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March 4, 2012, 16:07 |
interPhaseChangeFoam
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#1 |
Senior Member
mauricio
Join Date: Jun 2011
Posts: 172
Rep Power: 17 |
hello every1!
any1 familiar with this solver? interPhaseChangeFoam i was wondering whether cavitation takes place on both phases ? (perhaps this question is not applicable at all, sry but im not that familiar with the cavitation phenonemon ) *C file states: Code:
******************************* Description Solver for 2 incompressible, isothermal immiscible fluids with phase-change (e.g. cavitation). Uses a VOF (volume of fluid) phase-fraction based interface capturing approach. The momentum and other fluid properties are of the "mixture" and a single momentum equation is solved. The set of phase-change models provided are designed to simulate cavitation but other mechanisms of phase-change are supported within this solver framework. Turbulence modelling is generic, i.e. laminar, RAS or LES may be selected. ********************************** say we have water and oil.. which fits the description of 2 immiscible fluids.. in this case, what would VOF be tracking? the interface water-vapor or water-oil? when postprocessing the respective tutorial, /home/userx/OpenFOAM/userx-2.1.0/run/multiphase/interPhaseChangeFoam , i only get to c the alpha parameter regarding phases transport dict states: Code:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 2.1.0 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object transportProperties; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // phaseChange on; phaseChangeTwoPhaseMixture SchnerrSauer; pSat pSat [1 -1 -2 0 0] 2300; // saturation pressure sigma sigma [1 0 -2 0 0 0 0] 0.07; phase1 { transportModel Newtonian; nu nu [0 2 -1 0 0 0 0] 9e-07; rho rho [1 -3 0 0 0 0 0] 1000; } phase2 { transportModel Newtonian; nu nu [0 2 -1 0 0 0 0] 4.273e-04; rho rho [1 -3 0 0 0 0 0] 0.02308; } KunzCoeffs { UInf UInf [0 1 -1 0 0 0 0] 20.0; tInf tInf [0 0 1 0 0 0 0] 0.005; // L = 0.1 m Cc Cc [0 0 0 0 0 0 0] 1000; Cv Cv [0 0 0 0 0 0 0] 1000; } MerkleCoeffs { UInf UInf [0 1 -1 0 0 0 0] 20.0; tInf tInf [0 0 1 0 0 0 0] 0.005; // L = 0.1 m Cc Cc [0 0 0 0 0 0 0] 80; Cv Cv [0 0 0 0 0 0 0] 1e-03; } SchnerrSauerCoeffs { n n [0 -3 0 0 0 0 0] 1.6e+13; dNuc dNuc [0 1 0 0 0 0 0] 2.0e-06; Cc Cc [0 0 0 0 0 0 0] 1; Cv Cv [0 0 0 0 0 0 0] 1; } // ************************************************************************* // so can any1 give me some insights? this case is rather complex and slow to carry out many tests.. from what i could glean it seems that what the solver takes for immiscible 2 fluids is the water and its counterpart which appears with cavitation and henceforward the solver uses VOF to track the interface between water and its vapor.... is that right? at least this is what the interpretation of results tells me!.. if so i guess the description of the solver should change a little .. idk.. maybe it's just me thanks a lot!
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Best Regards /calim "Elune will grant us the strength" Last edited by calim_cfd; March 4, 2012 at 17:27. |
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March 5, 2012, 02:45 |
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#2 |
Senior Member
Kathrin Kissling
Join Date: Mar 2009
Location: Besigheim, Germany
Posts: 134
Rep Power: 17 |
Calim,
the solver only captures two phases. Therefore you would have to severly extend the solver to capture three or even four phases (oil, water, water- vapor and "oil-vapor"). So at the moment one phase plus its vapor-phase is captured. Best Kathrin |
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March 5, 2012, 02:50 |
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#3 | |
Senior Member
Anton Kidess
Join Date: May 2009
Location: Germany
Posts: 1,377
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Quote:
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June 6, 2012, 09:50 |
kinetic energy turbulence:
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#4 |
Member
vahid
Join Date: Feb 2012
Location: Mashhad-Iran
Posts: 80
Rep Power: 13 |
please help me
I want to add the kinetic energy Turbulence(k) in model <<sauer>> in solver <<interPhaseChangeFoam>>. when I Type wmake in terminal. I seen this message : phaseChangeTwoPhaseMixtures/SchnerrSauer/SchnerrSauer.C:79: error: k_ was not declared in this scope make: *** [Make/linux64GccDPOpt/SchnerrSauer.o] Error 1 Although I added the following line in the<<options>>: -I$(LIB_SRC)/turbulenceModels/incompressible/RAS/RASModel \ Then with enter the <<k_>>in model <<sauer>>as following : // * * * * * * * * * * * * * * Member Functions * * * * * * * * * * * * * * // Foam::tmp<Foam::volScalarField> Foam: PhaseChangeTwoPhaseMixtures::SchnerrSauer::rRb ( const volScalarField& limitedAlpha1 ) const { return pow ( ((*4*constant::mathematical: pi*n_)/3)*k_ *limitedAlpha1/(1.0 + alphaNuc() - limitedAlpha1), 1.0/3.0 ); } |
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April 8, 2013, 08:19 |
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#5 |
Member
ABE
Join Date: Jul 2012
Posts: 46
Rep Power: 13 |
I want to use OF to simulate cavitation. I can get relatively good results with older versions (i.e. 1.5). But by using new versions (2.1 or 2.2), results are not good (I can say awful).
