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Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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3D Mesh refinement within a domain

Posted Jan 30, 2014, 11:46 p.m. EST Mesh Version 4.4 6 Replies

Michael Maurer
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Sorry to ask such a basic question, but how do you refine the mesh for a specific region (not an entire domain) in 3D.

I cannot get 'Mesh Control Domains' to work for me, but i think this would be ideal, where I could place a sphere and set everything within this sphere to be mesh controlled. However when I attempt this and put the sphere in the 'Domains to include' and click build, the active switch turns to off, and the sphere does not disappear, it remains as a solid object which gets meshed.

In 2D I can control the mesh as above using lines and mesh control boundaries as per the user guide p969. Also in 2d I can use 'size' with point or boundary, but this does not seem to work in 3d, or makes minimal difference. (though this solution would not be ideal anyway).

Thank you for any help offered.
6 Replies Last Post Feb 2, 2014, 6:33 p.m. EST
Lasse Murtomäki
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Posted: 1 decade ago Jan 31, 2014, 3:54 a.m. EST
Hi

Select Domain instead of Entire model when meshing. See attached picture.

BR
Lasse
Hi Select Domain instead of Entire model when meshing. See attached picture. BR Lasse

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Lasse Murtomäki
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Posted: 1 decade ago Jan 31, 2014, 3:57 a.m. EST
Sorry, I replied to a question you did not ask ;)
Sorry, I replied to a question you did not ask ;)
Michael Maurer
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Posted: 1 decade ago Jan 31, 2014, 6:47 a.m. EST
Hi Lasse, thank you for the reply.

But yes can anyone explain how to refine a mesh in a specific part of a domain instead of the entire domain?
Hi Lasse, thank you for the reply. But yes can anyone explain how to refine a mesh in a specific part of a domain instead of the entire domain?
Magnus Ringh COMSOL Employee

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Posted: 1 decade ago Jan 31, 2014, 8:03 a.m. EST
Hi,

I think you are on the right track but that you might have misinterpreted the mesh visualization in 3D, which only shows the surface mesh. If you add a sphere inside a block as a mesh control domain, and select it in a separate Free Tetrahedral node (for example) with its own Size subnode, and then add another Free Tetrahedral node to mesh the remaining geometry (that is, the part of the block surrounding the sphere), then the mesh in the sphere can be finer (or coarser). You may want to turn off the "Smooth across removed control entities" check box in the settings for the Free Tetrahedral node for the remaining geometry if you want to have a more distinct difference between the mesh sizes at either side of the boundary between the domains. It's also useful to add a Mesh plot to a 3D Plot Group, perhaps with a filter to include only some of the mesh elements. See the attached screen shot for an example.

Best regards,
Magnus Ringh, COMSOL
Hi, I think you are on the right track but that you might have misinterpreted the mesh visualization in 3D, which only shows the surface mesh. If you add a sphere inside a block as a mesh control domain, and select it in a separate Free Tetrahedral node (for example) with its own Size subnode, and then add another Free Tetrahedral node to mesh the remaining geometry (that is, the part of the block surrounding the sphere), then the mesh in the sphere can be finer (or coarser). You may want to turn off the "Smooth across removed control entities" check box in the settings for the Free Tetrahedral node for the remaining geometry if you want to have a more distinct difference between the mesh sizes at either side of the boundary between the domains. It's also useful to add a Mesh plot to a 3D Plot Group, perhaps with a filter to include only some of the mesh elements. See the attached screen shot for an example. Best regards, Magnus Ringh, COMSOL
Michael Maurer
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Posted: 1 decade ago Jan 31, 2014, 11:56 p.m. EST
Hi Magnus,
Thank you for your reply, the screenshot is exactly what I am trying to achieve. I assume the sphere originally protruded out of the block and then disappeared when it was made a mesh control domain? However when I try to make the sphere a mesh control domain, it does not work (as described in my first post). The sphere remains as a solid piece of geometry being modelled.

Thanks for any help.
Hi Magnus, Thank you for your reply, the screenshot is exactly what I am trying to achieve. I assume the sphere originally protruded out of the block and then disappeared when it was made a mesh control domain? However when I try to make the sphere a mesh control domain, it does not work (as described in my first post). The sphere remains as a solid piece of geometry being modelled. Thanks for any help.
Michael Maurer
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Posted: 1 decade ago Feb 2, 2014, 6:33 p.m. EST
Can you use a mesh control domain to refine a mesh within a domain without the mesh control domain contributing to the actual geometry?

See attached picture as an example: I want to refine the mesh in my square object. I have used a circular mesh control domain, which seems to work if the circle is completely enclosed by the square, but if the circle is outside the square then the domain outside the square is meshed like it is part of the actual geometry (which it is not). Obviously it is easy in this example to control the mesh with better geometry of a mesh control domain, but I am trying to understand how to control the mesh in a complex 3D model.

Is this just not possible with a mesh control domain? Then how do you control the mesh within a complex 3D domain (without refining the entire domain)?

Thanks for any help.
Can you use a mesh control domain to refine a mesh within a domain without the mesh control domain contributing to the actual geometry? See attached picture as an example: I want to refine the mesh in my square object. I have used a circular mesh control domain, which seems to work if the circle is completely enclosed by the square, but if the circle is outside the square then the domain outside the square is meshed like it is part of the actual geometry (which it is not). Obviously it is easy in this example to control the mesh with better geometry of a mesh control domain, but I am trying to understand how to control the mesh in a complex 3D model. Is this just not possible with a mesh control domain? Then how do you control the mesh within a complex 3D domain (without refining the entire domain)? Thanks for any help.

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