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Nonlinear dynamic study used Frequency domain analysis

Posted 27 févr. 2023, 17:02 UTC−5 Studies & Solvers, Modeling Workflow, Structural Dynamics 3 Replies

Jackie Lin
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Hi, I wonder whether COMSOL can model nonlinear dynamic in frequencies domain analysis, specifically, achieving higher-harmonic generation. In my case, an incident wave with single frequency is propagating in an aluminum beam/plate. After impinging on a nonlinear material, higher-harmonic components are generated in the transmitted region.

Can I do this in the freqeuncy-domain analysis instead of time-domain one in COMSOL?

3 Replies Last Post 6 mars 2023, 10:33 UTC−5
Jeff Hiller COMSOL Employee

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Posted: 2 years ago 28 févr. 2023, 14:11 UTC−5

Hi Jackie,

See Structural Mechanics Module User's Guide, version 6.1, page 64: "In a frequency-domain analysis, you study the response to a harmonic steady state excitation for certain frequencies. Such a steady state can prevail once all transient effects have been damped out. The response must be linear, so that the single frequency harmonic excitation gives a pure harmonic response with the same frequency." . That condition does not seem to be met by your system.

Best,

Jeff

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Jeff Hiller
Hi Jackie, See Structural Mechanics Module User's Guide, version 6.1, page 64: "In a frequency-domain analysis, you study the response to a harmonic steady state excitation for certain frequencies. Such a steady state can prevail once all transient effects have been damped out. The response must be linear, so that the single frequency harmonic excitation gives a pure harmonic response with the same frequency." . That condition does not seem to be met by your system. Best, Jeff
Jackie Lin
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Posted: 2 years ago 5 mars 2023, 18:43 UTC−5

Hi Jackie,

See Structural Mechanics Module User's Guide, version 6.1, page 64: "In a frequency-domain analysis, you study the response to a harmonic steady state excitation for certain frequencies. Such a steady state can prevail once all transient effects have been damped out. The response must be linear, so that the single frequency harmonic excitation gives a pure harmonic response with the same frequency." . That condition does not seem to be met by your system.

Best,

Jeff

Hi Jeff, Thanks for your reply! Maybe I need to try time domain simulation then.

>Hi Jackie, > >See Structural Mechanics Module User's Guide, version 6.1, page 64: "In a frequency-domain analysis, you study the response to a harmonic steady state excitation for certain frequencies. Such a steady state can prevail once all transient effects have been damped out. >The response must be linear, so that the single frequency harmonic excitation gives a >pure harmonic response with the same frequency." . That condition does not seem to be met by your system. > >Best, > >Jeff Hi Jeff, Thanks for your reply! Maybe I need to try time domain simulation then.
Henrik Sönnerlind COMSOL Employee

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Posted: 2 years ago 6 mars 2023, 10:33 UTC−5

It may be useful to run a linearized frequency-domain study at the fundamental frequency in order to obtain approximate initial conditions for the time-domain analysis.

Here is an example showing that approach:

https://www.comsol.com/model/nonlinear-harmonic-response-105171

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Henrik Sönnerlind
COMSOL
It may be useful to run a linearized frequency-domain study at the fundamental frequency in order to obtain approximate initial conditions for the time-domain analysis. Here is an example showing that approach:

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