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Old   June 17, 2010, 08:18
Default cyclone separator multiphase help
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siddharth
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I am trying to model cyclone separator in CFX. Based on the previous help from this forum i modeled both air and aluminium particles as continuous medium. the solution converged after 1000 iteration.


Now i am trying to model air as continuous medium and aluminium as particle transport solid. i have used uniform particle distribution with min and max dia as 1micron and 100 micron respectively.For turbulence i have used SSG reynolds stress model. I have used point cone for particle injection. The solution is not getting converged and it is oscillating.

I have attached the ccl file.
I really need some help

Thank you
siddharth
-------------------------
cyclone_multiphase_v5_5_002.zip
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Old   June 17, 2010, 09:17
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Glenn Horrocks
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Reynolds stress turbulence models are always hard to converge. I seem to remember telling you this before - only use a RSM model if you really need it and for a particle transport model I doubt you need it.

Here are some tips:
http://www.cfd-online.com/Wiki/Ansys...gence_criteria
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Old   June 17, 2010, 09:25
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I choose SSG be cause it gave the better solution when both air and aluminium were continuous fluid
I am going to try with Shear stress model. Is this model ok for particle transport model?

Thanks
Siddharth
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Old   June 17, 2010, 20:38
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Glenn Horrocks
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As I said previously, if you are adding the complexity of a particle transport model then the last thing you need is making convergence even more difficult by using a RSM model. The extra "accuracy" you get from a RSM model will probably be lost in the multiphase behaviour anyway so there is little point. So SST is a much better choice. Only go to RSM if you can clearly show that SST is inadequate.
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Old   June 18, 2010, 00:47
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I tried with SST. The solver ran for 1000 iterations. The solution is not converged. It is still oscillating. And the domain imbalances are huge. Really need some help.

Thanks
Siddharth
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Old   June 18, 2010, 00:50
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Have you tried the tips on the cfd-online wiki page?
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