿射流轴沿着的抖动波包。这些模型的辐射声 源被计算并与源信号相关。结果系数矩阵的依赖性 对源分布的时空扩展进行了研究。截断效应及其影响 的波包的时间局部化的变化进行了研究。可以看出，高 在远场压力的振幅突发主导的相关系数的时空演变。 通过对人字形喷管和圆形喷管产生的亚音速喷流的测量结果的比较，可以看出，所得到的系数矩阵确实提供了时空信息 关于受与航空声学相同的物理现象影响的流动区域的解析信息 源头
Samples of typical causality correlation results for synchronized PIV and acoustic measurements on a rod-airfoil configuration and a cold jet are presented. The difficulties in interpreting the resulting correlation coefficients between turbulent ow quantities and the far-field pressure fluctuations are illustrated. An approach for the interpretation of the space time resolved coefficient matrix is demonstrated, with special attention to the influence of coherent structures in the flow topology. Two simplified models of the coherent structures in subsonic jets are analysed in order to contribute to the understanding and a meaningful interpretation of causality correlation results. The first model is simulating a distribution of correlated monopoles on the axis of a jet. The second is based on a jittering wave-packet along the jet-axis. The radiated sound from these modelled sources is calculated and correlated with the source signal. The dependency of the resulting coefficient matrix on the temporal and spatial extend of the source distribution is studied. Truncation effects and the influences of the temporally localized changes in the wave-packet are investigated. It can be shown that resulting high amplitude bursts in the far-field pressure are dominating the space-time evolution of the correlation coefficient. Supported by a comparison of recently obtained measurement results for a subsonic jet generated by a chevron nozzle and a round nozzle, it can be shown that the obtained coefficient matrix indeed provides space time resolved information about flow regions which are subject to the same physical phenomenon as the aeroacoustic source.