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Creating & Meshing Assemblies in 4.0

Posted Jun 4, 2010, 3:23 p.m. EDT Mesh Version 4.0 4 Replies

Andrew Prudil Nuclear Materials
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Hi,

I'm trying to work with assemblies in Comsol 4.0 and I've been unable to use the 'imprint' option to automatically make identity pairs and match mesh nodes. In comsol 3.5a, this was easily implemented by Draw>Create Pairs.

Has anyone had any success automatically creating identity pairs for assemblies and getting the imprint functionality to work? I have been unable to get my mesh to line up in Comsol 4.0 the way "create imprints" worked in Comsol 3.5.
Anyone have any ideas?
4 Replies Last Post Jun 8, 2010, 10:36 a.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jun 5, 2010, 6:26 a.m. EDT
Hi

In V4 you need to change the Geometry "Finish" function "from union" to "form assembly" and check the create imprints check box.
Thereafter it should be very similar to V3.5a ;)

DO not forget to create your pairs in "Definitions Contact or Identity Pairs" and define the physics in the physics domain add pairs: contact or identity + required item selections, if this i not already done while you set up your model

It's true that one need to search alittle to find back our old habits, and some must be fully renewed in V4

Have fun Comsoling
Ivar
Hi In V4 you need to change the Geometry "Finish" function "from union" to "form assembly" and check the create imprints check box. Thereafter it should be very similar to V3.5a ;) DO not forget to create your pairs in "Definitions Contact or Identity Pairs" and define the physics in the physics domain add pairs: contact or identity + required item selections, if this i not already done while you set up your model It's true that one need to search alittle to find back our old habits, and some must be fully renewed in V4 Have fun Comsoling Ivar
Andrew Prudil Nuclear Materials
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Posted: 1 decade ago Jun 5, 2010, 4:30 p.m. EDT
Thanks for the reply Ivar,
I have been trying what you have suggested without any luck. Here is a simple example file with mock geometry where this process does not work. Any ideas?
Thanks for the reply Ivar, I have been trying what you have suggested without any luck. Here is a simple example file with mock geometry where this process does not work. Any ideas?

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Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jun 7, 2010, 1:51 a.m. EDT
Hi

indeed I notice I must set up the identity by hand on you raxample. But as I do not know the materials you want to set there I do not fully understand your case, what I notice is tht you have a potential point of singularity the spiky last triangle at the left top of your sphere you could have 3-4 materials as borders for a sigle thin sharp edge. Not necesarily the best for numerical stability.

the link to a cercle and its tangeant is always delicate, it makes an infinetely sharp element edge

One thing, do you need all boundaries as assembeld ? why not regroup some of your sections after the split, then COMSOl will automatically treat these as "continuity and you will end up with one or two true assembly indentity items

Godd luck
ivar
Hi indeed I notice I must set up the identity by hand on you raxample. But as I do not know the materials you want to set there I do not fully understand your case, what I notice is tht you have a potential point of singularity the spiky last triangle at the left top of your sphere you could have 3-4 materials as borders for a sigle thin sharp edge. Not necesarily the best for numerical stability. the link to a cercle and its tangeant is always delicate, it makes an infinetely sharp element edge One thing, do you need all boundaries as assembeld ? why not regroup some of your sections after the split, then COMSOl will automatically treat these as "continuity and you will end up with one or two true assembly indentity items Godd luck ivar
Andrew Prudil Nuclear Materials
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Posted: 1 decade ago Jun 8, 2010, 10:36 a.m. EDT
Thank you for the suggestions, Ivar. The geometry in the file I uploaded is not actually the geometry of interest, but a simple example where I think the imprint functionality fails when creating a mesh. If you look at the mesh near the circle, you can clearly see that the mesh nodes are not matched on either side of the boundary as is supposed to be the case for imprints.

After more experimenting I have found that I can make the imprint functionality work on some geometries but fail on others, and I'm not really sure what the difference is. Can you explain to me why the imprint functionality failed around the circle in the uploaded example? When I try other geometries and zoom in on the mesh that is created it appears that they do not work either (geometries without tangents for example)?

Any ideas? Can you direct me to an example in comsol 4.0 where this feature is used successfully?
Thank you for the suggestions, Ivar. The geometry in the file I uploaded is not actually the geometry of interest, but a simple example where I think the imprint functionality fails when creating a mesh. If you look at the mesh near the circle, you can clearly see that the mesh nodes are not matched on either side of the boundary as is supposed to be the case for imprints. After more experimenting I have found that I can make the imprint functionality work on some geometries but fail on others, and I'm not really sure what the difference is. Can you explain to me why the imprint functionality failed around the circle in the uploaded example? When I try other geometries and zoom in on the mesh that is created it appears that they do not work either (geometries without tangents for example)? Any ideas? Can you direct me to an example in comsol 4.0 where this feature is used successfully?

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