Discussion Forum

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