Menu

Discussion Forum

New Discussion
Filter

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

What does phase mean in a stationary solver?

Posted Apr 18, 2013, 2:00 a.m. EDT 4 Replies

m0nk3y
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

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 Apr 18, 2013, 9:08 a.m. EDT
Pu Zhang
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 18, 2013, 3:32 a.m. EDT
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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 18, 2013, 4:16 a.m. EDT
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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 18, 2013, 8:13 a.m. EDT
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
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 18, 2013, 9:08 a.m. EDT

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

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.

Suggested Content