Energy Cascade

In a fully turbulent flow, at high Re, we have large eddies breaking up into smaller ones, and those break up as well until �finally the eddies are so small that they are dissipated by viscosity. Clearly the scale at which dissipation occurs depends on the viscosity. A poem by Lewis Fry Richardson:

Big whirls have little whirls,

Which feed on their velocity,

And little whirls have lesser whirls,

and so on to viscosity.

See Kolmogorov's 5/3 law for the energy in terms of wavenumber in the inertial subrange of wavenumbers before dissipation occurs.