TAKO. INTERNET SEIT 1996.
Olympus-OM

Re: leaking planes Re: [really OT] (was: Re: [OM] OM] OT - Titanium)

Subject: Re: leaking planes Re: [really OT] (was: Re: [OM] OM] OT - Titanium)
From: "gary edwards" <maitani@xxxxxxxxxxx>
Date: Tue, 10 Aug 1999 12:09:15 PDT
Any supersonic jet will have a pattern of oblique shock waves originating generally at the nozzle exit plane (the term "jet" is used here to refer to the stream of fluid discharged from the nozzle.) These shock waves reflect ("bounce") from the jet boundary back into the jet in the characteristic diamond pattern. The angle formed by the diamonds is related to the flow Mach number - faster=longer diamonds. These shock waves are visible in some cases due to the different index of refraction across the shock wave. Jet engines that do not produce a supersonic exhaust jet do not display shock diamonds. Most engines produce supersonic jets only when operating in afterburner ("reheat") and the articulated nozzle petals are closed down to form a convergent-divergent nozzle. All rocket engines have shock diamonds but in many cases (like the classic slow-motion Saturn V launch sequence), the diamonds are not visible due to the incandescence of the exhaust gases. The incandescence doesn't allow you to see through the jet.

OM Content: When photographing jet aircraft in afterburner you may have a better chance of capturing the shock diamonds if the exhaust jet is somewhat backlit. That is how we photographed control rocket simulators that used cold nitrogen as a working fluid.

Gary Edwards


From: Chris Barker <cmib@xxxxxxxxxxx>
Reply-To: olympus@xxxxxxxxxxxxxxx
To: olympus@xxxxxxxxxxxxxxx
Subject: Re: leaking planes Re: [really OT] (was: Re: [OM] OM] OT - Titanium)
Date: Tue, 10 Aug 1999 13:53:45 +0200

>on my page shortly thereafter. What causes the diamonds in the exhuast
>plume?
>
>/Acer Victoria
All "decent" engines have them (the Tornado's RB199 does not) - nb personal
prejudice, not scientific observation.  I believe that it is the formation
of Mach cones in the exhaust that shapes the flame into 'V' or diamond
shapes.

Chris

_______________________________________
Chris Barker <><       mailto:cmib@xxxxxxxxxxx
Box 2, Officers' Mess,
RAF Brueggen, BFPO25, UK.



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