CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   FLUENT (http://www.cfd-online.com/Forums/fluent/)
-   -   cavitation (http://www.cfd-online.com/Forums/fluent/101930-cavitation.html)

saida May 17, 2012 07:39

cavitation
 
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 ?

ghost82 May 20, 2012 03:48

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.

Daniele

saida May 20, 2012 08:29

naca0015
 
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.

ghost82 May 20, 2012 13:10

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

Daniele

saida May 21, 2012 06:32

pressure
 
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..

ghost82 May 21, 2012 07:09

If you don't know pressure inlet you should know velocity inlet. Pressure outlet should be known..

saida May 21, 2012 07:30

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

ghost82 May 21, 2012 07:37

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.

saida May 21, 2012 08:02

for outlet;i must put volume of fraction in 0 or no

ghost82 May 21, 2012 08:03

Cavitation will occour on the hydrofoil so your outlet has to be placed far enough to have 0% vapor fraction.

saida May 21, 2012 08:08

but i have probelem in my calcul.the residual of vf-phase 2(vapor) is not changed.it stabilized at 0

ghost82 May 21, 2012 08:34

This means that cavitation is not occurring.
What is your inlet velocity?try increasing the velocity
Are your simulation steady or transient?

saida May 21, 2012 08:44

velocity is 6 m/s for
c=200mm
ang =6
My simulation is in steady state

saida May 22, 2012 05:34

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

saida January 14, 2013 06:59

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 ?


All times are GMT -4. The time now is 13:14.