Multifractal particle distribution in compressible turbulence on a free surface.

The distribution of particles in compressible turbulence on a free surface is inhomogeneous. The floaters flee regions of fluid up-wellings and cluster into ridge-like structures near fluid down-wellings. The concentration of floaters is measured on the surface of a large tank of turbulently stirred water. The multifractal structure of the clusters is reflected in the moments of particle concentration. The results are compared with recent work of Bec $et. al.$ [J. Bec, K. Gawedzki and P. Horvai, Phys. Rev. Lett., 92, 224501 (2004)] conducted on synthetic velocity fields that follow the compressible Kraichnan model.