One question about the discretization of governing equation in OpenFOAM

JinBiao · December 14, 2011, 21:05

I found there is an extra term in some solvers. I am not sure about the reason. For example in the TEqn.H of buoyantBoussinesqSimpleFoam. The scalar matrix is constructed via

fvScalarMatrix TEqn
(
fvm::div(phi, T)
- fvm::Sp(fvc::div(phi), T)
- fvm::laplacian(kappaEff, T)
);

The second term seems not necessary here. And it also make the discretization become nonconservative. I wonder why this is necessary. In contrast in the UEqn.H in the same solver

tmp<fvVectorMatrix> UEqn
(
fvm::div(phi, U)
+ turbulence->divDevReff(U)
);

Such term does not appear. Can anyone explain why we need this?

Thanks a lot.

Best Regards,

Tarak · December 30, 2011, 03:49

Hii,

The line is added to have values of T bounded in the algorithms like SIMPLE where we have partial convergence of pressure. Check this: http://www.cfd-online.com/Forums/ope...silon-eqn.html

December 14, 2011, 21:05	One question about the discretization of governing equation in OpenFOAM	#1
JinBiao Member Jinbiao Xiong Join Date: Oct 2009 Location: China/Japan Posts: 50 Rep Power: 16	I found there is an extra term in some solvers. I am not sure about the reason. For example in the TEqn.H of buoyantBoussinesqSimpleFoam. The scalar matrix is constructed via fvScalarMatrix TEqn ( fvm::div(phi, T) - fvm::Sp(fvc::div(phi), T) - fvm::laplacian(kappaEff, T) ); The second term seems not necessary here. And it also make the discretization become nonconservative. I wonder why this is necessary. In contrast in the UEqn.H in the same solver tmp<fvVectorMatrix> UEqn ( fvm::div(phi, U) + turbulence->divDevReff(U) ); Such term does not appear. Can anyone explain why we need this? Thanks a lot. Best Regards, __________________ Jinbiao

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December 30, 2011, 03:49		#2
Tarak Senior Member Tarak Join Date: Aug 2010 Location: State College, PA Posts: 111 Rep Power: 15	Hii, The line is added to have values of T bounded in the algorithms like SIMPLE where we have partial convergence of pressure. Check this: http://www.cfd-online.com/Forums/ope...silon-eqn.html