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-   -   Turbulent timescale (http://www.cfd-online.com/Forums/openfoam/68151-turbulent-timescale.html)

didomenico September 8, 2009 11:11

Turbulent timescale
 
Dear all,

I am currently facing the problem of determining the local turbulent timescale, and I want to implement a function which does not depend from the kind of turbulence model used (LES/RAS).

Looking inside solvers which already implement it (i.e. reacting*Foam) I have discovered something like this

volScalarField tk = Cmix*sqrt(turbulence->muEff()/rho/turbulence->epsilon());

which should indeed represent a quite general approach. However, I have the following questions:

- why does the expression contain muEff() and not mut()? According to my knowledge muEff includes the molecular viscosity. Even if this latter may be negligible in cold, high-Reynolds flows, I am pretty sure that in combustion applications the two viscosity may locallybe comparable!

- is there any other possible approach I may use to get this quantity from both LES and RAS model?

Thanks in advance,
Max


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