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meshing a cylinder

Posted Oct 25, 2012, 7:15 a.m. EDT Geometry, Mesh Version 5.2 15 Replies

Blair Kirkpatrick
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Hi All,

I have been having some issues meshing a cylinder. When you define a cylinder in COMSOL, it splits the curved face into 4 quarters, and as a result, when I went to mesh the cylinder I was irregularities at these 4 points, where the mesh is clearly trying to conform to these 4 lines.
I would like to know how to solve this problem, so that my mesh is uniform around the length of this curved face. I have tried to get COMSOL to ignore the four edges, and I have also had it make a single composite face from the four individual ones. In both cases, when it came to meshing, the mesh acted like these lines were still there.

Any ideas?


B
15 Replies Last Post Nov 6, 2016, 3:19 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 Oct 25, 2012, 9:05 a.m. EDT
Hi

what about meshing the end surface i.e in tri() and then use a sweep mesh down the surface, that should better follow the "lines"

--
Good luck
Ivar
Hi what about meshing the end surface i.e in tri() and then use a sweep mesh down the surface, that should better follow the "lines" -- Good luck Ivar
Blair Kirkpatrick
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Posted: 1 decade ago Oct 25, 2012, 10:54 a.m. EDT
Ivar,

my problem is that I DON'T want them to follow these lines. From what I can work out, the mesh shouldn't "see" these lines, as I have gotten rid of them in the geometry.
Ivar, my problem is that I DON'T want them to follow these lines. From what I can work out, the mesh shouldn't "see" these lines, as I have gotten rid of them in the geometry.
Jeff Hiller COMSOL Employee

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Posted: 1 decade ago Oct 25, 2012, 11:02 a.m. EDT
Have you tried using Virtual Operations (under Geometry) to remove those lines?
Have you tried using Virtual Operations (under Geometry) to remove those lines?
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago Oct 25, 2012, 11:11 a.m. EDT
I tried Virtual Topology for a cylinder before to get rid of those lines but I believe it did not work. The resulting mesh however was always quite uniform and satisfactory. Blair maybe you can elaborate on what you find unacceptable about that mesh.
I tried Virtual Topology for a cylinder before to get rid of those lines but I believe it did not work. The resulting mesh however was always quite uniform and satisfactory. Blair maybe you can elaborate on what you find unacceptable about that mesh.
Jeff Hiller COMSOL Employee

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Posted: 1 decade ago Oct 25, 2012, 11:35 a.m. EDT
Geometry>Virtual Operations>Ignore Edges can definitely be used to remove those lines, if needed. See attached screenshot.
Geometry>Virtual Operations>Ignore Edges can definitely be used to remove those lines, if needed. See attached screenshot.

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Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago Oct 25, 2012, 11:56 a.m. EDT
Thanks Jeff. I just tried it now on my own cylinder :) and it doesn't work. Am I doing it differently? See attachment.
Thanks Jeff. I just tried it now on my own cylinder :) and it doesn't work. Am I doing it differently? See attachment.
Jeff Hiller COMSOL Employee

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Posted: 1 decade ago Oct 25, 2012, 12:25 p.m. EDT
Interesting.It seems that depending on the aspect ratio and depending on your mesh fineness setting the lines are either present in the mesh or not. My guess is that in the case where the lines are present it's because although the mesher is not forced to put nodes along those lines it decides to do so anyways on its own. This is only a guess though.
Interesting.It seems that depending on the aspect ratio and depending on your mesh fineness setting the lines are either present in the mesh or not. My guess is that in the case where the lines are present it's because although the mesher is not forced to put nodes along those lines it decides to do so anyways on its own. This is only a guess though.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Oct 25, 2012, 1:44 p.m. EDT
Hi

Well and I never try to remove them, as mostly I add such lines to force the mesher to be more symmetric ;)

--
Good luck
Ivar
Hi Well and I never try to remove them, as mostly I add such lines to force the mesher to be more symmetric ;) -- Good luck Ivar
Blair Kirkpatrick
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Posted: 1 decade ago Oct 26, 2012, 7:06 a.m. EDT
Yeah, that is exactly the problem I faced. Getting rid of the lines DID get rid of the lines, and yet the meshing somehow still saw them. I am trying to use quite a fine mesh (which I can't really avoid) so maybe that is the problem.

