Energy Cascade: Difference between revisions
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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: | 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, | |Big whirls have little whirls, | ||
|Which feed on their velocity, | |Which feed on their velocity, | ||
|And little whirls have lesser whirls, | |And little whirls have lesser whirls, | ||
|and so on to viscosity. | |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. | See Kolmogorov's 5/3 law for the energy in terms of wavenumber in the inertial subrange of wavenumbers before dissipation occurs. | ||
Revision as of 10:45, 21 May 2015
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.