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May 17, 2012, 07:39 |
cavitation
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#1 |
New Member
saadia
Join Date: May 2012
Posts: 19
Rep Power: 14 |
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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May 20, 2012, 03:48 |
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#2 |
Senior Member
Rick
Join Date: Oct 2010
Posts: 1,016
Rep Power: 26 |
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 |
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May 20, 2012, 08:29 |
naca0015
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#3 |
New Member
saadia
Join Date: May 2012
Posts: 19
Rep Power: 14 |
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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May 20, 2012, 13:10 |
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#4 |
Senior Member
Rick
Join Date: Oct 2010
Posts: 1,016
Rep Power: 26 |
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 |
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May 21, 2012, 06:32 |
pressure
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#5 |
New Member
saadia
Join Date: May 2012
Posts: 19
Rep Power: 14 |
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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May 21, 2012, 07:09 |
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#6 |
Senior Member
Rick
Join Date: Oct 2010
Posts: 1,016
Rep Power: 26 |
If you don't know pressure inlet you should know velocity inlet. Pressure outlet should be known..
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May 21, 2012, 07:30 |
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#7 |
New Member
saadia
Join Date: May 2012
Posts: 19
Rep Power: 14 |
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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May 21, 2012, 07:37 |
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#8 |
Senior Member
Rick
Join Date: Oct 2010
Posts: 1,016
Rep Power: 26 |
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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May 21, 2012, 08:02 |
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#9 |
New Member
saadia
Join Date: May 2012
Posts: 19
Rep Power: 14 |
for outlet;i must put volume of fraction in 0 or no
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May 21, 2012, 08:03 |
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#10 |
Senior Member
Rick
Join Date: Oct 2010
Posts: 1,016
Rep Power: 26 |
Cavitation will occour on the hydrofoil so your outlet has to be placed far enough to have 0% vapor fraction.
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May 21, 2012, 08:08 |
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#11 |
New Member
saadia
Join Date: May 2012
Posts: 19
Rep Power: 14 |
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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May 21, 2012, 08:34 |
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#12 |
Senior Member
Rick
Join Date: Oct 2010
Posts: 1,016
Rep Power: 26 |
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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May 21, 2012, 08:44 |
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#13 |
New Member
saadia
Join Date: May 2012
Posts: 19
Rep Power: 14 |
velocity is 6 m/s for
c=200mm ang =6° My simulation is in steady state |
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May 22, 2012, 05:34 |
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#14 |
New Member
saadia
Join Date: May 2012
Posts: 19
Rep Power: 14 |
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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January 14, 2013, 05:59 |
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#15 |
New Member
saadia
Join Date: May 2012
Posts: 19
Rep Power: 14 |
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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