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Meshing a 3D model with inclusions

Posted Feb 12, 2012, 4:16 a.m. EST Geometry, Mesh, Structural Mechanics Version 4.2, Version 4.2a 4 Replies

Noy Cohen
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Hello everyone,

I'm trying to solve a 3D model: A cube with a spherical inclusion inside under periodic boundary conditions. I'm having problem with the meshing. If I solve the problem without the inclusion, Comsol solves it only if the meshing is quadrilateral, and once I add the inclusion, I'm not able to mesh.

If I use the physics controlled mesh with extra fine elements, I get the error:
"Failed to find a solution.
Singular matrix.
Returned solution is not converged."

Does anybody have an idea of how to solve this problem?

Thank you.
4 Replies Last Post Feb 12, 2012, 8:26 a.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Feb 12, 2012, 6:34 a.m. EST
Hi

what is the size ration sphere cube, if > 1:10'000 you might have mesh quality issues, then one way is to add a "fictive" (interiour boundary of same material) sphere concentric with the small one to have a better control on the mesh size increase. Then you mesh first the small interiour, then next shell and finally the outer.

But you might have another issue too ;)

--
Good luck
Ivar
Hi what is the size ration sphere cube, if > 1:10'000 you might have mesh quality issues, then one way is to add a "fictive" (interiour boundary of same material) sphere concentric with the small one to have a better control on the mesh size increase. Then you mesh first the small interiour, then next shell and finally the outer. But you might have another issue too ;) -- Good luck Ivar
Noy Cohen
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Posted: 1 decade ago Feb 12, 2012, 6:50 a.m. EST
Hey,

Thanks for the reply.

I examine different sphere to cube ratio, but i think the minimum ratio will be 0.01. What I did is created a cube and a sphere and used the difference operation, and then another sphere. Then I used the "form union" command.

Then I have problems meshing...

How do i add a "fictive" boundary? I'm not familiar with that...

Thanks again...
Hey, Thanks for the reply. I examine different sphere to cube ratio, but i think the minimum ratio will be 0.01. What I did is created a cube and a sphere and used the difference operation, and then another sphere. Then I used the "form union" command. Then I have problems meshing... How do i add a "fictive" boundary? I'm not familiar with that... Thanks again...
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Feb 12, 2012, 6:56 a.m. EST
Hi

it's only useful if you have a very large size ration between your parts. Another point you do not need to take any difference or specific union node, two volumes fully embedded are "split up" in "Finish union" mode into two distinct domains

--
Good luck
Ivar
Hi it's only useful if you have a very large size ration between your parts. Another point you do not need to take any difference or specific union node, two volumes fully embedded are "split up" in "Finish union" mode into two distinct domains -- Good luck Ivar
Noy Cohen
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Posted: 1 decade ago Feb 12, 2012, 8:26 a.m. EST
Thanks...

Any other ideas how to approach this? I'm a bit reluctant to use the symmetry since I have periodic boundary conditions...
Thanks... Any other ideas how to approach this? I'm a bit reluctant to use the symmetry since I have periodic boundary conditions...

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