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Problems with mesh definition

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Hi,

I want to know if it is normal results change with the size of the mesh?

I am using RF module, and implemented one of Comsol examples the Branch-line Coupler, when I change the size ​​of the mesh (Course, Normal, Fine, Finer, etc) the final results (computed values) keeps constant.

But when I try to implement a simple microstrip line, and change the size of the mesh the final results also change.
It's normal? If not, where's my mistake? How do I find the optimal size of my Mesh?

Greats,
Daniel Santos

1 Reply Last Post 27 févr. 2014, 02:17 UTC−5

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Posted: 1 decade ago 27 févr. 2014, 02:17 UTC−5
Yes, the result depends on the mesh size! But this is clear you must
resolve all features of the solution in the mesh.

The promise of the finite element method is that, if the longest edge
in the mesh tends to zero the FEM-solution tends to the solution of
the differntial equation. But this is only true for infinite precision arithmetics.
On a computer you have round-off errors and a finer mesh can be worse.

For my problems I check the solution for steep gradients and refine if necessary.
But for other cases different rules could be found.

Regards

Jens
Yes, the result depends on the mesh size! But this is clear you must resolve all features of the solution in the mesh. The promise of the finite element method is that, if the longest edge in the mesh tends to zero the FEM-solution tends to the solution of the differntial equation. But this is only true for infinite precision arithmetics. On a computer you have round-off errors and a finer mesh can be worse. For my problems I check the solution for steep gradients and refine if necessary. But for other cases different rules could be found. Regards Jens

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