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-   -   Problems solving T Equation in separated flow using a second Order Closure Model (http://www.cfd-online.com/Forums/openfoam-programming-development/108533-problems-solving-t-equation-separated-flow-using-second-order-closure-model.html)

 pascool October 25, 2012 14:09

Problems solving T Equation in separated flow using a second Order Closure Model

Hi everybody,

I am trying to simulate the flow over a heated backward facing step by means of a modified simpleFoam solver which uses a second order Closure Model for the turbulent heat fluxes. The model worked pretty well in the heated turbulent channel. But it doesn't work for the Backward facing step in combination with a RSM turbulence model such as the LaunderGibson. I did a pre-calculation based on the RSM model and Fouriers Law for the scalar fluxes.
I already tried different solver settings and schemes in the fvSolvers and fvSolutions file.
Currently the files look as follows:
Code:

```/*--------------------------------*- C++ -*----------------------------------*\ | =========                |                                                | | \\      /  F ield        | OpenFOAM: The Open Source CFD Toolbox          | |  \\    /  O peration    | Version:  2.1                                  | |  \\  /    A nd          | Web:      www.OpenFOAM.org                      | |    \\/    M anipulation  |                                                | \*---------------------------------------------------------------------------*/ FoamFile {     version    2.0;     format      ascii;     class      dictionary;     location    "system";     object      fvSolution; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // solvers {     p     {         solver          PCG;         preconditioner  DIC;         tolerance      1e-08;         relTol          0.01;     }     U     {         solver          PBiCG;         preconditioner  DILU;         tolerance      1e-08;         relTol          0.1;     }     k     {         solver          PBiCG;         preconditioner  DILU;         tolerance      1e-08;         relTol          0.1;     }     epsilon     {         solver          PBiCG;         preconditioner  DILU;         tolerance      1e-08;         relTol          0.1;     }     R     {         solver          PBiCG;         preconditioner  DILU;         tolerance      1e-08;         relTol          0.1;     }     nuTilda     {         solver          PBiCG;         preconditioner  DILU;         tolerance      1e-08;         relTol          0.1;     }     T BICCG 1e-08 0.01; } SIMPLE {     nNonOrthogonalCorrectors 0; } relaxationFactors {     p              0.3;     U              0.5;     k              0.5;     epsilon        0.5;     R              0.5;     nuTilda        0.5;     T              0.3; } // ************************************************************************* //```
fvSchemes:
Code:

```/*--------------------------------*- C++ -*----------------------------------*\ | =========                |                                                | | \\      /  F ield        | OpenFOAM: The Open Source CFD Toolbox          | |  \\    /  O peration    | Version:  2.1                                  | |  \\  /    A nd          | Web:      www.OpenFOAM.org                      | |    \\/    M anipulation  |                                                | \*---------------------------------------------------------------------------*/ FoamFile {     version    2.0;     format      ascii;     class      dictionary;     location    "system";     object      fvSchemes; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // ddtSchemes {     default        steadyState; } gradSchemes {     default        Gauss linear;     grad(p)        Gauss linear;     grad(U)        Gauss linear; } divSchemes {     default        none;     div(phi,U)      Gauss upwind;     div(phi,k)      Gauss upwind;     div(phi,epsilon) Gauss upwind;     div(phi,R)      Gauss upwind;     div(R)          Gauss linear;     div(phi,nuTilda) Gauss upwind;     div((nuEff*dev(T(grad(U))))) Gauss linear;     div(phi,T)      Gauss upwind;     div((Dp&grad(p))) Gauss linear;     div((S&grad(p))) Gauss linear; } laplacianSchemes {     default        none;     laplacian(nuEff,U) Gauss linear corrected;     laplacian((1|A(U)),p) Gauss linear corrected;     laplacian(DkEff,k) Gauss linear corrected;     laplacian(DepsilonEff,epsilon) Gauss linear corrected;     laplacian(DREff,R) Gauss linear corrected;     laplacian(DnuTildaEff,nuTilda) Gauss linear corrected;     laplacian(((nu|0.7123)+(nut|0.86)),T) Gauss linear corrected;     laplacian(kappaEff,T) Gauss linear corrected; } interpolationSchemes {     default        linear;     interpolate(U)  linear; } snGradSchemes {     default        corrected; } fluxRequired {     default        no;     p              ; } // ************************************************************************* //```
The error message is as follows:

Code:

```#0  Foam::error::printStack(Foam::Ostream&) in "/home/pascal/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" #1  Foam::sigFpe::sigHandler(int) in "/home/pascal/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" #2  in "/lib/x86_64-linux-gnu/libc.so.6" #3  Foam::PBiCG::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const in "/home/pascal/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libOpenFOAM.so" #4  Foam::fvMatrix<double>::solve(Foam::dictionary const&) in "/home/pascal/OpenFOAM/OpenFOAM-2.1.1/platforms/linux64GccDPOpt/lib/libfiniteVolume.so" #5   at simpleFoam_YSC_q.C:0 #6   in "/home/pascal/OpenFOAM/pascal-2.1.1/platforms/linux64GccDPOpt/bin/simpleFoam_YSC_q" #7  __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6" #8   in "/home/pascal/OpenFOAM/pascal-2.1.1/platforms/linux64GccDPOpt/bin/simpleFoam_YSC_q" Floating point exception (core dumped)```
Any help appreciated!

Regards,
Pascal

 chegdan November 19, 2012 11:29

Can you post your code and let us know what model you are using? This error message is pretty general and could be a number of things. I did this one in the past using another scalar flux model other than the gradient diffusion hypothesis.

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