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Multiphase Modeling-Different Velocities at inlet

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Old   November 19, 2012, 01:24
Default Multiphase Modeling-Different Velocities at inlet
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Kamyar
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Hi

I am trying to simulate multiphase flow in a pipe. There are water, oil and air flowing simultaneously together. I could define three different regions for three phases by using field function. now I want to set a constant velocity for oil and water and different constant velocity for air. I do not know how to set it. anybody can help me?

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Old   November 19, 2012, 11:55
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I don't know if this will work or not, but it might be worth trying. If you have defined the volume fractions for the three phases, then just multiply the velocity that you want for each phase by that phase's volume fraction and add all three of these velocities:

air inlet velocity * air vf + water inlet velocity * water vf + oil inlet velocity * oil vf

This will give you the correct profile, I think.
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Old   November 20, 2012, 01:40
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The problem is that I want to have two different boundary conditions instead of one. Thanks for your suggestion though
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Old   November 20, 2012, 09:22
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What do you mean by different boundary conditions?
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Old   November 20, 2012, 10:42
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I want to have different constant values for liquid and gas phases. Oil and water need to have 0.5 m/s and air 1m/s velocity.
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Old   November 20, 2012, 11:23
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Then this field function should work:

<0.5 m/s> * ($oilvf + $watervf) + <1 m/s> * $airvf

(you need to define these field functions: oilvf, watervf, and airvf for inlet.)
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Old   November 22, 2012, 19:49
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Use an Eulerian-Eulerian approach. In STAR-CCM+ called segregated multiphase. A VOF approach is not suitable for doing this.
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