Mach wave

Mach wave

[′mäk ‚wav] (fluid mechanics) Also known as Mach line. A shock wave theoretically occurring along a common line of intersection of all the pressure disturbances emanating from an infinitesimally small particle moving at supersonic speed through a fluid medium, with such a wave considered to exert no changes in the condition of the fluid passing through it. A very weak shock wave appearing, for example, at the nose of a very sharp body, where the fluid undergoes no substantial change in direction.

Mach wave

A wave formed in front of a body when it is moving at the speed of sound. The waves do not move ahead of the body; they bunch up and form a Mach wave. A Mach wave is at right angles to the direction of movement of the body and is called a normal Mach wave. The air passing through a normal shock wave slows down to a subsonic speed while its pressure rises. A shock wave that forms on a sharp pointed object moving through the air at a speed greater than the speed of sound is called an oblique shock wave. Air passing through an oblique shock wave is slowed, but if the wave angle is less than about 70°, it will still be supersonic. The area bounded by the sides of an oblique shock wave forms the Mach cone. Also known as a Mach line.