Intermittency in turbulence

Summary

Intermittency in turbulence is the fact that the small scales of a turbulent flow are not statistically self-similar. Strong velocity gradients and intense vortices fill only a small and irregular part of the flow. They become rarer but more extreme at smaller scales. It shows up as a growth of the flatness of velocity increments at small separations. It also shows up as structure function exponents that depend nonlinearly on the order. It is the main known departure from the Kolmogorov 1941 theory and a central open problem in the theory of turbulence.