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-   -   Resolved Reynolds Stress in LES (http://www.cfd-online.com/Forums/fluent/121209-resolved-reynolds-stress-les.html)

yinyueqiang July 23, 2013 21:40

Resolved Reynolds Stress in LES
 
Hi All,

I am running a case using LES on Fluent, and trying to get the Reynolds stress(<u1'u2'>) distribution on some locations of the computation domain. So after my case have been running and averaged for abundant time, I click Results->Plot->Unsteady Statistics, and then found "Resolved UV Reynolds Stress". Does anyone know how this "Resolved UV Reynolds Stress" is defined? Is it still <u1'u2'> ? By indicating "Resolved", does it mean there is another part of (unresolved) Reynolds stress not included here? Thank you very much.

-Steve

flotus1 July 24, 2013 03:21

That is the basic idea behind LES. Only the large scales are resolved while the small scales are still modeled ("eddy viscosity").
Thus "Resolved Reynolds Stress" is the best guess for the actual Reynolds Stresses. In a well-resolved LES, the resolved part should be >90% of the total Reynolds stresses.

yinyueqiang July 24, 2013 11:16

Quote:

Originally Posted by flotus1 (Post 441623)
That is the basic idea behind LES. Only the large scales are resolved while the small scales are still modeled ("eddy viscosity").
Thus "Resolved Reynolds Stress" is the best guess for the actual Reynolds Stresses. In a well-resolved LES, the resolved part should be >90% of the total Reynolds stresses.

Many thanks Alex.

You mentioned the "Resolved Reynolds Stress" is only one part of the Reynolds stresses(the resolved part). Do you know if there is any method with which I can get the whole Reynolds stresses(not only the resolved part, but also the modeled part)? thanks again.


Steve

flotus1 July 24, 2013 11:48

Apart from a DNS, I cant think of a reliable method to obtain the "exact" Reynolds stresses.
But as already mentioned, if the LES is well-resolved, the differences should be negligible.


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