one phase outlet VOF - Model

Jim87 · May 6, 2013, 15:34

In order to model a filling process (for example an bucket getting filled with water) I tried to build an simulation where the first phase can get out of the bucket (displaced by phase 2). The second phase should fill the bucket and not get out of the outlet.

- I thought of a pressure outlet with a backflow volume fraction of 0.

- Looking at the velocity of phase 2. I noticed that phase 2. leaves the bucket through the outlet (picture).

What I might need is a semipermiable wall which could only be passed by the first phase, which is displaced by th second.

Does someone have an idea what boundary condition might fit?

RodriguezFatz · May 7, 2013, 02:58

Hold on. Did I get it right, your problem is, that the outlet shows a velocity of phase 2, but you want only phase 1 to leave it?
That does not matter! You need to create a custom field variable "velocity2 * volume-fraction2". You see the difference? You can have some velocity2 value there, but if volume-fraction is zero, nothing will leave at all...

Jim87 · May 7, 2013, 17:13

Testing the prssure outlet (ara weighted average for every volume typ (phase 1 and phase 2) I get the following two reports (picture).

If phase 2 is detected in the outlet the outlet is passable for the second phase.

The pressure outlet and its backflow volume fraction of one might not be the right solution.

Has anyone an other idea for this problem or can show me a possible fault of setting wrong monitors?

RodriguezFatz · May 8, 2013, 06:34

You pictures seem to look fine, what is the problem?

Jim87 · May 8, 2013, 06:44

In my opinion the surface monitor of the second phase should be 0 at any time.
I wanted the outlet to be semipermeable, phase two shouldn't pass this surface. Only the first phase would be able to leave the bucket.

Maybe I'm interpreting the monitors wrong, but if there is a detection of phase 2 at the outlet it leaves the bucket.

RodriguezFatz · May 8, 2013, 06:46

But how can that work? You put in incompressible water through the inlet. It has to leave the domain somewhere, when all air is gone...

subhas.hunasikatti@gmail. · November 13, 2013, 02:15

Originally Posted by victoryv

I don't know if this information helps you or not. I was getting the same error. I reduced the relaxation factors as I assumed it was due to divergence. It worked perfect. Btw, I was also running in parallel.

Hi friend , I am ding 2D model with considering parallel running in this i am getting floating point exception , after getting this i reduce the under relaxation factor value but still i am getting same, what i have to do .........?

May 7, 2013, 02:58		#2
RodriguezFatz Senior Member Philipp Join Date: Jun 2011 Location: Germany Posts: 1,297 Rep Power: 26	Hold on. Did I get it right, your problem is, that the outlet shows a velocity of phase 2, but you want only phase 1 to leave it? That does not matter! You need to create a custom field variable "velocity2 * volume-fraction2". You see the difference? You can have some velocity2 value there, but if volume-fraction is zero, nothing will leave at all... __________________ The skeleton ran out of shampoo in the shower.

May 8, 2013, 06:34		#4
RodriguezFatz Senior Member Philipp Join Date: Jun 2011 Location: Germany Posts: 1,297 Rep Power: 26	You pictures seem to look fine, what is the problem? __________________ The skeleton ran out of shampoo in the shower.

May 8, 2013, 06:46		#6
RodriguezFatz Senior Member Philipp Join Date: Jun 2011 Location: Germany Posts: 1,297 Rep Power: 26	But how can that work? You put in incompressible water through the inlet. It has to leave the domain somewhere, when all air is gone... __________________ The skeleton ran out of shampoo in the shower.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Weld surface deformation by VOF model	minhaj_iut	FLUENT	5	February 26, 2017 23:51
Thermal Phase Change model	Niru	CFX	0	February 21, 2013 13:13
Water subcooled boiling	Attesz	CFX	7	January 5, 2013 03:32
Heterogeneous reaction between phases with VOF model	sooroo3	Fluent UDF and Scheme Programming	0	February 15, 2011 02:59

May 8, 2013, 06:44		#5
Jim87 Member Stephan Langenberg Join Date: Sep 2011 Location: Germany Posts: 73 Rep Power: 14	In my opinion the surface monitor of the second phase should be 0 at any time. I wanted the outlet to be semipermeable, phase two shouldn't pass this surface. Only the first phase would be able to leave the bucket. Maybe I'm interpreting the monitors wrong, but if there is a detection of phase 2 at the outlet it leaves the bucket.

November 13, 2013, 02:15		#7
subhas.hunasikatti@gmail. Member subhas hunasikatti Join Date: Sep 2013 Posts: 32 Rep Power: 12	Originally Posted by victoryv I don't know if this information helps you or not. I was getting the same error. I reduced the relaxation factors as I assumed it was due to divergence. It worked perfect. Btw, I was also running in parallel. Hi friend , I am ding 2D model with considering parallel running in this i am getting floating point exception , after getting this i reduce the under relaxation factor value but still i am getting same, what i have to do .........?