The afﬁnity laws
Any machine that imparts velocity and converts a velocity to pressure can be categorized by a set of relationships that apply to any dynamic conditions. These relationships are referred to as the afﬁnity laws. They can be described as similarity processes, which follow the following rules:
- Capacity varies as the rotating speed — the peripheral velocity of the impeller.
- Head varies as the square of the rotating speed.
- Brake horsepower varies as the cube of the rotating speed.