What is the difference between taking mass flow rate from Openfoam and Parafoam?
 

Hi dear Foamers,

I am trying to understand whether my converged Openfoam solution is true or not. To estimate the accuracy of the solution I am observing the mass flow rate for inlet and outlet patches. I am modelling a square pipe geometry with simpleFoam and buoyantSimpleFoam.When I search how to find the mass flow rate in Openfoam, I found 2 ways:

1. It can be find from Openfoam postprocessing:
by typing postProcess -func 'flowRatePatch(name=inlet)' -latestTime in terminal,

2. It can be find from Paraview:
1. calculate with Mag(U) from calculator
2. apply Extract Block filter
3. apply Integrate Variables filter

(By the way, I am using air at room temperature, so its density is 1, it's density won't be change because of the incompressible flow)

These two ways are giving different mass flow rate values. I am wondering about what is the difference between finding mass flow rate from Openfoam postprocessing and Paraview?

I would be glad if you help.