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.

Conductive Media DC Application with nonlinear Boundary Conditions

Please login with a confirmed email address before reporting spam

Hello,

I want to simulate a voltage distribution. My geometry has a dirichlet boundary condition at the outflow (constant electric voltage) and should have a nonlinear inflow boundary condition. The other boundaries are electrical insulated.

But at the moment I am not sure how to achieve the nonlinear boundary condition. I hope anybody can help me. I am using the Conductive Media DC Application on COMSOL 3.5a.

The nonlinear inward current flow should depend on the potential at the boundary and a constant potential Vref. This means my boundary condition should look like this:
-n J = f ( Vref - V) , where
- J is the current density
- f is a nonlinear function (e.g. exp (...) + xy)
- Vref is a constant potential at a back contact
- V is the unknown potential at the boundary

I have tried to define a function f and to select the boundary condition "inward current flow". Then I have inserted f(-5 - V), for Vref=-5. This seems to work, when I click on solve their are no error messages, but I am not sure if this really works, because COMSOL cannot solve a nonlinear PDE with a linear solver, or? And now when I click on the boundary condition of the inflow boundary the unit is marked red, what does this mean?

I hope you can help me or have some helpful suggestions how to simulate this nonlinear boundary condition. Please contact me, if you need further information.

Thanks in advance, Felix



1 Reply Last Post May 20, 2010, 11:14 a.m. EDT

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago May 20, 2010, 11:14 a.m. EDT
Hi,

I found out that the red colored unit at my boundary setting means inconsistent unit and that the modification f(Vref - V[1/V]) eliminates the warning.

But I am still not sure, if my procedure is correct. Can anybody help me and tell me how to model a nonlinear boundary condition using the Conductive Media DC Application Model as described before? Can COMSOL automatically detect the nonlinearity? Which solver does COMSOL take?

Thanks in advance. Kind regards,
Felix
Hi, I found out that the red colored unit at my boundary setting means [b]inconsistent unit[/b] and that the modification [b]f(Vref - V[1/V])[/b] eliminates the warning. But I am still not sure, if my procedure is correct. Can anybody help me and tell me how to model a nonlinear boundary condition using the Conductive Media DC Application Model as described before? Can COMSOL automatically detect the nonlinearity? Which solver does COMSOL take? Thanks in advance. Kind regards, Felix

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.