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Old   August 19, 2010, 06:09
Default bubbleFoam validation case
  #1
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Balkrishna Patankar
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I faced the following difficulty.
I switch off the dispersed phase volume fraction at inlet . That is inlet alpha = uniform 0 and also the dispersed phase velocity . I keep my continuous phase velocity Ub = 0.1 m/s . Continuous properties are rho = 1000 kg/m3 , nu = 1e-06 m2/s . This means now i am studying single phase flow . I compared the results to simpleFoam results and have found a problem with the velocity plots in the plane z=0.2 on the same timestep . Specifically on the line joining (0 0.5 0.2) and (1 0.5 0.2) . Can someone help me resolve this issue ....
My blockMeshDict is as follows :
Code:
/*--------------------------------*- C++ -*----------------------------------* \
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  1.7.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

convertToMeters 1;

vertices        
(
 (0 0 0)
 (0.25 0 0)
 (0.25 0.25 0)
 (0 0.25 0)
 (0 0.75 0)
 (0.25 0.75 0)
 (0 1 0)
 (0.25 1 0)
 (0.75 0 0)
 (0.75 0.25 0)
 (1 0 0)
 (1 0.25 0)
 (0.75 0.75 0)
 (1 0.75 0)
 (0.75 1 0)
 (1 1 0)

 (0 0 2)
 (0.25 0 2)
 (0.25 0.25 2)
 (0 0.25 2)
 (0 0.75 2)
 (0.25 0.75 2)
 (0 1 2)
 (0.25 1 2)
 (0.75 0 2)
 (0.75 0.25 2)
 (1 0 2)
 (1 0.25 2)
 (0.75 0.75 2)
 (1 0.75 2)
 (0.75 1 2)
 (1 1 2)
 
);

blocks          
(
 hex (0 1 2 3 16 17 18 19) (10 10 10) simpleGrading (1 1 1)
 hex (3 2 5 4 19 18 21 20) (10 10 10) simpleGrading (1 1 1)
 hex (4 5 7 6 20 21 23 22) (10 10 10) simpleGrading (1 1 1)
 hex (1 8 9 2 17 24 25 18) (10 10 10) simpleGrading (1 1 1)
 hex (2 9 12 5 18 25 28 21) (10 10 10) simpleGrading (1 1 1)
 hex (5 12 14 7 21 28 30 23) (10 10 10) simpleGrading (1 1 1)
 hex (8 10 11 9 24 26 27 25) (10 10 10) simpleGrading (1 1 1)
 hex (9 11 13 12 25 27 29 28) (10 10 10) simpleGrading (1 1 1)
 hex (12 13 15 14 28 29 31 30) (10 10 10) simpleGrading (1 1 1)
 );

edges           
(
);

patches         
(
 patch inlet (
	      (2 5 12 9)
	      ) 

 patch outlet (
	       (16 19 18 17)
	       (19 20 21 18)
	       (20 22 23 21)
	       (17 18 25 24)
	       (18 21 28 25)
	       (21 23 30 28)
	       (24 25 27 26)
	       (25 28 29 27)
	       (28 30 31 29)
	      
       	       )

   wall fixedWalls 
    (
     (0 16 19 3)
     (3 19 20 4)
     (4 20 22 6)
     (6 22 23 7)
     (7 23 30 14)
     (14 30 31 15)
     (15 31 29 13)
     (13 29 27 11)
     (11 27 26 10)
     (10 26 24 8)
     (8 24 17 1)
     (1 17 16 0)
     (0 3 2 1)
     (3 4 5 2)
     (4 6 7 5)
     (5 7 14 12)
     (12 14 15 13)
     (9 12 13 11)
     (8 9 11 10)
     (1 2 9 8)
     )


    
);

mergePatchPairs 
(
);

// ************************************************************************* //
The velocity plots are on this page .... https://sites.google.com/site/balkrishnanitt/

Last edited by balkrishna; August 19, 2010 at 06:50.
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Old   August 20, 2010, 02:09
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Alberto Passalacqua
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How is the model set up in bubbleFoam? Are you using the turbulence model or performing a laminar simulation?

Best,
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GeekoCFD - A free distribution based on openSUSE 64 bit with CFD tools, including OpenFOAM. Available as live DVD/USB, hard drive image and virtual image.
OpenQBMM - An open-source implementation of quadrature-based moment methods
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Old   August 20, 2010, 02:12
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Balkrishna Patankar
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I am performing a laminar simulation .
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Old   August 20, 2010, 02:23
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Alberto Passalacqua
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Ignore my previous answer (removed). I generated the mesh, and run the case, noticing you have an expansion. Could you post your case setup?
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Last edited by alberto; August 20, 2010 at 02:51. Reason: Corrected answer
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Old   August 20, 2010, 02:52
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Balkrishna Patankar
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Thanks for the reply ...
I was unable to place an image of the mesh in the post ... I have uploaded the image of the mesh on the link ... Sorry for the inconvienience ....

