Statistics of two-particle dispersion in two-dimensional turbulence

Abstract

We investigate Lagrangian relative dispersion in direct numerical simulation of two-dimensional inverse cascade turbulence. The analysis is performed by using both standard fixed time statistics and an exit time approach. Our results are in good agreement with the original Richardson's description in terms of diffusion equation. The deviations are only of the quantitative nature. These deviations, and the observed strong sensitivity to the finite size effects, are associated with the long-range-correlated nature of the particles' relative motion. The correlation, or persistence, parameter is measured by means of a Lagrangian ``turning point'' statistics.