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-   -   A question about UEqn.H (interPhaseChangeFoam) (http://www.cfd-online.com/Forums/openfoam/106332-question-about-ueqn-h-interphasechangefoam.html)

Zheng.Zhi August 26, 2012 00:24

A question about UEqn.H (interPhaseChangeFoam)
 
the UEqn.H at interPhaseChangeFoam

fvVectorMatrix UEqn
(
fvm::ddt(rho, U)
+ fvm::div(rhoPhi, U)
- fvm::Sp(fvc::ddt(rho) + fvc::div(rhoPhi), U)
- fvm::laplacian(muEff, U)
- (fvc::grad(U) & fvc::grad(muEff))
//- fvc::div(muEff*(fvc::interpolate(dev2(fvc::grad(U) )) & mesh.Sf()))
);

but the UEqn.H at interFoam

fvVectorMatrix UEqn
(
fvm::ddt(rho, U)
+ fvm::div(rhoPhi, U)
- fvm::laplacian(muEff, U)
- (fvc::grad(U) & fvc::grad(muEff))
//- fvc::div(muEff*(fvc::interpolate(dev(fvc::grad(U)) ) & mesh.Sf()))
);

I don't understand why need - fvm::Sp(fvc::ddt(rho) + fvc::div(rhoPhi), U) at interPhaseChangeFoam , Could anybody please answer me ? thanks very much.

nimasam August 26, 2012 12:17

fvm::Sp(fvc::ddt(rho) + fvc::div(rhoPhi), U)
this term would be zero mathematically because
fvc::ddt(rho) + fvc::div(rhoPhi)
is global continuity equation, and i guess it is added to consider
any numerical error in global continuity equation

abe April 8, 2013 07:32

I am agree with Nimasam. It returns the continuity equation value. I have checked the results in two conditions with and without this term. Results are fairly the same. However, I should say that by using this term it seems that the convergence speed is much better.
PS: in the OF22, this term has been removed!

abe April 8, 2013 07:34

Quote:

Originally Posted by nimasam (Post 378752)
fvm::Sp(fvc::ddt(rho) + fvc::div(rhoPhi), U)
this term would be zero mathematically because
fvc::ddt(rho) + fvc::div(rhoPhi)
is global continuity equation, and i guess it is added to consider
any numerical error in global continuity equation


Hi, have you been able to use interPhaseChange in OF21 or 22?
I can get results by previous versions (i.e. OF1.5). But by these new versions results are not good at all.


ABE


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