problem in running icoFoam

Alucard · March 16, 2012, 05:34

Good morning I'm dealing with a "simple" problem:
A cylindrical gemoetry where the fluid enters from two lateral openings and flows out from a small central tube.

The reynolds has to be small (i'm doing some parametric study in the range [0:20] with Reynolds defined as:
Re=UR/v v=cinematic viscosity, R= external radius of the geometry and U the inlet horizontal velocity (supposed constant).

Well the boundary conditions are simply an exit (imposed pression value ) at the bottom of the small pipe and an inlet radial velocity. On the top I put a symetry condition
icoFoam doesn"t converge in any case also for a Stokes case ( I removed the convective terms in the momentum equations)...so i think i'm doing something stupid with the mesh.

Can someone help me?
Thank you!

here I copy the blockMeshDict (i copied and modified this file from an ancient discussion: http://www.cfd-online.com/Forums/ope...nder-mesh.html)

HTML 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;
    object      blockMeshDict;
}


// * * * * * * * * * * * * * * * * * * * * * * * * * *//
//meshGenApp blockMesh;
convertToMeters 0.017677664;
vertices
(
( 1.0 -1.0 -15.0) //0
( 1.0 1.0 -15.0)
( -1.0 1.0 -15.0)
( -1.0 -1.0 -15.0)

( 1.0 -1.0 -2.0) //4
( 1.0 1.0 -2.0)
( -1.0 1.0 -2.0)
( -1.0 -1.0 -2.0)

( 3.0 -3.0 0.0) //8
( 3.0 3.0 0.0)
( -3.0 3.0 0.0)
( -3.0 -3.0 0.0)

/*( 6.0 -6.0 0.0) //12
( 6.0 6.0 0.0)
( -6.0 6.0 0.0)
( -6.0 -6.0 0.0)
*/
( 40.0 -40.0 0.0) //12
( 40.0 40.0 0.0)
( -40.0 40.0 0.0)
( -40.0 -40.0 0.0)

( 3.0 -3.0 20.0) //16
( 3.0 3.0 20.0)
( -3.0 3.0 20.0)
( -3.0 -3.0 20.0)

( 40.0 -40.0 20.0) //20
( 40.0 40.0 20.0)
( -40.0 40.0 20.0)
( -40.0 -40.0 20.0)


/*( 6.0 -6.0 10.0) //20
( 6.0 6.0 10.0)
( -6.0 6.0 10.0)
( -6.0 -6.0 10.0)
*/
);
blocks
(
/*hex (0 1 2 3 4 5 6 7) (20 20 15) simpleGrading (1 1 1)         // tubo
hex (4 5 6 7 8 9 10 11) (20 20 10) simpleGrading (1 1 1)       //raccordo
hex (8 9 10 11 16 17 18 19) (20 20 50) simpleGrading (1 1 1)  //raccordo riportato fino in alto
hex (14 10 9 13 22 18 17 21) (30 20 50) simpleGrading (3 1 1) //
hex (15 11 10 14 23 19 18 22) (30 20 50) simpleGrading (3 1 1)//
hex (12 8 11 15 20 16 19 23) (30 20 50) simpleGrading (3 1 1) // 
hex (13 9 8 12 21 17 16 20) (30 20 50) simpleGrading (3 1 1)  //
*/

hex (0 1 2 3 4 5 6 7) (40 40 80) simpleGrading (1 1 1)         // tubo
hex (4 5 6 7 8 9 10 11) (40 40 80) simpleGrading (1 1 1)       //raccordo
hex (8 9 10 11 16 17 18 19) (40 40 100) simpleGrading (1 1 1)  //raccordo riportato fino in alto
hex (14 10 9 13 22 18 17 21) (60 40 100) simpleGrading (0.2 1 1) //
hex (15 11 10 14 23 19 18 22) (60 40 100) simpleGrading (0.2 1 1)//
hex (12 8 11 15 20 16 19 23) (60 40 100) simpleGrading (0.2 1 1) // 
hex (13 9 8 12 21 17 16 20) (60 40 100) simpleGrading (0.2 1 1)  //

