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How to take Advantage of Symmetry

Posted Feb 27, 2012, 5:05 a.m. EST Version 4.2 5 Replies

Sanjay Mukuntha Madhava
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I am modelling a device that is Symmetrical. How do i instruct COMSOL that the model is symmetrical and that it can perform calculations on only 1/4th of the Model and then integrate the result over the whole model.

Thanks and Regards
Sanjay
5 Replies Last Post Jun 23, 2017, 11:51 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 Feb 27, 2012, 6:01 a.m. EST
Hi

you need to use the symmetry boundaries (and take some care about fixed / free DoFs, as well as mode mapping if you look into eigenfrequenceies with symmetry, as then you must distinguis symmetry and antisymmetry modes.

If you look up the model library and the doc there are several examples therein with symmetries

--
Good luck
Ivar
Hi you need to use the symmetry boundaries (and take some care about fixed / free DoFs, as well as mode mapping if you look into eigenfrequenceies with symmetry, as then you must distinguis symmetry and antisymmetry modes. If you look up the model library and the doc there are several examples therein with symmetries -- Good luck Ivar
Sanjay Mukuntha Madhava
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Posted: 1 decade ago Feb 27, 2012, 6:11 a.m. EST
And where can i specify the symmetry boundary?
I have attached the model that i am working on
The deflection in the Z-axis is of interest, figured out it would be faster to compute in 2D but then again there i was not able to plot the deflection in the Z-axis.
It would be great if someone can help me out here.

Thanks and Regards
Sanjay
And where can i specify the symmetry boundary? I have attached the model that i am working on The deflection in the Z-axis is of interest, figured out it would be faster to compute in 2D but then again there i was not able to plot the deflection in the Z-axis. It would be great if someone can help me out here. Thanks and Regards Sanjay

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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 Feb 27, 2012, 8:20 a.m. EST
Hi

you need to cut a cake slice of 1/4 or 1/8 or even 1/16, starting from the centre, then apply symmetry boundaries on the two planar cacke boundaries passing through the axis of symmetry (and perhaps through a plane perpendicular to the exis of symmetry.

Note a symmetrical model build up with SYM or ANTISYM BC will have only responses compatible with these symmetric boundaries, and the loading should be symmetric 7 antisymmetric too

But one can also think along the lines of replacing the central cylinder by a rigid element and model only the beams first, then look at the plate modes.

However, in full volumetric mode one do not need to consider the overall hypotheses if each simplification. but there is the meshing issue, life is tough ;)

--
Good luck
Ivar
Hi you need to cut a cake slice of 1/4 or 1/8 or even 1/16, starting from the centre, then apply symmetry boundaries on the two planar cacke boundaries passing through the axis of symmetry (and perhaps through a plane perpendicular to the exis of symmetry. Note a symmetrical model build up with SYM or ANTISYM BC will have only responses compatible with these symmetric boundaries, and the loading should be symmetric 7 antisymmetric too But one can also think along the lines of replacing the central cylinder by a rigid element and model only the beams first, then look at the plate modes. However, in full volumetric mode one do not need to consider the overall hypotheses if each simplification. but there is the meshing issue, life is tough ;) -- Good luck Ivar
Wenle Weng
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Posted: 8 years ago Jun 23, 2017, 11:07 a.m. EDT
Hi Ivar,

I found this old thread as I have the same question. I just don't know exactly how to apply the symmetry/asymmetry BC to a 3D solid object. Are there any example models that I can look into? Many thanks!
Hi Ivar, I found this old thread as I have the same question. I just don't know exactly how to apply the symmetry/asymmetry BC to a 3D solid object. Are there any example models that I can look into? Many thanks!
Walter Frei COMSOL Employee

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Posted: 8 years ago Jun 23, 2017, 11:51 a.m. EDT
Hello,

If you'd like to find examples related to a topic such as "Symmetry" what you can do is go to the Application Library (go to the File Menu > Application Library) and then, within the "Search" field, enter your term of interest, such as "symmetry".

You'll find that a significant fraction of the example applications do exploit symmetry (in various ways) to reduce the model size.

Also, when using the Application Library, make sure to click the "Update COMSOL Application Libraries" button to download the latest updates, and newer examples, from our website.

You can also search these examples directly via our web page, so, for example:
www.comsol.com/search/?s=symmetry&subset=model_gallery


Best Regards,
Hello, If you'd like to find examples related to a topic such as "Symmetry" what you can do is go to the Application Library (go to the File Menu > Application Library) and then, within the "Search" field, enter your term of interest, such as "symmetry". You'll find that a significant fraction of the example applications do exploit symmetry (in various ways) to reduce the model size. Also, when using the Application Library, make sure to click the "Update COMSOL Application Libraries" button to download the latest updates, and newer examples, from our website. You can also search these examples directly via our web page, so, for example: https://www.comsol.com/search/?s=symmetry&subset=model_gallery Best Regards,

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