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The relative residual problem

Posted Jun 10, 2012, 5:16 p.m. EDT Version 4.3 4 Replies

Xingjian Chen
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I have set an easy 2D model which is a rectangular and a circle. But after I computer it, there is a error says"Failed to find a solution.The relative residual (1.9e+002) is greater than the relative tolerance.Returned solution is not converged." I don't know what happened. Any clues?

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4 Replies Last Post Jun 12, 2012, 3:11 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 Jun 11, 2012, 12:53 a.m. EDT
Hi

I cannot open it because its 4.3 and my 4.2a crashes (jams) when you I ;( its a bug, will not happend after 4.3 I have been told

But that error often comes often, for me, from a too coarse mesh, that does not allow to get a decent error norm. Sometimes from too poor (too far from espected results) initial conditions too

--
Good luck
Ivar
Hi I cannot open it because its 4.3 and my 4.2a crashes (jams) when you I ;( its a bug, will not happend after 4.3 I have been told But that error often comes often, for me, from a too coarse mesh, that does not allow to get a decent error norm. Sometimes from too poor (too far from espected results) initial conditions too -- Good luck Ivar
Xingjian Chen
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Posted: 1 decade ago Jun 11, 2012, 9:55 a.m. EDT
Thanks for your reply. I have checked my Mesh Setting which is set as "extremely fine". And the initial conditions are simple because I set them to room temperature 293.15[K]. The Model is very simple which is only contain a circle located in a rectangular. The circle has a heat source of 0.01W. There must me some other problems. I have get some screen shot for it(but I cannot upload).
One more thing, when I remove the circle(only a rectangular, Initial Temperature is 293.15[K]), the information shows that "The relative error (10) is greater than the relative tolerance.Returned solution is not converged." However, when I set the Initial Temperature is 0[K], there is no error any more.
Could you give me some more information?
Thanks for your reply. I have checked my Mesh Setting which is set as "extremely fine". And the initial conditions are simple because I set them to room temperature 293.15[K]. The Model is very simple which is only contain a circle located in a rectangular. The circle has a heat source of 0.01W. There must me some other problems. I have get some screen shot for it(but I cannot upload). One more thing, when I remove the circle(only a rectangular, Initial Temperature is 293.15[K]), the information shows that "The relative error (10) is greater than the relative tolerance.Returned solution is not converged." However, when I set the Initial Temperature is 0[K], there is no error any more. Could you give me some more information?
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jun 11, 2012, 11:09 a.m. EDT
Hi

normally you can upload, but you must first EDIT clear Solutions, clear Mesh and File reset history, then save with a new name and upload that (I'm still waiting for my v4.3 so I cannot read it just now, but within a few das I might ;)

--
Good luck
Ivar
Hi normally you can upload, but you must first EDIT clear Solutions, clear Mesh and File reset history, then save with a new name and upload that (I'm still waiting for my v4.3 so I cannot read it just now, but within a few das I might ;) -- Good luck Ivar
Magnus Ringh COMSOL Employee

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Posted: 1 decade ago Jun 12, 2012, 3:11 a.m. EDT
Hi,

I think this is related to the model's physics: It uses thermal insulation as the only boundary condition, so there is no heat flowing in or out, just a heat source in the domain. Then there is really no defined steady-state solution. Running a time-dependent study instead, COMSOL finds a solution, and you can see that the temperature in the circle keeps increasing.

Best regards,
Magnus Ringh
Hi, I think this is related to the model's physics: It uses thermal insulation as the only boundary condition, so there is no heat flowing in or out, just a heat source in the domain. Then there is really no defined steady-state solution. Running a time-dependent study instead, COMSOL finds a solution, and you can see that the temperature in the circle keeps increasing. Best regards, Magnus Ringh

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