# How to put volume fraction in function of an Axis? THAK YOU FOR YOUR HELP

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• Last Post 21 March 2019
• Topic Is Solved
michel posted this 20 March 2019

Hi ,

I am a student from Brazil, and I am new at CFD, so please forgive me for my english.

I am studying a multiphase flow on CFX

it is a hull that has water under and air as ideal gas above. 3D model.

i need to give the values of the volume fraction.       more precise on boundary>inlet>fluid values>volume fraction

the volume fractions are function of  Y axis (m).

there is a way to do a conditional? or something similar?.

I need something like:

from y=o m to y=5m, volume fraction air ==1.0

from y>5 to y=10, volume fraction water= 1.0

and from these "expression" i would put on boundary>inlet>fluid values>volume fraction.

I am also strugling with the boundary conditions. I am not sure if I should select Homogeneous model, at default domain>fluid models.

Also, what is the better turbulence model for this case?

if someone could help me, i´d really aprecciate!

As I said, I am new at CFD, so I apologise if i asking basic thing

sorry for the long text.

thank you for your help and attencion,

michel

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abenhadj posted this 20 March 2019

Yes: you can create an expression using the CFX Expression Language to do that. Example: if(y>1[m],1.0,0.0). Please check the Bump tutorial which might be helpful for you.

Best regards,

Amine

abenhadj posted this 20 March 2019

Tutorial: Free Surface Flow Over a Bump

Best regards,

Amine

michel posted this 20 March 2019

Thank you Amine

abenhadj posted this 21 March 2019

Please mark this as "Is Solved" michel! Merci

Best regards,

Amine