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Damping factor

Posted Jan 5, 2013, 5:40 a.m. EST Parameters, Variables, & Functions 5 Replies

PT
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can anybody explain what exactly the " Damping factor" in context of COMSOL?
5 Replies Last Post Oct 4, 2013, 4:30 p.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 5, 2013, 9:23 a.m. EST
Hi

perhaps, if you explain in which "physics" and a bit more to what you refer to ;)
Have you tried the help and to search over the doc ?

--
Good luck
Ivar
Hi perhaps, if you explain in which "physics" and a bit more to what you refer to ;) Have you tried the help and to search over the doc ? -- Good luck Ivar
PT
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Posted: 1 decade ago Jan 6, 2013, 5:30 a.m. EST
Hi
Ivar
Thanks for reply.
I have tried, Generally it is happen under following circumstances (as I understood).
Poor mesh quality, not proper boundary conditions, source term value. I have gone all these but not success.

I am using Navier-stokes and follow by Nernst-Planck. Navier-stokes portion solved properly but for second solution something is wrong which gives" non convergence, even when using minimum damping factor"........kind of error. The velocity of Navier-stokes is use in Nernst-Planck. That is why I want to understand about damping factor with respect to COMSOL. So i can fine source of error.


Hi Ivar Thanks for reply. I have tried, Generally it is happen under following circumstances (as I understood). Poor mesh quality, not proper boundary conditions, source term value. I have gone all these but not success. I am using Navier-stokes and follow by Nernst-Planck. Navier-stokes portion solved properly but for second solution something is wrong which gives" non convergence, even when using minimum damping factor"........kind of error. The velocity of Navier-stokes is use in Nernst-Planck. That is why I want to understand about damping factor with respect to COMSOL. So i can fine source of error.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jan 6, 2013, 5:38 a.m. EST
Hi

the best I know is what is descrivbed under: COMSOLMultiphysicsUsersGuide.pdf search for "damping factor"
the further down you have more on the "DAMPED NEWTON METHODS"


--
Good luck
Ivar
Hi the best I know is what is descrivbed under: COMSOLMultiphysicsUsersGuide.pdf search for "damping factor" the further down you have more on the "DAMPED NEWTON METHODS" -- Good luck Ivar
PT
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Posted: 1 decade ago Jan 9, 2013, 5:14 a.m. EST
Thanks
Thanks
Peyman Dordizadeh
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Posted: 1 decade ago Oct 4, 2013, 4:30 p.m. EDT
Hi

Damping factor is a coefficient which makes Newton's method slower but safer. I guess the reason its named like this is it damps the speed of calculation. Smaller this factor is, slower the simulation will move, but in the meantime safer and more convergent.
I have a question from Ivar to ask, is there anyway I could track the value of damping factor COMSOL uses in each iteration of the Newton's method? I'm talking about fully-coupled time-dependent solver.
I'm really not sure how to grab Ivar's attention to this topic which was posted 10 months ago. I hope he reads this :)
Many thanks.

Peyman.
Hi Damping factor is a coefficient which makes Newton's method slower but safer. I guess the reason its named like this is it damps the speed of calculation. Smaller this factor is, slower the simulation will move, but in the meantime safer and more convergent. I have a question from Ivar to ask, is there anyway I could track the value of damping factor COMSOL uses in each iteration of the Newton's method? I'm talking about fully-coupled time-dependent solver. I'm really not sure how to grab Ivar's attention to this topic which was posted 10 months ago. I hope he reads this :) Many thanks. Peyman.

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