Measurements of wall pressure fluctuations have been performed with arrays of MEMS microphones on a full-scale model of a business jet fore part. The boundary layers are characterised in terms of mean and root-mean-square velocity profiles and key parameters are computed to serve for the normalisation of pressure-related quantities. Frequency spectra are compared with classical models and strong discrepancies are highlighted, which are attributed to the non-canonical state of the boundary layers. The spatial structure of the pressure field is first characterised by the study of coherence and associated length scales. The hypothesis of auto-similarity on only one parameter, that is the frequency normalised by the separation to convective velocity ratio, is proven to reach its limits in the present case. In turn, the coherence length scales do not exhibit the classical $$-1$$ power law decay with frequency. The wavenumber–frequency formalism is used to differentiate the acoustic and hydrodynamic components of the pressure fluctuations in the spectral space. In the presence of an external acoustic source, the acoustic components are correctly extracted from the total field by spectral filtering, and the resulting frequency spectra are satisfactorily checked against the purely acoustic reference spectrum.

中文翻译：

---

全尺寸驾驶舱模型壁面压力波动的空间结构和波数滤波

已经使用 MEMS 麦克风阵列在公务机前部的全尺寸模型上进行了壁压波动的测量。边界层的特征在于平均速度和均方根速度剖面，并且计算关键参数以用于压力相关量的归一化。将频谱与经典模型进行比较，突出显示了强烈差异，这归因于边界层的非规范状态。压力场的空间结构首先通过对相干性和相关长度尺度的研究来表征。仅对一个参数的自相似性假设，即由分离与对流速度比归一化的频率，被证明在当前情况下达到了其极限。反过来，相干长度尺度不表现出经典的 $$-1$$ 幂律随频率衰减。波数-频率形式用于区分光谱空间中压力波动的声学和流体动力学分量。在存在外部声源的情况下，通过频谱滤波从总场中正确提取声学分量，并根据纯声学参考频谱对产生的频谱进行令人满意的检查。