  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.
