Transonic

In a transonic flow occur in the flow field of a compressible fluid at the same flow rates in areas with sub - and supersonic range.

In an aircraft, which is still flying with less than the speed of sound, the sound speed can be exceeded in the flow around locally. The transition in the flow path of the air from supersonic to subsonic flow is connected to a compression shock, which causes a high flow resistance and has an influence on the pressure distribution on the aircraft. Therefore, long time, exceeding the speed of sound with aircraft an unsolved challenge, for which the term sound barrier was coined.

For aircraft, the transonic range is about flight Mach numbers from 0.8 to 1.2. The airspeed at which a transonic flow condition occurs is referred to by the critical Mach number.