[Andrea_85]

Hello,

i want to output the weighted average of temperature on a given plane as postProcessing using functionObject (i am using "execFlowFunctionObject -time myTime" to run it as postprocessing). I added these lines to my controlDict:

 surfacePlane
    {
        type swakExpression;
        valueType surface;
        surfaceName testPlane;
        surface {
            type plane;
            basePoint       (0.0040125 1.25e-4 0);
            normalVector    (1 0 0);
            interpolate false;
        }
        verbose true;
        expression "T*area()/sum(area())";
        accumulations (
              sum
        );
    }

However, it seems it does not recognize the field "T". I get this error

--> FOAM FATAL ERROR:
 Parser Error for driver SampledSurfaceValueExpressionDriver at "1.1-2" :"field T not existing or of wrong type"
"T*area()/sum(area())"
  ^^
--|

what am i doing wrong?
i am using openfoam 2.3

Thanks,

andrea