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-   -   LES-kOmegaSSTSAS (http://www.cfd-online.com/Forums/openfoam/78005-les-komegasstsas.html)

aut_iut July 9, 2010 08:40

LES-kOmegaSSTSAS
 
Dear Foamer,


My case is a basic case related to turbulent flow over a cylinder. In fact I am going to compare lift&Drag coeffs with the literature data. I succeeded to use RAS-kOmegaSST already.
But my results were not accurate enough. Since the accuracy of LES models are better than RAS, I tried to use LES-kOmegaSSTSAS turbulence model for my case. After running, the execution process crashed with the following errors.
I think these errors are because of initial values for the turbulence model or used solvers. Am I right? Any body has an idea for the initial values of the nuSgs? I also changed the timeStep, but this has no effect.


Time = 0.008

Courant Number mean: 0.00534794 max: 0.0800331
DILUPBiCG: Solving for Ux, Initial residual = 0.0314821, Final residual = 2.40782e-07, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0.00938822, Final residual = 1.69819e-07, No Iterations 1
DILUPBiCG: Solving for Uz, Initial residual = 0.0736961, Final residual = 3.42136e-07, No Iterations 1
GAMG: Solving for p, Initial residual = 0.429489, Final residual = 0.0295009, No Iterations 3
time step continuity errors : sum local = 9.5465e-08, global = -7.2069e-10, cumulative = -2.89625e-09
GAMG: Solving for p, Initial residual = 0.112661, Final residual = 1.77703e+31, No Iterations 1000
time step continuity errors : sum local = 4.46134e+25, global = 1.33676e+07, cumulative = 1.33676e+07
DILUPBiCG: Solving for k, Initial residual = 1, Final residual = 9.30655e+08, No Iterations 1001
bounding k, min: -10819.8 max: 8259.16 average: -4.75152
DILUPBiCG: Solving for omega, Initial residual = 1, Final residual = 63348.9, No Iterations 1001
bounding omega, min: -5.33351e+37 max: 2.06354e+44 average: 2.12765e+40
ExecutionTime = 21.42 s ClockTime = 24 s

Time = 0.01

Courant Number mean: 4.0992e+26 max: 2.81609e+27
DILUPBiCG: Solving for Ux, Initial residual = 0.765954, Final residual = 1.00338, No Iterations 1001
DILUPBiCG: Solving for Uy, Initial residual = 0.910766, Final residual = 118092, No Iterations 1001
DILUPBiCG: Solving for Uz, Initial residual = 0.999613, Final residual = 1.01149, No Iterations 1001
#0 Foam::error::printStack(Foam::Ostream&) in "/home/OpenFOAM/OpenFOAM-1.6.x/lib/linuxGccDPOpt/libOpenFOAM.so"
#1 Foam::sigFpe::sigFpeHandler(int) in "/home/OpenFOAM/OpenFOAM-1.6.x/lib/linuxGccDPOpt/libOpenFOAM.so"
#2 Uninterpreted:
#3 Foam::GAMGSolver::scalingFactor(Foam::Field<double >&, Foam::Field<double> const&, Foam::Field<double> const&, Foam::Field<double> const&) const in "/home/OpenFOAM/OpenFOAM-1.6.x/lib/linuxGccDPOpt/libOpenFOAM.so"
#4 Foam::GAMGSolver::scalingFactor(Foam::Field<double >&, Foam::lduMatrix const&, Foam::Field<double>&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&, Foam::Field<double> const&, unsigned char) const in "/home/OpenFOAM/OpenFOAM-1.6.x/lib/linuxGccDPOpt/libOpenFOAM.so"
#5 Foam::GAMGSolver::Vcycle(Foam::PtrList<Foam::lduMa trix::smoother> const&, Foam::Field<double>&, Foam::Field<double> const&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::PtrList<Foam::Field<double> >&, Foam::PtrList<Foam::Field<double> >&, unsigned char) const in "/home/OpenFOAM/OpenFOAM-1.6.x/lib/linuxGccDPOpt/libOpenFOAM.so"
#6 Foam::GAMGSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/home/OpenFOAM/OpenFOAM-1.6.x/lib/linuxGccDPOpt/libOpenFOAM.so"
#7 Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/home/OpenFOAM/OpenFOAM-1.6.x/lib/linuxGccDPOpt/libfiniteVolume.so"
#8
in "/home/OpenFOAM/OpenFOAM-1.6.x/applications/bin/linuxGccDPOpt/pisoFoam"
#9 __libc_start_main in "/lib/tls/i686/cmov/libc.so.6"
#10
in "/home/OpenFOAM/OpenFOAM-1.6.x/applications/bin/linuxGccDPOpt/pisoFoam"
Floating point exception


Best regards,
Rasoul

waynezw0618 July 9, 2010 09:36

Why not use nut from SST result as initial guess for SAS. Actually It is SST based SAS which is not the tranditional LES method

aut_iut July 9, 2010 10:31

Dear wayne,

Thank you for your fast reply. But, It's impossible to use nut from RAS-kOmegaSST for LES-kOmegaSSTSAS. Because in the latter model there is no nutwallFunction and we have to use nuSgs instead of nut. Anyway I tried your suggestion and faced with the following error:

--> FOAM FATAL ERROR:

request for RASModel RASProperties from objectRegistry region0 failed
available objects of type RASModel are

0
(
)

Any other suggestion?

waynezw0618 July 9, 2010 11:50

you could modify the boundary type in file of k and omega
it is problem of wall function
http://www.cfd-online.com/Forums/ope...roperties.html


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