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Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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extracting FE matrix equation system

Posted 2012年6月14日 GMT-4 09:44 Low-Frequency Electromagnetics, Interfacing Version 4.2a 6 Replies

Matias Pozzi
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Hi people!

I have small issue and I cannot figure out how to solve it. I need your help.

I need to extract my stiffness tensor from the FE matrix system into matlab. I know that there is the function mphmatrix but that extracts all the model and I need just 1 domain in particular.

Have you ever did this? Can you give me a hint on that?

Thanks!

Matias
6 Replies Last Post 2012年10月26日 GMT-4 09:57
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 2012年6月14日 GMT-4 16:09
Hi

indeed model reduction on arbitrary modes s a domain were I feel COMSOl still has some serious improvements to do, we will see what has been implemented in V4.3 now, when it arrives.

I can only suggest to ask support, so they see I'm not the only one asking for this ;)

--
Good luck
Ivar
Hi indeed model reduction on arbitrary modes s a domain were I feel COMSOl still has some serious improvements to do, we will see what has been implemented in V4.3 now, when it arrives. I can only suggest to ask support, so they see I'm not the only one asking for this ;) -- Good luck Ivar
Matias Pozzi
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Posted: 1 decade ago 2012年6月15日 GMT-4 19:01
Thanks Ivar,

I already did that, let see v4.3 ;)

regards,
/Matt
Thanks Ivar, I already did that, let see v4.3 ;) regards, /Matt
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 2012年6月16日 GMT-4 03:57
Hi

That's good, often COMSOL deveoppers are rather reactive and suggestions come rapidly in the new versions, at least if anough of us ask for them ;)

You have one place in the last version where you can reduce the model and analysit it with a few modes, and NOT necesarily the adjacent first moes, its in the frequency domain modal. Only thing the damping sub nodes do not seem to work properly in 4.2 and I'm not sure they managed to mend it for 4.3 but it will certainly be done int he following patches. But I do not know how to export a M&D matrix from this reduced model, this would be ideal (for me)

--
Good luck
Ivar
Hi That's good, often COMSOL deveoppers are rather reactive and suggestions come rapidly in the new versions, at least if anough of us ask for them ;) You have one place in the last version where you can reduce the model and analysit it with a few modes, and NOT necesarily the adjacent first moes, its in the frequency domain modal. Only thing the damping sub nodes do not seem to work properly in 4.2 and I'm not sure they managed to mend it for 4.3 but it will certainly be done int he following patches. But I do not know how to export a M&D matrix from this reduced model, this would be ideal (for me) -- Good luck Ivar
Mattia Montanari
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Posted: 1 decade ago 2012年10月26日 GMT-4 06:50

Hi

That's good, often COMSOL deveoppers are rather reactive and suggestions come rapidly in the new versions, at least if anough of us ask for them ;)

You have one place in the last version where you can reduce the model and analysit it with a few modes, and NOT necesarily the adjacent first moes, its in the frequency domain modal. Only thing the damping sub nodes do not seem to work properly in 4.2 and I'm not sure they managed to mend it for 4.3 but it will certainly be done int he following patches. But I do not know how to export a M&D matrix from this reduced model, this would be ideal (for me)

--
Good luck
Ivar


Hi everybody,
I think I'm facing the same problem but I'm not really sure if I understood correctly.

Did you mean that is not possible to extract, let's say, the stiffness matrix for a transient problem where the mesh changes among the time steps?

Thanks!

Mattia
[QUOTE] Hi That's good, often COMSOL deveoppers are rather reactive and suggestions come rapidly in the new versions, at least if anough of us ask for them ;) You have one place in the last version where you can reduce the model and analysit it with a few modes, and NOT necesarily the adjacent first moes, its in the frequency domain modal. Only thing the damping sub nodes do not seem to work properly in 4.2 and I'm not sure they managed to mend it for 4.3 but it will certainly be done int he following patches. But I do not know how to export a M&D matrix from this reduced model, this would be ideal (for me) -- Good luck Ivar [/QUOTE] Hi everybody, I think I'm facing the same problem but I'm not really sure if I understood correctly. Did you mean that is not possible to extract, let's say, the stiffness matrix for a transient problem where the mesh changes among the time steps? Thanks! Mattia
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 2012年10月26日 GMT-4 07:31
Hi
Ideally what I would like is to extract is a state space matrix w.r.t. some global variable in/out, that is not yet possible, from my undertanding, only the full matrix, that is defined then on the mesh. I

f you change the mesh per time step, I would lso understand that your issue becomes tougher, with moere to handle

--
Good luck
Ivar
Hi Ideally what I would like is to extract is a state space matrix w.r.t. some global variable in/out, that is not yet possible, from my undertanding, only the full matrix, that is defined then on the mesh. I f you change the mesh per time step, I would lso understand that your issue becomes tougher, with moere to handle -- Good luck Ivar
Mattia Montanari
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Posted: 1 decade ago 2012年10月26日 GMT-4 09:57
Hi

I've opened up a new discussion to present my question which is, however, not too far from the one presented here.

Thank you!

Mattia
Hi I've opened up a new discussion to present my question which is, however, not too far from the one presented here. Thank you! Mattia

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