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Convergence Problem

Posted 24.01.2017, 05:22 GMT-5 Heat Transfer & Phase Change, Studies & Solvers Version 5.1 4 Replies

Antia Gomez
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Hello Everyone!

A beginner of COMSOL software calls for help. Even though it is a thorough model with simple geometry, it doesn't converge.

When I add Heat Source term to the model it fails to converge if the range is selected to end around 20ms. Practically it shouldn't bring up any problems since Qgen term kicks in until 723K.

To me it feels like a solver problem. The values and material info are taken from an article meaning they are supposed to be correct.

Any ideas to solve this?

Thanks in advance.

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4 Replies Last Post 25.01.2017, 01:52 GMT-5
Sergei Yushanov Certified Consultant
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Posted: 8 years ago 24.01.2017, 13:02 GMT-5
Antia,

Attached please find converged model - it was slightly under-meshed.

Regards,
Sergei
Antia, Attached please find converged model - it was slightly under-meshed. Regards, Sergei
Antia Gomez
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Posted: 8 years ago 24.01.2017, 13:45 GMT-5
Thanks for your help Sergei! But unfortunately your COMSOL version is higher than mine therefore I cant open it, can you please explain what you did while refining the mesh? Also does it give any result when time is selected as 30ms, 40ms and 50ms?
Thanks for your help Sergei! But unfortunately your COMSOL version is higher than mine therefore I cant open it, can you please explain what you did while refining the mesh? Also does it give any result when time is selected as 30ms, 40ms and 50ms?
Sergei Yushanov Certified Consultant
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Posted: 8 years ago 24.01.2017, 14:17 GMT-5
Antia,

Add Free Tetrahedral node and set Element Size to Finer. After 10 ms temperature is exponentially growing, as shown in the attached image.

Regards,
Sergei
Antia, Add Free Tetrahedral node and set Element Size to Finer. After 10 ms temperature is exponentially growing, as shown in the attached image. Regards, Sergei
Antia Gomez
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Posted: 8 years ago 25.01.2017, 01:52 GMT-5
Thank you for fast response Sergei!

When I do exactly what you said, the reciprocal of step size starts to increase after overall progress reaches to 56%, ultimately leading to convergence error. Did you add stop condition to prevent it from going to inf? Or did you change any solver config to have that graph?
Thank you for fast response Sergei! When I do exactly what you said, the reciprocal of step size starts to increase after overall progress reaches to 56%, ultimately leading to convergence error. Did you add stop condition to prevent it from going to inf? Or did you change any solver config to have that graph?

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