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 The information provided may be out of date.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.

Finding the angle of a deformed surface?

Please login with a confirmed email address before reporting spam


Hi all,
I'm running a solid mechanics simulation where the two ends of a cylinder will get deformed/bent by a small amount.
When visualizing the results, how would I extract the angle of the surface?

My idea would be:
- derived values / surface integration over: nx
- derived values / surface integration over: ny
- derived values / surface integration over: nz

then normalize by the area of the surface, and calculate the direction of the average surface normal.

what's the most straightforward way to implement this?

thanks,
Anders

1 Reply Last Post 2013年3月20日 GMT-4 08:25
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 2013年3月20日 GMT-4 08:25
Hi

the angles w.r.t. the X,Y,Z coordinate are given by the COMSOL variables 0.5*(solid.curlUX, ...Y, ...Z)
As any Curl operator, these are obtained from differences of two "derivable" variables, so round-off errors might appear

These variables are fields hence depending on (x,y,z,t) so you need to average them over a domain or boundary, and if you use edges in 3D you have to test how these operators heritage their values from average of the local boundaries.

And do not forget that the average of a twisting surface remains often close to "0" rotation, even at high angles ;)

Now if you want to express that on boundary coordinates you need to do an appropriate coordinate transform

Another way is to use the Global variables from the Rigid Connector BC but this has the drawback to make your part also 100% rigid so you should apply these BC to parts that do not flex, only acting as "rigid bodies" on your model

--
Good luck
Ivar
Hi the angles w.r.t. the X,Y,Z coordinate are given by the COMSOL variables 0.5*(solid.curlUX, ...Y, ...Z) As any Curl operator, these are obtained from differences of two "derivable" variables, so round-off errors might appear These variables are fields hence depending on (x,y,z,t) so you need to average them over a domain or boundary, and if you use edges in 3D you have to test how these operators heritage their values from average of the local boundaries. And do not forget that the average of a twisting surface remains often close to "0" rotation, even at high angles ;) Now if you want to express that on boundary coordinates you need to do an appropriate coordinate transform Another way is to use the Global variables from the Rigid Connector BC but this has the drawback to make your part also 100% rigid so you should apply these BC to parts that do not flex, only acting as "rigid bodies" on your model -- 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.