Steel, cast iron, copper, aluminium etc

Brass and bronze

Hard surfacing materials such as stellite

All of these

Tempering

Annealing

Normalising

Spheroidising

Kelvin

Joule

Clausis

Gay-Lussac

At the same speed and in the same direction

At the same speed but in opposite direction

At different speeds and in the same direction

At different speeds in the opposite direction

Sub-sonic flow

Sonic flow

Super-sonic flow

Hyper-sonic flow