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-   -   Bug in LES eddy viscosity GenEddyVis.C??-- compressible (http://www.cfd-online.com/Forums/openfoam-programming-development/111682-bug-les-eddy-viscosity-geneddyvis-c-compressible.html)

alundilong January 12, 2013 21:38

Bug in LES eddy viscosity GenEddyVis.C??-- compressible
 
1 Attachment(s)
Here is the function return effective stress tensor term in momentum equation from GenEddyVis.C (OpenFOAM-2.1.1).

tmp<fvVectorMatrix> GenEddyVisc::divDevRhoBeff(volVectorField& U) const
{
return
(
- fvm::laplacian(muEff(), U) - fvc::div(muEff()*dev2(T(fvc::grad(U))))
);
}

my question is
where is the term for the trace of the subgrid scale stresses?
It should looks like this or others..., anyway, k them is missing, and I didn't see anywhere account for it.

tmp<fvVectorMatrix> GenEddyVisc::divDevRhoBeff(volVectorField& U) const
{
return
(
- fvm::laplacian(muEff(), U) - fvc::div(muEff()*dev2(T(fvc::grad(U))))
+ 2.0/3.0*fvc::grad(rho()*k())
);
}

My derivation is attached, please give me some suggestions?

gregor January 17, 2013 11:16

Hi Edward,

as far as i know you can absorb the missing term into pressure by defining a new pressure as p*=p+p_SGS where p_SGS is -1/3*rho*k_SGS but following the argument of Erlebacher et. al 1991 (Toward the large-eddy simulation of compressible turbulent flows) p.159 the influence off the sgs pressure is neglectible compared to the thermodynamical pressure (for moderate Mach numbers).


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