Q1=Q2(P2/P1)^.5 ,where it does come from!

[Sean Miller]

Pump Flow versus speed for a fixed diameter impeller:
1) Q1/Q2 = N1/N2
N1 = original speed N2 = New Speed Q1 = original flow Q2 = New flow
Pump pressure versus speed for a fixed diameter impeller
2) H1/H2 = (N1/N2) ^2
H1 = original head H2 = New head

therefore N1/N2 = SQRT ( H1/H2) and substituting for N1/N2 in 1)
Q1/Q2 = Sqrt(H1 / H2)
Solve for Q2
Q2 = Q1 / (Sqrt (H1 / H2))

 

[LittleInch]

Where does it come from?

Appears to have the pressure ration the wrong way around, but clearly you've found it somewhere?


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[PersonalProfile]

The following may be of interest:

The laws are derived using the Buckingham π theorem.

Ex:

https://en.wikipedia.org/wiki/Affinity_laws