# Double Boundary

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 June 28, 2007, 05:08 Double Boundary #1 Dr. Flow Squad Guest   Posts: n/a 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?

 June 28, 2007, 06:05 Re: Double Boundary #2 Joe Guest   Posts: n/a Turn off the particles as they strike that particular wall?

 June 28, 2007, 07:12 Re: Double Boundary #3 Dr. Flow Squad Guest   Posts: n/a It's an Euler-Euler approach. Two "fluids" and no particles.

 June 28, 2007, 07:50 Re: Double Boundary #4 Sameer Guest   Posts: n/a 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

 June 28, 2007, 07:59 Re: Double Boundary #5 Dr. Flow Squad Guest   Posts: n/a Degassing conditon. Doesn't it work the other way around? Letting only the continuous phase to leave?

 June 28, 2007, 08:04 Re: Double Boundary #6 Joe Guest   Posts: n/a "degassing" boundary condition. Commonly used for chem reactor studies.

 June 28, 2007, 11:17 Re: Double Boundary #7 Robin Guest   Posts: n/a 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

 June 29, 2007, 01:30 Re: Double Boundary #8 Dr. Flow Squad Guest   Posts: n/a 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.

 June 29, 2007, 11:07 Re: Double Boundary #9 Robin Guest   Posts: n/a What physically prevents gas from exiting the bottom?

 July 7, 2007, 15:54 Re: Double Boundary #10 Dr Flow Sqaud Guest   Posts: n/a a "snail". -

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