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 The information provided may be out of date.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.

Identity pairs, identity maps, continuity

Please login with a confirmed email address before reporting spam

Hello,

I'm using comsol 4.2 in 1D-PDE mode (weak form). My model is made of two domains( [O1 L1] and [O2 L2] ) on which are solved two different PDEs. There is only one variable for each PDE (u11 and u12).

In the attached mph file, there are 2 Dirichlet conditions at boundaries 1 and 4 and I would like to "link" the two domains by setting a "continuity" between boudaries 2 and 3 in order to have u11(L1)=u12(O2).

Do I have so set identity pairs or something else ?

Thank you,


1 Reply Last Post Feb 24, 2012, 2:37 a.m. EST
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 Feb 24, 2012, 2:37 a.m. EST
Hi

what about taking a look at this thread, here we discuss something close ;)

www.comsol.eu/community/forums/general/thread/26354/#p71571

You have not yet understood the fields (les champs) variables versus global variables, this is somewhat confusing in COMSOL as the notation for a dependent variable is only u11, but it means in a 1D temporal case u11(x,t), and in fact most variables are ONLY defined as fields.

With your case of distinct domains and physics, and no "common boundary" (assembly OR Union mode is no difference in your case, a formula applying to all domains must contain only global cvariables, or links to fileds that have been madde global via an integration or average or other coupling operator.

The way to pick any value of a point, and to get it as a global variable is to define a variable as the integration over a single point, the integration operator then gives you the definition on where to load in the "x" spatial value, and the sum over a single point is the value AT the point (it's somewhat heavy, but mathematically correct, and compatible with the COMSOL notation logic)

--
Good luck
Ivar
Hi what about taking a look at this thread, here we discuss something close ;) http://www.comsol.eu/community/forums/general/thread/26354/#p71571 You have not yet understood the fields (les champs) variables versus global variables, this is somewhat confusing in COMSOL as the notation for a dependent variable is only u11, but it means in a 1D temporal case u11(x,t), and in fact most variables are ONLY defined as fields. With your case of distinct domains and physics, and no "common boundary" (assembly OR Union mode is no difference in your case, a formula applying to all domains must contain only global cvariables, or links to fileds that have been madde global via an integration or average or other coupling operator. The way to pick any value of a point, and to get it as a global variable is to define a variable as the integration over a single point, the integration operator then gives you the definition on where to load in the "x" spatial value, and the sum over a single point is the value AT the point (it's somewhat heavy, but mathematically correct, and compatible with the COMSOL notation logic) -- 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.