Menu

Discussion Forum

New Discussion
Filter

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 The information provided may be out of date.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.

gradient of divergence

Posted Apr 20, 2014, 8:55 a.m. EDT Parameters, Variables, & Functions Version 4.4 2 Replies

Tianyu Dong
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hi all,

Is it possible to represent the gradient of the divergence of a vector field in the Coefficient Form PDE other than using the Weak Form?

Thanks,
Tony
2 Replies Last Post Apr 21, 2014, 6:21 a.m. EDT
Pu Zhang
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 20, 2014, 10:16 a.m. EDT
Definitely you can. But I think you need to somehow manipulate the form of the expression in order to do that.
Definitely you can. But I think you need to somehow manipulate the form of the expression in order to do that.
Tianyu Dong
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 21, 2014, 6:21 a.m. EDT
Thanks Pu.
We have:
grad div F = [F1xx+F2yx, F1xy+F2yy]; (1)
div(c*grad F) = [c11*(F1xx+F1yy)+c12*(F2xx+F2yy), c21*(F1xx+F1yy)+c22*(F2xx+F2yy)] (2)
where c=[c11, c12; c21, c22], hence, it seems to me that mixed partial derivative terms in (1) never appear no matter how to choose the coefficient c if we use the Coefficient Form PDE to represent the gradient of divergence. Am I correct?

Thanks,
Tony
Thanks Pu. We have: grad div F = [F1xx+F2yx, F1xy+F2yy]; (1) div(c*grad F) = [c11*(F1xx+F1yy)+c12*(F2xx+F2yy), c21*(F1xx+F1yy)+c22*(F2xx+F2yy)] (2) where c=[c11, c12; c21, c22], hence, it seems to me that mixed partial derivative terms in (1) never appear no matter how to choose the coefficient c if we use the Coefficient Form PDE to represent the gradient of divergence. Am I correct? Thanks, Tony

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