CFD Online Discussion Forums - Mass flow through arbitrary holes not on a boundary

Hi!

I'm simulating the flow through a micro gas turbine engine combustion chamber in order to determine the mass flow distribution through the different sets of holes. My simulation runs and I am able to get results and convergence. The only problem I have is obtaining the mass flow or surface averaged velocity through the holes, because they are not on a boundary.

Please see attached image for reference.

I have tried many things and I am still unable to determine the mass flow through these holes.

My first attempt was to try and define a plane per hole in the controlDict file and then limit the plane to the hole's diameter. Here is the code:

Code:

functions

{

    A1

    {

        type            faceSource;

        functionObjectLibs ("libfieldFunctionObjects.so");

        enabled         true;

        outputControl   outputTime;

        log             true;

        valueOutput     true;

        source          sampledSurface;

    surfaceFormat     vtk;

        sampledSurfaceDict//faceZoneDict//

        {

            type            plane;    // always triangulated

            basePoint       (-0.040571 -0.0233665 -0.1528);

            normalVector    (-0.040571 -0.0233665 0);

        zone        A11;            

        }

        operation       areaAverage;

        fields

        (

            U

        );

    }

};

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

I tried to define the zones in the topoSetDict file:

Code:

actions

(

    {

        name    A11;

        type    cellSet;

        action  new;

        source  cylinderToCell;

        sourceInfo

        {

               p1       (-0.040874 -0.023541 -0.1528); 

               p2       (-0.040268 -0.023192 -0.1528);  

            radius   0.0008;

        }

    }

)

However when the code is run the surface averaged velocity over the entire plane is calculated, instead of the surface averaged velocity through the hole.

Another approach I took was to create concetric rings as baffles around the combustor where each of the sets of holes are located using snappyHexMesh (as this is how the entire geometry is meshed). The patches are created, but now the simulation won't run, because they demand that I define a boundary condition on those patches. Please see attached picture .

I tried defining a cyclic condition on the master and slave patches, but I am unable to.

Any help in this regard would be greatly appreciated.

Regards,
Chenelle