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Segregated vs fully coupled approach in the frequency-domain perturbation step
Posted 1 juin 2012, 04:38 UTC−4 Low-Frequency Electromagnetics, Studies & Solvers, Structural Mechanics Version 4.2a 1 Reply
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Hi,
I’m dealing with a model involving the magnetic actuation of a MEMS structure.
Two physics are involved: Solid mechanics and Magnetic Fields.
The magnetic field is generated by a wire carrying a current I = Is +linper(Id) (Is = static component, Id = dynamic component).
The MEMS device is subjected, through its boundaries, to a magnetic force, activated by the “force calculation” feature in the Magnetic Fields physics.
I’ve performed a “Small signal analysis-Frequency domain” study and I’ve noticed a strange thing:
the frequency domain-perturbation step gives a “physical” result (non-zero displacement vs frequency) only if a fully-coupled approach is employed in the corresponding solver sequence.
If otherwise, the default setting (i.e. Segregated) is maintained, the displacement of the structure is zero for any frequency.
It seems that in this last case the dynamic component of the magnetic force is not considered.
Am I missing some setting (maybe in the solvers) ?
Any hint?
Thanks in advance for the answer.
Alessandro
I’m dealing with a model involving the magnetic actuation of a MEMS structure.
Two physics are involved: Solid mechanics and Magnetic Fields.
The magnetic field is generated by a wire carrying a current I = Is +linper(Id) (Is = static component, Id = dynamic component).
The MEMS device is subjected, through its boundaries, to a magnetic force, activated by the “force calculation” feature in the Magnetic Fields physics.
I’ve performed a “Small signal analysis-Frequency domain” study and I’ve noticed a strange thing:
the frequency domain-perturbation step gives a “physical” result (non-zero displacement vs frequency) only if a fully-coupled approach is employed in the corresponding solver sequence.
If otherwise, the default setting (i.e. Segregated) is maintained, the displacement of the structure is zero for any frequency.
It seems that in this last case the dynamic component of the magnetic force is not considered.
Am I missing some setting (maybe in the solvers) ?
Any hint?
Thanks in advance for the answer.
Alessandro
1 Reply Last Post 1 juin 2012, 05:02 UTC−4
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Posted:
1 decade ago
Hi
I have indeed noticed that when we couple complex multiple physics the solver chooses a sequence, but often one can or must adapt a little. I prefer using direct solvers so long I have enough ram and that my physics are reasonably coupled, but in certain cases this is not possible.
Then when we start to tweak the solver, I notice that COMSOl stops updating them when required if we go back and changes something in the physics, this is probably because COMSOL assumes we want full control, but I tend to forget this and my results are wrong.
The only way out, delete the solvers and restart from scratch which often means one have to reset the 2 pages of Results nodes of the postprocessing.
This happens often if I change some physics, something one should not do (my experience) on a model once run once (without deleting solver sequence and restart from there)
--
Good luck
Ivar
I have indeed noticed that when we couple complex multiple physics the solver chooses a sequence, but often one can or must adapt a little. I prefer using direct solvers so long I have enough ram and that my physics are reasonably coupled, but in certain cases this is not possible.
Then when we start to tweak the solver, I notice that COMSOl stops updating them when required if we go back and changes something in the physics, this is probably because COMSOL assumes we want full control, but I tend to forget this and my results are wrong.
The only way out, delete the solvers and restart from scratch which often means one have to reset the 2 pages of Results nodes of the postprocessing.
This happens often if I change some physics, something one should not do (my experience) on a model once run once (without deleting solver sequence and restart from there)
--
Good luck
Ivar