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Old   June 28, 2007, 05:08
Default Double Boundary
  #1
Dr. Flow Squad
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Can I in CFX create a boundary that has double settings? For a multiphase application I would like to have the continuous air phase to treat a specific surface as wall, but for the dispersed solid particles the surface should be an outlet. Can it be done?
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Old   June 28, 2007, 06:05
Default Re: Double Boundary
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Joe
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Turn off the particles as they strike that particular wall?
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Old   June 28, 2007, 07:12
Default Re: Double Boundary
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Dr. Flow Squad
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It's an Euler-Euler approach. Two "fluids" and no particles.
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Old   June 28, 2007, 07:50
Default Re: Double Boundary
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Sameer
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Hi Dr Flow Squad!

U can try the following suggestion.

In Boundary details of an outlet define Degassing Condition in the option of Mass and Momentum,So that it will allow only dispersed phase to go out and it will restrict continuous phase to leave.

Hope it will work.

Sameer
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Old   June 28, 2007, 07:59
Default Re: Double Boundary
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Dr. Flow Squad
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Degassing conditon. Doesn't it work the other way around? Letting only the continuous phase to leave?
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Old   June 28, 2007, 08:04
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Joe
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"degassing" boundary condition. Commonly used for chem reactor studies.
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Old   June 28, 2007, 11:17
Default Re: Double Boundary
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Robin
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No, the degassing condition will allow the dispersed phase to leave. However, it is only applicable to "degassing", i.e. bubbles rising and leaving the top. I don't recall the details but it has something to do with the hydrostatic pressure.

What is it you are trying to model? There may be another approach.

Regards, Robin
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Old   June 29, 2007, 01:30
Default Re: Double Boundary
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Dr. Flow Squad
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I'm simply modelling a good old fashion cyclone. the loading is rather high, and I also want to determine the separation efficiency due to loading so I'm using a Euler-Euler approach instead of particles. But I want all my gas to exit at the top of the cyclone, whereas "particles" that touch the bottom surface should be collected.
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Old   June 29, 2007, 11:07
Default Re: Double Boundary
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Robin
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What physically prevents gas from exiting the bottom?
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Old   July 7, 2007, 15:54
Default Re: Double Boundary
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Dr Flow Sqaud
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a "snail". -
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