Fluid Mechanics, Pumps and Water Systems

Fluid mechanics is the study of liquids and gases at rest and in motion, and of the forces they exert. It underpins the design of pumps, pipelines and water systems that move and distribute fluids in homes, industry and agriculture. A pump is a machine that adds energy to a liquid to raise its pressure or lift it to a higher level, overcoming friction, gravity and resistance within a piping network.

Pumps fall into two broad families. Positive-displacement pumps, such as piston and gear pumps, trap a fixed volume of fluid and force it onward with each cycle, making them well suited to high pressures and precise flow. A piston-and-crank mechanism is a classic example, converting rotary motion into the reciprocating stroke that draws fluid in and pushes it out. Dynamic pumps, of which the centrifugal pump is the most common, use a spinning impeller to accelerate the fluid and convert that velocity into pressure, handling large flows efficiently.

A water system links pumps with pipes, valves, tanks and controls to deliver supply where it is needed and remove waste. Key concepts include head, the height to which a pump can raise water; flow rate, the volume delivered per unit time; and cavitation, the damaging formation of vapour bubbles when local pressure falls too low. Animations help by showing how impellers and pistons move fluid and how pressure builds along a system, making invisible internal flows easier to understand.

Frequently asked questions

What is the difference between a centrifugal and a positive-displacement pump?

A centrifugal pump uses a spinning impeller to add velocity and then pressure, suiting high flows. A positive-displacement pump traps and pushes a fixed volume each cycle, suiting high pressures and steady metering.

What is pump head?

Head is the height, usually expressed in metres of liquid, to which a pump can raise a fluid. It represents the energy the pump adds against gravity and friction.

What causes cavitation?

Cavitation occurs when the pressure of a liquid drops below its vapour pressure, forming bubbles that collapse violently and can erode pump components.