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Old   February 16, 2008, 23:53
Default New to particles
  #1
Dre
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So I'm new to particle tracking.

I've been charged with the task of designing a cyclonic separator to separate small objects that will stay at the bottom, and the dust and debris will exit the separator.

Now my question is can this be achieved in CFX using particle tracking? Again I'm not familiar with this feature, but my idea is along these lines :

1) Inject particles of different density at the inlet

2) Play around with the airspeed and geometry until the lighter particles exit and the heavier ones stays at the bottom

So is my proposed methodology on track, or is this not possible at all?
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Old   February 17, 2008, 06:11
Default Re: New to particles
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Glenn Horrocks
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Hi,

Yes, this can be done and the approach you describe should work.

The tricky bit will be getting the flow right. It is well known that cyclones cannot be modelled using k-e based models. You might be able to model it using the curvature correction in the SST model but check it before you use it, but you may be forced to use RSM or LES models.

The flow will be transient in some regimes and for these cases your only chance of a accurate simulation is LES.

But if you want my suggestion for a starting point use a RSM model. You will need to ensure you do a good quality mesh as these models do not converge well on poor quality meshes.

Glenn Horrocks
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Old   February 18, 2008, 12:41
Default Re: New to particles
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Dre
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I don't think that I have the horsepower to run an LES simulation.

I was actually thinking of doing the analysis using a laminar model. This is because that the speeds are relatively low and it deals with a big vortex, not really turbulence. I may be way off though!
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Old   February 18, 2008, 18:13
Default Re: New to particles
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Glenn Horrocks
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Hi,

If the flow is laminar then no problem. If the flow is turbulent then this will not help. Simulating a turbulent flow without a turbulence model will mean your flow will either not converge or just be plain wrong. Turbulence models don't add too much overheads to a simulation, and quite often speed it up by stabilising it.

Whether you need LES will depend on what flow regime you aer operating in. If the vortex is stationary a normal RSM turbulence model should be OK, but if it moves around then you will probably need LES.

Glenn Horrocks
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