[ufocfd]

Im posting this because it took me a while to set up correctly, so maybe it will be useful to others. It monitors the flow and logs the results.

I needed to monitor the average velocity at a plane within the mesh (not a patch or boundary condition), so I was able to use an STL file to specify the plane location (just a flat plate), using sampledTriSurfaceMesh.

I used the code below which is added to the controlDict file - you can change the operation to average, areaAverage,min,max etc. Note the STL file need to be completely within the mesh domain, or you will get warning messages.

surfaceFieldValue1
{
name midradsurf;
type surfaceFieldValue;
libs ("libfieldFunctionObjects.so");

writeControl timeStep;
writeInterval 1;
writeFields false;
log true;

operation average; //areaAverage, average, max, min
fields (U);
regionType sampledSurface;
surfaceFormat stl;

sampledSurfaceDict
{
type sampledTriSurfaceMesh;
surface midradsurf.stl; // <<<<<<< stl file
source cells;
interpolate true;
}

}