functions
{
    cuttingplane_average
    {
        type            faceSource;
        functionObjectLibs ("libfieldFunctionObjects.so");

        enabled         true;
        outputControl   outputTime;

        // Output to log&file (true) or to file only
        log             true;

        // Output field values as well
        valueOutput     false;  //true;

        // Type of source: patch/faceZone/sampledSurface
        source          sampledSurface;

        sampledSurfaceDict
        {
                type cuttingPlane;
                planeType           pointAndNormal;
                pointAndNormalDict
                {
                        basePoint       (0 0 0);  
                        normalVector    (0 0 1);
                }
                source cells; // sample cells or boundaryFaces
                interpolate true;
        }

        // Operation: areaAverage/sum/weightedAverage ...
        operation       areaAverage;

        fields
        (
            p
            U
        );
    }