[toboto]

Dear all,

I am totally confused regarding how the diagonal coefficient in OpenFOAM is calculated.

I know that this is done using the negSumDiag() function as follows:

 void Foam::lduMatrix::negSumDiag()
   51 {
   52     const scalarField& Lower = const_cast<const lduMatrix&>(*this).lower();
   53     const scalarField& Upper = const_cast<const lduMatrix&>(*this).upper();
   54     scalarField& Diag = diag();
   55 
   56     const labelUList& l = lduAddr().lowerAddr();
   57     const labelUList& u = lduAddr().upperAddr();
   58 
   59     for (label face=0; face<l.size(); face++)
   60     {
   61         Diag[l[face]] -= Lower[face];
   62         Diag[u[face]] -= Upper[face];
   63     }
   64 }

I think (correct me if I am wrong) this implies column wise summation. This contradicts all explanations of this function on this forum.

Is this valid for any case, i.e. even if the matrix isn't symmetric?

Can you please provide a reference on the relation between diagonal and off-diagonal coefficients for different flow cases?

Best regards.