Multiphase Modeling-Different Velocities at inlet

sizyef · November 19, 2012, 00:24

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, 10:55

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, 00:40

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, 08:22

What do you mean by different boundary conditions?

sizyef · November 20, 2012, 09:42

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, 10:23

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, 18:49

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

November 19, 2012, 00:24	Multiphase Modeling-Different Velocities at inlet	#1
sizyef New Member Kamyar Join Date: Nov 2009 Posts: 4 Rep Power: 16	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

November 22, 2012, 18:49		#7
abdul099 Senior Member Join Date: Oct 2009 Location: Germany Posts: 636 Rep Power: 21	Use an Eulerian-Eulerian approach. In STAR-CCM+ called segregated multiphase. A VOF approach is not suitable for doing this. __________________ We do three types of jobs here: GOOD, FAST AND CHEAP You may choose any two!

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November 19, 2012, 10:55		#2
triple_r Senior Member Reza Join Date: Mar 2009 Location: Appleton, WI Posts: 116 Rep Power: 17	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.

November 20, 2012, 00:40		#3
sizyef New Member Kamyar Join Date: Nov 2009 Posts: 4 Rep Power: 16	The problem is that I want to have two different boundary conditions instead of one. Thanks for your suggestion though

November 20, 2012, 08:22		#4
triple_r Senior Member Reza Join Date: Mar 2009 Location: Appleton, WI Posts: 116 Rep Power: 17	What do you mean by different boundary conditions?

November 20, 2012, 09:42		#5
sizyef New Member Kamyar Join Date: Nov 2009 Posts: 4 Rep Power: 16	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.

November 20, 2012, 10:23		#6
triple_r Senior Member Reza Join Date: Mar 2009 Location: Appleton, WI Posts: 116 Rep Power: 17	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.)