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Old   April 16, 2013, 11:45
Question Fluid mixing problem in bubble column
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I'm a beginner to fluent and currently working on a project to simulate flow patterns in a bio gas reactor. Mixing in the tank is achieved by bubbling of air through 10 pipes arranged in a circular pattern.
My main problem was with the large dimensions of the tank (H = 20m, D = 9.5 m) and compared to the pipes ( D= 7.5 cm) which gave me around 1 million CVs.
Here are some of the operating conditions.
pressure at top of the liquid level = 40 m bar
pipe introduces air at a pressure of 2 bar and air velocity around 2 m/s.

I've used velocity inlet and pressure outlet BCs and bit confused about which values to be used at boundaries.
I've used for operating pressure= 0, gauge pressure at pressure outlet = 1 atm+40 mbar and initial guage pressure at velocity inlet = 2 bar. But the static pressure profile i got was not seems OK...!!!
And it take lot of iterations to converge at transient state..!!!

Can anybody give me some feedback to get through with this problem??

Thanks in advance

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Old   June 30, 2013, 18:44
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for gas, I suggest you use mass-flow-inlet and out flow
when you have the pressure, the use pressure inlet for inlet, and pressure outlet for the top
with this size of reactor, I'm not sure if 1 million meshes are enough! try to use a smaller one first
Hossein Amini
PhD student in Biochemical Engineering; Computational Science and Engineering department;
North Carolina Agricultural and Technical State University
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