This study utilized a Mach 2 wind tunnel, Research Cell 19 (RC-19), where the panel specimen became part of the test section top wall. Two stereo digital image correlation (3D-DIC) systems simultaneously acquired displacement measurements both with and without flow by filming the front and back sides of the panel. The two DIC results were then compared to note if any changes between the two measurements could be attributed to light refraction distortions. Various flow conditions were investigated including varying stagnation pressures and multiple shock angles to characterize and quantify potential distortions over a range of conditions. Previous work showed that the distortions were largely quasi-static in nature which had little or no bearing on vibration measurement however, static deflections caused by thermal gradients and less than ideal boundary conditions could be important for finite element model updating. Current results indicate that distortions at the shock wave foot were present in the DIC displacement results however, the level of distortion could be considered the same magnitude of typical sources of measurement noise and not significant.

中文翻译：

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可见光折射对 2 马赫流量中薄板高速立体数字图像相关性测量的影响

本研究利用了 2 马赫风洞，即 Research Cell 19 (RC-19)，其中面板样本成为测试部分顶壁的一部分。两个立体数字图像相关 (3D-DIC) 系统通过对面板的正面和背面进行拍摄，同时获取有流动和无流动的位移测量值。然后将两个 DIC 结果进行比较，以注意两次测量之间的任何变化是否可归因于光折射失真。研究了各种流动条件，包括不同的停滞压力和多个冲击角，以表征和量化一系列条件下的潜在变形。以前的工作表明，扭曲在本质上主要是准静态的，对振动测量几乎没有影响，然而，由热梯度和不太理想的边界条件引起的静态挠度对于有限元模型更新可能很重要。目前的结果表明，DIC 位移结果中存在冲击波脚的失真，然而，失真水平可以被认为与典型测量噪声源的幅度相同，并不显着。