CFD-Post: streamline movement from stat. to rot. part

**Anny** · April 17, 2015, 06:30

Hey everyone,

I am trying to simulate the flow in a centrifugal pump.

Doing some test runs I recognized an abrupt cut in the "movement" of the streamlines between the rotating parts and the stationair parts like there is a missing interaction between the moving and rotating parts. The pictures attached should make it clear. Do I have to work it out in CFD Post or before in CFX Pre?

Thank you all very much for your time... again!

**Anny** · April 17, 2015, 06:31

The picture of the streamlines

brunoc · April 17, 2015, 08:21

You're getting the correct behavior.

The abrupt change in the streamlines is due to the fact that CFX (and most CFD software, in fact) solves the momentum equations on rotating domains using the rotating reference frame. The result is that the velocity vector inside the rotating domain does not have the $\omega R$ component in its circumferential component.

If you want to plot the velocity field on the stationary reference frame, use Velocity in Stn Frame.

That's all in the documentation.

Cheers

**Anny** · April 17, 2015, 09:33

Thank you very much for the explanation Bruno! I didnt thourd of the missing circumferential component in the stationary parts! ... I am going to search/ read now more about adding cyldrical coordinates to not symmetric parts and using turbo.
I apologie in advance for might having to ask some questions about it later

Cheers

April 17, 2015, 06:30	CFD-Post: streamline movement from stat. to rot. part	#1
Anny New Member Join Date: Jan 2015 Posts: 19 Rep Power: 11	Hey everyone, I am trying to simulate the flow in a centrifugal pump. Doing some test runs I recognized an abrupt cut in the "movement" of the streamlines between the rotating parts and the stationair parts like there is a missing interaction between the moving and rotating parts. The pictures attached should make it clear. Do I have to work it out in CFD Post or before in CFX Pre? Thank you all very much for your time... again!

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April 17, 2015, 08:21		#3
brunoc Senior Member Bruno Join Date: Mar 2009 Location: Brazil Posts: 277 Rep Power: 21	You're getting the correct behavior. The abrupt change in the streamlines is due to the fact that CFX (and most CFD software, in fact) solves the momentum equations on rotating domains using the rotating reference frame. The result is that the velocity vector inside the rotating domain does not have the $\omega R$ component in its circumferential component. If you want to plot the velocity field on the stationary reference frame, use Velocity in Stn Frame. That's all in the documentation. Cheers

April 17, 2015, 09:33		#4
Anny New Member Join Date: Jan 2015 Posts: 19 Rep Power: 11	Thank you very much for the explanation Bruno! I didnt thourd of the missing circumferential component in the stationary parts! ... I am going to search/ read now more about adding cyldrical coordinates to not symmetric parts and using turbo. I apologie in advance for might having to ask some questions about it later Cheers