Secondly , I am not seeking convergence ... All that I am saying is if I switch off my dispersed phase , my equations reduce to those solved by simpleFoam and hence should give the same results at the same time on the same mesh .

Do clarify me if I am wrong somewhere ....

Last edited by balkrishna; August 20, 2010 at 03:10.
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Old   August 20, 2010, 03:20
Default Case setup
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Alpha :
Code:
/*--------------------------------*- C++ -*----------------------------------* \
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  1.7.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    object      alpha;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 0 0 0 0 0 0];

internalField  uniform 0 ;
boundaryField
{
    inlet           
    {
        type            fixedValue;
        value           uniform 0;
    }

    outlet          
    {
      type            zeroGradient;
    }

    fixedWalls           
    {
        type            zeroGradient;
    }


}

// ************************************************************************* //
Pressure
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  1.7.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    object      p;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform 0;
boundaryField
{
    inlet
    {
        type            zeroGradient;
    }

    outlet
    {
        type            fixedValue;
        value           uniform 0;
    }

    fixedWalls
    {
        type            buoyantPressure;
        value           uniform 0;
    }

    defaultFaces
    {
        type            empty;
    }
}

// ************************************************************************* //
Ub velocity of continuous phase
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  1.7.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volVectorField;
    object      Ub;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform (0 0 0);
boundaryField
{
    inlet           
    {
        type            fixedValue;
        value           uniform (0 0 0.1);
    }

    outlet          
    {
      type            zeroGradient;
    }

    fixedWalls           
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }


}

// ************************************************************************* //
Ua velocity of dispersed phase
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  1.7.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volVectorField;
    object      Ua;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform (0 0 0) ;

boundaryField
{
    inlet           
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }

    outlet          
    {
      type            zeroGradient;
    }

    fixedWalls           
    {
        type            fixedValue;
        value           uniform (0 0 0);
    }


}

// ************************************************************************* //
k
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  1.7.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    object      k;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

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

internalField   uniform 1e-8;

boundaryField
{
    inlet           
    {
        type            fixedValue;
        value           uniform 1e-8;
    }

    outlet          
    {
        type            inletOutlet;
        inletValue      uniform 1e-8;
        value           uniform 1e-8;
    }

    fixedWalls           
    {
        type            zeroGradient;
    }

    defaultFaces    
    {
        type            empty;
    }
}

// ************************************************************************* //
epsilon
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  1.7.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       volScalarField;
    object      epsilon;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dimensions      [0 2 -3 0 0 0 0];

internalField   uniform 0.1;

boundaryField
{
    inlet           
    {
        type            fixedValue;
        value           uniform 0.1;
    }

    outlet          
    {
      type       zeroGradient;     
    }

    fixedWalls           
    {
        type            zeroGradient;
    }

    
}

// ************************************************************************* //
controlDict
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  1.7.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      controlDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

application     bubbleFoam;

startFrom       startTime;

startTime       0;

stopAt          endTime;

endTime         2;

deltaT          0.001;

writeControl    runTime;

writeInterval   0.5;

purgeWrite      0;

writeFormat     ascii;

writePrecision  6;

writeCompression uncompressed;

timeFormat      general;

timePrecision   6;

runTimeModifiable yes;


// ************************************************************************* //
fvSchemes
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  1.7.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      fvSchemes;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

ddtSchemes
{
    default         Euler;
}

gradSchemes
{
    default         Gauss linear;
}

divSchemes
{
    default         none;
    div(phia,Ua)    Gauss limitedLinearV 1;
    div(phib,Ub)    Gauss limitedLinearV 1;
    div(phib,k)     Gauss limitedLinear 1;
    div(phib,epsilon) Gauss limitedLinear 1;
    div(phi,alpha)  Gauss limitedLinear01 1;
    div((-nuEffa*grad(Ua).T())) Gauss linear;
    div((-nuEffb*grad(Ub).T())) Gauss linear;
}

laplacianSchemes
{
    default         none;
    laplacian(nuEffa,Ua) Gauss linear corrected;
    laplacian(nuEffb,Ub) Gauss linear corrected;
    laplacian((rho*(1|A(U))),p) Gauss linear corrected;
}

interpolationSchemes
{
    default         linear;
}

snGradSchemes
{
    default         corrected;
}

fluxRequired
{
    default         no;
    p               ;
}


// ************************************************************************* //
fvSolution
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  1.7.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "system";
    object      fvSolution;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

solvers
{
    p
    {
        solver          PCG;
        preconditioner  DIC;
        tolerance       1e-10;
        relTol          0;
    }

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

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

    alpha
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance       1e-10;
        relTol          0;
    }

    beta
    {
        solver          PBiCG;
        preconditioner  DILU;
        tolerance       1e-10;
        relTol          0;
    }

