Pleaseee Need help to calculate air flow rate urgeeent

i want to calculate airflow rate in paraview
i did the CFD simulation through openfoam and my case basically is consisting of cylinder with 24 holes on that cylinder and these holes blow the air inside the room
i am trying to calculate total volumetric airflow rate from inlet boundary patch
the inlet boundary patch as i mentioned contatin these 24 holes
each hole surface for sure has mesh that mean each surface has many cells
my idea which i am not sure is correct or no: to have a normal velocity magnitude normal to the surface at the center of the hole surface
and if i get this velocity magnitude normal to each hole surface i can then multiply by the hole area and then i multiply by number of holes maybe

and i want to do the same also for the outlet which is just a rectangular surface at the side of the room
i am new to paraview so please share with me the best and the accurate way to achieve my goal

thanks in advance

Regarding your idea: seems correct, except that you also need to consider that your airflow may not be constant over the whole area of each whole. Implementation wise I would propose these steps:
1.Create a slice through all your holes. Sounds like your geometry is fairly simple so a planar slice should do the trick.
2. Calculate surface area of each cell that intersects this slice (integrate filter will likely do what you need).
3. Calculate normal velocity normal to slice.
4. combine steps 2 and 3.

Since you indicate you are a beginner I highly reccomend this tutorial series by Cyprien Rusu: This will get you up to speed within a day. What you want to do is absolutely possible. May just take some fidgeting. Once you have something in Paraview to share which you need feedback on, feel free to respond to the topic again and I’ll see how I can help. Good luck!