Posted on 01/05/2006 5:44:41 AM PST by EnjoyingLife
Shock waves play important roles in modern physics and engineering, military operations, materials processing and medicine. Historically, the study of shock waves has taught us much about the properties of gases and material responses to a sudden energy input, and has contributed to the development of gas lasers and the field of plasma dynamics.
Recent attacks by terrorists using improvised explosive devices have reinforced the importance of understanding blasts, explosions and the resulting shock waves. These waves can be powerfully damaging in their own right, but in addition, studying them can help to quantify their originating explosions and can provide insight into how buildings and airplanes can be hardened to resist damage resulting from such blasts.
Their almost-total invisibility has given shock waves a mystique that has been exploited by Hollywood in countless scenes where explosions send heroes diving for cover. Like sound waves, shock waves are as transparent as the air through which they travel. Usually they can only be seen clearly by special instruments under controlled conditions in the laboratory.
Now, however, our research group has taken modern high-speed videography equipment and combined it with some classical visualization methods to image shock waves from explosions and gunshots in more realistic environments. This allows us to capture the development and progress of these wave fronts on a scale that has not been possible in the past.
(Excerpt) Read more at americanscientist.org ...
Watch what the invisible shock wave does to the water in this supersonic flyby of my--it's hard to for me to say this without choking up--of my...of my...of my United States Navy F-14 Tomcat, found and explained at http://www.galleryoffluidmechanics.com/shocks/sfb.htm
From the interesting discussion at http://www.digg.com/science/Rare_photo_of_Space_Shuttle_Sonic_Boom comes "Prandtl-Glauert Condensation Cloud on a F/A-18F Super Hornet 'Rhino' from VFA-122 'Flying Eagles' Flight Demonstration at Salinas 2005":
http://www.sawmillcreek.org/showthread.php?p=269893
http://www.sawmillcreek.org/attachment.php?attachmentid=24437
| Figure 4. A U.S. Navy Blue Angel F-18 fighter flying transonically over San Francisco Bay leaves some visible clues of shock waves. The air around the plane is compressed by the shock waves, then immediately expands and produces visible moisture condensation. Shock waves also induce a “wind” immediately behind them that is strong enough to leave a track of white water on the bay. |
| Figure 1. High-speed photography freezes in time an instant of the discharge of a .30-06-caliber rifle. The fast exposure captures the bullet as it emerges at about Mach 2.5, but the spherical shock wave of the muzzle blast and the sweptback shock waves behind the bullet are normally invisible. While this image was captured on film, new digital video technology that can capture the waves' distortion of a background pattern has enabled some classical optical techniques to enter the modern age, where they can image high-resolution details of ballistic events with a large field of view and under realistic conditions. Because flows are standardized to move from left to right in fluid dynamics, some images in this article are printed in reverse. |
| Photograph courtesy of Gary S. Settles. |
| Figure 11. This full-scale schlieren image shows the discharge of a .44 Magnum revolver. Two spherical shock waves are seen, one centered about the gun’s muzzle (the muzzle blast) and a second centered on the cylinder. The supersonic bullet is visible at the far left. This weapon produces a bright muzzle flash and a cloud of products of gunpowder combustion that envelops the hands of the shooter. Such high-speed images help forensics experts understand the transfer of gunpowder traces to the hands when firing a gun. |
| Photograph courtesy of Gary S. Settles. |
Cool
An amazing read. TY for posting it.
Check out the picture in post#2. We've seen the Blue Angels during their practices many times at the Pensacola Naval Air Station, and have seen them do this manuever. It is WAY cool seeing it in person!
Fake pic.
First, aircraft are NOT allowed to go to supersonic flight at low level near populated areas in the US. Second, a military pilot would NEVER fly under the Golden Gate bridge or he would probably lose his wings forever.
Well, you should read the article. You're correct that images displayed do not portray visual light, but they are not computer generated. They are direct observations.
I still say that it is fake.
A few days ago there was a "Myth Busters" episode where they fired various weapons through 1-2 feet of water, attempting to penetrate ballistic gel. The purpose was to find out if diving under the surface of water would protect one from gunfire (the "myth"). Turned out the WATER apparently caused high speed (i.e. high fps) projectiles, including .50 caliber to shatter into small pieces before reaching the gel. A question for Freeper "ballistics techies" - What is the (fps) speed of the fragments from an exploding mortar or artillery round in IED configuration? Would water shields (tanks,bags etc)be of any use in protecting personnel against IEDs? I'm not saying it would, just asking the question.
I've got the butter. Where's my fuze? Where's my fuze?
but fortunately the butter is too stable to explode.
Awwww, darn!
Depends. 9mm projectiles went some distance in water, so if the shrapnel is ballistically similar, it would take an awful lot of water to stop them. Kevlar is probably better.
http://chamorrobible.org/gpw/gpw-The-Spectacular-Clouds-of-the-Transonic-Flight-Regime.htm (6th photo from the top)
http://chamorrobible.org/gpw/gpw-20050914.htm
Buzzing the Bay Area is a Fleet Week tradition. Back when DiFi was Mayor of SF, she would work herself up into a lather for a solid week before Fleet Week, threatening the Navy with all sorts of reprisals if they buzzed the city (or The City, as they call it in SF). Then, like clockwork, the Blue Angels would come through the Golden Gate at treetop level as soon as the carrier was in range.
I don't know if they actually flew under the bridge, though...
Actually, if you look at that pic, the aircraft is a long way from the bridge. That is a cropped shot of a picture taken with a very long lens, probably from the Emeryville waterfront. That aircraft could be miles from the bridge.
Come on! That is so obviously faked! Look at how crisp the FA-18 is in relation to the other objects. With a jet moving at 750 mph you will either have to pan with the plane (and cause the background to blur) or hold still and speed up the shutter. In the case of a 1/1000th sec exposure, the plane will move about a foot during that time and show up as a blur.
That couldn't be true because ship movements, arrivals and departures are a secret. ;^)
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