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Adding an extra variable

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Hello,
I'm considering a diffusion problem, where I have several species in a solution and couple of electrodes. Additionaly to the field variables c1,c2... (i.e. concentrations of different species) I would like to add an extra variable Ep(t) - the potential of one of the electrodes which is defined by a certain constraint. This constraint actually signifies a constant value of the sum of fluxes of all species over the whole electrode. The important point is that the Ep is not explicitly encountered in this constraint, but only implicitly through the boundary condition which couples fluxes and potential.

How can I do this with Comsol?
I've tried to add a 'Global Constraint', but since Ep(t) is not explicitly encountered in the condition I can't understand how to link it with the boundary condition.

Thank you in advance.

0 Replies Last Post Apr 25, 2012, 5:12 a.m. EDT
COMSOL Moderator

Hello Oleksandr Oliynyk

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