[Amps] Wind! In series or parallel?

[Martin Sole]

Wind as in air.

The more I think about moving this stuff the more I realise I just don't 
yet follow.

Tube specs for 1 tube state 9cfm as an example.

2 tubes operating together need 18cfm, right? or still only 9 total? Or 
different again?

If I'm measuring airflow what is the relationship between total air and 
individual tube air?

Does it matter?

Thoughts?

Martin, HS0ZED