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Degassing boundary condition in Fluent?

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Old   March 24, 2009, 09:18
Default Degassing boundary condition in Fluent?
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JP
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Hi, I am running a simulation of a bubble column with a free liquid surface on top, in Fluent.
I need to set a boundary condition for the top surface, where the air bubbles can escape, but the liquid cannot. In Fluent, currently all I can do is to set this surface as a pressure outlet with backflow volume fraction of air as zero. But this does not prevent the liquid from leaving the boundary.
Is it possible to set the boundary condition so that air can leave the boundary but liquid cannot? (Similar to the degassing B.C. in CFX)
I am running the mixture model, with 2D geometry, bubbles injected from bottom.
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Old   August 17, 2011, 22:26
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The same question to you, Pray for reply
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Old   August 18, 2011, 08:46
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Looks like there was no straight forward method to do this. I had taken a taller air section in the top, so that liquid does not leave the boundary. I had also patched the top region with air.
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Old   November 23, 2015, 13:56
Default degassing boundary condition
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Hi,

I'm working on a bubble column. I was wondering that how can I modify settings in the degassing boundary condition ? close to the water surface, it under predicts velocity for both air and water. Is there any way that I can fix this problem near the water surface ? the flow pattern with degassing boundary is correct however, velocities near the water surface is very low comparing with experimental values.

Thanks a lot
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