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In parametric sweep, is it possible to use the eigenfrequency of last solution as the seed to the current eigenvalue problem?

Posted Nov 10, 2011, 7:00 p.m. EST RF & Microwave Engineering, Studies & Solvers, Structural Mechanics Version 4.1 4 Replies

Hossein Mousavi
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Hi,

I'm doing a parametric sweep over some parameter (kx). For each value of kx, I trying to find one eigenfrequency. But my problem is that I want to use the solution for the previous value of kx as an input to the current value of kx.

Specifically, I want to use the value of the previous eigenfrequency as an input to the "search around frequency... " field of the eigenvalue solver for the current kx. Is this possible?

I know that you can use the previous solution as the initial value of the new solution but it doesn't let me specify the eigenfrequency of the previous solution as the initial guess of eigenfrequency of the new problem.

Thank you.
4 Replies Last Post Oct 30, 2012, 8:31 a.m. EDT
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Hello Hossein Mousavi

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Michal Mruczkiewicz
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Posted: 1 decade ago Dec 12, 2011, 6:36 p.m. EST
Hi, I have exacly the same problem to solve. Do you know already how to do it?

Hi, I have exacly the same problem to solve. Do you know already how to do it?
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Dec 13, 2011, 1:16 a.m. EST
Hi

my way is the manual one, first an eigenfrequency analysis, then a frequency sweep around one of the modes I identified previously. As often damping used are low, the "range()" definition around a peak is slightly delicate, one should get the points on both side of the resonance, but not just on, as the amplitude tend to make the solver diverge

--
Good luck
Ivar
Hi my way is the manual one, first an eigenfrequency analysis, then a frequency sweep around one of the modes I identified previously. As often damping used are low, the "range()" definition around a peak is slightly delicate, one should get the points on both side of the resonance, but not just on, as the amplitude tend to make the solver diverge -- Good luck Ivar
Felix Guldner
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Posted: 1 decade ago Oct 30, 2012, 7:35 a.m. EDT
Hi,

I have the same question. For computing a mechanical band structure I do a parametric sweep of the wave vector k. Now I want that, for every k, the computed eigenfrequency of the step before is used as "search around frequency". In that way I want to make sure that only one band is calculated and that I do not jump to another band while varying k.

Does anyone have an idea how to do that?

Thanks and best regards
Felix
Hi, I have the same question. For computing a mechanical band structure I do a parametric sweep of the wave vector k. Now I want that, for every k, the computed eigenfrequency of the step before is used as "search around frequency". In that way I want to make sure that only one band is calculated and that I do not jump to another band while varying k. Does anyone have an idea how to do that? Thanks and best regards Felix
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Oct 30, 2012, 8:31 a.m. EDT
Hi

that looks like my issue about how to define simply the time steps from a periodic function, such to have closely defined points around steep gradients.
Currently there is no easy function built-in COMSOl that I know about.
So probably one would have to call some outside Matlab function that can read in a time series and output a time stepping with intervalles inversely proportional to the slope of the input fucntion.

In your case it would be frequency steps based on a frequency domain amplitude signal previously calculated

Sorry i have no ready made answer for this one.

--
Good luck
Ivar
Hi that looks like my issue about how to define simply the time steps from a periodic function, such to have closely defined points around steep gradients. Currently there is no easy function built-in COMSOl that I know about. So probably one would have to call some outside Matlab function that can read in a time series and output a time stepping with intervalles inversely proportional to the slope of the input fucntion. In your case it would be frequency steps based on a frequency domain amplitude signal previously calculated Sorry i have no ready made answer for this one. -- Good luck Ivar

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