Menu

Discussion Forum

New Discussion
Filter

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.

Variable Coefficients in Coefficient form PDE

Posted May 21, 2020, 5:46 p.m. EDT Parameters, Variables, & Functions, Equation-Based Modeling Version 5.3 2 Replies

Kyle
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hello,

I am working to solve the following two equations in the attached images in COMSOL for a non-dimensionalized reaction diffusion problem. I am using the coefficient form PDE module in COMSOL 5.3. For some reason, the result I obtain is vastly different depending on if I define the term to be inside d_a (the damping coefficient), or if i divide the whole equation by and define c (the diffusion coefficient) and f (the source term) appropriately. These two cases should be entirely equivalent, but they are significantly different. Why? Which is correct?

Thank you!

Attachments:

2 Replies Last Post May 22, 2020, 9:47 a.m. EDT
Jeff Hiller COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 5 years ago May 21, 2020, 6:52 p.m. EDT
Updated: 5 years ago May 21, 2020, 6:54 p.m. EDT

You can't simply move the (1-r^2) term inside the divergence, if I understand correctly what you're doing.

is not the same as

Jeff

-------------------
Jeff Hiller
You can't simply move the (1-r^2) term inside the divergence, if I understand correctly what you're doing. 1/(2*(1-r^2))*\nabla . \nabla \phi is not the same as \nabla . ((1/(2*(1-r^2))*\nabla \phi) Jeff
Kyle
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 5 years ago May 22, 2020, 9:47 a.m. EDT
Updated: 5 years ago May 22, 2020, 9:47 a.m. EDT

aha - i'm just incapable of reading the equation in comsol properly, of course they are not the same.. thanks..

aha - i'm just incapable of reading the equation in comsol properly, of course they are not the same.. thanks..

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