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Torsional waves propagate in cylinder using 2D axis-symmetric module?

Posted Jun 8, 2021, 4:09 a.m. EDT Structural & Acoustics, Acoustics & Vibrations Version 5.6 3 Replies

Hao Qiu
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Hi,

I am going to simulate a torsional waves propagating problems using the structural mechanics module in COMSOL v5.6. The wave guide is a rod with a hole and the waves are propagating along the axial direction.

Since the geometry is axis-symmetric, I want to use 2D axisymmetric boundary condition to simulate this problem.

Cyclic boundary in 3D can be a solution but it is still time consuming because I wave to simulate wave at high frequency.

I have seen similar problem described in online paper and the author solve the problem in 2D axis-symmetric. The paper is Scattering of the fundamental shear horizontal mode from steps and notches in plates published in JASA in 2003. The author wrote: "The advantage is that the axisymmetric analysis allows displacements in the direction normal to the element ~the circumferential direction!; this degree of freedom is included in most implementations of axisymmetric elements in order to allow analyses of problems with nonzero circumferential harmonics."

However, I can only find Tr (radial) and Tz (axial) when I add a "boundary load" in COMSOL.

I wonder if this kind of problem can not be solve in COMSOL in a 2D way?

If it can be solved, how can I do it?

Thanks

Hao

3 Replies Last Post Jun 18, 2021, 4:42 p.m. EDT
Jeff Hiller COMSOL Employee

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Posted: 3 years ago Jun 8, 2021, 9:31 a.m. EDT

Hello Hao,

Your post is quite timely: we are working on adding this capability in our next release, planned for the Fall.

Best,

Jeff

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Jeff Hiller
Hello Hao, Your post is quite timely: we are working on adding this capability in our next release, planned for the Fall. Best, Jeff
Hao Qiu
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Posted: 3 years ago Jun 8, 2021, 10:05 a.m. EDT
Updated: 3 years ago Jun 8, 2021, 10:56 a.m. EDT

Hi Jeff,

That would be great!

I found there are special "General Axisymmetric Elements" in some commercial softwares for solving this kind of problem (axisymmetric geometry with non-axisymmetric load--especially torsional load).

If the new capability in COMSOL v5.7 can be used to solve axisymmetric geometry with non-axisymmetric load? Or with torsional load only?

Anyway, it's great to hear this news! Can't wait to try it! Thank you for your effort in improving COMSOL.

Best regards, Hao

Hi Jeff, That would be great! I found there are special "General Axisymmetric Elements" in some commercial softwares for solving this kind of problem (axisymmetric geometry with non-axisymmetric load--especially torsional load). If the new capability in COMSOL v5.7 can be used to solve axisymmetric geometry with non-axisymmetric load? Or with torsional load only? Anyway, it's great to hear this news! Can't wait to try it! Thank you for your effort in improving COMSOL. Best regards, Hao
Henrik Sönnerlind COMSOL Employee

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Posted: 3 years ago Jun 18, 2021, 4:42 p.m. EDT

Non-axisymmetric loads would require a Fourier decomposition of the load, and a harmonic series of displacements to be summed. Although this is in principal possible, it is not within the scope of the project for the upcoming release. Actually, the gain when compared to a full 3D model is probably not that large, and it will be limited to linear problems. It can have certain advantages in terms of computational efficiency, but it also comes with a cost in terms of complicated pre- and postprocessing.

Note that you, already in 5.6, can allow general circumferential displacements for studies in frequency domain (the Circumferential mode extension option).

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Henrik Sönnerlind
COMSOL
Non-axisymmetric loads would require a Fourier decomposition of the load, and a harmonic series of displacements to be summed. Although this is in principal possible, it is not within the scope of the project for the upcoming release. Actually, the gain when compared to a full 3D model is probably not that large, and it will be limited to linear problems. It can have certain advantages in terms of computational efficiency, but it also comes with a cost in terms of complicated pre- and postprocessing. Note that you, already in 5.6, can allow general circumferential displacements for studies in frequency domain (the *Circumferential mode extension* option).

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

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