CONCENTRATION FLUCTUATIONS IN 2-DIMENSIONAL TURBULENCE

The dispersion of a cloud of passive test particles in homogeneous and isotropic two-dimensional turbulence is studied by direct numerical s imulation. The basic statistical properties of the concentration of th e cloud are analyzed with particular attention to space-time variation s in the center-of-mass frame. Approximate analytical expressions for the concentration and the concentration fluctuations can be obtained f rom the power spectrum of the velocity fluctuations.