A 3D volumetric technique for measuring the evolution over time of the kinematic and geometric characteristics of the bubble population in multiphase flows at moderate void fraction is here proposed. The method is based on a shadowgraphy approach and requires a set of calibrated and synchronized cameras, each placed in front of a bright screen. Synchronized, 2D images of the bubbly flow are analyzed to extract the outline of the bubbles as seen from every camera. Then, each bubble is separately identified as a 3D volume described by the intersection of the cones having vertices on the optical center of each camera and passing through the contour of the bubble. Details about the implementation of the procedure, including the further refinements of the first rough bubble identification and the optimization of the number and geometric arrangement of the points of view, are reported against the results obtained on a reference set of spheres of known dimensions. Application on isolat...

中文翻译：

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用于气泡流的3D拉格朗日描述的阴影摄影方法

本文提出了一种3D体积技术，用于测量中等空隙率下多相流中气泡总体运动学和几何特性随时间的演变。该方法基于皮影摄影方法，需要一组校准和同步的摄像机，每个摄像机都放置在明亮的屏幕前。分析气泡流的同步2D图像，以提取从每个摄像机看到的气泡轮廓。然后，将每个气泡分别标识为3D体积，该3D体积由在每个相机的光学中心具有顶点并通过气泡轮廓的圆锥的相交部分描述。有关程序执行的详细信息，根据已知尺寸的参考球体上获得的结果，报告了包括首次粗气泡识别的进一步改进以及视点的数量和几何排列的优化在内的内容。在隔离剂上的应用