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Eventually the flow expands enough so that its pressure is again below ambient, at which point the expansion fan reflects from the contact discontinuity (the outer edge of the flow). The reflected waves, called the compression fan, cause the flow to compress. If the compression fan is strong enough,
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Diamond patterns can similarly form when a nozzle is under-expanded (exit pressure higher than ambient) in lower atmospheric pressure at higher altitudes. In this case, the expansion fan is first to form, followed by the oblique shock.
374:, are observed to have regularly-spaced knots of enhanced radio emissions. The jets travel at supersonic speed through a thin "atmosphere" of gas in space, so it is hypothesized that these knots are shock diamonds.
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As the exhaust passes through the normal shock wave, its temperature increases, igniting excess fuel and causing the glow that makes the shock diamonds visible. The illuminated regions either appear as disks or
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261:
93:, when it is operated in an atmosphere. The "diamonds" are actually a complex flow field made visible by abrupt changes in local density and pressure as the exhaust passes through a series of standing
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another oblique shock wave will form, creating a second Mach disk and shock diamond. The pattern of disks and diamonds would repeat indefinitely if the gases were ideal and frictionless; however,
196:. This locates the first shock diamond, and the space between it and the nozzle is called the "zone of silence". The distance from the nozzle to the first shock diamond can be approximated by
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which can expose the location of gun emplacements to the enemy. It was found that when the ratio between the flow pressure and atmospheric pressure is close, which can be achieved with a
177:, a reduction in velocity causes its static temperature to be substantially increased. The exhaust is generally over-expanded at low altitudes, where air pressure is higher.
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When artillery pieces are fired, gas exits the cannon muzzle at supersonic speeds and produces a series of shock diamonds. The diamonds cause a bright
201:
497:
130:
153:
USAF F-22 Raptor flying in knife edge during a high-speed low-altitude pass over
Airventure in full afterburner with Mach diamonds at sunset
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611:- This link has useful diagrams. Aerospaceweb.org is a non-profit site operated by engineers and scientists in the aerospace field.
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was the first to describe a strong shock normal to the direction of fluid flow, the presence of which causes the diamond pattern.
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As the flow exits the nozzle, ambient air pressure will compress the flow. The external compression is caused by
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Shock diamonds are most commonly associated with jet and rocket propulsion, but they can form in other systems.
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shear at the contact discontinuity causes the wave pattern to dissipate with distance.
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Barnes, Luke; Filipovic, Miroslav; Norris, Ray; Velović, Velibor; Conversation, The.
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544:"Shock Diamonds In Space: Extragalactic Afterburner From PKS 0637-752 | Science 2.0"
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Shock diamonds are the bright areas seen in the exhaust of this statically mounted
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inclined at an angle to the flow. The compressed flow is alternately expanded by
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to the end of the muzzle balances the pressures and prevents shock diamonds.
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571:"Astronomers have detected one of the biggest black hole jets in the sky"
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601:- shock diamonds forming in NASA's methane engine built by
256:{\displaystyle x=0.67D_{0}{\sqrt {\frac {P_{0}}{P_{1}}}},}
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of the gases exiting the nozzle is less than the ambient
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of an aerospace propulsion system, such as a supersonic
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Shock diamonds form when the supersonic exhaust from a
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Michael L. Norman; Karl-Heinz A. Winkler (July 1985).
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27:Visible wave pattern in a supersonic exhaust plume
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485:Liquid chromatography-mass spectrometry
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30:Not to be confused with the mineral
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518:Florida International University
514:"Exhaust Gases' Diamond Pattern"
482:Niessen, Wilfried M. A. (1999).
609:"Shock Diamonds and Mach Disks"
520:. 12 March 2004. Archived from
458:"Shock Diamonds and Mach Disks"
1:
456:Scott, Jeff (17 April 2005).
145:with shock diamonds behind it
330:competition-winning landing.
186:Prandtl-Meyer expansion fans
70:patterns that appear in the
133:taking off with afterburner
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605:, NASA website, 4 May 2007
384:Index of aviation articles
298:, giving them their name.
29:
290:is atmospheric pressure.
276:is the nozzle diameter,
119:Lockheed SR-71 Blackbird
117:Shock diamonds behind a
326:Xoie rocket during the
322:Shock diamonds beneath
129:Shock diamonds from an
45:Pratt & Whitney J58
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328:Lunar Lander Challenge
283:is flow pressure, and
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389:Plume (hydrodynamics)
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66:) are a formation of
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394:Rocket engine nozzle
324:Masten Space Systems
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314:Alternative sources
182:oblique shock waves
625:Physical phenomena
524:on 7 December 2011
460:. Aerospaceweb.org
427:Los Alamos Science
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548:www.science20.com
499:978-0-8247-1936-4
422:"Supersonic Jets"
269:is the distance,
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190:normal shock wave
159:propelling nozzle
16:(Redirected from
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550:. 27 August 2014
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640:Aerodynamics
578:. Retrieved
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552:. Retrieved
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526:. Retrieved
522:the original
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462:. Retrieved
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352:muzzle brake
344:muzzle flash
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167:air pressure
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630:Shock waves
171:exhaust gas
143:F-22 Raptor
95:shock waves
49:afterburner
619:Categories
528:6 November
464:6 November
400:References
364:radio jets
358:Radio jets
173:stream is
103:Ernst Mach
79:jet engine
72:supersonic
635:Aerospace
490:CRC Press
338:Artillery
304:turbulent
194:Mach disk
175:adiabatic
109:Mechanism
580:13 March
575:phys.org
554:13 March
434:: 38–71.
378:See also
296:diamonds
91:scramjet
368:quasars
32:diamond
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265:where
87:ramjet
83:rocket
362:Some
89:, or
582:2024
556:2024
530:2011
494:ISBN
466:2011
370:and
212:0.67
131:F-16
97:and
192:or
141:An
62:or
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408:^
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288:1
285:P
281:0
278:P
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271:D
267:x
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243:1
239:P
233:0
229:P
220:0
216:D
209:=
206:x
121:.
51:.
34:.
20:)
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