SELF-SIMILAR SPATIOTEMPORAL STRUCTURE OF INTERMATERIAL BOUNDARIES IN CHAOTIC FLOWS

The evolution of macroscopic material closed filaments in a time-perio dic chaotic 2D flow is simulated for cases with large, small, and very small islands of regular motion using an algorithm that preserves spa tial continuity. The length of the stretched filament increases much f aster than predicted by the Liapunov exponent. In chaotic regions, the filament asymptotically evolves into a self-similar structure with pe rmanent spatial nonuniformities in density. Filament densities and loc al length scales corresponding to different times are described by fam ilies of frequency distributions with invariant shape that can be coll apsed onto a single curve by means of a simple scaling. [S0031-9007(98 )07190-7].