Hi
I think you can define a new field newfield=alpha*u and use fvc::laplacian(k,new) good luck 
But I need the implicit (fvm::laplacian), not the explicit (fvc::laplacian) term.
If there is no such term, it should be possible to use something like fvm::laplacian(k,u)*diag(alpha) for . diag(alpha) would be a sparse diagonal matrix with the entries of the field alpha on it's diagonal, but I don't think such matrix exists in Openfoam. What do you think, does it make sense to implement it? Thanks Gunnar 
Hi
I do not know:( 
How about a little chain rule? i.e. split into:
Code:
\nabla \cdot ( k \alpha \nabla u ) + \nabla \cdot ( k u \nabla \alpha ) 
Hi
But you loose conservative form. 
First of all the equation appears to be not consistent, the first and last terms are vectorial, meanwhile the second one is scalar.
Regards. 
Hi Gunnar,
If the only think you need is modification of the discretization matrix (by multiplying diag(alpha)), then you can change the matrix itself. See the PISO algorithm from icoFoam: http://openfoamwiki.net/index.php/IcoFoam You can do similar and: 1. discretize alpha 2. UEqn.A() = UEqn.A()*alpha_discretized maybe will work... ZMM 

Hi Kai,
Of course, I would proceed using this transformation. Currently I have some issues with laplacian operator in OFoam as well. Could you see my post: http://www.cfdonline.com/Forums/ope...nproblem.html Maybe you will have some suggestions... Thanks ZMM 
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