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What is advection term of incompressible turbulence model

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Old   December 5, 2008, 01:29
Default Hi everyone: i have find in
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wayne.zhang
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Hi everyone:

i have find in kEpsilon and KomegaSST,both k , epsilone,Omega equation has the advection term like this:
+ fvm::div(phi_, k_)
- fvm::Sp(fvc::div(phi_), k_)

but i think the div(phi_)should be "0" for incompressible flow. and why not write as :
- fvm::Sp(fvc::div(k_), phi_)
or
- fvm::Sp(fvm::div(k_), phi_)

thanks

yours wayne
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Old   December 5, 2008, 03:47
Default Hi Wayne, there has already be
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Ville Tossavainen
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Hi Wayne, there has already been discussion about this matter. Try to search for it, because I cannot remember the details. You shouldn't worry too much about it, since the divergence term goes to zero as the solution converges.
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Old   December 6, 2008, 08:46
Default hi Ville thanks,i will se
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hi Ville

thanks,i will search it now.if you find please tell me .there are some similar term in the diffusion term too :

tmp<fvvectormatrix> kEpsilon::divDevReff(volVectorField& U) const
{
return
(
- fvm::laplacian(nuEff(), U)
- fvc::div(nuEff()*dev(fvc::grad(U)().T()))
);
}

the red part will be 1/3*nuEff*grad(div(U)),and for incompressible flow it will be zero too.

the problem is that these terms should be zero in theory,but not in numerical,so i don`t know why add these terms here with the danger of introduce the numerical error. i think maybe there is something i do not know.so any one could help me ?

thanks

yours wayne
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