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Trouble with Structure/Mesh
Posted Jan 23, 2012, 6:24 a.m. EST Geometry, Mesh 3 Replies
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Hi, I have a trouble with a structure I want to mesh. I do not know how much the problem lies in the meshing and how much in the structure creation.
I created the structure Diamond (file attached) and it works fine. I wanted to change it slightly and the result is AlternativeDiamond (attached). In alternative diamond I encountered numerous problems. Without heavy changes in the element size parameters the structure couldn't be meshed. Once I got it meshed it has Geometric entity indices up to 35 which is far to high for this structure.
Is there a solution to solve the problems related to AlternativeDiamond.mph, if no would it help if I learned how to use NX7.5 to make the CAD files and then import them into Comsol?
I created the structure Diamond (file attached) and it works fine. I wanted to change it slightly and the result is AlternativeDiamond (attached). In alternative diamond I encountered numerous problems. Without heavy changes in the element size parameters the structure couldn't be meshed. Once I got it meshed it has Geometric entity indices up to 35 which is far to high for this structure.
Is there a solution to solve the problems related to AlternativeDiamond.mph, if no would it help if I learned how to use NX7.5 to make the CAD files and then import them into Comsol?
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3 Replies Last Post Jan 23, 2012, 9:16 a.m. EST
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Posted:
1 decade ago
Hi
the intersection of almost adjacent spheres or circles in 2D, is always topologically delicate, you have silver fillets and other issues. Also I suspect tat the internal COMSOL graphics driver is not as good as the higher quality CAD driver of the most advanced (and far expensiver) tools.
Turn on the transparency you will see part of the mesh inside too
I.e. in your Advanced geometry, open the selection list view, then activate domain and scan through your domains, compare it to the standard diamond:
you will see some extra domains, coming from the intersection, and perhaps also from your resolution settings, such as 9,10,11,12, 17,18,19,20, 23,24,25,26, 32,33,34,35,36 these are very small, they might even overlap, and will produce thousand of fine elements, including forcing the rest of the connecting mesh to be very dense, for nothing, I believe.
and deleting them might just give you a hole in your geometry, neither not acceptable.
I do not see any easy way out, perhaps try with a CAD tool and import the shape to COMSOL, or change the way you make differences in COMSOL
Do not forget that you can make multiple copies/moves in one go (of an object, by defining an array in the x,y,z entries)
--
Good luck
Ivar
the intersection of almost adjacent spheres or circles in 2D, is always topologically delicate, you have silver fillets and other issues. Also I suspect tat the internal COMSOL graphics driver is not as good as the higher quality CAD driver of the most advanced (and far expensiver) tools.
Turn on the transparency you will see part of the mesh inside too
I.e. in your Advanced geometry, open the selection list view, then activate domain and scan through your domains, compare it to the standard diamond:
you will see some extra domains, coming from the intersection, and perhaps also from your resolution settings, such as 9,10,11,12, 17,18,19,20, 23,24,25,26, 32,33,34,35,36 these are very small, they might even overlap, and will produce thousand of fine elements, including forcing the rest of the connecting mesh to be very dense, for nothing, I believe.
and deleting them might just give you a hole in your geometry, neither not acceptable.
I do not see any easy way out, perhaps try with a CAD tool and import the shape to COMSOL, or change the way you make differences in COMSOL
Do not forget that you can make multiple copies/moves in one go (of an object, by defining an array in the x,y,z entries)
--
Good luck
Ivar
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Posted:
1 decade ago
Thanks for your answer. I didn't find the selection list "view" but thanks for telling me where the problem lies. One way out you suggested is to change the way I make differences in COMSOL. What exactly do you mean by this suggestion?
Also thanks for the tip with the copy operations.
Also thanks for the tip with the copy operations.
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Posted:
1 decade ago
Hi
try the Alt V "Selection list"
or select from the main window File - Edit => "View" button
sometimes you get different results depending on the order you subtract objects, I expect it's related to the sizes and some kind of tolerances adjustment based on sizes, it seems to be there at least for very large size ratio objects. But I haven't investigated it in detail
--
Good luck
Ivar
try the Alt V "Selection list"
or select from the main window File - Edit => "View" button
sometimes you get different results depending on the order you subtract objects, I expect it's related to the sizes and some kind of tolerances adjustment based on sizes, it seems to be there at least for very large size ratio objects. But I haven't investigated it in detail
--
Good luck
Ivar