Test of the Fluctuation Relation in lagrangian turbulence on a free   surface
  The statistics of lagrangian velocity divergence are studied for an assembly of particles in compressible turbulence on a free surface. Under an appropriate definition of entropy, the two-dimensional lagrangian velocity divergence of a particle trajectory represents the local entropy rate, a random variable. The statistics of this rate are shown to be in agreement with the fluctuation relation (FR) over a limited range. The probability distribution functions (PDFs) obtained in this analysis exhibit features different from those observed in previous experimental tests. 
M. M. Bandi, J. R. Cressman Jr., W. I. Goldburg