);
edges
(
arc 2 1 (0.0 1.414214 -15.0)
arc 1 0 (1.414214 0.0 -15.0)
arc 0 3 (0.0 -1.414214 -15.0)
arc 3 2 (-1.414214 0.0 -15.0)
arc 6 5 (0.0 1.414214 -2.0)
arc 5 4 (1.414214 0.0 -2.0)
arc 4 7 (0.0 -1.414214 -2.0)
arc 7 6 (-1.414214 0.0 -2.0)
arc 10 9 (0.0 4.242641 0.0)
arc 9 8 (4.242641 0.0 0.0)
arc 8 11 (0.0 -4.242641 0.0)
arc 11 10 (-4.242641 0.0 0.0)
/*arc 14 13 (0.0 8.485281 0.0)
arc 13 12 (8.485281 0.0 0.0)
arc 12 15 (0.0 -8.485281 0.0)
arc 15 14 (-8.485281 0.0 0.0)
*/
arc 14 13 (0.0 56.56856 0.0)
arc 13 12 (56.56856 0.0 0.0)
arc 12 15 (0.0 -56.56856 0.0)
arc 15 14 (-56.56856 0.0 0.0)

arc 18 17 (0.0 4.242641 20.0)
arc 17 16 (4.242641 0.0 20.0)
arc 16 19 (0.0 -4.242641 20.0)
arc 19 18 (-4.242641 0.0 20.0)
/*arc 22 21 (0.0 8.485281 10.0)
arc 21 20 (8.485281 0.0 10.0)
arc 20 23 (0.0 -8.485281 10.0)
arc 23 22 (-8.485281 0.0 10.0)
*/

arc 22 21 (0.0 56.56856 20.0)
arc 21 20 (56.56856 0.0 20.0)
arc 20 23 (0.0 -56.56856 20.0)
arc 23 22 (-56.56856 0.0 20.0)
);

patches
(
patch outlet
(
(0 3 2 1)
)
patch symmetry
(
(16 17 18 19)
(17 21 22 18)
(18 22 23 19)
(20 16 19 23)
(20 21 17 16)
)

patch inlet1
(
(14 15 23 22)
)
patch inlet2
(
(13 12 20 21)
)

patch walls
(
(13 14 22 21) //lat walls
(15 12 20 23) //lat walls

(12 13 9 8) //bottom walls
(13 14 10 9) //bottom walls
(14 15 11 10) //bottom walls
(15 12 8 11) //bottom walls

(4 5 9 8)
(5 6 10 9)
(6 7 11 10)
(7 4 8 11)

(0 1 5 4)
(1 2 6 5)
(2 3 7 6)
(3 0 4 7)

)

);
mergePatchPairs
(
);

And for U and p:

HTML Code:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.1.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volVectorField;
    object      U;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform (0 0 0);

boundaryField
{
    inlet1
    {
        type            fixedValue;
        value           uniform (1. 0 0);
    }
    inlet2
    {
        type            fixedValue;
        value           uniform (-1. 0 0);
    }
    walls
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }
    symmetry
    {
        type            zeroGradient;
//        type            fixedValue;
//        value           uniform (0 0 0);

    }

    outlet
    {
        type            zeroGradient;
    }

   
}

// ************************************************************************* //

HTML Code:

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2.1.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    object      p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform 0;

boundaryField
{
    inlet1
    {
        type            zeroGradient;
    }
    inlet2
    {
        type            zeroGradient;
    }
    symmetry
    {
        type            zeroGradient;
    }

    walls
    {
        type            zeroGradient;
    }


    outlet
    {
        type            fixedValue;
        value           uniform 0;
    }

}

// ************************************************************************* //

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