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为了定量显示空腔高速复杂流动结构,采用均布的小圆点作为背景纹影(BOS)的背景点,利用视频测量(VM)成熟的小圆点图像定位与匹配技术,克服了现有图像互相关技术对BOS的限制;推导非平行光穿过流场的偏折位移/角计算公式,基于VM的共线方程,准确计算从背景点到相机摄影中心的光束穿过流场产生的偏折位移场和光程差场(OPD)。FL-21风洞的某空腔高速(马赫数为0.6~2.0)复杂流动结构的视频测量结果表明:本方法可清楚分辨出亚微米量级的光程差差异与微弧度量级的偏折角差异,定量显示空腔高速流动产生的波/涡/剪切层的位置、强弱及其相互关系,为复杂流动结构与气动光学效应的测量与显示提供新的途径,其光路简单、无需价格昂贵的相干光源,具有应用前景。
In order to quantitatively display the high-speed and complicated cavity flow structure, a uniformly distributed small dot is used as a background point of a background image (BOS), and a mature dot image positioning and matching technology of a video measurement (VM) is adopted to overcome the existing image Cross-correlation technique is used to limit the BOS. The formula of deflection displacement / angle of non-parallel light passing through the flow field is deduced. Based on the collinearity equation of VM, the bias of the beam passing through the flow field from the background point to the camera center is accurately calculated Fold displacement field and optical path difference (OPD). Video measurements of a complex flow structure at a cavity of FL-21 wind tunnel (Mach number of 0.6-2.0) show that this method clearly distinguishes between sub-micron optical path difference differences and micro-arc order deflection angles The difference and quantitative display of the position, the strength and the weakness of the wave / vortex / shear layer generated by the high-speed flow in the cavity provide a new way for the measurement and display of complex flow structures and aerodynamic optics. The optical path is simple and requires no price Expensive coherent light source, with application prospects.