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Convergence Problem icoFoam steady flow over an airfoil

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Old   January 5, 2011, 22:18
Default Convergence Problem icoFoam steady flow over an airfoil
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Lucas Vieira
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Hi everyone,

I am trying to simulate steady flow over an airfoil and I'm having problems converging to the solution with icoFoam.

I'm using a ICEM mesh that i exported to fluent format (msh) and converted with
fluentMesh3DToFoam:

I am working with a comparation between OpenFOAM and CFX,
but i am new at OF.

The utility checkMesh set Mesh OK.

This is my case:
http://uploaddearquivos.com.br/downl...o/PROIC.tar.gz

Thank you.
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Old   January 6, 2011, 09:49
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Lucas Vieira
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I tried this morning some changes in the fvschemes fvsolution
I also tried to run in simpleFoam

and i got this:

Code:
 Time = 52

Lookup gradScheme for grad(U)
Lookup divScheme for div((nuEff*dev(grad(U).T())))
Lookup laplacianScheme for laplacian(nuEff,U)
Lookup fluxRequired for U
Lookup gradScheme for snGradCorr(U)
Lookup gradScheme for snGradCorr(U)
Lookup gradScheme for snGradCorr(U)
Lookup divScheme for div(phi,U)
Find relax for U
Lookup relaxationFactor for U
Lookup gradScheme for grad(p)

    From function solution::solverDict(const word&)
    in file matrices/solution/solution.C at line 241
    Lookup solver for U
smoothSolver:  Solving for Ux, Initial residual = 0.0237871, Final residual = 0.000128133, No Iterations 1
smoothSolver:  Solving for Uy, Initial residual = 0.317853, Final residual = 0.00208853, No Iterations 1
smoothSolver:  Solving for Uz, Initial residual = 8.9633e-05, Final residual = 4.39538e-07, No Iterations 1
Lookup interpolationScheme for interpolate(U)


--> FOAM FATAL ERROR: 
Continuity error cannot be removed by adjusting the outflow.
Please check the velocity boundary conditions and/or run potentialFoam to initialise the outflow.
Total flux              : 3.36963e+38
Specified mass inflow   : 1.60459e+38
Specified mass outflow  : 0
Adjustable mass outflow : 4.20186e+20


    From function adjustPhi(surfaceScalarField& phi, const volVectorField& U,const volScalarField& p
    in file cfdTools/general/adjustPhi/adjustPhi.C at line 115.

FOAM exiting
hear is my system files:

Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  1.7.1                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

application     simpleFoam;   //  which solver (for documentation)

startFrom       startTime;              //  firstTime, startTime, latestTime

startTime       0;                      //  set > 0 to continue

stopAt          endTime;                //  writeNow, endTime, nextWrite, ...

endTime         600;                    //  Latest timestep allowed

deltaT          1;                      //  simple counter for steadyState

writeControl    adjustableRunTime;      //  or uncommon: cpuTime, clockTime

writeInterval   50;                     //  time step write interval

purgeWrite      0;                      //  1 recycles time steps storage
                                        //  0 keeps all time steps on disk

writeFormat     ascii;                  //  ascii: readable, binary: smaller

writePrecision  6;                      //  precision for ascii format

writeCompression uncompressed;          //  compressed for gzipped files

timeFormat      general;                //  fixed, scientific or general

timePrecision   6;                      //  precision for time handling

runTimeModifiable yes;                  //  yes: OF reads dictionaries each
                                        //  time step

graphFormat     raw;                    //  raw, gnuplot, xmgr, jplot

//libs()        for user libraries, p.e. user boundary conditions
//functions()   for special functions
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  1.7.1                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      fvSchemes;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

ddtSchemes
{
    default         steadyState;
}

gradSchemes
{
    default         Gauss linear;
    grad(p)         faceLimited leastSquares 0 1;
    grad(U)         Gauss linear;
}

divSchemes
{
    default         none;
    div(phi,U)      Gauss upwind;
    div(phi,nuTilda) Gauss linearUpwind Gauss linear;
    div((nuEff*dev(grad(U).T()))) Gauss linear;
}

laplacianSchemes
{
    default         none;
    laplacian(nuEff,U) Gauss linear limited 0.7;
    laplacian((1|A(U)),p) Gauss linear limited 0.7;
    laplacian(DnuTildaEff,nuTilda) Gauss linear corrected;
    laplacian(1,p)  Gauss linear corrected;
}

interpolationSchemes
{
    default         linear;
    interpolate(U)  linear;
}

snGradSchemes
{
    default         limited 0.7;
}

fluxRequired
{
    default         no;
    p               ;
}


// ************************************************************************* //
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  1.7.1                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

solvers
{
    p
    {
        solver          GAMG;
        tolerance       1e-07;
        relTol          0.001;
        smoother        GaussSeidel;
        nPreSweeps      1;
        nPostSweeps     2;
        cacheAgglomeration true;
        nCellsInCoarsestLevel 500;
        agglomerator    faceAreaPair;
        mergeLevels     1;
    }

    U
    {
        solver          smoothSolver;
        smoother        GaussSeidel;
        nSweeps         2;
        tolerance       1e-08;
        relTol          0.01;
    nSweeps         1;              // setting for smoothSolver
        maxIter         100;            // limitation of iterations number

    }

    nuTilda
    {
        solver          smoothSolver;
        smoother        GaussSeidel;
        nSweeps         2;
        tolerance       1e-08;
        relTol          0.1;
    }
}

SIMPLE
{
    nNonOrthogonalCorrectors 6;
    convergence         1e-5;
    pRefCell        0;
    pRefValue       0;
}

relaxationFactors
{
    default         0;
    p               0.003;
    U               0.007;
    nuTilda         0.007;
}


// ************************************************************************* //
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Old   January 6, 2011, 12:08
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Travis Carrigan
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For the gradSchemes try:
default cellLimited leastSquares 1.0;

For the divSchemes try:
div(phi,U) Gauss linearUpwindV Gauss linear;
div(phi,nuTilda) Gauss upwind;

For pressure solver:
p GAMG tolerance 1e-8 and relTol 0

For other solvers:
PBiCG using DILU preconditioner with tolerances 1e-8 and relTol 0 rather than using smoothSolver

Try also dropping the nNonOrthogonalCorrectors down to 2, and increase the relaxation factors:
p 0.2
U 0.5
nuTilda 0.5
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Old   January 10, 2011, 15:24
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Lucas Vieira
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thanks for your reply, but the problem was the mesh, i changed the mesh and
everything works fine.
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Old   February 17, 2011, 18:24
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William
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Quote:
Originally Posted by Lucas View Post
thanks for your reply, but the problem was the mesh, i changed the mesh and
everything works fine.
what did you change in your mesh? smaller cell sizes?
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Old   February 18, 2011, 13:46
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In fact i made a complete new mesh, because the last was horrible, with high number of non-orthogonal cells.
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