finite area non-orthogonal treament errors vs finite volume operators
The treatment of non-orthogonality in fam::laplcian operator differs from fvm:laplacian. In this simple fixed BC temperature 2D slab, the same mesh is used for fam and fvm. While in fvm the gradx(T)is smooth in fam presents non-uniformity, specially close to the patches. See aGradTx vs vGradTx.
laplacianFaFoam.tar is the fa solver laplacianFoam is the fv solver.
The case cavity.tar contains the mesh and set up.
The issue seems to be related to how the non-orthogonality is treated in the fam::laplacian, special care should be taken for the non-orthogonality on the boundaries.