CFD Online Discussion Forums - [swak4Foam] run-time function/expression evaluation at a part of a cross section

Dear foamers,

I am trying to calculate the mass flow (and other quantities) during run-time with functions/expressions from swak4foam. So far, I successfully managed to compute these values at a randomly defined plane which slices the complete domain. Now, I would like to calculate these values at a part/subset of this cross section, e.g. a circle which lies in this plane.

Here is a short description on how I am trying to achieve this:
1) Use topoSet to define a sphere with the desired radius. Create a zone of the cells within this sphere.
2) Use functions in the controlDict to define the plane of interest and calculate whatever needed. Using zone, I expect to "intersect" the sphere with the plane and thus create the desired circle.

The only thing that I was able to achieve was that the plane I am looking at has been reduced to about half its original size (looks kind of random in ParaView). Thus, also the calculated mass flow has reduced accordingly. BUT, the mass flow is still computed on the whole of the remaining plane. So, no sign of successful "intersection"...

I already searched the internet and found the following resources:
http://openfoamwiki.net/index.php/TopoSet
https://github.com/OpenFOAM/OpenFOAM...et/topoSetDict
http://www.cfd-online.com/Forums/ope...ing-plane.html
http://openfoamwiki.net/images/2/2a/...esentation.pdf
But, none of these could answer my question completely...

And here follows a code snippet of the topoSetDict:

Code:

actions

(

  {

    name        apertureSphereZone;

    type        cellSet;

    action      new;

    source      sphereToCell;

    sourceInfo

    {

        centre  (-1 0 0);

        radius  0.18;

    }

  }

  {

    name        apertureSphereZone;

    type        cellZoneSet;

    action      new;

    source      setToCellZone;

    sourceInfo

    {

        set     apertureSphereZone;

    }

  }

);

And a snippet from the controlDict with the functions:

Code:

libs (

    "libgroovyBC.so"

    "libsimpleFunctionObjects.so"

    "libsimpleSwakFunctionObjects.so"

    "libswakFunctionObjects.so"

    "libgroovyStandardBCs.so"

);



functions

(

flowAperture

{

    type        swakExpression;

    valueType   surface;

    surfaceName aperturePlane;

    surface

    {

        type            plane;

        basePoint       (-1 0 0);

        normalVector    (1 0 0);

        interpolate     true;

        zone            apertureSphereZone;

    }

    expression  "U.x*rho";

    writeSurfaceOnConstruction true;

    surfaceFormat       vtk;

    accumulations

    (

        min

        max

        weightedAverage

        integrate

    );

    outputControlMode   timeStep;

    outputInterval      1;

    verbose             true;

}

);

I ask you the following:
A) Am I on the right track?
B) Are there alternatives? Could one use e.g.

Code:

condition "(pow(pos().y,2)+pow(pos().z,2)) < pow(0.18,2)";

within the swakExpression to achieve the same?

Every hint will be appreciated! Thanks in advance for your support!
Happy foaming to you all,
Silvan