Crossover behavior in turbulent velocity fluctuations

We develop a simple model of the evolution of turbulence velocity differences from inertial scales to dissipative scales by taking into account the effect of the viscosity. Our model suggests that the fluctuations of the viscous scales in turbulence result in a nontrivial crossover region in the velocity structure functions. We also discuss the importance of recognizing this crossover region when interpreting the experimental results. Assuming a finite and fixed spatial resolution, the model predicts a transition in the flatness at finite Reynolds number. We relate this observation with the reported transition by Tabeling et al. [Phys. Rev. E 53, 1613 (1996)], which is analyzed in detail and compared with our model.