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-   -   VOF Volume fraction in Velocity inlet (https://www.cfd-online.com/Forums/fluent/73854-vof-volume-fraction-velocity-inlet.html)

 aruelle March 18, 2010 09:40

VOF Volume fraction in Velocity inlet

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

 sega March 18, 2010 12:53

Quote:
 Originally Posted by aruelle (Post 250625) 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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