[wenxu]

hi,everyone:
In the src/finitevolume/fvm/fvmSup.C,there is the code:
(1)template<class Type>
Foam::tmp<Foam::fvMatrix<Type> >
Foam::fvm::Su
(
const DimensionedField<Type, volMesh>& su,
const GeometricField<Type, fvPatchField, volMesh>& vf
)
{
const fvMesh& mesh = vf.mesh();

tmp<fvMatrix<Type> > tfvm
(
new fvMatrix<Type>
(
vf,
dimVol*su.dimensions()
)
);
fvMatrix<Type>& fvm = tfvm();

fvm.source() -= mesh.V()*su.field();

return tfvm;
}

(2)template<class Type>
Foam::tmp<Foam::fvMatrix<Type> >
Foam::fvm::Sp
(
const DimensionedField<scalar, volMesh>& sp,
const GeometricField<Type, fvPatchField, volMesh>& vf
)
{
const fvMesh& mesh = vf.mesh();

tmp<fvMatrix<Type> > tfvm
(
new fvMatrix<Type>
(
vf,
dimVol*sp.dimensions()*vf.dimensions()
)
);
fvMatrix<Type>& fvm = tfvm();

fvm.diag() += mesh.V()*sp.field();

return tfvm;
}

(3)template<class Type>
Foam::tmp<Foam::fvMatrix<Type> >
Foam::fvm::SuSp
(
const DimensionedField<scalar, volMesh>& susp,
const GeometricField<Type, fvPatchField, volMesh>& vf
)
{
const fvMesh& mesh = vf.mesh();

tmp<fvMatrix<Type> > tfvm
(
new fvMatrix<Type>
(
vf,
dimVol*susp.dimensions()*vf.dimensions()
)
);
fvMatrix<Type>& fvm = tfvm();

fvm.diag() += mesh.V()*max(susp.field(), scalar(0));

fvm.source() -= mesh.V()*min(susp.field(), scalar(0))
*vf.internalField();

return tfvm;
}

The code in red colour, for the EXPLICIT the operator is "-=" from the source term of the fvmatrix. for the IMPLICIT the operator is "+=" from the the diagnal term of the fvmatrix. what that mean? i think the source term is rho*phi*V, so where is the "phi"? (i don't know the fvmatrix's diagnal and source stands for? )

And for the IMPLICIT/EXPLICIT, when susp.field() greater than zero, it is the same as the IMPLICIT, i could understand that. but when susp.field less than zero, it should be use EXPLICIT, but you know that it subtract the rho*phi*V from the source of the fvmatrix, I really confused with it....

anyone could so kind to help me, thank you in advance.