Wavelet analysis of transonic buffet on a two-dimensional airfoil with vortex generators
Wavelet analysis of transonic buffet on a two-dimensional airfoil with vortex generators
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DOI：
10.1007/s00348-016-2261-2
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发表时间：
2016-10
影响因子：
2.4
通讯作者：
T. Kouchi;Shingo Yamaguchi;S. Koike;T. Nakajima;Mamoru Sato;H. Kanda;S. Yanase
中科院分区：
文献类型：
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作者：
T. Kouchi;Shingo Yamaguchi;S. Koike;T. Nakajima;Mamoru Sato;H. Kanda;S. Yanase
利用快速分幅聚焦纹影成像技术，对带和不带涡流发生器的二维跨音速翼型的激波抖振进行了可视化研究。聚焦纹影显示结果表明，安装涡流发生器后，翼型绕流的三维性明显增强。这意味着成像系统的窄焦深是准确捕捉具有VG的情况下由于抖振引起的冲击振荡特性的关键。时间分辨成像还显示，非周期性成分包括在冲击振荡由于抖振的情况下与VG。这使得傅立叶分析无法应用。我们使用小波分析来提取具有VG的情况下的冲击振荡的特征。小波频谱图表明，即使在VG控制抖振时，具有抖振频率的低频振荡仍然间歇地包含在冲击振荡中。低频振荡的出现率随涡流发生器间距和攻角的增大而增大。
We visualized the shock buffets on a two-dimensional transonic airfoil with and without vortex generators (VGs) by using a fast-framing focusing schlieren imaging. The focusing schlieren visualization showed that the flow three-dimensionality around the airfoil became remarkable with installing the VGs. This implies that narrow depth of focus of imaging systems was a key to accurately capture the characteristics of the shock oscillation due to the buffet for the cases with VGs. The time-resolved imaging also revealed that non-periodic components were included in the shock oscillation due to the buffet for the cases with VGs. This prevented Fourier analysis from being applied. We used wavelet analysis to extract the characteristic of the shock oscillation for the cases with VGs. The wavelet spectrograms revealed that the low-frequency oscillation having the buffet frequency was still included intermittently in the shock oscillation even when VG controlled the buffet. The rate of appearing the low-frequency oscillation increased with increasing both the interval between VGs and the angle of attack.