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

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

PISO
{
    nCorrectors     2;
    nNonOrthogonalCorrectors 0;
    nAlphaCorr      2;
    correctAlpha    no;
    pRefCell        0;
    pRefValue       0;
}


// ************************************************************************* //
g
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  1.7.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
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  );


// ************************************************************************* //
RASProperties
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  1.7.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "constant";
    object      RASProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

RASModel        laminar;

turbulence      off;

printCoeffs     off;


// ************************************************************************* //
transportProperties
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  1.7.0                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "constant";
    object      transportProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

rhoa            rhoa [ 1 -3 0 0 0 0 0 ] 1;

rhob            rhob [ 1 -3 0 0 0 0 0 ] 1000;

nua             nua [ 0 2 -1 0 0 0 0 ] 1.6e-05;

nub             nub [ 0 2 -1 0 0 0 0 ] 1e-06;

da              da [ 0 1 0 0 0 0 0 ] 0.003;

db              db [ 0 1 0 0 0 0 0 ] 0.0001;

Cvm             Cvm [ 0 0 0 0 0 0 0 ] 0.5;

Cl              Cl [ 0 0 0 0 0 0 0 ] 0;

Ct              Ct [ 0 0 0 0 0 0 0 ] 1;


// ************************************************************************* //
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Old   August 20, 2010, 03:47
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Alberto Passalacqua
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You are correct. The result should be the same.

Did you use the same numerical schemes and the same tolerances in the linear solvers also in simpleFoam?

Also, set to zero the lift (Cl), virtual mass coefficients (Cvm) and Ct (not necessary in theory, since bubbleFoam uses a formulation depending on alpha, so these term should be zero automatically).

Best,
Alberto
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OpenQBMM - An open-source implementation of quadrature-based moment methods

Last edited by alberto; August 20, 2010 at 03:58. Reason: precised question and added clarification
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Old   August 20, 2010, 03:50
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Will recheck on the same .... Thanks for the help ...

Last edited by balkrishna; August 20, 2010 at 04:16.
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Old   August 20, 2010, 04:38
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Yes checked it .... the schemes are the same ....
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Old   August 20, 2010, 05:17
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But they should not matter as alpha or the dispersed phase is 0 . Those equations are written for the dispersed phase ....
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Old   August 20, 2010, 12:32
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Yes that's correct. I was just removing everything term that makes the two equations different.

The only additional difference I see in your files is g. There is no g in simpleFoam.

Best,
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Old   August 20, 2010, 12:34
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inclusion of g is only going to affect the pressure contours ... not the velocity plots ...
thanks ...
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Old   August 20, 2010, 12:45
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I did not imply this is going to cause a difference in the velocity plot, just that the only physical element of difference is that one in the equations.

The difference in the two solutions is located essentially at the walls, and the rest of the profile adapts as a consequence.

At what tolerance is the solution converged? Would you share a case so I can take a look at it (I sent my email address if you cannot upload)?

Best,
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Old   August 20, 2010, 16:36
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Since I was a bit puzzled by the problem, because I did a similar validation in the past, I run a simpler case of a flow between two parallel plates.

You find the cases here: http://dl.dropbox.com/u/659842/bubbl...bleFoam.tar.gz

And as you can see in the attached picture, the velocity profiles are identical.

Best,
Attached Files
File Type: pdf bubbleFoamSimpleFoamComparison.pdf (24.6 KB, 55 views)
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Old   August 21, 2010, 03:15
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your test case works great . have you found any problem in my case setup ?
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Old   August 21, 2010, 03:33
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Hi,

the case you sent me stops at 2 seconds, which is not enough for the solution to reach convergence. You might want to run the case with a larger time step (0.1 for example, or a bit smaller if you want residuals to be low) until t = 1000.

Additionally, the contour plots show quite a clear influence of the mesh on the solution, mainly due to the non-uniformity and the jumps in grid size between the different blocks.

I hope this helps.

Best,
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Old   August 27, 2010, 03:40
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I wish to modify bubble Foam of 2 phases to n phase and add heat transfer and species mixing to it .. One stumbling block i came across was the way the alpha equation was programmed .
it consists of the following line in the header file alphaEqn.H
Code:
 word scheme("div(phi,alpha)");

    surfaceScalarField phir = phia - phib;
This means they perform the phase calculation as stated in the wiki here . How does one extend the relative flux to n phase ...
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Old   August 27, 2010, 03:50
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Silva and Lage did it and have a conference paper on this topic. Check your email :-)
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Old   August 27, 2010, 04:00
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thanks a lot .....
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Old   August 30, 2010, 01:46
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Thanks for the link .... Can i get the source code of the solver ?? The implementation of the algorithm is the tough aspect in OpenFOAM .....
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