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Particle study in cyclone separator

Question asked by 1-CSA37M on Mar 9, 2010
Latest reply on Nov 22, 2010 by Bill McEachern

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I'm analyzing a cylcone separator with air and solid particles.

I have problems with calculating and displaying the particle trajectories. It says in the result summary box that their 'fate' is "maximum time step". However, the 'residence time' for all 20 particles is between 1 and 2 seconds. I have specified the maximum time to 3600 seconds on the settings tab when i set up the particle study.

In help it says:

"Maximum time. Stops the particle's trajectory when the particle traveling time has reached the specified maximum value."

Why does it stop before it satisfies this criterium? Have I overlooked or misunderstood something?

Se attached for pictures of cyclone and dialog boxes.

Thanks!

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Cyclone separator.jpg102.4 KB
Particle study settings.jpg174.6 KB

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Richard Stevenson Mar 24, 2010 10:32 AM
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what is the reflection setting for your study?
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- 1-CSA37M @ Richard Stevenson on Mar 24, 2010 10:42 AM
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  Ideal reflection.
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David Paulson Mar 24, 2010 12:09 PM
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If you hide your flow trajectories then you will able to see the particles better. You can also increase the number of particles displayed.
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- 1-CSA37M @ David Paulson on Mar 24, 2010 12:28 PM
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  There are no particle trajectories in the image I've posted. The image is to show the geometry of the cyclone to make things clear. And, increasing the number of particles does not solve the issue I'm experiencing. Thanks for the input anyways.
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  - David Paulson @ 1-CSA37M on Mar 24, 2010 2:07 PM
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    Your results summary indicates that you do have particles but they are not being displayed. So, your settings are fine, and almost identical to the settings I used in a similar study which I have attached as a jpeg. When you RMB click Injection does it display "show" or "hide"?
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    Oil Separator Particle Study.JPG76.9 KB
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    - 1-CSA37M @ David Paulson on Mar 24, 2010 2:19 PM
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      Sorry about the confusion, but the image and the dialog boxes are not connected. The image is purely to show the geometry. The reason I also display the flow paths is that I want to hide some geometric features that my client wants to be confidential.
      
      I have no trouble displaying the particle trajectories. The issue is that the trajectories terminate by some reason I cannot understand.
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      - David Paulson @ 1-CSA37M on Mar 25, 2010 1:12 AM
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        I now understand that your particle trajectories are visible, but they end prematurely. I tried to replicate the "Maximum time step" you are getting in your results summary by changing the particle size in my study, but my particles only were absorbed because that is my wall condition, not reflection. But you might see if your results change if you make your particles smaller or larger. For my designs I have to run a number of different particle sizes to reflect the real input stream. Or you could just change your wall condition to "absorb" and see if you get the same "Maximum time step" message in the results summary.
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1-CSA37M Mar 25, 2010 3:33 AM
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I asked my VAR about this issue, and they asked the development team which after a while replied the following:

"The 'maximum time step' is limited by the 'maximum iteration count' at 100 000. There is SPR 477646 to increase the user-defined 'maximum iteration count' to values greater than 100 000. The developers were not currently able to say in what version this setting will be increased. Unfortunately there is no workaround."

I.e. I know why this happens, but I can't really do anything about it.

Also, particles may 'get stuck' in vortices etc which is relevant for this case.
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- David Harrold @ 1-CSA37M on Nov 22, 2010 1:39 PM
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  Hi Maria,
  That's an interesting problem.
  Would decreasing the mesh quality help? I'd assume that a coarser mesh would yield a lower iteration count. I know that's not the right way to solve the problem, but it would be interesting to know if it had an effect.
  
  I am modeling a similar cyclone separator and did not run into the issue you had. The "max time steps" works as expected. I'm running SW 2011, SP0.0, so maybe the issue has been fixed. Here's a picture:
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  - Bill McEachern @ David Harrold on Nov 22, 2010 1:47 PM
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    I ran into the same problem in one I just did a couple days ago in 2011 sp0. It went off to the developers as well.
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Particle study in cyclone separator

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