Pair dispersion in turbulence

We study the statistics of pair dispersion in two-dimensional turbulence. Direct 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 seeded with a large separation. This phenomenon is related to the formation of fronts in passive scalar advection. (C) 2000 Elsevier Science B.V. All rights reserved.