The functional you choose does not need to converge to zero, no. In the case shown here, for example, it does not converge to zero. The algorithm is improving the accuracy of this functional by adjusting the mesh.

Regarding “Longest” vs. “Mesh Initialization”. The “longest” or “regular” methods will always work, but will only refine the mesh. The “mesh initialization” can both refine and coarsen the mesh but may, in rare circumstances, fail. There is no one method which will always be best for every case, you may want to try both. ]]>

A second question is about the use of “Longest” vs. “Mesh Initialization” as refinement method: I cannot find an explanation on what the difference is an I cannot chose the best for my model.

Thanks,

Roberto

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In particular, meshing considerations are a topic we’ve addressed before:

http://www.comsol.com/blogs/how-to-implement-mesh-refinement-study/

http://www.comsol.com/blogs/meshing-considerations-linear-static-problems/ ]]>