has anybody got good cavitating results with OF2.1 or 2.2? Any idea or comment is highly appreciated, and thank you in advance. ABE |
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April 15, 2013, 06:34 |
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#6 |
Member
David Hora
Join Date: Mar 2009
Location: Zürich, Switzerland
Posts: 63
Rep Power: 17 |
Same problem here. I created a bug report:
http://www.openfoam.org/mantisbt/view.php?id=817 Best regards David |
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April 15, 2013, 06:55 |
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#7 | |
Member
ABE
Join Date: Jul 2012
Posts: 46
Rep Power: 13 |
Quote:
Thanks for reply, and creating the bug report. ABE |
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April 15, 2013, 08:32 |
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#8 |
New Member
Stefano Gaggero
Join Date: Mar 2013
Posts: 23
Rep Power: 13 |
Thank you david,
I have the same problem and I posted a new thread a week ago. http://www.cfd-online.com/Forums/ope...m-2-2-0-a.html My results (a simple cavitating 2D wing profile) are awful with OF 2.2.x. Instead, with OF 2.1.1 they correlate well with available experiments. Stefano |
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April 15, 2013, 09:24 |
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#9 |
Member
ABE
Join Date: Jul 2012
Posts: 46
Rep Power: 13 |
I saw your post. Your results with OF2.1.1, generally speaking, seems to be good. However, I have used OF2.1.x and results were not so accurate.
Moreover, I have encountered another issue. Right after restarting the simulation in OF22x, if the amount of vapor be considerable, the pressure field will be disrupted. ABE |
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April 16, 2013, 09:30 |
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#10 |
Senior Member
Sandy Lee
Join Date: Mar 2009
Posts: 213
Rep Power: 18 |
Hi , who know what is the meanings of "cAlpha"? And how to give its numbers ?
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April 16, 2013, 09:54 |
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#11 |
Member
ABE
Join Date: Jul 2012
Posts: 46
Rep Power: 13 |
Hi Sandy,
You can find the description of cAlpha here: http://www.geocities.jp/penguinitis2...interFoam.html cAlpha is a constant representing the degree of compression used to calculate the relative flux, as long as I know. In my cases, I set it equal to zero because I did not consider relative velocity and compressibility of phases interface. ABE |
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April 19, 2013, 00:56 |
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#12 |
Senior Member
Sandy Lee
Join Date: Mar 2009
Posts: 213
Rep Power: 18 |
Hi abc, what is your meanings? I always restart a simulation of cavitation based on the fields of no cavitation. What's wrong with it, you think?
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April 19, 2013, 01:02 |
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#13 | |
Senior Member
Sandy Lee
Join Date: Mar 2009
Posts: 213
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Quote:
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April 22, 2013, 05:50 |
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#14 |
Member
ABE
Join Date: Jul 2012
Posts: 46
Rep Power: 13 |
Hi Sandy,
I meant that in the case that you stop the simulation, and then want to continue it, the pressure filed will be completely corrupted in the first iterations of new run. In the small amount of vapor, you may not get in trouble by this issue but when the amount of vapor is considerable, getting convergence would be very difficult. ABE |
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April 22, 2013, 22:49 |
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#15 | |
Senior Member
Sandy Lee
Join Date: Mar 2009
Posts: 213
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Quote:
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April 23, 2013, 01:04 |
cAlpha1
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#16 |
Senior Member
Nima Samkhaniani
Join Date: Sep 2009
Location: Tehran, Iran
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cAlpha is usually assigned between 1-4 and almost 1 is suitable
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April 23, 2013, 03:14 |
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#17 |
Member
ABE
Join Date: Jul 2012
Posts: 46
Rep Power: 13 |
From the type of error, it could be anything. I do not have any specific idea now, but I am curious about the differences between values which are stored for next iterations and values which are written out.
When you restart the simulation, I think all of the fluxes, and face values are recalculated based on the cell center values which you had written out, which for sure is different from the continuous simulation. |
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April 23, 2013, 03:38 |
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#18 |
Member
David Hora
Join Date: Mar 2009
Location: Zürich, Switzerland
Posts: 63
Rep Power: 17 |
The reason for the bad results is a bug. An interim solution is presented in the bug report. The results seem to agree with version 2.0 but are still a bit different from 1.6.
If you have problems directly after the restart, it could help to remove correctPhi from the solver: pimpleControl pimple(mesh); // #include "../interFoam/correctPhi.H" #include "CourantNo.H" #include "setInitialDeltaT.H" Best regards David Last edited by david; April 24, 2013 at 04:03. |
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April 24, 2013, 05:40 |
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#19 |
Member
ABE
Join Date: Jul 2012
Posts: 46
Rep Power: 13 |
True, I have checked, and I should say that by adding the interim correction (http://www.openfoam.org/mantisbt/view.php?id=817), the problems will be solved (in my case, flow behind a 2d flat plate).
Now the shape of the cavity and pressure fields are more accurate, and besides, the restart issue that I mentioned before has been solved. I just have added a small modification. In my case, in some time steps the MULES solver was not able to bound the alpha value between zero and one (although this values were used as the inputs of the solver) which could lead to divergence. So, I added the following limiter right after the MULES solver as interim solution: alpha1 = min(max(alpha1, scalar(0.0)),scalar(1.0)); About emitting the correctPhi, thanks David I will try that. |
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