Richardson Pair Dispersion in Two-Dimensional Turbulence

Abstract

We report the first experimental study of the dispersion of pairs of passive particles, performed in a controlled two-dimensional turbulent flow, in which Kolmogorov-Kraichnan scaling $E(k)\ensuremath{\sim}{k}^{\ensuremath{-}5/3}$ holds. The Richardson ${t}^{3}$ law is observed, and strongly non-Gaussian behavior is obtained for the Lagrangian distributions of separations. The process is shown to be isotropic, and self-similar in time. The observations, which fit well in the Kolmogorov framework, jeopardize the relevance of the L\'evy walk approach.