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-   -   Multiphase Modeling-Different Velocities at inlet (http://www.cfd-online.com/Forums/star-ccm/109470-multiphase-modeling-different-velocities-inlet.html)

sizyef November 19, 2012 01:24

Multiphase Modeling-Different Velocities at inlet
 
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?

Thank You

triple_r November 19, 2012 11:55

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.

sizyef November 20, 2012 01:40

The problem is that I want to have two different boundary conditions instead of one. Thanks for your suggestion though

triple_r November 20, 2012 09:22

What do you mean by different boundary conditions?

sizyef November 20, 2012 10:42

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.

triple_r November 20, 2012 11:23

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.)

abdul099 November 22, 2012 19:49

Use an Eulerian-Eulerian approach. In STAR-CCM+ called segregated multiphase. A VOF approach is not suitable for doing this.


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