Menu

Discussion Forum

New Discussion
查找

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 The information provided may be out of date.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.

How to define a surface charge that depends on electrostatic potential (stationary solver)

Posted 2011年10月21日 GMT-4 15:08 Low-Frequency Electromagnetics, Materials, Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers Version 4.2 2 Replies

George123
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hi There,

I am using COMSOL 4.2 and I have a 1D electrostatic model. At one boundary, I have a simple fixed potential boundary condition, which is no problem to implement. At the other boundary, I would like to define a surface charge density that depends on the potential at that same boundary. For example, it would be similar to the following equation: Q[C/m^2] = Q_0*exp(-phi/E_A). I would then like the solver to calculate the appropriate value of phi (electric potential) at the boundary and elsewhere in the model, based on the constraint between phi and the surface charge defined at the boundary (which depends on phi).

Does anyone know how I can do this? It seems there should be an easy, straightforward way to define a self-referencing boundary condition.

Thanks in advance,

George
2 Replies Last Post 2012年5月10日 GMT-4 05:01
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 2011年10月22日 GMT-4 06:12
Hi

in the doc of 3.5 somewhere there was an example (or was it the Model library?) of a thermal case (rectangle) where one boundary was driven by an an equation based ont he integration of another boundary.

The way to mix new variables Global with weak constrains, integration coupling operators is very nice in COMSOL, but you need to train it a litle when you start ;). Try to sketch out on a peac of paper hwat you want to do, the variables linkled, the one missing, and I'm sure you'll find it out

--
Good luck
Ivar
Hi in the doc of 3.5 somewhere there was an example (or was it the Model library?) of a thermal case (rectangle) where one boundary was driven by an an equation based ont he integration of another boundary. The way to mix new variables Global with weak constrains, integration coupling operators is very nice in COMSOL, but you need to train it a litle when you start ;). Try to sketch out on a peac of paper hwat you want to do, the variables linkled, the one missing, and I'm sure you'll find it out -- Good luck Ivar
Peng Wang
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 2012年5月10日 GMT-4 05:01
How about your case, George?
Now I'm aslo facing some questions similar to yours.
Maybe we could help each other for the topic defining a changeable surface charge density vs. some parameters.
How about your case, George? Now I'm aslo facing some questions similar to yours. Maybe we could help each other for the topic defining a changeable surface charge density vs. some parameters.

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