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Aeroacoustic investigation of an oscillating airfoil in the pre- and post-stall regime
Aerospace Science and Technology ( IF 5.6 ) Pub Date : 2020-05-29 , DOI: 10.1016/j.ast.2020.105880
Yannick D. Mayer , B. Zang , Mahdi Azarpeyvand

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.



中文翻译:

失速前和失速状态下摆动翼型的航空声学研究

本研究描述了正弦振荡的NACA 0012机翼的空气动力学和空气声学特性的实验研究。实验是在空气声学风洞中进行的,该风洞具有独特设计的凯夫拉尔壁测试部分。在实验之前,对这些凯夫拉尔墙进行了仔细的校准,并显示出可提供可靠而准确的空气动力学和空气声学测量结果。对于升力曲线的极点,远场噪声谱和非稳态表面压力谱,已经研究了两种不同的感兴趣方案,即失速前和失速攻角方案。有趣的是,当升力曲线极磁滞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以令人满意的精度预测振荡翼型的非稳态表面压力谱。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处变得无效。而是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,短时傅立叶变换分析表明,表面压力谱的增加是动态失速旋涡周期性产生和对流的直接结果。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,短时傅立叶变换分析表明,表面压力谱的增加是动态失速旋涡周期性产生和对流的直接结果。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,短时傅立叶变换分析表明,表面压力谱的增加是动态失速旋涡周期性产生和对流的直接结果。

更新日期:2020-05-29
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