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Joule Heating and Thermal Expansion

Posted Apr 15, 2015, 1:25 p.m. EDT MEMS & Nanotechnology, Heat Transfer & Phase Change, MEMS & Piezoelectric Devices, Geometry, Mesh, Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers, Structural Mechanics 2 Replies

Nisarg Gandhi
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Hello,

I'm trying to solve the problem of Joule Heating and Thermal Expansion by applying current via terminal.
Somehow I'm getting the following error.

"Failed to find a solution.
Singular matrix.

There are 246274 void equations (empty rows in matrix) for the variable comp1.V.
at coordinates: (1.25e-005,7.316e-005), (1.25472e-005,7.31286e-005), (1.25945e-005,7.30971e-005), (1.25e-005,7.308e-005), (1.25472e-005,7.30486e-005), ...
and similarly for the degrees of freedom (empty columns in matrix).
Returned solution is not converged."

I know some kind of BC are needed but I'm not able to figure it out.
Can someone please help me to find out which kind of BC is needed to solve the issue?
Or if there is any other problem?

My model can be found on this link:
1drv.ms/1b3ALa8
(I had to post a onedrive link as file size is higher.)
2 Replies Last Post Apr 15, 2015, 5:25 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 15, 2015, 2:06 p.m. EDT
Hi
First when you upload a file, start to remove the solution and the mesh: Solver -> Clear All Solutions, Mesh -> Clear All Mesh + File -> Compact Model. Then Save As with a new name ( I usually add an underscore "_" to the file name. And then upload, we can always rerun the simulation.

For you error, my guess is that you solve for. The Joule hearing and the structure over all domains and some of them have material properties that are not complete i.e. electric conductivity... But it's only a guess, need the model and access to my licence to get a better feeling.

--
Good luck
Ivar
Hi First when you upload a file, start to remove the solution and the mesh: Solver -> Clear All Solutions, Mesh -> Clear All Mesh + File -> Compact Model. Then Save As with a new name ( I usually add an underscore "_" to the file name. And then upload, we can always rerun the simulation. For you error, my guess is that you solve for. The Joule hearing and the structure over all domains and some of them have material properties that are not complete i.e. electric conductivity... But it's only a guess, need the model and access to my licence to get a better feeling. -- Good luck Ivar
Nisarg Gandhi
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Posted: 10 years ago Apr 15, 2015, 5:25 p.m. EDT
Hello Ivar,

Thanks a lot for your prompt reply.
Actually I started building a model in COMSOL 4.4 and then I noticed that by default COMSOL considers electric conductivity as "0". And this was the reason causing singularity of the matrix.

As it's a default value by COMSOL, I didn't notice it earlier.

Best regards,
Nisarg.

P.S. You are a great contributor to the community. For last 15 days I was facing many problems in COMSOL for this particular problem and your answers helped quite a lot. Thanks. :)
Hello Ivar, Thanks a lot for your prompt reply. Actually I started building a model in COMSOL 4.4 and then I noticed that by default COMSOL considers electric conductivity as "0". And this was the reason causing singularity of the matrix. As it's a default value by COMSOL, I didn't notice it earlier. Best regards, Nisarg. P.S. You are a great contributor to the community. For last 15 days I was facing many problems in COMSOL for this particular problem and your answers helped quite a lot. Thanks. :)

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