Fig. 1. Equipment configuration for stereo-DPIV flow visualization viewed from above (xz plane). The laser light sheet (shown in blue) is positioned in the center of the flow tank. Two cameras are placed at a wide angle relative to the laser light sheet (A). The thick black arrow (A) represents wake flow, which is shown with a relatively large lateral trajectory angle (i.e. high magnitude of W, which is flow in the z dimension) to illustrate differences between the field of view of the two cameras. The red and green dotted lines and arrows for the left and right cameras, respectively, represent the different fields of view of each camera and the resulting two-dimensional views of flow movement in opposite directions. Each camera's lens is tilted relative to the camera (B) in the Scheimpflüg configuration so that the light sheet plane, the image plane and the lens principal plane intersect at a common line (depicted here as an orange circle), and the plane of best focus is the light sheet plane. The Scheimpflüg configuration results in a clear and sharp image of particles illuminated by the light sheet, despite the large camera angles. See Materials and methods for more details.

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