Specific Suction Speed may be used to determine what pump geometry - radial, mixed flow or axial - to use for maximum efficiency and prevent cavitation. Suction Specific Speed is commonly used as a basis for estimating the safe operating range of a pump.
Nss = ω q^1/2 / N^3/4
where
Nss = Suction Specific Speed
ω = pump shaft rotational speed (rpm)
q = flow rate capacity ( l/s)
N = Required Net Positive Suction Head for the pump at the best efficiency point (m)