MODELS OF INTERMITTENCY IN HYDRODYNAMIC TURBULENCE

A heurisitic model for evolution of the probability distribution (PDF) of transverse velocity gradient s in incompressible Navier-Stokes turbulence is distilled from an analytical closure for Burgers turbulence. At all Reynolds number scrR, the evolved PDF is s-1/2 exp(-const×ss21/2) for large. The model suggests that skewness and flatnesses are asymptotically independent of scrR, and that cascade to smaller scales is not a fractal process. For Burgers dynamics, both simulations and the analytical closure give a PDF -1 exp(-const×21/2) for large negative velocity gradient. © 1990 The American Physical Society.