# Volume fraction of the whole geometry

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• Last Post 15 February 2019
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gunjanauti posted this 15 February 2019

How can I access the volume fraction of the whole geometry of the problem? C_VOF(c,t) gives the volume fraction of the particular cell but I want to access the Volume fraction of the whole domain.

Moreover how can add a source term for volume fraction equation? where should I hook the UDF for that?

abenhadj posted this 15 February 2019

1/UDF for Source term: Can be hooked in the Source Term of the phase after selecting the cell zone

2/C_VOF is the volume fraction in a cell. If you want to get it overall you need to loop over the cell. Please tell me what you want to do here.

If you want to get an average value you can just the report function in ANSYS Fluent and plot them over the time.

Best regards,

Amine

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abenhadj posted this 15 February 2019

You can do that in the GUI: Report> Volume Integral of VOF to get the volume of particular phase for the whole domain. The ratio will be volume-weighted average. Check "Computing volume Integrals" in the manual.

Best regards,

Amine

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abenhadj posted this 15 February 2019

What do you want to get? Volume of phase in the whole geometry?

Best regards,

Amine

gunjanauti posted this 15 February 2019

Volume fraction of the phase in the whole geometry at a given time step. Basically the solution of the volume fraction equation.

abenhadj posted this 15 February 2019

For Source Term you need to hook the UDF into the VOF equation.

Best regards,

Amine

gunjanauti posted this 15 February 2019

How? There is no term in the GUI afaik for vof equation. Are there any text commands that give access to it?

gunjanauti posted this 15 February 2019

For example, if I am working in a cylindrical geometry, I want the volume fraction of vapor for the whole cylinder. Do I need to write a DEFINE_ADJUST macro and calculate it or is there a direct macro or function for that? Because C_VOF(c,t) gives the value locally (only about the mentioned cell). Which means if C_VOF(c,t) =1 then for a given cell all the fluid is in the primary phase.

I want to calculate alpha (void fraction) globally.

abenhadj posted this 15 February 2019

Then you need either to do it from GUI (Reports) or via UDF. In the UDF you need to sum C_VOF*C_VOLUME over all cells or access the Report definition in the UDF.

Again what do you want: a volume average value of VOF of the phase or you want to know the volume of phase in the geo/ volume of the geo?

Best regards,

Amine

gunjanauti posted this 15 February 2019

I want volume of phase/ volume of geo.

Thanks!

Gunjan

gunjanauti posted this 15 February 2019

Thanks a lot!