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Old   October 5, 2007, 09:04
Default DPM
  #1
jack
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Hello, One doubt, is it required for DPM that the size of my particule is smaller than the size of my first cell next to the wall in case where the particle reach the wall? If it is not the case could it be an explanation for incomplete particles? Thnak u in advance
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Old   October 5, 2007, 22:47
Default Re: DPM
  #2
Woo Meng Wai
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Hi Jack,

The main assumption in using the DPM in FLUENT is that the particles are point particles. This implies that the volume of the particles are small and insignificant compared to the sizze of the cells.

Incomplete particles: The typical root of this problem is that the number of steps set for each DPM iteration is insufficient. As a result, the particles are tracked to the maximum number of step before being able to reach any boundary.

You can change these settings by:

Define --> DPM--> Tracking--> maximum time steps

Try increasnig the maximum time steps. The max is 9999999999.

Another possible root to the problem is recirculation of particles within the geometry rpeventing it from reachign the boundary. You can check the flow pattern to see if there is such tendencies.

Do let me know if this works

cheers, Woo

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Old   October 6, 2007, 04:48
Default Re: DPM
  #3
jack
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thank you for your answer. So you mean that the size of the particles is not a problem compare to the size of the mesh... When I track my particle i can see that there are no recirculation. Particles seem to reach the wall but there are noted incomplete, and i tried to increase the nbr of DPM iteration but without much improvement. But i will try as you say with the tracking. Thanks a lot anyway
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Old   October 8, 2007, 04:15
Default Re: DPM
  #4
fluid
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What kind of injection do you have? Have you the possibility to track the injections separately in order to discern among theit trajectories? In this way you can find which particles are incomplete...
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Old   October 10, 2007, 02:56
Default Re: DPM
  #5
jack
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i inject from a surface with discretize point. I am already tracking these particle separatly with 10 tries and always some tries are incomplete eventhough the display shows particles going to wall
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Old   October 10, 2007, 04:12
Default Re: DPM
  #6
fluid
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Sorry, probably you said but I forgot it but why do you think that a particle that reach the wall should be complete? Isn't it possible that after reaching the wall it could reflect/bound and if it stays there it is incomplete? What b.c. condition have you set for DPM behaviour of your walls?
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Old   October 10, 2007, 05:09
Default Re: DPM
  #7
jack
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no because i trap them on the wall. I set my BC on that wall as trap. Trap particles can not be by definition incomplete. Thnaks for your ideas
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Old   October 10, 2007, 07:29
Default Re: DPM
  #8
jack
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"Define --> DPM--> Tracking--> maximum time steps " i said that i already did that of course before to post, but doesnt change anything. I didnt try 999999999999 because it take to much time. Thnak you anyway
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Old   October 10, 2007, 08:46
Default Re: DPM
  #9
jack
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hi, my particles actually stopped just before the wall if i use a zoom. My problem is a 2D, so the wall is an edge. I can really not explain that. Maybe a bug in the track particle
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