[ce73stargazer]

Hi there.

I did some multiphase problem with OpenFOAM and I used probe sampling to extract alpha.water at certain location to find out the water level changes over the simulation time.

Meanwhile, I am wondering if there is any function available in OpenFOAM to extract the whole domain's water level at any specific time step, for example at t =10s.

I went through the user manual without much luck, anyone has any suggestion?


Cheers
Zhifang

[tomf]

Hi,

I think generating an isosurface of alpha=0.5 might work for you. You can than make a vtk surface that you could plot in paraview. I guess the following would work for version 3.0, maybe also 4.0, but syntax may have changed.

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  3.0.x                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/

surfaces
{
    type            surfaces;
    functionObjectLibs ("libsampling.so");
    outputControl   outputTime;

    surfaceFormat   vtk;
    fields          (p U k epsilon);

    interpolationScheme cellPoint;

    surfaces
    (
        isoAlpha
        {
            type            isoSurface;
            isoField        alpha.water;
            isoValue        0.5;
            interpolate     true;
        }
    );
}


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

For inspiration try this:

grep -r isoSurface $FOAM_TUTORIALS

Cheers,
Tom

[ce73stargazer]

Originally Posted by tomf

Hi,

I think generating an isosurface of alpha=0.5 might work for you. You can than make a vtk surface that you could plot in paraview. I guess the following would work for version 3.0, maybe also 4.0, but syntax may have changed.

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  3.0.x                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/

surfaces
{
    type            surfaces;
    functionObjectLibs ("libsampling.so");
    outputControl   outputTime;

    surfaceFormat   vtk;
    fields          (p U k epsilon);

    interpolationScheme cellPoint;

    surfaces
    (
        isoAlpha
        {
            type            isoSurface;
            isoField        alpha.water;
            isoValue        0.5;
            interpolate     true;
        }
    );
}


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

For inspiration try this:

grep -r isoSurface $FOAM_TUTORIALS

Cheers,
Tom

Hi Tom

Thanks for your reply, but I dont quite get what you meaning but using a isosurface of alpha.water=0.5. From my point of view, water surface level is obtained by summing up all the product of alpha.water value and the relevant cells size, the usual VOF way. Hence, the results be bias, if i just put a single threshold for it, as the water level change will no be well presented.

Dont you mind explaining this a bit further. Thanks in advance.

[tomf]

I think that if your cell sizes are small enough there would not be much difference in between both methods. I guess your method would be more accurate, but it would require some coding. Maybe you can compare my method with your probing to see if there is a big difference. I am not sure how your method should be implemented, so I can not help you with that.

Regards,
Tom