Proceedings PaperDigital photogrammetry for determination of tracer particle coordinates in turbulent flow research
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For many tasks in turbulent flow research the simultaneous determination of tracer particle coordinates with high spatial and temporal density is required as a basis for particle tracking velocimetry (PTV). As a simultaneous, non-contact and automation-friendly method digital photogrammetry is a suitable tool to provide this information on-line. This paper describes the implementation of a system based on three CCD-cameras, which can determine the coordinates of up to 900 particles per image triplet. After an overview about the hardware used for acquisition and storage of three synchronous sequences with some hundred images each, the chain of algorithms for a completely automatic processing of the sequences is shown. These algorithms deal with some special problems arising from the task, for example the multimedia geometry, the high particle density which leads to overlapping particles in the images, and the fact that there is no continuous surface in object space, which causes ambiguities in matching. It will be shown, that these ambiguities can only be solved reliably by a system with at least three cameras.