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Warning: New constraint force nodes detected: these are not stored !

Posted Nov 27, 2009, 7:38 a.m. EST Computational Fluid Dynamics (CFD) Version 4.1 7 Replies

Steven Delrue
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Hi everyone,

I was trying to model a boundary condition (using assemblies) which varies in time (depending on some parameters). However, when I solve my model, I get the following warning:

New constraint force nodes detected: these are not stored !

Is there anyone who can tell me what this warning means?

Thx,
Steven
7 Replies Last Post Mar 15, 2011, 5:54 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 Nov 27, 2009, 10:08 a.m. EST
Hi

I got those messages also the other day, I was wrking in assembly mode, with "no imprints" and had defined bounary conditions with bolean limits, using ALE on one side of the geometry, with force analysis on one part.

When I mesh coarse I get the message, by meshing finer they did not appear.

From what I got out, was that some of the ALE nodes were moving in and out of my boundary conditions settings, the solver detected that it should also inlcude/substract new/old nodes for the force clculations, but it was not able to "on the fly" during solving. The force measurements were also somewhat wrong, but the rest seemed to solve OK.

by decreasing mesh size, I did not get any warnings and the results seemd better.

Normally I start with a coarse mesh, and decrease until I have less than 10% changes on the results, while I check the warnings and other

Hope this helps
Ivar
Hi I got those messages also the other day, I was wrking in assembly mode, with "no imprints" and had defined bounary conditions with bolean limits, using ALE on one side of the geometry, with force analysis on one part. When I mesh coarse I get the message, by meshing finer they did not appear. From what I got out, was that some of the ALE nodes were moving in and out of my boundary conditions settings, the solver detected that it should also inlcude/substract new/old nodes for the force clculations, but it was not able to "on the fly" during solving. The force measurements were also somewhat wrong, but the rest seemed to solve OK. by decreasing mesh size, I did not get any warnings and the results seemd better. Normally I start with a coarse mesh, and decrease until I have less than 10% changes on the results, while I check the warnings and other Hope this helps Ivar
Certified Consultant
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Posted: 1 decade ago Nov 27, 2009, 10:36 a.m. EST
Hi Steven and Ivar. The warning messsage in itself can be considered a bug. It does not affect the reliability of your solution.

For details see
www.comsol.com/support/knowledgebase/1056/

Niklas
Hi Steven and Ivar. The warning messsage in itself can be considered a bug. It does not affect the reliability of your solution. For details see http://www.comsol.com/support/knowledgebase/1056/ Niklas
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Nov 27, 2009, 11:03 a.m. EST
Hello Niklas

Well I though there were no bugs in COMSOL ;)

In fact you confirm what I suspected, as I was interested in the reaction forces, I will continue to take some cautions when such warnings appear, but as I said above, the results were reasonnable, therefore I was, and I'm still not, alarmed, but ... warned.

have a nice week-end
Ivar
Hello Niklas Well I though there were no bugs in COMSOL ;) In fact you confirm what I suspected, as I was interested in the reaction forces, I will continue to take some cautions when such warnings appear, but as I said above, the results were reasonnable, therefore I was, and I'm still not, alarmed, but ... warned. have a nice week-end Ivar
Nils Eivind Kamfjord
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Posted: 1 decade ago Mar 8, 2011, 11:41 a.m. EST
If this was a bug in 2009, is it then "re introduced" in 4.1 ?

I keep getting this warning now in a fairly simple turbulent model.
If this was a bug in 2009, is it then "re introduced" in 4.1 ? I keep getting this warning now in a fairly simple turbulent model.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Mar 8, 2011, 3:25 p.m. EST
Hi

It's not a bug, in my view, it's a is says a warning, and warnings are to be analysed to see if they interact with your model results, In some cases it could be dramatic, even if mostly it's harmless.

Fo me so far it is linked to the ALE and the large displacements observed over boundaries with exrternal force/flux conditions

--
Good luck
Ivar
Hi It's not a bug, in my view, it's a is says a warning, and warnings are to be analysed to see if they interact with your model results, In some cases it could be dramatic, even if mostly it's harmless. Fo me so far it is linked to the ALE and the large displacements observed over boundaries with exrternal force/flux conditions -- Good luck Ivar
Jim Freels mechanical side of nuclear engineering, multiphysics analysis, COMSOL specialist
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Posted: 1 decade ago Mar 8, 2011, 10:16 p.m. EST
My approach to this problem, but do not actually know for sure is to consider the check box that can be unchecked to evaluate reaction forces. That is what I do to eliminate this warning message. Unless you need to actually know the reactionary forces, it is not needed.

My approach to this problem, but do not actually know for sure is to consider the check box that can be unchecked to evaluate reaction forces. That is what I do to eliminate this warning message. Unless you need to actually know the reactionary forces, it is not needed.
Jérémie GIRARDOT
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Posted: 1 decade ago Mar 15, 2011, 5:54 a.m. EDT
Thanks for this help, I have the same problem, but not with an ALE model. I will try again first with a finer mesh and second by uncheck this box.

I'll keep you in touch

regards

--
--
Jérémie GIRARDOT
Thanks for this help, I have the same problem, but not with an ALE model. I will try again first with a finer mesh and second by uncheck this box. I'll keep you in touch regards -- -- Jérémie GIRARDOT

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