In physics, a
shock wave or
shock is a type of propagating disturbance. When a
wave moves faster than the local
speed of sound in a
fluid it is a shock wave. Like an ordinary wave, a shock wave carries energy, and can propagate through a medium; however it is characterized by an abrupt, nearly discontinuous change in
pressure,
temperature and
density of the medium. In supersonic flows, expansion is achieved through an
expansion fan also known as a
Prandtl-Meyer expansion fan.