Tomographic PIV for Beveled Trailing Edge Aeroacoustics
Tomographic PIV for Beveled Trailing Edge Aeroacoustics
复制标题
用于斜角后缘气动声学的断层成像 PIV
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
S. Morris
中科院分区：
文献类型：
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作者：
S. Pröbsting;Abhineet Gupta;F. Scarano;Yaoyi Guan;S. Morris
本文研究了由曲率半径R与板厚T之比和封闭的25°后缘角定义的倾斜后缘绕流场，它在参数上类似于各种从尖锐到钝化的后缘流动。特别是，对于气动声学产生的后缘噪声和振动结构问题，在这些不同的条件下，后缘附近的非定常表面压力的特性是有意义的。作为非定常表面压力传感器的补充，高速层析粒子图像测速仪(PIV)可以提供关于流场的时间分辨和体积信息。多帧相关方法的最新进展和基于PIV数据的压力重建方法的引入允许估计与非定常压力相关的量，否则需要复杂的模型仪器。目前的贡献集中在R/T=10的情况下。已经进行了声相控阵麦克风测量，并通过对相关震源区域上的源图进行积分来确定声压级。高速层析PIV测量的可视化显示了逆压梯度的结构，分离了靠近尾缘的流动。基于PIV的重建和测量的非定常表面压力谱显示在更大的频率范围内是一致的。得到了速度起伏沿展向相干长度的估计值，表明分离剪切层下部的相干长度减小。与零压力梯度边界层相比，重建的压力谱显示倾斜边缘的非定常表面压力对流速度随频率的增加而减小。
This study investigates the flow field around beveled trailing, defined by the ratio of radius of curvature R to plate thickness T and the enclosed 25° trailing edge angle, which parametrically resembles a variety of trailing edge flows ranging from sharp to blunt. In particular, for aeroacoustically generated trailing edge noise and vibro-structural problems the characteristics of the unsteady surface pressure near the trailing edge are of interest under these different conditions. Complementary to unsteady surface pressure sensors, highspeed tomographic Particle Image Velocimetry (PIV) can provide time-resolved and volumetric information on the flow field. Recent advances of multi-frame correlation methods and the introduction of pressure reconstruction methods based on PIV data allow for estimation of quantities related to the unsteady pressure, which otherwise requires complex instrumentation of the model. The present contribution focuses on the case R/T=10. Acoustic phased array microphone measurements have been performed and the sound pressure level has been determined by integration of the source maps over the relevant source region. Visualizations of the high-speed tomographic PIV measurements reveal the structure of the adverse pressure gradient, separating flow close to the trailing edge. PIV based reconstructed and measured unsteady surface pressure spectra show agreement over an extended range of frequencies. Estimates of the spanwise coherence length of velocity fluctuations are obtained, showing a decrease of the coherence length in the lower part of the separating shear layer. In contrast to a zero pressure gradient boundary layer, the reconstructed pressure spectra show a decrease of unsteady surface pressure convection velocities with increasing frequency for the beveled edge.