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Fundamental question on the scales modelled by the k-epsilon model.

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Old   November 2, 2023, 14:57
Default Fundamental question on the scales modelled by the k-epsilon model.
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Turbulent motions occur over a wide range of length and time
scales. The k-epsilon model however, models a single time and length
scale at any location in the domain. The time scale is k/epsilon
and the length scale is k^(3/2)/epsilon. If this time scale is very
large (say 100 seconds) the length scale is also large.

This modelled time scale may be interpreted as a residence time.
The time it would take a particle to go around the eddy. The large
value of the length scale would be interpreted as the size of this
"modelled" eddy.

I am trying to conclude (recall) what happens at this extreme
(very large modelled eddy) condition in terms of turbulence levels.
The turbulent viscosity may be shown to be proportional to the ratio of
the length scale squared divided by the time scale. This would imply
that the larger the time scale the lower the turbulence levels at this
location. (?)

Any feedback would be greatly appreciated.
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k-e model, length scale, time scale, turbulence levels

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