[Skymaas]

Hey guys,


I am fairly new to openFOAM so bear with me on this:

In this study, I will be trying the find the uniformity index after an expansion and in order to calculate this, i need to know the velocities after the guide vanes(See attached picture).
I have tried to create a plane just after the guide vanes in Pointwise, which did not work. Then i tried using createPatch, but this did not work either.
Can anyone point me in the direction of how to achieve the velocities at a specific plane, after the guide vanes?

[tomf]

Hi,

Working with the surfaces functionObject, something like the following, could work if you make an stl of the plane that you want to look for the velocities. You should get a high enough resolution on this stl.

    velocities_on_plane
    {
        type            surfaces;
        functionObjectLibs ("libsampling.so");
        writeControl   writeTime;

        surfaceFormat   vtk;
        fields          (U);

        interpolationScheme cellPoint;

        surfaces
        (      
            Plane
            {
                type            sampledTriSurfaceMesh;
                surface         Plane.stl;
                source          cells;
                interpolate     true;
            }       
        );
    }

[Skymaas]

Hi tomf,


Thanks for your response!
How is one going to include a STL. file in the main geometry?

[tomf]

Hi

You do not do it like that. Just place a separate plane.stl into a folder called constant/triSurface/ like you would for making a mesh using snappyHexMesh. This plane.stl you have to create separately. I do not know what software you have available, but there should be multiple solutions to this. OpenFOAM will interpolate to this plane.

Hope this helps.
Cheers,
Tom

[olesen]

Originally Posted by Skymaas

Hey guys,
I am fairly new to openFOAM so bear with me on this:

In this study, I will be trying the find the uniformity index after an expansion and in order to calculate this, i need to know the velocities after the guide vane.

It is actually a bit easier than that. Uniformity Index is part of surface field functions in 1806 and later - without you needing to write any code.
The plane can either be a regular cutting plane, or from an stl, etc via a distanceSurface with distance = 0.
The latter can be rather important to obtain proper sampling per cell. There is a small example in the tutorials (compressible/rhoSimpleFoam/squareBend) that you can work from.