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-   -   Hydrostatic Pressure in a cube (http://www.cfd-online.com/Forums/openfoam/109735-hydrostatic-pressure-cube.html)

andreas November 25, 2012 08:20

Hydrostatic Pressure in a cube
 
Dear Foamers,

I would like to understand how to implement hydrostatic pressure on a wall. I am a beginner with OF.

For that, I created a simple cube mesh:
Code:

convertToMeters 1;

vertices
(
    (0 0 0)
    (0 0 1)
    (0 1 1)
    (0 1 0)
    (1 0 0)
    (1 0 1)
    (1 1 1)
    (1 1 0)
);

blocks
(
    hex (0 1 2 3 4 5 6 7) (40 40 40) simpleGrading (1 1 1)
);

edges
(
);

boundary
(
    walls
    {
        type wall;
        faces
        (
            (0 1 2 3)
            (4 5 6 7)
        (4 0 1 5)
        (5 6 2 1)
        (7 6 2 3)
        (4 7 3 0)
        );
    }
);

I want the hydrostatic pressure, so I used buoyantPressure for p:

Code:

dimensions      [0 2 -2 0 0 0 0];

internalField  uniform 0;

boundaryField
{

    walls
    {
        type            buoyantPressure;
    value        uniform 0;
    }


}

The velocity type is pressureInletVelocity and the value is uniform(0 0 0).

I also created a g folder in "constant":

Code:

FoamFile
{
    version    2.0;
    format      ascii;
    class      uniformDimensionedVectorField;
    location    "constant";
    object      g;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 1 -2 0 0 0 0];
value          ( 0 0 -9.81 );

The fluid is not supposed to move since it is a closed cube.
I don't know exactly what solver should I use but it seems that pisoFoam is ok.

So here is the fvSolution:

Code:

solvers
{
    p
    {
        solver          PCG;
        preconditioner  DIC;
        tolerance      1e-06;
        relTol          0;
    }

    U
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance      1e-05;
        relTol          0;
    }
}

PISO
{
    nCorrectors    2;
    nNonOrthogonalCorrectors 0;
    pRefCell        0;
    pRefValue      0;
}

And for the fvSchemes, I used an existing one:

Code:

ddtSchemes
{
    default        Euler;
}

gradSchemes
{
    default        Gauss linear;
    grad(p)        Gauss linear;
}

divSchemes
{
    default        none;
    div(phi,U)      Gauss linear;
}

laplacianSchemes
{
    default        none;
    laplacian(nu,U) Gauss linear corrected;
    laplacian((1|A(U)),p) Gauss linear corrected;
}

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

snGradSchemes
{
    default        corrected;
}

fluxRequired
{
    default        no;
    p              ;
}

Here are the TransportProperties:
Code:

nu              nu [ 0 2 -1 0 0 0 0 ] 0.01;
transportModel    Newtonian;

Here is the terminal response:
Code:

--> FOAM FATAL IO ERROR:
keyword div((nuEff*dev(T(grad(U))))) is undefined in dictionary "/home/ubuntu/openfoam/simu/cube/system/fvSchemes::divSchemes"

I don't know what model should I use for div((nuEff*dev(T(grad(U))))?
Or maybe it is a wrong solver for a simple case like that?
Thank you for your help!

Horus November 25, 2012 16:53

I don't know if pisoFoam is right solver for this kind of problem.

For the error message you posted, simple add this expression to the divSchemes dictionary or set a default entry, e.g.
Code:

divSchemes
{   
    default        Gauss linear;
    div(phi,U)      Gauss linear;
    div((nuEff*dev(T(grad(U))))) Gauss linear;
 }


andreas November 26, 2012 04:42

Thank you for your answer!

I added that line in the fvSchemes, as well as the
Code:

laplacian(nuEff,U)    Gauss linear corrected;
in the laplacianSchemes.

Still, the terminal doesn't find the "g" folder:
Code:

--> FOAM FATAL ERROR:

    request for uniformDimensionedVectorField g from objectRegistry region0 failed
    available objects of type uniformDimensionedVectorField are

0
(
)

Where is the objectRegistry region0?
I tried to copy/paste the g in all the folders (0,constant,system) still doesn't work.

Thanks for your help!


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