Pair dispersion in turbulence

We study the statistics of pair dispersion in two-dimensional turbulence. D irect numerical simulations show that the probability distribution function (pdf) of pair separations is in agreement with the Richardson prediction. The pdf of doubling times follows dimensional scaling and shows a long tail which is the signature of close approaches between particles initially see ded with a large separation. This phenomenon is related to the formation of fronts in passive scalar advection. (C) 2000 Elsevier Science B.V. All rig hts reserved.