参考 $FOAM_ETC/caseDicts/postProcessing/flowRate/flowRatePatch。
OpenFOAM-4.0 可以直接在controlDict中使用 #includeFunc 语句 [1],用法参考user-guide [2]。
[1] https://github.com/OpenFOAM/OpenFOAM-dev/commit/dd20d9086889ccbf993e8648d8e8f070f1b16b79
[2] http://cfd.direct/openfoam/user-guide/post-processing-cli/