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Old 08-21-2008, 09:21 AM
infinitemass is offline
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Atlantic city airshow shockwave

Caught a great shot of that cool shockwave cone coming off the back of a fighter as it approaches the speed of sound.
This is a still from the video.
Great show. Right over the water in Altantic City.
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Old 08-22-2008, 01:19 AM
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Re: Atlantic city airshow shockwave

Nice. We don't get supersonic runs in TN.
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Old 08-22-2008, 07:38 AM
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Re: Atlantic city airshow shockwave

I don`t think he was supposed to hit that speed. They fly over the water just off the beach. Here`s the clip that I got the still from.
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Old 08-22-2008, 08:42 AM
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Re: Atlantic city airshow shockwave

a stunning picture indeed. We are extremely lucky to be able to witness such an incredible aerodynamic phemnomena. Often misinterpreted and ill-explained, what you are really seeing is a Prandtl-Glauart Singularity cloud caused by the amplification of pressure disturbances at or near the speed of sound. This is caused a mathematical singularity at Mach 1. I looked into the math and confirmed it theoretically. Under the right conditions the Singularity can be visualized by the human eye as a result of the reduction in local pressure and moisture condensation caused by the amplification. With the drop in pressure at points around the vehicle, there is a corresponding drop in local temperature leading to condensation (assuming the air is near the saturation point) causing a cloud. For us to see this around an aircraft as seen here, there has to be sufficient moisture present when the aircraft goes transonic.

Often assumed, the outline of the cloud DOES NOT define the edge of the shockwave (shockwaves cause an INCREASE in pressure and temperature across them - the opposite trends needed for condensation and formation of clouds). Despite obvious visual similarities, it's very deceptive (as is most of fluid mechanics) - the PG cloud shape DOES NOT outline a shockwave. The two formations are NOT related, and caused by two unrelated aerodynamic mechanisms. The PG cloud only manifests itself very close to the speed of sound - it DOES NOT form at subsonic or supersonic conditions - only in a very tight band around Mach 1.

If you want to see good shockwaves go to a wind tunnel equipped with Schlieren or Shadowgraph equipment. you can also see them well on the wing of an airliner if the sun is in the right place and if the pilot is going fast enough. But a lot of things have to come together for it to happen.
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Old 08-22-2008, 08:53 AM
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Re: Atlantic city airshow shockwave

Did a little research and it seems both definitions are correct?

One view of this phenomenon is that it exhibits the effect of compressibility and the so-called "N-wave". The N-wave is the time variant pressure profile seen by a static observer as a sonic compression wave passes. The overall three-dimensional shock wave is in the form of a cone with its apex at the supersonic aircraft. This wave follows the aircraft. The pressure profile of the wave is composed of a leading compression component (the initial upward stroke of the "N"), followed by a pressure descent forming a rarefaction of the air (the downward diagonal of the "N"), followed by a return to the normal ambient pressure (the final upward stroke of the "N"). The rarefaction may be thought of as the "rebounding" of the compression due to inertial effects
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Old 08-22-2008, 08:59 AM
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Re: Atlantic city airshow shockwave

Holy . And I just wanted to see the cool pic. jk
Nice explanation guys
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Old 08-22-2008, 09:24 AM
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Re: Atlantic city airshow shockwave

Yeah..........
What they said. I was searching for the right words. (Great explanation and great video!)
WT
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Old 08-22-2008, 03:07 PM
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Re: Atlantic city airshow shockwave



JK, Those were both very good explanations, and I can honestly say I learned something today. Thanks for explaining... Besides the military, are there any airshows that allow supersonic flight?
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Old 08-22-2008, 04:00 PM
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Re: Atlantic city airshow shockwave

Quote:
Originally Posted by infinitemass View Post
Did a little research and it seems both definitions are correct?

One view of this phenomenon is that it exhibits the effect of compressibility and the so-called "N-wave". The N-wave is the time variant pressure profile seen by a static observer as a sonic compression wave passes. The overall three-dimensional shock wave is in the form of a cone with its apex at the supersonic aircraft. This wave follows the aircraft. The pressure profile of the wave is composed of a leading compression component (the initial upward stroke of the "N"), followed by a pressure descent forming a rarefaction of the air (the downward diagonal of the "N"), followed by a return to the normal ambient pressure (the final upward stroke of the "N"). The rarefaction may be thought of as the "rebounding" of the compression due to inertial effects
let's give credit where credit is due when we post things - this is taken directly from http://en.wikipedia.org/wiki/Prandtl...rt_singularity
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Old 08-22-2008, 09:04 PM
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Re: Atlantic city airshow shockwave

Yep, I was there.
I decided not to take the video camera this year.
It seems like you miss so much of the airshow looking through the veiw finder.
I live 3 minutes away from the Atlantic City airport. I see the F-16 all day long.
At this years airshow, my favorite was seeiing four F-22's come in and peel off, then one by one come in and do a full afterburn verticle climb.
Four all together was awsome for me.

I did find a video of the F-22 @ the 08 AC airshow.

F-22 Raptors formation break (2 min 51 sec)
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