Can someone please help me with this fluid mechanics problem?

Question

Explain, in detail, the relationship when impeller diameter varies in centrifugal pumps for capacity, total head and power. Do not merely give the equations but explain them. Use examples if you need

Answer 1

Equations per link:

http://www.engineeringtoolbox.com/affini...

The affinity laws are simple proportions, shouldn't require much explanation.

Volume is linear with diameter. If you double the diameter, you double the volume.

Pressure comes from centrifugal force, V²/R. Thus, it's proportion is by the square of the diameters.

Power is pressure x volume. Thus, it's proportions are by the cube of the diameters.