Aeroacoustic investigation of an oscillating airfoil in the pre- and post-stall regime
Aeroacoustic investigation of an oscillating airfoil in the pre- and post-stall regime
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失速前和失速后状态下振荡翼型的气动声学研究
DOI：
10.1016/j.ast.2020.105880
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发表时间：
2020
影响因子：
5.6
通讯作者：
M. Azarpeyvand
中科院分区：
文献类型：
--
作者：
Y. Mayer;B. Zang;M. Azarpeyvand
本研究描述了对正弦振荡 NACA 0012 翼型的空气动力学和气动声学特性的实验研究。实验在气动声学风洞中进行，该风洞具有独特设计的凯夫拉壁测试部分。在实验之前，这些凯夫拉纤维壁经过仔细校准，并证明可以提供可靠且准确的空气动力学和空气声学测量。已经检查了两种不同的感兴趣区域，即失速前和失速后攻角区域的升力曲线极坐标、远场噪声谱和非稳态表面压力谱。有趣的是，当升力曲线极滞后在预失速迎角较小时，可以使用基于位置的加权平均方法从其静态对应物中以令人满意的精度预测振荡翼型的非定常表面压力谱。另一方面，由于存在显着的动态失速滞后，这种方法在失速后角度变得无效。相反，在动态失速条件下观察到平均表面压力和远场噪声谱的增加。此外，短时傅里叶变换分析表明，表面压力谱的增加是动态失速涡的周期性产生和对流的直接结果。
The present study describes an experimental investigation of the aerodynamic and aeroacoustic characteristics of a sinusoidally oscillated NACA 0012 airfoil. The experiments were conducted in an aeroacoustic wind tunnel with a uniquely designed Kevlar-walled test section. Prior to experiments, these Kevlar walls were calibrated carefully and shown to provide reliable and accurate aerodynamic and aeroacoustic measurements. Two different regimes of interest, namely the pre- and post-stall angle of attack regimes, have been examined for lift curve polars, far-field noise spectra and unsteady surface pressure spectra. Interestingly, when the lift curve polar hysteresis is small at pre-stall angles of attack, the unsteady surface pressure spectra of the oscillating airfoil can be predicted with satisfactory accuracy using a position-based weighted averaging approach from its static counterparts. On the other hand, such a method becomes invalid at post-stall angles due to the presence of a significant dynamic stall hysteresis. Instead, an increase in the mean surface pressure and far-field noise spectra is observed at dynamic stall conditions. Furthermore, a short-time Fourier transform analysis reveals that the increase of the surface pressure spectra is a direct result of the periodic production and convection of dynamic stall vortices.