# VOF Volume fraction in Velocity inlet

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 March 18, 2010, 09:40 VOF Volume fraction in Velocity inlet #1 New Member   amélie ruelle Join Date: Mar 2010 Posts: 1 Rep Power: 0 Hello I am using a VOF model for the simulation of a diphasic flow entering a pipe and then spilled in a tank. The entry of the diphasic flow is defined as a velocity inlet. The volume fraction of the velocity inlet in fixed to 0,3. Convergence is ok. Moreover, i saw different works where the volume fraction of the velocity inlet is different from 1 or 0. Nevertheless, i read in an Ansys document that for velocity inlet, only one phase can enter; therefore, only one phase can have the inlet volume fraction set to 1 and nonzero inlet velocity. So, can somebody help me about this? Is it allowed and physically correct to impose a volume fraction of 0,3 to a velocity inlet with the vof model? Thank you very much for your help, Amélie

March 18, 2010, 12:53
#2
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Sebastian Gatzka
Join Date: Mar 2009
Location: Frankfurt, Germany
Posts: 729
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Quote:
 Originally Posted by aruelle Hello I am using a VOF model for the simulation of a diphasic flow entering a pipe and then spilled in a tank. The entry of the diphasic flow is defined as a velocity inlet. The volume fraction of the velocity inlet in fixed to 0,3. Convergence is ok. Moreover, i saw different works where the volume fraction of the velocity inlet is different from 1 or 0. Nevertheless, i read in an Ansys document that for velocity inlet, only one phase can enter; therefore, only one phase can have the inlet volume fraction set to 1 and nonzero inlet velocity. So, can somebody help me about this? Is it allowed and physically correct to impose a volume fraction of 0,3 to a velocity inlet with the vof model? Thank you very much for your help, Amélie
For a volume fraction you will need a volume, where a boundary is a face.
So this does not make sense.

You want to set up 30% of the inlet with phase one and 70% of the inlet with phase two? Am I guessing right?

I would split up the inlet into two (30%/70%) and define the VOF-variable to 0 at the one and 1 at the other.
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