Automatic particle tracking in a three-dimensional flow field
Date
1985
Authors
Racca, Roberto Giacomo
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Abstract
A technique has been developed whereby the three-dimensional motion of tracers in a fluid flow is automatically analyzed. Simultaneous orthogonal views of the tracer-seeded flow were recorded by a single high speed cine camera through a split field mirror system, and successively converted to machine readable form by a video digitizer. The images were digitally enhanced to separate the tracers from the contrasting background even in conditions of poor picture quality. Algorithms were developed to match the projections of individual tracers in the two views. obtain the three-dimensional co-ordinates, follow the tracers from frame to frame and compute the velocity vectors along the particle trajectories. Eulerian information was derived from the pooled velocity data points by interpolation on a regular spatial grid. Tests of the method on various types of particle trajectories obtained in a small water tunnel have shown that the tracking is reliable even for rapidly changing and closely spaced paths.