Mach wave
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(′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.
McGraw-Hill Dictionary of Aviation:
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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.
Wikipedia on Answers.com:
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Mach wave
In fluid dynamics, a Mach wave is a pressure wave traveling with the speed of sound caused by a slight change of pressure added to a compressible flow. These weak waves can combine in supersonic flow to become a shock wave if sufficient Mach waves are present at any location. Such a shock wave is called a Mach stem or Mach front. Thus it is possible to have shockless compression or expansion in a supersonic flow by having the production of Mach waves sufficiently spaced (cf. isentropic compression in supersonic flows). A Mach wave is the weak limit of an oblique shock wave (a normal shock is the other limit). They propagate across the flow at the Mach angle μ [1]:
where M is the Mach number.
Mach waves can be used in schlieren or shadowgraph observations to determine the local Mach number of the flow. Early observations by Ernst Mach used grooves in the wall of a duct to produce Mach waves in a duct, which were then photographed by the schlieren method, to obtain data about the flow in nozzles and ducts. Mach angles may also occasionally be visualized out of their condensation in air, as in the jet photograph below.
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McGraw-Hill Science & Technology Dictionary
McGraw-Hill Dictionary of Scientific and Technical Terms. Copyright © 2003, 1994, 1989, 1984, 1978, 1976, 1974 by McGraw-Hill Companies, Inc. All rights reserved.
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McGraw-Hill Dictionary of Aviation
An Illustrated Dictionary of Aviation.. Copyright © 2005 by McGraw-Hill Companies, Inc. All rights reserved.
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Mach line
(fluid mechanics)
Supersonic flow
(fluid mechanics)
Supersonic flight
(aeronautical engineering)
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