Shock waves
Fluid mechanics-One-dimensionnal compressible flow

A shockwave is a very thin zone of flow, less than 1 mm thick, which marks the transition from supersonic velocity upstream to subsonic velocity downstream. In the same space, pressure rises sharply. As a result, the fluid particles passing through the shockwave undergo an extremely high deceleration rate of up to 10⁹ to 10¹⁰ m /s², or around one billion g. It's this violent impact, producing a real shock on the particles, which is the origin of the name given to this transition zone.

There are straight (or flat) shockwaves and oblique shockwaves.