Glossary · Pumps & performance

Affinity Laws

Mathematical relationships that describe how pump performance parameters (flow rate, head, and power) change with variations in impeller diameter or rotational speed. FluidFlow automatically applies these laws when modeling changes in pump speed or impeller diameter.

Formula: 
Q₂/Q₁ = (N₂/N₁) × (D₂/D₁) 
H₂/H₁ = (N₂/N₁)² × (D₂/D₁)² 
P₂/P₁ = (N₂/N₁)³ × (D₂/D₁)³

Where:

Q_n	Booster volumetric flowrate at point “n”
N_n	Booster impeller shaft speed at point “n”
H_n	Generated booster head at point “n”
P_n	Booster duty power required at point “n”
P_n	Booster impeller size at point “n”

Application: Used in FluidFlow to optimize pump performance by adjusting speed or impeller size to match system requirements and optimize energy consumption.

Go deeper

Article Applying Pump Affinity Laws in FluidFlow Article Pump Affinity Laws: Predicting Performance

Existing glossary definition · Approved route and link structure

Start with guided FluidFlow training

Free, structured modules that build real models — the fastest way from theory to a working network.

Free Training