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Old   October 8, 2014, 07:47
Default potentialFoam not working properly
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Hi there!

I am running potentialFoam to initially solve the airflow over a cube, but I am not getting a reasonable velocity field. It runs, but it seems that it has done nothing by the results. The flow is not developed at all.
I also would like to ask if potentialFoam can run several iterations (I want 10 in this case) as any oher solver and write the correspondent output folders (1, 2, 3, ...), since it seems that it is not the case.

I attach my controlDict file

CONTROLDICT
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;
    location    "system";
    object      controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

application     potentialFoam;

startFrom       startTime;

startTime       0;

stopAt          endTime;

endTime         10;

deltaT          1;

writeControl    timeStep;

writeInterval   1;

purgeWrite      0;

writeFormat     ascii;

writePrecision  6;

writeCompression off;

timeFormat      general;

timePrecision   6;

runTimeModifiable true;


// ************************************************************************* //
I upload an image of the Velocity field after running potentialFoam

Thank you.
Attached Images
File Type: jpg Vfield.jpg (17.1 KB, 13 views)
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Old   October 8, 2014, 08:38
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Alexey Matveichev
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Hi,

it'll be much easier for everybody if you attach case files to the message. Otherwise there will be lots of standard questions:

1. What are your BCs?
2. What are your ICs?
3. Can you show your fvSchemes and fvSolution?

Concerning you question about " ... run several iterations ... ". No, if you take a look at source code of potentialFoam, it's supposed to run just one iteration.
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Old   October 8, 2014, 11:12
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Thanks for your rapid response, These are the schemes and the 0/U file. I am using a typical inlet-outles, wall for the floor and the surface of the cube and symmetry for the wrap of the domain configuration.

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;
    location    "system";
    object      fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

solvers
{
    p
    {
        solver          GAMG;
        tolerance       1e-07;
        relTol          0.08;
        smoother        GaussSeidel;
        nPreSweeps      0;
        nPostSweeps     2;
        cacheAgglomeration true;
        nCellsInCoarsestLevel 10;
        agglomerator    faceAreaPair;
        mergeLevels     1;
        maxIter            100;
    }

    U
    {
        solver          smoothSolver;
        smoother        symGaussSeidel;
        tolerance       1e-07;
        relTol          0.1;
    }
}

potentialFlow
{
    nNonOrthogonalCorrectors 8;
}

relaxationFactors
{
    fields
    {
        p               0.3;
    }
    equations
    {
        U               0.7;
    }
}
fvSchemes

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;
    location    "system";
    object      fvSchemes;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

ddtSchemes
{
    default         steadyState;
}

gradSchemes
{
    default         leastSquares;
}

divSchemes
{
    default         none;
}

laplacianSchemes
{
    default         Gauss linear corrected;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         corrected;
}

fluxRequired
{
    default         no;
    p               ;
}


// ************************************************************************* //
BC

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
{
    OUTLET
    {
        type            uniformFixedValue;
        uniformValue    constant (5 0 0);
    }
    INLET
    {
        type            uniformFixedValue;
        uniformValue    constant (5 0 0);
    }
    
// GROUND, WALL and DENSITY are physical walls    

    GROUND
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    WALL
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    DENSITY
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    
    
    SYM_RIGHT
    {
        type            symmetryPlane;
    }
    SYM_UP
    {
        type            symmetryPlane;
    }
    SYM_LEFT
    {
        type            symmetryPlane;
    }
}


// ************************************************************************* //
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Old   October 8, 2014, 11:47
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Alexey Matveichev
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Hi,

well, in general the following BCs are imposed (btw you've forgotten pressure boundary conditions):

inlet: U - fixed value, p - zero gradient
outlet: U - zero gradient, p - fixed value

Also I'm not quite sure in two things:

1. Necessity for this potentialFoam run.
2. Symmetry of the flow.
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Old   October 8, 2014, 12:41
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I use the symmetryPlane as a numerical trick to impose a non-viscous wall (the normal to the fake wall component of the velocity is null end the gradient is null)

Are you suggesting that the imposed BC can be the problem? Which BC do you suggest? It is a very simple incompressible flow entering a tunnel, for examle.

Thanks.
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Old   October 8, 2014, 13:16
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Alexey Matveichev
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Another possibility is that you've messed up the direction of the velocity. As your screenshot lacks coordinate axes, maybe (5 0 0) is directed into the wall and not along the tunnel

If you'd like to simulate incompressible flow in the tunnel, I'd suggest you to use pimpleFoam (if you're interested in transient state) or simpleFoam (if you need steady state). Use fixed value BC for velocity at the inlet, zero gradient BC for velocity at the outlet; and vice-a-versa for pressure: zero gradient at the inlet, fixed value at the outlet.

Quote:
I use the symmetryPlane as a numerical trick to impose a non-viscous wall (the normal to the fake wall component of the velocity is null end the gradient is null)
Do you mean slip BC?
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Old   October 8, 2014, 14:29
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Yep, slip BC was what I meant.

Thank you vey much alexeym, great help!
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