Problem: volume fraction of gas bubble with twoPhaseEulerFoam

morteza1991 · April 20, 2015, 04:06

Hi every body,
I'm trying to simulate gas bubble in openFoam with twoPhaseEulerFoam. Flow is simulated correctly but volume fraction of gas bubble are wrong since it is not 1 as I expected.
I think my problem is caused by phase properties document but I don't know what it is.I'm kind of new user of openFoam. please tell me what should I do ?!

vishal3 · April 20, 2015, 07:33

Hi Morteza

May I know the details of your case?? What exactly do you want??
Which OF version are you using???

morteza1991 · April 20, 2015, 08:23

Thank you for your reply, I try to simulate a two phase flow consists of Water and N2 gas in rectangular channel. As you know,N2 gas is undissolved gas, so alpha in gas bubbles must be 1 but alpha according to result, is around 0.5.
Also I'm using openfoam 2.3.1

mihaipruna · April 20, 2015, 14:49

I assume this solver uses the VOF method, so the interface will not be sharp. Maybe relative to the size of your bubbles , it gets smeared resulting in values less than 1.
Try with a more refined grid.

Also, I saw this tutorial , might help:
http://www.tfd.chalmers.se/~hani/kur...PhaseEuler.pdf

hester · April 21, 2015, 17:42

Hello,

twoPhaseEulerFoam assumes two interpenetrating fluids. Therefore you get the wrong volume fraction values.
Have a look at interFoam. It is using VOF and should be able to model the phase fractions better.
http://www.tfd.chalmers.se/~hani/kur...Hemida_VOF.pdf

Regards,
hester

April 20, 2015, 14:49		#4
mihaipruna Senior Member Mihai Pruna Join Date: Apr 2010 Location: Boston Posts: 195 Rep Power: 16	I assume this solver uses the VOF method, so the interface will not be sharp. Maybe relative to the size of your bubbles , it gets smeared resulting in values less than 1. Try with a more refined grid. Also, I saw this tutorial , might help: http://www.tfd.chalmers.se/~hani/kur...PhaseEuler.pdf __________________ Mihai Pruna's Bio

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April 20, 2015, 07:33		#2
vishal3 New Member Vishal Join Date: Feb 2013 Posts: 28 Rep Power: 13	Hi Morteza May I know the details of your case?? What exactly do you want?? Which OF version are you using???

April 20, 2015, 08:23		#3
morteza1991 New Member morteza javid Join Date: Apr 2015 Posts: 2 Rep Power: 0	Thank you for your reply, I try to simulate a two phase flow consists of Water and N2 gas in rectangular channel. As you know,N2 gas is undissolved gas, so alpha in gas bubbles must be 1 but alpha according to result, is around 0.5. Also I'm using openfoam 2.3.1

April 21, 2015, 17:42		#5
hester Member Join Date: May 2014 Location: Germany Posts: 32 Rep Power: 12	Hello, twoPhaseEulerFoam assumes two interpenetrating fluids. Therefore you get the wrong volume fraction values. Have a look at interFoam. It is using VOF and should be able to model the phase fractions better. http://www.tfd.chalmers.se/~hani/kur...Hemida_VOF.pdf Regards, hester