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Time continuity error & FAN patch

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Old   April 16, 2015, 08:10
Default Time continuity error & FAN patch
  #1
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Francesco
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Hi all,

I try to simulate a ducted fan in the tail of a body.
If the fixed jump is below 1000 there is no movment in the mass of air (Paraview cant plot the velocity or pressure field), if i increase the pressure jump after few iteration (simpleFoam) diverge in the time continuity error..

I don't know were the problem could be. Tell me all the information you need to uderstand what could be wrong.
Thanks.
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Old   April 16, 2015, 08:30
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  #2
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Francesco
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P Initial condition
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.3.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 2 -2 0 0 0 0];

internalField   uniform 0;

boundaryField
{
    frontAndBack
    {
        type            slip;
    }
    outlet
    {
        type            fixedValue;
        value           uniform 0;
    }
    inlet
    {
        type            zeroGradient;
    }
    lowerWall
    {
        type            zeroGradient;
    }
    upperWall
    {
        type            slip;
    }
    Corpo
    {
        type            zeroGradient;
    }
    Case
    {
        type            zeroGradient;
    }
    cyclicFaces_master
    {
        type            fan;
        patchType       cyclic;
        jump            uniform 0;
        value           uniform 0;
        jumpTable       polynomial
        1((2000 0));
    }
    cyclicFaces_slave
    {
        type            fan;
        patchType       cyclic;
        value           uniform 0;
    }
}


// ************************************************************************* //
U initial condition
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.3.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volVectorField;
    location    "0";
    object      U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 1 -1 0 0 0 0];

internalField   uniform (0 0 0);

boundaryField
{
    frontAndBack
    {
        type            slip;
    }
    outlet
    {
        type            inletOutlet;
        inletValue      uniform (0 0 0);
        value           uniform (0 0 0);
    }
    inlet
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    lowerWall
    {
        type            slip;
    }
    upperWall
    {
        type            slip;
    }
    Corpo
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    Case
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    cyclicFaces_master
    {
        type            cyclic;
    }
    cyclicFaces_slave
    {
        type            cyclic;
    }
}


// ************************************************************************* //
Omega
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.3.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      omega;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 0 -1 0 0 0 0];

internalField   uniform 226;

boundaryField
{
    frontAndBack
    {
        type            slip;
    }
    outlet
    {
        type            inletOutlet;
        inletValue      uniform 2.26;
        value           uniform 2.26;
    }
    inlet
    {
        type            fixedValue;
        value           uniform 2.26;
    }
    lowerWall
    {
        type            slip;
    }
    upperWall
    {
        type            slip;
    }
    Corpo
    {
        type            omegaWallFunction;
        value           uniform 226;
        Cmu             0.09;
        kappa           0.41;
        E               9.8;
        beta1           0.075;
        value           uniform 226;
    }
    Case
    {
        type            omegaWallFunction;
        value           uniform 226;
        Cmu             0.09;
        kappa           0.41;
        E               9.8;
        beta1           0.075;
        value           uniform 226;
    }
    cyclicFaces_master
    {
        type            cyclic;
    }
    cyclicFaces_slave
    {
        type            cyclic;
    }
}


// ************************************************************************* //
Nut
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.3.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      nut;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 2 -1 0 0 0 0];

internalField   uniform 0;

boundaryField
{
    frontAndBack
    {
        type            calculated;
        value           uniform 0;
    }
    outlet
    {
        type            calculated;
        value           uniform 0;
    }
    inlet
    {
        type            calculated;
        value           uniform 0;
    }
    lowerWall
    {
        type            calculated;
        value           uniform 0;
    }
    upperWall
    {
        type            calculated;
        value           uniform 0;
    }
    Corpo
    {
        type            nutkWallFunction;
        Cmu             0.09;
        kappa           0.41;
        E               9.8;
        value           uniform 0;
    }
    Case
    {
        type            nutkWallFunction;
        Cmu             0.09;
        kappa           0.41;
        E               9.8;
        value           uniform 0;
    }
    cyclicFaces_master
    {
        type            cyclic;
    }
    cyclicFaces_slave
    {
        type            cyclic;
    }
}


// ************************************************************************* //
K
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.3.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    location    "0";
    object      k;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 2 -2 0 0 0 0];

internalField   uniform 0.105;

boundaryField
{
    frontAndBack
    {
        type            slip;
    }
    outlet
    {
        type            inletOutlet;
        inletValue      uniform 0.105;
        value           uniform 0.105;
    }
    inlet
    {
        type            fixedValue;
        value           uniform 0.105;
    }
    lowerWall
    {
        type            slip;
    }
    upperWall
    {
        type            slip;
    }
    Corpo
    {
        type            kqRWallFunction;
        value           uniform 0.105;
    }
    Case
    {
        type            kqRWallFunction;
        value           uniform 0.105;
    }
    cyclicFaces_master
    {
        type            cyclic;
    }
    cyclicFaces_slave
    {
        type            cyclic;
    }
}


// ************************************************************************* //
FVSolution
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.3.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

solvers
{
    p
    {
        solver           GAMG;
        tolerance        1e-7;
        relTol           0.01;
        smoother         GaussSeidel;
        nPreSweeps       0;
        nPostSweeps      2;
        cacheAgglomeration on;
        agglomerator     faceAreaPair;
        nCellsInCoarsestLevel 10;
        mergeLevels      1;
    }

    U
    {
        solver           smoothSolver;
        smoother         GaussSeidel;
        tolerance        1e-8;
        relTol           0.1;
        nSweeps          1;
    }

    k
    {
        solver           smoothSolver;
        smoother         GaussSeidel;
        tolerance        1e-8;
        relTol           0.1;
        nSweeps          1;
    }

    omega
    {
        solver           smoothSolver;
        smoother         GaussSeidel;
        tolerance        1e-8;
        relTol           0.1;
        nSweeps          1;
    }
}

SIMPLE
{
    nNonOrthogonalCorrectors 0;
}

potentialFlow
{
    nNonOrthogonalCorrectors 10;
}

relaxationFactors
{
    fields
    {
        p               0.4;
    }
    equations
    {
        U               0.7;
        k               0.7;
        omega           0.7;
    }
}

cache
{
    grad(U);
}

// ************************************************************************* //
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Old   April 22, 2015, 12:14
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  #3
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Francesco
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Ok,after some try i think that the error become from the inlet boudary condition that is a fixedInletValue of 0. When i increase the velocity the continuity error remain small.

A question, wich BC i have to use, if i want that there is no inlet and outlet constrain. I mean, if i want to simulate a fan in a free air without knowing the fan mass flow, only the pressure jump...
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Old   April 22, 2015, 12:36
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Alexander Bartel
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Hi zephiro,

I have copied this BCs from some tutorial for my case, when I want to let the BCs be computed
Code:
    inlet
    {
        type            pressureInletOutletVelocity;
        phi             phi;
        value           $internalField;
    }
for pressure or velocity

and
Code:
    outlet
    {
        type            inletOutlet;
        inletValue      $internalField;
        value           $internalField;
    }
for k epsilon etc.

I hope it helps

otherwise the calculated BC could help... just a guess
http://cfd.direct/openfoam/user-guide/boundaries/

regards
Alex
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Old   April 22, 2015, 12:39
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Francesco
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Thanks for your reply, now i try youre suggestion, i'm sure it will work.

Best regards
Francesco
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