Anomalous diffusion in a linear system of vortices

An experimental study of the dispersion of a passive tracer in linear array of stationary vortices is performed. The range of Peclet number which is investigated extends from 2×10 4 to 2×10 5 . An anomalous diffusion regime is observed, characterized by a number of eddies growing like t 1 /3 (where t is the time). The shape of the diffusion front is measured and is shown to be a «universal» function of the reduced variable Pe − 1/4(x/t 1 /3). Comparison of the concentration profils obtained experimentally with the theory leads to a remarkable agreement