Abstract This paper deals with the development of a three-dimensional (3D) array for imaging aeraocoustic sources in the open section of an anechoic wind-tunnel, together with the associated signal processing techniques, and presents an application to the case of a wall-mounted airfoil in a flow. The 3D antenna is made of 256 digital Micro ElectroMechanical Systems (MEMS) microphones, arranged into three nearly perpendicular planar arrays enclosing the test section, the lower part of the flow being bounded by a rigid planar surface. The source under consideration is a wall-mounted NACA 0012 airfoil located in the wind-tunnel flow at a chord-based Reynolds number of 5.33 × 105 for angles of attack at 0°, 4°, 10° and 20°, generating several broadband sources of noise. A configuration with two wall-mounted airfoils in a flow using a similar large array system is also studied. The data processing is based on the beamforming technique associated to a deconvolution method (CLEAN-SC) developed in 3D and to a dipolar radiation model. The flow effects on propagation are taken into account in the beamforming technique by using the Amiet's method in terms of angle correction. The application to the airfoil demonstrates that the performances of the 3D source localization method are excellent for the wall-mounted airfoil, due to the high number of microphones and to the “tunnel” geometry allowing to surround the sources in the flow. The different sources of noise that are to be expected are accurately identified in the third-octave bands under investigation, and are in good agreement with experimental results published in the literature. The presented results prove that a tunnel-type array including several hundreds of microphones associated to an appropriate array processing technique performs very well for studying in 3D complex aeroacoustic sources, and that cheap MEMS microphones are good candidates for measuring the sound radiation efficiently.

中文翻译：

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隧道形MEMS麦克风阵列对流致噪声源的三维识别

摘要 本文讨论了用于在消声风洞的开放部分中成像空气声源的三维 (3D) 阵列的开发，以及相关的信号处理技术，并介绍了在壁面情况下的应用。安装在流动中的翼型。3D 天线由 256 个数字微机电系统 (MEMS) 麦克风组成，排列成三个几乎垂直的平面阵列，包围测试部分，流动的下部由刚性平面限定。所考虑的源是壁挂式 NACA 0012 翼型，位于风洞流中，基于弦的雷诺数为 5.33 × 105，攻角为 0°、4°、10° 和 20°，产生多个宽带噪声源。还研究了使用类似的大型阵列系统在流动中具有两个壁挂式翼型的配置。数据处理基于与 3D 中开发的去卷积方法 (CLEAN-SC) 和偶极辐射模型相关的波束成形技术。在角度校正方面，通过使用 Amiet 方法，在波束形成技术中考虑了流动对传播的影响。对翼型的应用表明，壁挂式翼型的 3D 源定位方法的性能非常出色，这是由于大量麦克风和允许围绕流动中的源的“隧道”几何形状。在所研究的第三个倍频程频带中准确识别了预期的不同噪声源，并且与文献中发表的实验结果非常吻合。所呈现的结果证明，包括与适当阵列处理技术相关联的数百个麦克风的隧道型阵列在研究 3D 复杂气动声源方面表现非常好，并且廉价的 MEMS 麦克风是有效测量声辐射的良好候选者。