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DEP Model using Comsol 4.3

Posted 12 déc. 2012, 12:04 UTC−5 Version 4.2a 4 Replies

Soumya Gangopadhyay
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Hello,
I am trying to do a DEP simulation in Comsol 4.3 and I want to apply an AC signal of 10V 14KHz in a pair of electrodes. I am presently using AC/DC model. I am able to apply a DC signal but I am not getting the AC signal.

My question is how can I apply an AC signal in those pair of electrodes? Because I am not getting any procedure to apply AC signal in Comsol.

Please help me, my complete project depends on this.
4 Replies Last Post 17 janv. 2013, 00:56 UTC−5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 12 déc. 2012, 14:33 UTC−5
Hi

An AC signal is of the type A0*sin(2*pi*freq*t), but if you solve with a time series solver you must wait fr ages. You get quicker the correct result for a steady value of the amplitude A0, by setting your terminal to A0 and using the frequency doamin solver and define your frequency in the solver tab. Then COMSOL uses the harmonic development of the equations, this solves fa quicker than a time series that is mainly to be used for transients, and not for steaady state responses.

Note that if you have 3 phase AC signals, you need to use complex amplitudes to account for the phase component, check the doc for "phasor"

--
Good luck
Ivar
Hi An AC signal is of the type A0*sin(2*pi*freq*t), but if you solve with a time series solver you must wait fr ages. You get quicker the correct result for a steady value of the amplitude A0, by setting your terminal to A0 and using the frequency doamin solver and define your frequency in the solver tab. Then COMSOL uses the harmonic development of the equations, this solves fa quicker than a time series that is mainly to be used for transients, and not for steaady state responses. Note that if you have 3 phase AC signals, you need to use complex amplitudes to account for the phase component, check the doc for "phasor" -- Good luck Ivar
Soumya Gangopadhyay
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Posted: 1 decade ago 13 déc. 2012, 08:51 UTC−5
Hello Ivar,
Thank you very much for your help. I have done what you have said. But now its showing the following error
"Undefined value found.
- Detail: NaN or Inf found when solving linear system using SOR."
I have tried much to solve it but every time its showing the same error in case of low frequencies and in case
of high frequencies the result is not even converging and running for ages.

Can you help please.
Hello Ivar, Thank you very much for your help. I have done what you have said. But now its showing the following error "Undefined value found. - Detail: NaN or Inf found when solving linear system using SOR." I have tried much to solve it but every time its showing the same error in case of low frequencies and in case of high frequencies the result is not even converging and running for ages. Can you help please.
WENJIE WU
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Posted: 1 decade ago 16 janv. 2013, 14:05 UTC−5
Dear Ivar Kjelberg:
I am also using DEP to do particle tracking.
In the help documentation of ‘Dielectrophoretic Force’, I saw
--------------------------------------------------------------------------------------------------------------------------------------------------------------
When the particle relative permittivity is greater than the relative permittivity of the fluid, the particles are attracted to regions where the absolute electric field is strong. When the particle relative permittivity is less than the relative permittivity of the fluid, the particles are attracted to regions where the absolute electric field is weak.
------------------------------------------------------------------------------------------------------------------------------------------------------------
But as we know, pDEP or nDEP also depends on media&particles’s conductivity and frequency of E-field applied…..
My college told me that COMSOL 4.2a ‘Dielectrophoretic Force‏’ defaults DC-dielectrophoresis, which means frequency=0 and hence conductivity will no longer be useful…..
Is that true?

Thanks very much!
James WU from the Chinese University of Hong Kong
Dear Ivar Kjelberg: I am also using DEP to do particle tracking. In the help documentation of ‘Dielectrophoretic Force’, I saw -------------------------------------------------------------------------------------------------------------------------------------------------------------- When the particle relative permittivity is greater than the relative permittivity of the fluid, the particles are attracted to regions where the absolute electric field is strong. When the particle relative permittivity is less than the relative permittivity of the fluid, the particles are attracted to regions where the absolute electric field is weak. ------------------------------------------------------------------------------------------------------------------------------------------------------------ But as we know, pDEP or nDEP also depends on media&particles’s conductivity and frequency of E-field applied….. My college told me that COMSOL 4.2a ‘Dielectrophoretic Force‏’ defaults DC-dielectrophoresis, which means frequency=0 and hence conductivity will no longer be useful….. Is that true? Thanks very much! James WU from the Chinese University of Hong Kong
Soumya Gangopadhyay
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Posted: 1 decade ago 17 janv. 2013, 00:56 UTC−5
To,
James WU

In case of DEP , AC signal is necessary because if you apply DC the electrical field of the electrodes will overlap with each other and your particle wouldn't be able to move.
To, James WU In case of DEP , AC signal is necessary because if you apply DC the electrical field of the electrodes will overlap with each other and your particle wouldn't be able to move.

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