REPRESENTING AND VISUALIZING FLUID-FLOW IMAGES AND VELOCIMETRY DATA BY NONLINEAR DYNAMICAL-SYSTEMS

Nonlinear phase portraits are employed to represent the streamlines of scalar flow images generated by particle tracing experiments. The flo w fields are decomposed into simple component flows based on the criti cal point behavior. A Taylor series model is assumed for the velocity components, and the model coefficients are computed by considering bot h local critical point and global how field behavior. A merge and spli t procedure for complex flows is presented, in which patterns of neigh boring critical point regions are combined and modeled. The concepts a re extended to the compression of vector field data by using orthogona l polynomials derived from the Taylor series model. A critical point s cheme and a block transform are presented. They are applied to velocit y fields measured in particle image velocimetry experiments and genera ted by computer simulations. Compression ratios ranging from 15:1 to 1 00:1 are achieved. (C) 1995 Academic Press, Inc.