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What does phase mean in a stationary solver?

Posted 18 apr 2013, 02:00 GMT-4 4 Replies

m0nk3y
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Does phase have any meaning when using a stationary solver?

I have a study node with two steps: a time-harmonic step (frequency domain) followed by a stationary step. When looking at plots of the solution, the results from the stationary step seem to vary with phase. Has anyone encountered this behaviour before?
4 Replies Last Post 18 apr 2013, 09:08 GMT-4
Pu Zhang
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Posted: 1 decade ago 18 apr 2013, 03:32 GMT-4
The solution of harmonic study usually is complex. The plot couldn't shows a complex number. As I understand the phase value could be used to decide which part of the complex number you want to plot.
The solution of harmonic study usually is complex. The plot couldn't shows a complex number. As I understand the phase value could be used to decide which part of the complex number you want to plot.
m0nk3y
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Posted: 1 decade ago 18 apr 2013, 04:16 GMT-4
In my case the frequency response is solving for pressure (acoustics), which does vary harmonically as I expected. Changing the phase of the solution when plotting then corresponds to how far into the cycle the variation is, as I understand it.

I am then using values from pressure acoustics to create body forces for laminar flow (which is the next study step). These are of the form p*conj(p), and so don't vary harmonically - they are constant. I have checked that this is the case by plotting the body forces and varying the phase of solution - they remain constant. However, the velocity field does seem to vary harmonically when the phase is changed.

Does this mean that if I put a stationary step along with a frequency response step that all variables solved for will be harmonic? Or is phase other than 0 meaningless for variables solved for using a stationary solver?
In my case the frequency response is solving for pressure (acoustics), which does vary harmonically as I expected. Changing the phase of the solution when plotting then corresponds to how far into the cycle the variation is, as I understand it. I am then using values from pressure acoustics to create body forces for laminar flow (which is the next study step). These are of the form p*conj(p), and so don't vary harmonically - they are constant. I have checked that this is the case by plotting the body forces and varying the phase of solution - they remain constant. However, the velocity field does seem to vary harmonically when the phase is changed. Does this mean that if I put a stationary step along with a frequency response step that all variables solved for will be harmonic? Or is phase other than 0 meaningless for variables solved for using a stationary solver?
Pu Zhang
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Posted: 1 decade ago 18 apr 2013, 08:13 GMT-4
It seems your second study is not linear, then probably the complex numbers and phase have different meaning. I can't tell what they are then.
It seems your second study is not linear, then probably the complex numbers and phase have different meaning. I can't tell what they are then.
Edgar J. Kaiser Certified Consultant
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Posted: 1 decade ago 18 apr 2013, 09:08 GMT-4

Hi,

the phase setting just multiplies the solution with the factor exp(i*Pi*phase/180). This means that your plots look different at different phase angles because the plot only considers the real component and the magnitude of the result is shifted to the imaginary axis.

Cheers
Edgar

--
Edgar J. Kaiser
www.emphys.com
Hi, the phase setting just multiplies the solution with the factor exp(i*Pi*phase/180). This means that your plots look different at different phase angles because the plot only considers the real component and the magnitude of the result is shifted to the imaginary axis. Cheers Edgar -- Edgar J. Kaiser http://www.emphys.com

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