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steady state solutions with periodic waveforms

Posted 21.03.2012, 10:12 GMT-4 Version 4.2a 3 Replies

Kenneth Stalder
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I am trying to impose a periodic waveform on an electrode using the wv1 function in the Electric Currents module (ec), and have defined it in the definition section with amplitude, frequency, etc. Its a square wave with a smoothed risetime. The coupled physics problem I am working with is a coupled electrical-thermal model. I can get a transient solver to work, but the steady state solver gives and error. Is it not possible to get a steady state solution with a periodically varying potential? Is it possible to derive root-mean-square (RMS) for potential, current, etc?
3 Replies Last Post 21.03.2012, 13:42 GMT-4
Edgar Kaiser
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Posted: 1 decade ago 21.03.2012, 10:28 GMT-4

You can do that in a frequency domain study, but only with harmonic oscillations. The stationary solver cannot consider any time dependant phenomena.
If your model is all linear you could try to decompose your excitation function into its harmonic components, run a frequency domain parametric study using those components and add the results.
This will probably require the use of Matlab.

Cheers
Edgar
You can do that in a frequency domain study, but only with harmonic oscillations. The stationary solver cannot consider any time dependant phenomena. If your model is all linear you could try to decompose your excitation function into its harmonic components, run a frequency domain parametric study using those components and add the results. This will probably require the use of Matlab. Cheers Edgar
Kenneth Stalder
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Posted: 1 decade ago 21.03.2012, 12:50 GMT-4
OK, thanks.

What about computing and plotting root-mean-square (RMS) currents, voltages, etc.? Is there a builit in function that computes this, or do I have to do the integrations myself?
OK, thanks. What about computing and plotting root-mean-square (RMS) currents, voltages, etc.? Is there a builit in function that computes this, or do I have to do the integrations myself?
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 21.03.2012, 13:42 GMT-4
Hi

if you have solved a time series study, then you can extract, in the Results derived values the time behaviour of any given variable or equation, in the last tab you can add a function on this series, rms average min max ... but be sure you use an full number of periods for average values, or that you use some windowing function.

The frequency domain values have also rms output (had at least) check the doc for the variable names, some included the rms in thier names

--
Good luck
Ivar
Hi if you have solved a time series study, then you can extract, in the Results derived values the time behaviour of any given variable or equation, in the last tab you can add a function on this series, rms average min max ... but be sure you use an full number of periods for average values, or that you use some windowing function. The frequency domain values have also rms output (had at least) check the doc for the variable names, some included the rms in thier names -- Good luck Ivar

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