Thanks to all of you for your help, just seems a very strange problem.

B
Yeah, that is exactly the problem I faced. Getting rid of the lines DID get rid of the lines, and yet the meshing somehow still saw them. I am trying to use quite a fine mesh (which I can't really avoid) so maybe that is the problem. Thanks to all of you for your help, just seems a very strange problem. B
Jesus Lucio
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Posted: 1 decade ago Oct 26, 2012, 11:32 a.m. EDT
Hello to all,

I don't know if Blair is saying it in the last message, but I get rid of the lines if I ignore BOTH the vertices AND the edges of the cylinder. I send the image.

Jesus.
Hello to all, I don't know if Blair is saying it in the last message, but I get rid of the lines if I ignore BOTH the vertices AND the edges of the cylinder. I send the image. Jesus.
Boris Breuer
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Posted: 1 decade ago Feb 12, 2014, 8:59 a.m. EST
Hi,

I stumbled upon this thread trying to create a hollow cylinder mesh in COMSOL.
Suffice to say all your help did not help, at least not for COMSOL 4.3b.
The way I did manage to mesh my hollow cylinder (as can be seen in the attached image) was by ignoring the inner faces while keeping the checkbox "ignore adjacent edges and vertices" checked.

COMSOL 4.3b solution:
geometry→right-click→virtual operations→ignore faces

Greetings,

Boris
Hi, I stumbled upon this thread trying to create a hollow cylinder mesh in COMSOL. Suffice to say all your help did not help, at least not for COMSOL 4.3b. The way I did manage to mesh my hollow cylinder (as can be seen in the attached image) was by ignoring the inner faces while keeping the checkbox "ignore adjacent edges and vertices" checked. COMSOL 4.3b solution: geometry→right-click→virtual operations→ignore faces Greetings, Boris
Yi Yan
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Posted: 10 years ago Feb 16, 2015, 3:09 a.m. EST
Hi Ivar

I have a little bit different question but on the same topic -- meshing a cylinder.
As you mentioned we can mesh on one surface and do sweep all the way to the one surface. However, I cannot find a way to mesh structured grid on the source surface which can be easily done on rectangular surface, please see attachment if you don't mind. In that picture, I have extremely fine mesh near the four walls (almost like black strips) where my boundaries locate.
So if I want to do the same thing for a pipe, extremely fine mesh near the walls, could I accomplish this task in comsol by any ways?
Thank you very much.

Yi
Hi Ivar I have a little bit different question but on the same topic -- meshing a cylinder. As you mentioned we can mesh on one surface and do sweep all the way to the one surface. However, I cannot find a way to mesh structured grid on the source surface which can be easily done on rectangular surface, please see attachment if you don't mind. In that picture, I have extremely fine mesh near the four walls (almost like black strips) where my boundaries locate. So if I want to do the same thing for a pipe, extremely fine mesh near the walls, could I accomplish this task in comsol by any ways? Thank you very much. Yi

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Lasse Murtomäki
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Posted: 10 years ago Feb 16, 2015, 3:52 a.m. EST
Hi

If you can use 2D axisymmetric model, it can be done with meshing first the top and bottom of lines with

Edge --> Distribution -->

and then mapped mesh in the pipe. See attached a suggestion.

br
Lasse
Hi If you can use 2D axisymmetric model, it can be done with meshing first the top and bottom of lines with Edge --> Distribution --> and then mapped mesh in the pipe. See attached a suggestion. br Lasse

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Haitian Hao
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Posted: 8 years ago Nov 4, 2016, 5:13 p.m. EDT
Hi Yi,

Have you solved this problem? I have exactly the same question with you! Really what to know how to mesh a circular face like this! (Finer near the edge and coarser at the center).

Thanks,
Haitian
Hi Yi, Have you solved this problem? I have exactly the same question with you! Really what to know how to mesh a circular face like this! (Finer near the edge and coarser at the center). Thanks, Haitian
Lasse Murtomäki
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Posted: 8 years ago Nov 6, 2016, 3:19 a.m. EST
How about this? Due to geometry the center is bound to be tightly meshed.

Lasse
How about this? Due to geometry the center is bound to be tightly meshed. Lasse

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