Menu

Discussion Forum

New Discussion
Filtra

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 The information provided may be out of date.

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.

Permanent magnet force calculation error

Posted 3 lug 2012, 07:33 GMT-4 Low-Frequency Electromagnetics Version 4.2a 5 Replies

Lorenz Eberhardt
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hello everybody,
I'm trying to compute the force between a sphere permanent magnet and a iron ball.
The system is successfully solved but when i try to compute the force I get a lot of failed to evaluate variable errors.
Anybody has an idea why I get this error?
Model is attached.

Attachments:

5 Replies Last Post 4 lug 2012, 07:39 GMT-4
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 3 lug 2012, 09:27 GMT-4
Hi

if you include the total force of source and destination = magnet and iattracted ron you should get a net "0" or thereabout. What about trying to solve for two forces, one for each shpere and compare the two (with opposed signes)

--
Good luck
Ivar
Hi if you include the total force of source and destination = magnet and iattracted ron you should get a net "0" or thereabout. What about trying to solve for two forces, one for each shpere and compare the two (with opposed signes) -- Good luck Ivar
Lorenz Eberhardt
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 3 lug 2012, 09:46 GMT-4
Thank you for your reply.
I don't get any result, I get the error message that the variable dnphi cannot be evaluated at the boundaries of the sphere no matter which sphere I choose.
The thing worked in 3 d, but I wanted to save computing force, so I did it in 2d axisymmetric.
The name of the variable (dnphi) shows also that I have probably done something wrong with the 2d axisymmtric geometry.
Thank you for your reply. I don't get any result, I get the error message that the variable dnphi cannot be evaluated at the boundaries of the sphere no matter which sphere I choose. The thing worked in 3 d, but I wanted to save computing force, so I did it in 2d axisymmetric. The name of the variable (dnphi) shows also that I have probably done something wrong with the 2d axisymmtric geometry.
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 4 lug 2012, 03:04 GMT-4
Hi

it did solve OK for me but I have v4.3, when I split the force (with different 2 names) into two.
But, I noticed that the error(differences) was quite large, I didnt have time to check out why. Back in 4.2 sometimes I got more preciese results with MF rather than MFNC, even if I had no curent. And from v3.5 I know that force estimation is very mesh density and mesh shape dependent

--
Good luck
Ivar
Hi it did solve OK for me but I have v4.3, when I split the force (with different 2 names) into two. But, I noticed that the error(differences) was quite large, I didnt have time to check out why. Back in 4.2 sometimes I got more preciese results with MF rather than MFNC, even if I had no curent. And from v3.5 I know that force estimation is very mesh density and mesh shape dependent -- Good luck Ivar
Lorenz Eberhardt
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 4 lug 2012, 07:17 GMT-4
Thank you, it worked when I took MF.
Thank you, it worked when I took MF.
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 4 lug 2012, 07:39 GMT-4
Hi

Interesting, I wounder what is so different between MF and MFNC, in case you find out pls report back

--
Good luck
Ivar
Hi Interesting, I wounder what is so different between MF and MFNC, in case you find out pls report back -- Good luck Ivar

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