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.

Cauchy boundary conditions

Please login with a confirmed email address before reporting spam

Hi all,

I have a domain with a circular boundary. On this circular boundary, I want to implement Cauchy bcs - that is for a function u, I want to specify u and -n * grad(u) on the boundary. How exactly do I do this? In COMSOL, it seems that by choosing the Dirichlet bcs (from Physics -> Boundary settings --> etc.) we can almost do this because there are two equations to set: 1) R = 0 and 2) -n* (grad(u) +...) = G + dR/du^T * mu = 0. We can set R = u - c, to have u = c at the boundary. To set the normal derivative of u at the boundary, we can specify G appropriately, but then we have this Lagrange multiplier term. I want to get rid of this, that is to just have -n*grad(u) = G. How do I do this?

Thanks,
John Smith

0 Replies Last Post 28 dic 2010, 01:25 GMT-5
COMSOL Moderator

Hello John Smith

Your Discussion has gone 30 days without a reply. If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help.

If you do not hold an on-subscription license, you may find an answer in another Discussion or in the Knowledge Base.

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.