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.

fluxes in convection diffusion model

Please login with a confirmed email address before reporting spam

Hey,
I'm trying to rebuild the semiconductor diode model from the comsol model library (v. 3.3) with comsol 5.2 and i have a problem concerning calculating the fluxes.
I used weak dirichlet bondary conditions and tried calculate the fluxes using the lagrange multipliers/the calculate boundary fluxes option. But the fluxes i get are neither conserved nor zero for the case where no voltage is applied, how can that happen within a stationary study?

Edit: Meanwhile, i rebuild the model in one dimension with comsol 4.4 and the problem still remains.

2 Replies Last Post 2016年8月18日 GMT-4 13:13

Please login with a confirmed email address before reporting spam

Posted: 8 years ago 2016年8月18日 GMT-4 10:30
UPDATE i now tried a the same problem with smaller dimensions (length of diode 1e-7m) and the error vanishes. Obvisiously it seems to scale with the length dimensions, does anyone have an idea? The mesh element size does not seem to have a big impact. except for jumps that happen in the space dependent current density that are increasing with smaller element size. So it seems to be a numerical problem.
UPDATE i now tried a the same problem with smaller dimensions (length of diode 1e-7m) and the error vanishes. Obvisiously it seems to scale with the length dimensions, does anyone have an idea? The mesh element size does not seem to have a big impact. except for jumps that happen in the space dependent current density that are increasing with smaller element size. So it seems to be a numerical problem.

Please login with a confirmed email address before reporting spam

Posted: 8 years ago 2016年8月18日 GMT-4 13:13
Problem solved by using the General Form PDE interface instead of the Convection-Diffusion module.
Problem solved by using the General Form PDE interface instead of the Convection-Diffusion module.

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.