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Current Source and Violation of Current Conservation

Posted Apr 22, 2015, 5:45 p.m. EDT Low-Frequency Electromagnetics, MEMS & Nanotechnology, Plasma Physics, RF & Microwave Engineering, MEMS & Piezoelectric Devices, Battery Design, Materials, Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers Version 4.3, Version 4.4 2 Replies

James Chinn
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Hi I'm using the electric currents interface. My model uses the "current source" feature and the solution COMSOL gives clearly violates current conservation. Has anyone else experienced this? And does anyone have an explanation of why this is happening - it doesn't make sense to me why this would be happening.

Thanks
James
2 Replies Last Post Apr 24, 2015, 6:21 p.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 10 years ago Apr 23, 2015, 2:53 a.m. EDT
Hi

my experience with COMSOL "violating" conservation laws are always due to poor model resolution, or approximation in defining the model. Items like mesh resolution, integration step ... nonphysical BC's or numerical singularities can easily introduce large errors. That is why model V&V is so important, and COMSOL, as you are doing it allows to check many variables by different means.

Now for us out here to be able to answer and consider your case in a better way, it would be much easier if you explained your model, or made a simplified version that you shear with us.

For me, when I see that my results from my COMSOL model is "violating" a law, I suspect first of all my model set-up and not the software, as COMSOL has been checked by many ways and by a large community.
But it happens, even for the best, that some typos enter the formulas under the hood, or that we users set up a case that was not well checked and that COMSOL need some corrections, so it's always worth to chase discrepancies to try to understand them, but that means studying in detail, not just broad statements.

--
Good luck
Ivar
Hi my experience with COMSOL "violating" conservation laws are always due to poor model resolution, or approximation in defining the model. Items like mesh resolution, integration step ... nonphysical BC's or numerical singularities can easily introduce large errors. That is why model V&V is so important, and COMSOL, as you are doing it allows to check many variables by different means. Now for us out here to be able to answer and consider your case in a better way, it would be much easier if you explained your model, or made a simplified version that you shear with us. For me, when I see that my results from my COMSOL model is "violating" a law, I suspect first of all my model set-up and not the software, as COMSOL has been checked by many ways and by a large community. But it happens, even for the best, that some typos enter the formulas under the hood, or that we users set up a case that was not well checked and that COMSOL need some corrections, so it's always worth to chase discrepancies to try to understand them, but that means studying in detail, not just broad statements. -- Good luck Ivar
James Chinn
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Posted: 10 years ago Apr 24, 2015, 6:21 p.m. EDT
Thanks Ivar,

You were right - upon reflection I noticed my boundary conditions were off.

James
Thanks Ivar, You were right - upon reflection I noticed my boundary conditions were off. James

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