A unique technique, the Doppler Picture Velocimetry (DPV), for measuring and visualizing velocities especially in hypersonic gas flows is presented. By means of a Michelson interferometer (MI) the Doppler shifted light scattered by tracers is transformed into an image showing Fizeau fringes. The image fringe distribution provides information on the Doppler frequency shift which is related to the velocity of the particles crossing a light sheet plane. To overcome former disadvantages of DPV, the optical set-up as well as the processing scheme have been improved significantly. Two schemes have been tested in recent times for fringe processing: 1) an alternative process, the Least Square Estimators (LES) and 2) an algorithm based on a technique using Fast Fourier Transformations (FFT) to examine the DPV images in the frequency domain. The new DPV algorithms now allow an automated calculation of the velocity profiles from the Doppler pictures without manual fringe tracing as it had to be done in the past. Both methods are compared by means of Mach 6 flows around a wedge and a sphere produced in the ISL high energy shock tunnel STA. TiO2 particles are illuminated by a laser light sheet which was perpendicularly arranged to the main flow direction. Light observation via the MI from the side (90° to illumination) informs on the vertically oriented velocity through the DPV images.

中文翻译：

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用于自动多普勒图像测速 (DPV) 评估的新型处理工具

介绍了一种独特的技术，即多普勒图像测速 (DPV)，用于测量和可视化速度，尤其是在高超声速气流中。通过迈克尔逊干涉仪 (MI)，示踪剂散射的多普勒频移光被转换成显示斐索条纹的图像。图像条纹分布提供有关多普勒频移的信息，该频移与穿过光片平面的粒子速度有关。为了克服 DPV 以前的缺点，光学设置以及处理方案都得到了显着改进。最近测试了两种用于条纹处理的方案：1) 替代过程，最小二乘估计器 (LES) 和 2) 基于使用快速傅立叶变换 (FFT) 来检查频域中的 DPV 图像的技术的算法. 新的 DPV 算法现在允许根据多普勒图像自动计算速度剖面，而无需像过去那样手动进行条纹追踪。两种方法都通过在 ISL 高能激波隧道 STA 中产生的楔形和球体周围的 6 马赫流量进行比较。TiO2 颗粒由垂直于主流方向排列的激光片照射。通过 MI 从侧面（与照明成 90°）进行的光观察通过 DPV 图像告知垂直方向的速度。TiO2 颗粒由垂直于主流方向排列的激光片照射。通过 MI 从侧面（与照明成 90°）进行的光观察通过 DPV 图像告知垂直方向的速度。TiO2 颗粒由垂直于主流方向排列的激光片照射。通过 MI 从侧面（与照明成 90°）进行的光观察通过 DPV 图像告知垂直方向的速度。