Mach number

Fluid mechanics The Mach number is the ratio of the speed of a moving body to the speed of sound in the surrounding fluid M = v /c where c is the speed of sound.

The Mach number is used in fluid mechanics, aerodynamics and aeronautics. This especially refers to supersonic flight where the speed is greater than that of sound, and hypersonic flight.

For M<1, on a un écoulement subsonique, pour M=1 un écoulement sonique (état critique), pour M>1 supersonic flight (hypersonic for M>5).