The Navier-Stokes equations and observable turbulent motions of fluids

In external conditions which do not depend on time the Navier-Stokes equations can define more than one possible stable steady state of turbulent motion; but only the states with a sufficiently slow relaxation are observable. Relaxation (due to perturbations) depends on additional parameters. This could explain the observed lack of similarity in the Reynolds number for turbulent motions of incompressible fluids. The observable state is determined by Fokker-Planck equations. The influence of the material parameters and of the experimental conditions is considered.