A DYNAMICAL SYSTEM FORMALISM FOR THE STUDY OF PASSIVE SCALAR FIELDS

摘要

A new dynamical system formalism is proposed for the study of the geometry of passive scalar fields in turbulent flows. This formalism has been employed to investigate the relationship between the topology of diffusing passive scalars and the hydrody-namic topology of homogeneous isotropic turbulence. DNS of forced homogeneous isotropic turbulence at Re_λ ≈47 with Sc = 1 in a 128~3 cube was undertaken to generate the data base for this study. This investigation found two principal conclusions: first, the topology of a diffusing scalar (excluding convection) has characteristic length-scales much smaller than hydrodynamic ones, and second, compressible-like topologies are found for the scalar field even for a constant-density fluid flow.