Experimental investigation of aerofoil tonal noise generation
Experimental investigation of aerofoil tonal noise generation
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DOI：
10.1017/jfm.2014.156
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发表时间：
2014-04
影响因子：
3.7
通讯作者：
S. Pröbsting;J. Serpieri;F. Scarano
中科院分区：
文献类型：
--
作者：
S. Pröbsting;J. Serpieri;F. Scarano
摘要本文研究了NACA 0012翼型在中等攻角（0、1、2和4攻角）和雷诺数（10万~ 27万）下的音调噪声发射机理。同时时间分辨粒子图像测速（PIV）的气动声源区域附近的后缘和声学测量在远场进行，以建立流动结构和声发射之间的对应关系。这些实验的结果，并在过去的研究中，一些选定的情况下进行分析。声发射特性和平均流场的主要特征与以前的研究中提出的数据一致。时间分辨分析表明，下游对流涡结构，从增长的剪切层不稳定性，相干通过后缘的频率等于主音。因此，散射的旋涡结构和其相关的壁压波动被确定为音调生成机制的情况下，在这里调查。此外，在后缘附近的声压和速度信号的小波分析示出了类似的周期性振幅调制，其与声谱中的多个音调峰相关联。在压力侧的声压和速度波动的周期性振幅调制也观察到过渡时，被迫在吸力侧，表明压力侧事件单独的原因。
Abstract The present study investigates the mechanisms associated with tonal noise emission from a NACA 0012 aerofoil at moderate incidence ( $0^{\circ },1^{\circ },2^{\circ }$ and $4^{\circ }$ angle of attack) and with Reynolds numbers ranging from 100 000 to 270 000. Simultaneous time-resolved particle image velocimetry (PIV) of the aeroacoustic source region near the trailing edge and acoustic measurements in the far field are performed in order to establish the correspondence between the flow structure and acoustic emissions. Results of these experiments are presented and analysed in view of past research for a number of selected cases. Characteristics of the acoustic emission and principal features of the average flow field agree with data presented in previous studies on the topic. Time-resolved analysis shows that downstream convecting vortical structures, resulting from growing shear layer instabilities, coherently pass the trailing edge at a frequency equal to that of the dominant tone. Therefore, the scattering of the vortical structures and their associated wall pressure fluctuations are identified as tone generating mechanisms for the cases investigated here. Moreover, wavelet analysis of the acoustic pressure and velocity signals near the trailing edge show a similar periodic amplitude modulation which is associated with multiple tonal peaks in the acoustic spectrum. Periodic amplitude modulation of the acoustic pressure and velocity fluctuations on the pressure side are also observed when transition is forced on the suction side, showing that pressure-side events alone can be the cause.