CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM Running, Solving & CFD (http://www.cfd-online.com/Forums/openfoam-solving/)
-   -   Cavitating in Foam14 (http://www.cfd-online.com/Forums/openfoam-solving/59519-cavitating-foam14.html)

zjucfd June 26, 2007 08:06

Does anybody know about cavita
 
Does anybody know about cavitating solver in Foam1.4? I first run the tutorials case of Nozzle2D, it works well. Then I attempted to try the flow around a hyrofoil, but got bad results. The pressure vary a lot, beyond my imagination, even below zero at some spots. The only reason I can figure out is that the solver introduced the barotropic model, which allows the liquid to be compressible. Could anybody give me a hint that what can I do. Thanks a lot!

hartinger June 26, 2007 08:53

Hey, what is the pressure r
 
Hey,

what is the pressure range you're expecting from experiments or analytical solutions? What are you getting?

Does the flow field look reasonable? experiments?

Mesh good enough? Timestep appropriate? Is the solution smooth?

cavitatingFoam can produce and handle negative pressure. Sure, it is not physical?

regards
markus

zjucfd June 26, 2007 11:02

Hi, I let the outlet pressu
 
Hi,

I let the outlet pressure fixed at 1.e5pa, and the inlet velocity 0.6m/s. In order to run a no-cavitation case as a test, the saturation vapour pressure is set to a very low value, ensuring that no cavitation occurs.

But the obtained flow field is very odd. The maximum value of velocity reaches about 50m/s, and the pressure reaches 5pa. so, it looks unreasonable at all.

What's going wrong with my calculation? It's due to the boundary conditions? of which I'm not very sure. Can you recommend me some materials about this cavitation model in Foam1.4?

thanks,
best regards!
Scofield

hartinger June 26, 2007 12:00

to check whether your boundary
 
to check whether your boundary conditions are correct, apply them to the nozzle2D case. with such a low speed you shoudn't have any problems

zjucfd June 26, 2007 12:20

Dear Hartinger, I have sent
 
Dear Hartinger,

I have sent you an e_mail with my case files enclosed. It's very kind of you to give me some advice on it. I think my case is different from nozzle2D, which is a pressure driven flow.

zjucfd June 27, 2007 12:09

Does anybody can take a look a
 
Does anybody can take a look at my case files? I suppose that the inlet pressure is fixed at 1e5pa, and velocity about 1m/s. Thanks a lot!


zjucfd June 27, 2007 21:54

sorry, the mesh file is too bi
 
sorry, the mesh file is too big to upload.
http://www.cfd-online.com/OpenFOAM_D...hment_icon.gif 0.tar.gz
http://www.cfd-online.com/OpenFOAM_D...hment_icon.gif constant.tar.gz
http://www.cfd-online.com/OpenFOAM_D...hment_icon.gif system.tar.gz

benru July 6, 2007 04:20

I tried to perform cavitatingF
 
I tried to perform cavitatingFoam from tutorial (nozzle2D) - and calcs was stopped with errors :

Exec : cavitatingFoam . nozzle2D
Date : Jul 06 2007
Time : 12:18:28
Host : r117-1
PID : 6746
Root : /home/rmukhamadeev/OpenFOAM/rmukhamadeev-1.4/run/tutorials/cavitatingFoam
Case : nozzle2D
Nprocs : 1
Create time

Create mesh for time = 0

Reading thermodynamicProperties

Reading transportProperties

Reading field p

Creating compressibilityModel

Selecting compressibility model linear
Reading field U

Reading/calculating face flux field phiv

Reading/calculating face flux field phi

phiv Courant Number mean: 0 max: 0 acoustic max: 0.298593

Starting time loop

phiv Courant Number mean: 0 max: 0 acoustic max: 0.298593
deltaT = 1.19999e-10
Time = 1.19999e-10

smoothSolver: Solving for rho, Initial residual = 0.50711, Final residual = 0.254106, No Iterations 1000
max-min rho: 832.754 828.236
max-min gamma: 0 0
#0 Foam::error::printStack(Foam:http://www.cfd-online.com/OpenFOAM_D...part/proud.gifstream&)
#1 Foam::sigFpe::sigFpeHandler(int)
#2 Uninterpreted: [0xb7f6d420]
#3 Foam::polyMesh::calcDirections() const
#4 Foam::polyMesh::directions() const
#5 Foam::fvMatrix<foam::vector<double> >::solve(Foam::Istream&)
#6 Foam::lduMatrix::solverPerformance Foam::solve<foam::vector<double> >(Foam::tmp<foam::fvmatrix<foam::vector<double> > > const&)
#7 main
#8 __libc_start_main
#9 __gxx_personality_v0 at ../sysdeps/i386/elf/start.S:122

Could anybody point a cause ? Need help !

Ruben

benru July 6, 2007 05:59

Thank you, will try Ruben
 
Thank you, will try

Ruben

idosil August 9, 2007 02:30

Hello all, I am trying to u
 
Hello all,

I am trying to understand the cavitatingFoam solver and have a few questions:

1. in UEqn - the viscosity term appears twice, once implicit with the laplacian operator and a second time explicit as div of (muf grad U). Should not each term be multiplied by 0.5?

2. in pEqn - I understand that both p.boundaryField().updateCoeffs() and U.correctBoundaryConditions() fix recalculate boundary condition for these fields. what is the difference?

3. in pEqn - rUA and HbyA are recalculated at each inner iteration but the UEqn equation matrixs were build only once outside of this loop. does the matrixs implicitly change when the boundary or fields are recalculated?

Thanks, Ido


All times are GMT -4. The time now is 07:33.