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Error linking Heat Transfer in Fluids and Turbulent Flow (Spalart-Allmaras)

Posted Apr 18, 2011, 4:20 p.m. EDT Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD), Studies & Solvers Version 4.1 10 Replies

Daniel Bateman
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I am using COMSOL Class Kit 4.1 to model a pretty simple flow of hot air in a vertical pipe. I was able to get the model to working using Laminar flow (all are steady state studies) and the Heat Transfer in Liquids physics, but I get this error in trying to get the turbulent physics to work: Constraint found for variables in different Segregated groups. Try to merge these groups.

I disabled the Laminar Physics before adding the Turbulent module and I am using separate studies under the same model.

How do I merge the constraints or other wise troubleshoot this error???

Thank You.
10 Replies Last Post May 4, 2013, 3:05 a.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Apr 18, 2011, 4:45 p.m. EDT
Hi

you can go into the solver segregated nodes and group the default two (or more) groups into one, manually, by adding the parameters to the first group and then deleting the second, once all variables have been transferred. That is what COMSOL proposes by such a message, I have tried a few times, and it sometimes works

--
Good luck
Ivar
Hi you can go into the solver segregated nodes and group the default two (or more) groups into one, manually, by adding the parameters to the first group and then deleting the second, once all variables have been transferred. That is what COMSOL proposes by such a message, I have tried a few times, and it sometimes works -- Good luck Ivar
Daniel Bateman
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Posted: 1 decade ago Apr 19, 2011, 5:20 p.m. EDT
Thanks, doing that seems to have moved the calulations closer to a solution BUT

now I get: Undefined value found.
- Detail: NaN_or_Inf_found_when_solving_linear_system_using_SOR

I assume there is now an illegal opeations occuring, but how to I resolve this error??

Thanks Again..
Thanks, doing that seems to have moved the calulations closer to a solution BUT now I get: Undefined value found. - Detail: NaN_or_Inf_found_when_solving_linear_system_using_SOR I assume there is now an illegal opeations occuring, but how to I resolve this error?? Thanks Again..
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Apr 20, 2011, 12:53 a.m. EDT
Hi

Thats tougher, perhaps something like a 1/0 in the equations somewhere. Do not forget that often variables are fields f(x,y,z) and are mapped on the mesh elements via their locations x,y,z hence you can get easily some singularities

--
Good luck
Ivar
Hi Thats tougher, perhaps something like a 1/0 in the equations somewhere. Do not forget that often variables are fields f(x,y,z) and are mapped on the mesh elements via their locations x,y,z hence you can get easily some singularities -- Good luck Ivar
Daniel Bateman
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Posted: 1 decade ago Apr 21, 2011, 11:31 a.m. EDT
So I tried a new approach and attempted to recreate my model from scratch using the Conjugate Heat Transfer-Low Re K-E physics model rather than linking the separate HT and Turbulent physics.

BUT

I am not able to select any part of my geometry in the Turbulent portion of the Conjugate module in order to set my inlet, outlet, and wall conditions. I am able to select geometry to set a heat transfer boundary (set temperature), but noting for the fluids side. Is there a work around for this or some kind of unique procedure required to model in the conjugate physics???

Thank You,
Brett
So I tried a new approach and attempted to recreate my model from scratch using the Conjugate Heat Transfer-Low Re K-E physics model rather than linking the separate HT and Turbulent physics. BUT I am not able to select any part of my geometry in the Turbulent portion of the Conjugate module in order to set my inlet, outlet, and wall conditions. I am able to select geometry to set a heat transfer boundary (set temperature), but noting for the fluids side. Is there a work around for this or some kind of unique procedure required to model in the conjugate physics??? Thank You, Brett
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Apr 21, 2011, 1:10 p.m. EDT
Hi

that's bizarre, I can select external boundaries and apply inlet, outlets ... under the physics Laminar as well as Turbulent Flow branch (depending on turbulent switch settings) are you in the latest patch 3 ? v4.1.0.185 ? could that be it ?, in case see the main web site "Support Product updates"

--
Good luck
Ivar
Hi that's bizarre, I can select external boundaries and apply inlet, outlets ... under the physics Laminar as well as Turbulent Flow branch (depending on turbulent switch settings) are you in the latest patch 3 ? v4.1.0.185 ? could that be it ?, in case see the main web site "Support Product updates" -- Good luck Ivar
Daniel Bateman
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Posted: 1 decade ago Apr 28, 2011, 10:47 a.m. EDT
Hi,

Okay I fixed the boundary selection problem (it was me, not COMSOL), but now that I have a resonable looking solution from the Conjugate HT/Low Re k-E module I keep getting this warning:

New constraint force nodes detected: these are not stored !

Are these Reynolds stresses and/or does 'new' refer to succsesive iterations of the GMRES or somethig?

I can't tell how to interept the impact of this warning on the solution generated.

Any ideas?

Thank You!
Hi, Okay I fixed the boundary selection problem (it was me, not COMSOL), but now that I have a resonable looking solution from the Conjugate HT/Low Re k-E module I keep getting this warning: New constraint force nodes detected: these are not stored ! Are these Reynolds stresses and/or does 'new' refer to succsesive iterations of the GMRES or somethig? I can't tell how to interept the impact of this warning on the solution generated. Any ideas? Thank You!
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Apr 28, 2011, 11:20 a.m. EDT
Hi

I believe that is linked to the ALE (do you use ALE), from my understanding its not the most critical warning, could imply lower precision on some of the flux calulations

--
Good luck
Ivar
Hi I believe that is linked to the ALE (do you use ALE), from my understanding its not the most critical warning, could imply lower precision on some of the flux calulations -- Good luck Ivar
Richa Kumari
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Posted: 1 decade ago Sep 18, 2011, 1:57 a.m. EDT
thanku you Ivar.it helped me..
thanku you Ivar.it helped me..
Hamad Aziz
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Posted: 1 decade ago May 3, 2013, 7:02 p.m. EDT

Hi

you can go into the solver segregated nodes and group the default two (or more) groups into one, manually, by adding the parameters to the first group and then deleting the second, once all variables have been transferred. That is what COMSOL proposes by such a message, I have tried a few times, and it sometimes works

--
Good luck
Ivar


Hi,

I am having problem with segregated solvers as well, but what you suggested, doesn't that defeat the purpose of using segregated solvers? if you put all the parameters to a single group than that would make it a (kind of) fully coupled?

Thanks
[QUOTE] Hi you can go into the solver segregated nodes and group the default two (or more) groups into one, manually, by adding the parameters to the first group and then deleting the second, once all variables have been transferred. That is what COMSOL proposes by such a message, I have tried a few times, and it sometimes works -- Good luck Ivar [/QUOTE] Hi, I am having problem with segregated solvers as well, but what you suggested, doesn't that defeat the purpose of using segregated solvers? if you put all the parameters to a single group than that would make it a (kind of) fully coupled? Thanks
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago May 4, 2013, 3:05 a.m. EDT
Hi

indeed its worthwile playing a little with the segregated groups, or fully coupled mode, but to sort the items, think over the logic in your moel, what is master what is slave, why ...

--
Good luck
Ivar
Hi indeed its worthwile playing a little with the segregated groups, or fully coupled mode, but to sort the items, think over the logic in your moel, what is master what is slave, why ... -- Good luck Ivar

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