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alternating current in Conductive Media DC

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Hello,

I´ve got a question regarding to a model I´m working on in the Conductive Media DC Module: the model consist of a splitted sediment core on which the resistivity is measured by a small Wenner array (1cm electrode distance). My model works fantastic if I define currents of -1mA and 1mA for the outer electrodes (A and B). But now I´d like to use an alternating current (sinus-like). Is it possible to get a time dependent current source? How can I realize it?

I´ve tried to solve the model, to turn around current signs (1mA for A and -1mA for B) and to restart it. But this would look like a somewhat angular sinus function...

maybe someone of you has an idea, how I can realize a really alternating current???

Thanks for all helpfull comments,

Daniel

2 Replies Last Post 06.03.2015, 17:38 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 01.02.2012, 15:21 GMT-5
Hi

there are two ways to simulate alternative, oscillating, loads or currents:
a) the time domain with a sin(2*pi*f*t) function and you solve directly each periode with multiple steps and
b) the harmonic development approach, where you define the ampliude and if required phase, then define a frequency or a frequency domain to excite

The latter takes far lesstime and effort to solve, but you are in a continuous mode, and you do not see transients. In the latest solver versions (from v4.2a) there are frequency time solvers for special combinations.

Now no all physics are set up to use either/or time dependent solvers or harmonic frequency domain solvers as this requires to develop the physics behind correctly, the choices in 3.5 were far less abondants (unfortunately for you ;)

--
Good luck
Ivar
Hi there are two ways to simulate alternative, oscillating, loads or currents: a) the time domain with a sin(2*pi*f*t) function and you solve directly each periode with multiple steps and b) the harmonic development approach, where you define the ampliude and if required phase, then define a frequency or a frequency domain to excite The latter takes far lesstime and effort to solve, but you are in a continuous mode, and you do not see transients. In the latest solver versions (from v4.2a) there are frequency time solvers for special combinations. Now no all physics are set up to use either/or time dependent solvers or harmonic frequency domain solvers as this requires to develop the physics behind correctly, the choices in 3.5 were far less abondants (unfortunately for you ;) -- Good luck Ivar

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Posted: 9 years ago 06.03.2015, 17:38 GMT-5
Hi Ivar,
I am trying to model an acoustic wave traveling through a sample holder using the acoustic-piezoelectric interaction module in 4.3a. I have one piezoelectric element that creates a sin wave, and then another element receiving the sin wave. If I use the time domain to apply one full sine wave, will the solver solve for time past the applied wave?
That might be unclear, but I'm trying to capture waves that are received after the source has stopped. Thank you!
Katie
Hi Ivar, I am trying to model an acoustic wave traveling through a sample holder using the acoustic-piezoelectric interaction module in 4.3a. I have one piezoelectric element that creates a sin wave, and then another element receiving the sin wave. If I use the time domain to apply one full sine wave, will the solver solve for time past the applied wave? That might be unclear, but I'm trying to capture waves that are received after the source has stopped. Thank you! Katie

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