Relative spatial diffusion in turbulent media

Starting from the Langevin equation a nonlinear evolution equation describing the mean square distance of initially close tagged particles in a turbulent medium is obtained. The equation is the same as that derived for a turbulent plasma by Misguich and Balescu using renormalized kinetic theory. The approach is extended to incorporate stable drift in connection with the diffusion of macro particles in a turbulent fluid. The initial ≈t3 and intermediate exponential growth of the mean square distance subsist even under the presence of stable drift in agreement with many confirmed observations.