Menu

Discussion Forum

New Discussion
Filter

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Volume integration

Posted Nov 23, 2009, 5:06 p.m. EST 3 Replies

Johan Gustafsson
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hi,

I am a COMSOL-beginner with what I guess might be a quite basic question. How (if possible) can I use Subdomain Integration Variables to get the volume of a subdomain in 2D axisymmetry mode. I need to set the density of a domain from the mass.

Thanks,
Johan
3 Replies Last Post Dec 18, 2009, 6:14 a.m. EST
Michael Hochman
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Nov 23, 2009, 7:32 p.m. EST
An easy way would just be to define a subdomain integration coupling variable, name it "volume," and use 1 as your expression. Now your volume variable will contain the actual volume of that subdomain. I just tried this method for a simple rectangular geometry and it seems to work fine.

I should point out that I tried this with plane-strain mode, I'm not sure if you need to do anything differently for axisymmetric mode. But you can easily try it with simple geometry (that you know the answer to) and see if it works.

Good luck,

Mike
An easy way would just be to define a subdomain integration coupling variable, name it "volume," and use 1 as your expression. Now your volume variable will contain the actual volume of that subdomain. I just tried this method for a simple rectangular geometry and it seems to work fine. I should point out that I tried this with plane-strain mode, I'm not sure if you need to do anything differently for axisymmetric mode. But you can easily try it with simple geometry (that you know the answer to) and see if it works. Good luck, Mike
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Nov 27, 2009, 5:55 p.m. EST
Hi

for axisymmetry you must use the "2*pi*r" with some care, it can be applied by a click for the BC (boundary conditions since 3.5) but must be applied by "hand" for boundary integration variables.

As suggested, by trying out on simple cases, and studying the units of COMSOL you can find easily the correct dimensions to apply (always check units 30 years later I start to understand that statement from my physics teacher ;)

COMSOL requires some "thinking" and pysics knowledge, but it has far more freedom than other "out-of the box" FEM programmes.

Good luck
Ivar
Hi for axisymmetry you must use the "2*pi*r" with some care, it can be applied by a click for the BC (boundary conditions since 3.5) but must be applied by "hand" for boundary integration variables. As suggested, by trying out on simple cases, and studying the units of COMSOL you can find easily the correct dimensions to apply (always check units 30 years later I start to understand that statement from my physics teacher ;) COMSOL requires some "thinking" and pysics knowledge, but it has far more freedom than other "out-of the box" FEM programmes. Good luck Ivar
Johan Gustafsson
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Dec 18, 2009, 6:14 a.m. EST
Thanks! Works great!

Regards,
Johan
Thanks! Works great! Regards, Johan

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.

Suggested Content