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Old   May 17, 2012, 07:39
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Hey,

I am using Fluent to simulate the flow with cavitation
around hydrofoil (naca 0015) using fluent and I'm trying to use a multiphase flow (water liquid and water vapor). I checked fluent's tutorials about cavitation and they said that I should have two inlets (Inlet 1 as liquid and Inlet 2 as vapor) but in Gambit when I defined Inlet 1 and Inlet 2 on the same inlet face boundary, fluent wasn't able to see both inlets and it shows only 1 inlet... what should I do to define a multiphase flow?? and if i want use udf of cavitation to give the source term in equation of Volume Fraction Equation
how i can introduce this udf in fluent ?
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Old   May 20, 2012, 03:48
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You have to choose the mixture model, setup two phases (liquid and water), and enable cavitation.
In your boundary conditions panel you will have to set the inlet (that is only one) conditions: you will note that you could select mixture, phase-1 and phase-2.
For phase-2 (vapor) you will be able to set a volume fraction at the inlet (if it exists).
For udf:
click Define->User-Defined->functions->interpreted

deselect use contributed ccp and select display assembly listing.
Browse for your source file and click on compile.
If in fluent command window you wont see any error, you can proceed with your simulation.

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Old   May 20, 2012, 08:29
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Thanks alot!. I used the mixture model

can you gave me the procedure to follow with details because I did not understand if I use the patch method of fluid or no.
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Old   May 20, 2012, 13:10
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You haven't to pach anything. It depends on your case, but usually the inlet has no vapor and cavitation occurs somewhere inside your domain during the simulation.
You can check this example:
http://hpce.iitm.ac.in/website/Manua...f/tg/tut18.pdf

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Old   May 21, 2012, 06:32
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Tks alot.

I have a problem to calculate the pressure of the inlet and outlet.

can you tell me how I calculate this pressure please..
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Old   May 21, 2012, 07:09
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If you don't know pressure inlet you should know velocity inlet. Pressure outlet should be known..
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Old   May 21, 2012, 07:30
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please tell me if is true or no

velocity inlet is the velocity of flow for mixture

then i chose inlet to phase 2 (vapor) and put volume of fraction at 0

pressure outlet is calculated by sum of operating pressure and vaporisation pressure and i put volume of fraction (vapor) at 0
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Old   May 21, 2012, 07:37
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Velocity inlet is the velocity of mixture (100% liquid) entering your domain.
Pressure outlet is the pressure you measure at your outlet.
If you specify operating density 100.000 Pa and at your outlet you have atmospheric pressure, your outlet pressure will be 0 Pa.
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Old   May 21, 2012, 08:02
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for outlet;i must put volume of fraction in 0 or no
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Old   May 21, 2012, 08:03
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Cavitation will occour on the hydrofoil so your outlet has to be placed far enough to have 0% vapor fraction.
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Old   May 21, 2012, 08:08
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but i have probelem in my calcul.the residual of vf-phase 2(vapor) is not changed.it stabilized at 0
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Old   May 21, 2012, 08:34
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This means that cavitation is not occurring.
What is your inlet velocity?try increasing the velocity
Are your simulation steady or transient?
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Old   May 21, 2012, 08:44
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velocity is 6 m/s for
c=200mm
ang =6
My simulation is in steady state
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Old   May 22, 2012, 05:34
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when i change velocity to 10m/s I noticed that there is a change in the structure of the flow but the residuals of vf-pahse 2 remains stable despite that there is a convergence of other parameters
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Old   January 14, 2013, 06:59
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Hey,

I am using Fluent to simulate the flow with cavitation
around hydrofoil (naca 0015) using fluent and I'm trying to use a multiphase flow (water liquid and water vapor). I checked fluent's tutorials about cavitation and they said that I should have two inlets (Inlet 1 as liquid and Inlet 2 as vapor) but in Gambit when I defined Inlet 1 and Inlet 2 on the same inlet face boundary, fluent wasn't able to see both inlets and it shows only 1 inlet... what should I do to define a multiphase flow?? and if i want use udf of cavitation to give the source term in equation of Volume Fraction Equation
how i can introduce this udf in fluent ?
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