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Avoided 4 inverted elements by using linear geometry shape order

Posted Nov 3, 2010, 1:15 p.m. EDT 3 Replies

J
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Hi Guys,

I just received this error message in the GUI, when I tried to solve my model:

"Avoided 4 inverted elements by using linear geometry shape order". Any idea of the meaning?

J
3 Replies Last Post Nov 4, 2010, 9:25 a.m. EDT
Kai Herbrig
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Posted: 1 decade ago Nov 3, 2010, 4:46 p.m. EDT
This is a quite clear message.

The polynom order of the geometric shape functions of some elements were lowered (from may be quadratic) to linear order, because with a higher order polynom the elements became inverted. With an linear order they won't. Your mesh is too distorted in this region (very low mesh element quality!). The results will be not very accurate.

Check the doc
This is a quite clear message. The polynom order of the geometric shape functions of some elements were lowered (from may be quadratic) to linear order, because with a higher order polynom the elements became inverted. With an linear order they won't. Your mesh is too distorted in this region (very low mesh element quality!). The results will be not very accurate. Check the doc
J
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Posted: 1 decade ago Nov 4, 2010, 9:01 a.m. EDT
Maybe it's a dumb question, but: this problems happened just when I added another line on the geometry and I didn't create a composite object putting everything together. Why this? Moreover, the geometry of the default free mesh element is not already linear? I mean, triangles with straight edges?

Thanks
Maybe it's a dumb question, but: this problems happened just when I added another line on the geometry and I didn't create a composite object putting everything together. Why this? Moreover, the geometry of the default free mesh element is not already linear? I mean, triangles with straight edges? Thanks
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Nov 4, 2010, 9:25 a.m. EDT
Hi

pls note that a "composite geometry" in COMSOL is the equivalent of an "assembly" in most CAD tools (i.e. SolidWorks) so this item is treated specifically as a unit first, then other geoemtrical objects are added and analysed in the "geomanalyse() process to give FEM (geometrical) "Entities" onto which you may apply physics and BC's. So you might have different results when you pass the "finish" flag of COMSOL (old 3.5 geomanalyse() process)

And do not confuse COMSOLS "assembly" mode that has nothing to do with a CAD assembly ;)

--
Good luck
Ivar
Hi pls note that a "composite geometry" in COMSOL is the equivalent of an "assembly" in most CAD tools (i.e. SolidWorks) so this item is treated specifically as a unit first, then other geoemtrical objects are added and analysed in the "geomanalyse() process to give FEM (geometrical) "Entities" onto which you may apply physics and BC's. So you might have different results when you pass the "finish" flag of COMSOL (old 3.5 geomanalyse() process) And do not confuse COMSOLS "assembly" mode that has nothing to do with a CAD assembly ;) -- Good luck Ivar

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