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Uncertain about damped (complex) frequency notation

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Hi!

I could use help in fully understanding the notation of damped (complex) frequencies. From my understanding: The real part marks the damped frequency, and the imaginary part marks the damping.

Now, if the complex frequency is: omega=omega_d+i*damping, then the undamped frequency omega_0 is:

omega_0=sqrt(omega_d^2+2*damping^2)

Is this correct?

Thanks for the help!

4 Replies Last Post 10 mar 2011, 11:20 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 9 mar 2011, 12:15 GMT-5
Hi

almost, check it out with examples like this (see attached 4.1.0.185 file) now its there:)

or take a look at

en.wikipedia.org/wiki/Vibration#Damped_and_undamped_natural_frequencies

--
Good luck
Ivar
Hi almost, check it out with examples like this (see attached 4.1.0.185 file) now its there:) or take a look at http://en.wikipedia.org/wiki/Vibration#Damped_and_undamped_natural_frequencies -- Good luck Ivar


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Posted: 1 decade ago 10 mar 2011, 07:43 GMT-5
Thanks for the model!

So I what I am seeing is: f_d+zeta*f_n*i

The reason that I am uncertain: in acoustic eigenmode simulations this seems to not work out. Notation should be the same... What am I not getting?
Thanks for the model! So I what I am seeing is: f_d+zeta*f_n*i The reason that I am uncertain: in acoustic eigenmode simulations this seems to not work out. Notation should be the same... What am I not getting?

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 10 mar 2011, 10:00 GMT-5
HI

i do (unfortunately) not have the acoustic module so I have no experience with the specific physics used, could it be that there is a fluid damping feature that changes your constant (probably related to the viscosity, but I haven't opened my acoustic structure books for a few years ;)

--
Good luck
Ivar
HI i do (unfortunately) not have the acoustic module so I have no experience with the specific physics used, could it be that there is a fluid damping feature that changes your constant (probably related to the viscosity, but I haven't opened my acoustic structure books for a few years ;) -- Good luck Ivar

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Posted: 1 decade ago 10 mar 2011, 11:20 GMT-5
Thanks!
Thanks!

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