rarefaction wave

rarefaction wave

[¦rer·ə¦fak·shən ‚wāv] (fluid mechanics) A pressure wave or rush of air or water induced by rarefaction; it travels in the opposite direction to that of a shock wave directly following an explosion. Also known as suction wave.

expansion wave

In supersonic flow, expansion waves occur when bodies begin to narrow, making more space available. In passing through an expansion wave, air velocity increases, while temperature and pressures are reduced. A simple wave or progressive disturbance in the isentropic flow of a compressible fluid, such that the pressure and density of a fluid particle decrease on crossing the wave in the direction of its motion. It is the opposite of a compression wave. Also called a rarefaction wave. See also compression wave.