Detection, quantification, and tracking of vortices using streamline geometry

We present two techniques for vortex detection in 2D velocity fields, based on the macroscopic geometric properties of streamlines. The methods do not depend on the local flow patterns at a single point used in many other vortex detection techniques. Both methods begin by covering the full domain with a large number of streamlines, and select the curves with circular or looping geometry. The first method uses local cumulations of curvature centers which may indicate that many streamlines are circling around a cluster of closely spaced center points. The second method detects looping patterns in streamlines by looking at the cumulative changes of direction, as represented by the winding angle. The second method is very effective in detecting weak vortices, as it does not depend on velocity magnitude but only on the pattern. The methods can be used for quantification of vortices using numerical attributes which are suitable for feature tracking in time dependent flows. We present results of the methods with stationary and time-dependent CFD data sets. (C) 2000 Elsevier Science Ltd. All rights reserved.