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-   -   kOmegaSST_LowRe in OpenFOAM-1.5-dev (http://www.cfd-online.com/Forums/openfoam-solving/85724-komegasst_lowre-openfoam-1-5-dev.html)

vaina74 March 5, 2011 09:22

kOmegaSST_LowRe in OpenFOAM-1.5-dev
 
Hi, foamers.

I've always been using k-omega SST turbulent model with wall functions so far (with appropriate y+). Now I'm interested in a low Re model, I want to check how much it can affect my results. Maybe the difference is not so important for my case and my applications, in view of hardware and time consumption.
If I'm correct, I can still use kOmegaSST OpenFOAM turbulent model and an appropriate finer mesh with a resulting y+≈1. But I also saw that OpenFOAM-1.5-dev implemented a kOmegaSST_LowRe. What's the difference with an usual kOmegaSST model with a y+≈1 mesh? Are there different settings for k and omega close to wall surfaces (I always use zeroGradient)? I looked for that in the forum but I couldn't find anything useful.

vaina74 March 28, 2011 15:15

I tried to run a simulation and I simply substitute kOmegaSST with kOmegaSST_LowRe in RASProperties, but I obtain an error:
Code:

Selecting incompressible transport model Newtonian
Selecting RAS turbulence model kOmegaSST_LowRe
[0] [1]
[1]
[1] keyword kOmegaSST_LowReCoeffs is undefined in dictionary "/home/maurizio/OpenFOAM/maurizio-1.5-dev/run/low_Re/propeller/processor1/constant/RASProperties"
[1]
[1] file: /home/maurizio/OpenFOAM/maurizio-1.5-dev/run/low_Re/propeller/processor1/constant/RASProperties from line 17 to line 188.
[1]
[1]    From function dictionary::subDict(const word& keyword)
[1]    in file db/dictionary/dictionary.C at line 288.
[1]
FOAM parallel run exiting
[1]

[0]
[0] keyword kOmegaSST_LowReCoeffs is undefined in dictionary "/home/maurizio/OpenFOAM/maurizio-1.5-dev/run/low_Re/propeller/processor0/constant/RASProperties"
[0]
[0] file: /home/maurizio/OpenFOAM/maurizio-1.5-dev/run/low_Re/propeller/processor0/constant/RASProperties from line 17 to line 188.
[0]
[0]    From function dictionary::subDict(const word& keyword)
[0]    in file db/dictionary/dictionary.C at line 288.
[0]
FOAM parallel run exiting
[0]
[naospcm4:04902] MPI_ABORT invoked on rank 1 in communicator MPI_COMM_WORLD with errorcode 1
[naospcm4:04901] MPI_ABORT invoked on rank 0 in communicator MPI_COMM_WORLD with errorcode 1

Have to add any coefficients somewhere? I thought they were all included in the same file. Could you help me?

vaina74 March 28, 2011 16:11

OK, I solved. I included in RASProperties the following coefficients (suggested in kOmegaSST_LowRe.H):
Code:

kOmegaSST_LowReCoeffs
{
    Cmu        0.09;
    alphaK1    0.85034;
    alphaK2    1.0;
    alphaOmega1 0.5;
    alphaOmega2 0.85616;
    alphah      1.0;    // only for compressible
    beta1      0.075;
    beta2      0.0828;
    betaStar    0.09;
    gamma1      0.5532;
    gamma2      0.4403;
    a1          0.31;
    c1          10.0;
}



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