- **OpenFOAM**
(*http://www.cfd-online.com/Forums/openfoam/*)

- - **anisotropic diffusion fvm::laplacian**
(*http://www.cfd-online.com/Forums/openfoam/111178-anisotropic-diffusion-fvm-laplacian.html*)

anisotropic diffusion fvm::laplacianHi,
I have had a look at the implicit discretization of anisotropic diffusion (fvm::laplacian). It seems to me that the implementation is wrong. At least I haven't yet managed to figure out why the coefficients are as they are. It is fairly easy to follow in Ferzinger & Peric how the non-orthogonal correction approach is done for scalar "gamma" fields. For tensor fields it's a bit more tricky. What is being passed to the uncorrected (implicit) laplacian function is the scalar field sfGammaSn.For me it would make sense to pass a vector field sfGamma and then split the derivative nabla(vf) into a derivative along d and a derivative along sfGamma_{unity}.I think the way fvm::laplacian is implemented now shouldn't even work for scalar "gammas" right?Otherwise there wouldn't exist a template version for fvm::laplacians for scalars. I would appriciate if anybody can exchange thoughts on this topic / approves my thoughts / teaches me wrong / explains to me the implementation. Cheers, Michi template<class Type, class GType> tmp<fvMatrix<Type> > gaussLaplacianScheme<Type, GType>::fvmLaplacianUncorrected ( const surfaceScalarField& gammaMagSf, actually passes sfGammaSn const GeometricField<Type, fvPatchField, volMesh>& vf ) { tmp<surfaceScalarField> tdeltaCoeffs = this->tsnGradScheme_().deltaCoeffs(vf); const surfaceScalarField& deltaCoeffs = tdeltaCoeffs(); tmp<fvMatrix<Type> > tfvm ( new fvMatrix<Type> ( vf, deltaCoeffs.dimensions()*gammaMagSf.dimensions()*v f.dimensions() ) ); fvMatrix<Type>& fvm = tfvm(); fvm.upper() = deltaCoeffs.internalField()*gammaMagSf.internalFie ld(); fvm.negSumDiag(); |

I figured out that the coeffs indeed correspond to what I've derived
which is (Sf dot Gamma dot Sf)/(Sf dot d) ... for the uncorrected laplacian. I hope I didn't confuse anyone that read this message! If so, sorry! |

All times are GMT -4. The time now is 08:48. |