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.

Unknown variable in COMSOL AC/DC module

Please login with a confirmed email address before reporting spam

Hi everyone.

I have some problem in AC/DC module with simulation of external surface charge accumulation on dielectric shielding. After defined 4 boundaries wich are surfaces of dielectirc shielding while computing solution appears an error shown below:

Failed to evaluate variable.
- Variable: nF
- Geometry: 1
- Boundary: 4 5 6 12
Failed to evaluate expression.
- Expression: d((test(mod1.es.sigs)*(mod1.es.sigst-nF-nFe)*mod1.es.d)*(dvol),{test@3}).

I have no idea what are this nF and nFe variable. Anyone knows what this nF and nFe means? Best regards Rafał


1 Reply Last Post 3 dic 2021, 04:49 GMT-5
Lipeng Liu COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 3 years ago 3 dic 2021, 04:49 GMT-5
Updated: 3 years ago 3 dic 2021, 05:11 GMT-5

Hi Rafał,

I think what will help you out here, is the Equation View in the COMSOL Desktop. It will help you investigate the equations (and variables) used in a physics feature.

In this case, you can see the variables nF and nFe refer to the Normal ion current density and Normal electron current density, respectively.

However, without seeing your model, it is difficult to provide you an anwer about why the error appears. Please send the model to our customer support: https://www.comsol.com/support

Regards, Lipeng

Hi Rafał, I think what will help you out here, is the Equation View in the COMSOL Desktop. It will help you investigate the equations (and variables) used in a physics feature. In this case, you can see the variables nF and nFe refer to the Normal ion current density and Normal electron current density, respectively. However, without seeing your model, it is difficult to provide you an anwer about why the error appears. Please send the model to our customer support: https://www.comsol.com/support Regards, Lipeng

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.