Turbulent transport and the random occurence of coherent events

Abstract

We suggest that the transport properties and dissipation rates of a wide class of turbulent flows are determined by the random occurrence of coherent events which correspond to certain orbits which we call homoclinic excursions in the high dimensional strange attractor. Homoclinic excursions are trajectories in the noncompact phase space that are attracted to special orbits which connect saddle points in the finite region of phase space to infinity and represent organized structures in the flow field. This picture also suggests that one can compute fluxes using a relatively low dimensional description of the flow. A method for extracting the organized structures from a time-series is given and provides a local analogue of the notion of Lyapunov exponents.