CFD Online Discussion Forums - Uniform surface sampling?

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Uniform surface sampling?

Hello,

I would like to export field values from a nonuniform grid using a uniform sampling grid.

Any suggestions?

mapFields seems terribly inefficient since it only does one time step at a time (I have a few 100 time steps I want to export)

the sample utility 'works' but I don't see how to specify uniform sampling for a surface.

Thanks for your help!

Quote:

Originally Posted by RebelLion (Post 590097)

Are you wanting to sample a solid surface e.g. a wall? Or a plane you have defined?

For the former you can't as far as I know. You need to change it to a patch then use sample.

Once you've changed your solid object to a patch (in your processor/constant/polymesh/boundary files) use:

Code:

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

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

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

|  \\    /   O peration     | Version:  2.3.0                                 |

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

|    \\/     M anipulation  |                                                 |

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

FoamFile

{

    version     2.0;

    format      ascii;

    class       dictionary;

    object      sampleDict;

}

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



setFormat raw;

surfaceFormat vtk;



interpolationScheme cellPoint;



// Fields to sample.

fields

(

    p

);



sets

(

);



surfaces

(

    cubes

    {

        type             patch;

        patches         ("cubes");

    }

);





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

For the second use something like this:

Code:

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

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

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

|  \\    /   O peration     | Version:  2.4.0                                 |

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

|    \\/     M anipulation  |                                                 |

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

FoamFile

{

    version     2.0;

    format      ascii;

    class       dictionary;

    object      sampleDict;

}

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





setFormat raw;

surfaceFormat vtk;



// optionally define extra controls for the output formats

formatOptions

{

    ensight

    {

        format  ascii;

    }

}





sets

(

    

);





surfaces

(

    constantPlane

    {

        type            plane;    // always triangulated

        basePoint       (0 0 3.5);

        normalVector    (0 0 1);



    }



   



);





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

Hi kingjewel1. Thanks for the reply.

My goal is to export field values of a plane I define. I can do that using your second suggestion.

My problem is that I want the exported results to be interpolated onto a uniform grid. When exporting a 1D line set, uniform distribution is a sampleDict option but I can not find similar functionality for 2D surfaces. Any other ideas? or even other post-processing suggestions?

Thanks again!

Hello,

Have you got a solution for your question ? I am trying to do the same thing.

Thanks !

Lu ZHOU

One way I found to do so is to define a plane source (under source menu) and then use the filter Resample with Dataset. To setup the filter use your data as the "input" and the plane as the "source". Sample periodicity is set under the plane properties, X Resolution and Y Resolution.

Good luck and let me know if you have any further questions