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Particle tracking problem with MRF

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Old   September 20, 2013, 05:47
Default Particle tracking problem with MRF
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Jianye Xia
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Hi all,

I have encountered the problem with particle tracking in a stirred tank simulation with the Multiple Reference Frame method, the setting of my model is like this:

Firstly, I use Freeze/Roter (MRF) to get the initial steady state velocity field in the stirred tank reactor,
Then, freeze the velocity field and inject the particles at one small boundary (inlet of the stirred tank), one way coupling (particles have no effect on the velcoity of liquid) of these particles was used, I aslo active the expert parameter of 'pt tracks in absolute frame', but the resulted trajectories of each particle showed that it discontinued at the interface between non-rotating zone and rotating zone.

Has any body met with this probem of particle tracking with MRF?

Any comments and suggestions is appreciated!

Jianye
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Old   September 20, 2013, 06:17
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Glenn Horrocks
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FAQ:

http://www.cfd-online.com/Wiki/Ansys...f_reference.3F
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Old   September 20, 2013, 06:53
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Jianye Xia
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Thanks, Glenn!

I red that, but my problem is not the streamline but particle trajectory.
The trajectory disconnected across the station/rotating interface.

Jianye
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Old   September 20, 2013, 07:48
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Glenn Horrocks
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Streamline or particle track, the effect is the same. The change in reference frame means tracks do not appear continuous.
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Old   September 20, 2013, 08:22
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Jianye Xia
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Glenn, can you make it more clear?

Quote:
To see continuous streamlines plot the variable "Velocity in stationary frame". This is referenced to the stationary frame regardless of whether the frame is rotating or not, so will be continuous. You might need to access this variable using the puzzlingly labelled "..." button
How can I find the "..." button? Does it in the cfx5post.exe GUI?

When I process the particle trakcing results, there is "Res PT for Particle" in the model tree, when I double clicked it, there was no options for selecting "Velocity in stn frame" in the setting panel of "Res PT for Particle".

I have toggle on the expert parameter of "'pt tracks in absolute frame'", that should be mean that the particle will follow the velocity in stationary fram, am I right?

And what does it mean by "To see continuous streamlines plot the variable "Velocity in stationary frame". "?

How did you do that? can you provide more details ? Thanks a lot!
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Old   September 20, 2013, 08:27
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The FAQ is referring to CFD-Post.

I am not aware of the "pt tracks in absolute frame" expert parameter but I presume it does what it says it does and those tracks should be continuous.

Plotting the variable "Velocity in stationary frame" is relevant to streamlines only. This option is not available for particle tracks.
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Old   September 20, 2013, 08:40
Default It is sure not continuous
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Jianye Xia
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See attached figure: the red arrow point the disconnectied trajectories

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Old   September 21, 2013, 06:18
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I am not sure what is happening there. Have you checked your particle termination parameters?
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Old   September 22, 2013, 16:13
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I have also checked with the termination parameters, but it did also not work!

Any other clues?
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