// patchAverage_inlet
// {
//         type faceSource;
//         functionObjectLibs ("libfieldFunctionObjects.so");
//         log no;
//         valueOutput yes;
//         outputControl adjustableRunTime;
//         outputInterval .001;
//         source patch;
//         sourceName inlet;
//         surfaceFormat null;
//         operation areaAverage;
//         fields ( p );
// }

dp
{
    patch1          inlet;
    patch2          outlet;

    type            fieldValueDelta;
    functionObjectLibs ("libfieldFunctionObjects.so");
    operation       subtract;
    enabled         true;
    outputControl   adjustableRunTime;
    outputInterval  .001;
    log             false;
    region1
    {
        regionType      patch;
        name            $patch1;
        type            surfaceRegion;
        libs            ("libfieldFunctionObjects.so");
        writeControl    timeStep;
        writeInterval   1;
        writeFields     false;
        log             false;
        operation       areaAverage;
        fields          ( p );
    }
    region2
    {
        regionType      patch;
        name            $patch2;
        type            surfaceRegion;
        libs            ("libfieldFunctionObjects.so");
        writeControl    timeStep;
        writeInterval   1;
        writeFields     false;
        log             false;
        operation       areaAverage;
        fields          ( p );
    }
}