CFD Online Discussion Forums - Two drops coalescing on substrate not conserving volume

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Two drops coalescing on substrate not conserving volume

Hi All

Can you help with the following issue?

Version: OpenFOAM 6 on Ubuntu 18.04 interFoam
Simulation: two water drops on a substrate coalescing
Issue: the drops are falling right through the substrate (-z direction). What am I missing?

My blockMesh is here

Code:

/*--------------------------------*- C++ -*----------------------------------*\

| =========                 |                                                 |

| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |

|  \\    /   O peration     | Version:  5                                     |

|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |

|    \\/     M anipulation  |                                                 |

\*---------------------------------------------------------------------------*/

FoamFile

{

    version     2.0;

    format      ascii;

    class       dictionary;

    object      blockMeshDict;

}

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



convertToMeters 0.01; // cm --> m



xmin -4;

xmax 5;

ymin -3;

ymax 3;

zmin 0;

zmax 3.5;



xcells 180;

ycells 120;

zcells 70;



vertices

(

    ($xmin $ymin $zmin)

    ($xmax $ymin $zmin)

    ($xmax $ymax $zmin)

    ($xmin $ymax $zmin)

    ($xmin $ymin $zmax)

    ($xmax $ymin $zmax)

    ($xmax $ymax $zmax)

    ($xmin $ymax $zmax)

);



blocks

(

    hex (0 1 2 3 4 5 6 7) ($xcells $ycells $zcells) simpleGrading (1 1 1)

);



edges

(

);



boundary

(

    base

    {

        type wall;

        faces

        (

            (1 5 4 0)

        );

    }



    openBoundaries

    {

        type patch;

        faces

        (

            (0 4 7 3)

            (3 7 6 2)

            (2 6 5 1)

            (4 5 6 7)

            (0 3 2 1)

        );

    }

);



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

alpha.water.orig is here

Code:

/*--------------------------------*- C++ -*----------------------------------*\

  =========                 |

  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox

   \\    /   O peration     | Website:  https://openfoam.org

    \\  /    A nd           | Version:  6

     \\/     M anipulation  |

\*---------------------------------------------------------------------------*/

FoamFile

{

    version     2.0;

    format      ascii;

    class       volScalarField;

    object      alpha.water;

}

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



dimensions      [0 0 0 0 0 0 0];



internalField   uniform 0;



boundaryField

{

    base

    {

        type           constantAlphaContactAngle;

        theta0         106;

        limit          gradient;

        value          uniform 0;

    }



    openBoundaries

    {

        type            inletOutlet;

        inletValue      uniform 0;

        value           uniform 0;

    }

}



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

p_rgh is here

Code:

/*--------------------------------*- C++ -*----------------------------------*\

  =========                 |

  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox

   \\    /   O peration     | Website:  https://openfoam.org

    \\  /    A nd           | Version:  6

     \\/     M anipulation  |

\*---------------------------------------------------------------------------*/

FoamFile

{

    version     2.0;

    format      ascii;

    class       volScalarField;

    object      p_rgh;

}

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



dimensions      [1 -1 -2 0 0 0 0];



internalField   uniform 0;



boundaryField

{

    base

    {

        type            fixedFluxPressure;

        value           uniform 0;

    }



    openBoundaries

    {

        type            totalPressure;

        p0              uniform 0;

    }

}



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

U is here

Code:

/*--------------------------------*- C++ -*----------------------------------*\

  =========                 |

  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox

   \\    /   O peration     | Website:  https://openfoam.org

    \\  /    A nd           | Version:  6

     \\/     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

{

    base

    {

        type            noSlip;

    }

    openBoundaries

    {

        type            pressureInletOutletVelocity;

        value           uniform (0 0 0);

    }

}





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

I'm happy to supply any other relevant info. Thank you so much.

Nevermind I'm an idiot. Was setting the wrong plane as the wall in blockMeshDict. Please ignore

Hello joshmckraney! Even though this post is from long ago, would you please help me on how to simulate two droplets using OpenFOAM? Currently I'm able to simulate one droplet with setFields and setAlphaField, but not two. Thank you beforehand!

Quote:

Originally Posted by ktayna (Post 863632)

What does you setFields file look like? Can you post it here? All you should have to do is copy the block of code you use for the first drop for the second (change drop center and radius if you want, of course)

Quote:

Originally Posted by joshmccraney (Post 863639)

Hello Josh! Here is my setFields and my setAlphaField. My setFields is working alright, I think the problem lies on my setAlphaField; it only builds the alpha field for the second droplet when there are two droplets specified in it.

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

defaultFieldValues
(
volScalarFieldValue alpha.phase1 0
);

regions
(
// Droplet 1
cylinderToCell
{
p1 (0.5 0.5 -1);
p2 (0.5 0.5 1);
radius 0.1;
fieldValues
(
volScalarFieldValue alpha.phase1 1
);
}

// Droplet 2
cylinderToCell
{
p1 (1.5 0.5 -1);
p2 (1.5 0.5 1);
radius 0.1;
fieldValues
(
volScalarFieldValue alpha.phase1 1
);
}
);

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

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

field alpha.phase1;
type cylinder;
radius 0.1;
direction (0 0 1);
origin (0.5 0.5 0);

field alpha.phase1;
type cylinder;
radius 0.1;
direction (0 0 1);
origin (1.5 0.5 0);

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

Quote:

Originally Posted by ktayna (Post 863656)

Right, sorry it’s been a few years since I’ve used OF (have since graduated). So you’ll want to run setFields command twice. Once for first drop and once for second drop. For the second drop just comment out all of the commands you use for the first drop. Make sense?

Quote:

Originally Posted by joshmccraney (Post 863657)

You mean, the setAlphaField command? The setFields command works alright.

I'll try that and come back to report. Thank you!

Hello! I have solved my issue, so I want to put it here in case someone else ever find this problem. Running the command twice didn't work: when I ran the second time, the first droplet would be erased, as if it was the first time the command was ran. Ultimately, I stopped using "setAlphaField" and it works just fine using only the "setFields" command. I am not sure why it didn't work before, and I'm not sure why it is working now, but it is! Thank you :)

Quote:

Originally Posted by ktayna (Post 866116)

Sorry, didn’t see your second reply. And think I was thinking of funkSetFields, which I think would run twice when you want to add a phase. But makes sense, should only need to run setFields once. Nice job