Visable Shock Waves

[Tolmosoff]

When I was a teen and our San Joaquin valley had supper sonic jets over our valley that rattled windows with sonic boombs.

 

Shock waves can be seen visually. There was a supper sonic jet over head with a thin cloud layer and about 3/4 mile behind there I saw a large shock wave following. The shock waves travel in straight lines one after another.

[insane_alien]

and are you going to bring up any points for discussion?

 

i'll even start, you didn't see the shockwave, you say its effects on the cloud layer. if you seen the shockwave itself then you would have seen it extending from the aircraft itself.

 

it is however possible to make shokwaves directly visible but this requires special conditions and cameras. http://en.wikipedia.org/wiki/Schlieren_photography

[Tolmosoff]

No, the shock wave did not come from the front of jet. It was following way behind in striaght lines one after the other. Cloud cover was very thin so I was able to see them from underneath the clouds ground up.

 

Well then What the hell was that I seen ?. Please explain.

 

Jet and shock wave both was the same speed.

[insane_alien]

well, the shockwave starts at the nose of the jet(and other shockwaves will start at the leading edges of pretty much everything else on the jet).

 

what you seen was the disturbance in the cloud layer caused by the shockwave.

[Tolmosoff]

No binocuars and no special lense were used.

 

So the thin clouds made the waves visible.

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Then the shock wavw was hitting the cloud layer, right ?.

 

Both jet and shock wave traveled the same speed.

[insane_alien]

yes, the shockwave hit the clouds but it wasn't travelling as fast as the jet.

 

the shockwave was travelling at the speed of sound.

 

i'll show you what i mean using ripples on a pond as an example.

 

if you drag your finger or something through the water you'll have a shockwave coming off your finger which is seen as a ripple. this ripple isn't moving as fast as your finger. if you look towards the edge, you'll see the point where the shockwave hits the edge moving as fast as your finger. same thing happening with the shockwave and the cloud layer.

[swansont]

As there was no news link in th OP, this has been moved out of the news section and into physics

[iNow]

Did you see something like this:

 

 

 

http://apod.nasa.gov/apod/ap070819.html

Explanation

: Is this what a sonic boom looks like? When an airplane travels at a speed faster than sound, density waves of sound emitted by the plane cannot precede the plane, and so accumulate in a cone behind the plane. When this shock wave passes, a listener hears all at once the sound emitted over a longer period: a sonic boom. As a plane accelerates to just break the sound barrier, however, an unusual cloud might form. The origin of this cloud is still debated. A leading theory is that a drop in air pressure at the plane described by the Prandtl-Glauert Singularity occurs so that moist air condenses there to form water droplets. Above, an F/A-18 Hornet was photographed just as it broke the sound barrier. Large meteors and the space shuttle frequently produce audible sonic booms before they are slowed below sound speed by the Earth's atmosphere.

[Tolmosoff]

Nice picture but not what i saw.

 

And no --the shock wave traveled just as fast as the jet

[iNow]

Then, are you suggesting that this is what you saw:

 

These dramatic photographs of free-flight models of the X-15 being fired into a wind Tunnel vividly detail the ahock-wave patterns for airflow at Mach 3.5 (left) and at Mach 6 (right).

 

??

 

If so, I sort of doubt that (as per IAs posts above).

 

http://history.nasa.gov/SP-60/ch-5.html

 

The major consequence of flight to high spced is the effect on airflow, because of the elasticity (compression and expansion) of air. At the slowest speeds, subsonic, the effects are not pronounced. As airflow velocities increase, the air becomes compressed, and pressure begins to pile up ahead of each part of the aircraft, until finally distinct pressure waves, or shock waves, form. The transonic airflow region is where shock waves first appear on an aircraft, though these shocks may be only local in nature. It is a region of mixed and erratic flow between subsonic and supersonic flow, which causes abrupt changes in lift and drag forces and airplane stability. As speed is further increased, local regions of subsonic flow disappear, and the flow is everywhere supersonic. The air has become further compressed. The shock waves are now distinct and trail aft in the form of a wedge, or cone, behind any object that interferes with the airstream. While a shock wave is normally less than .001-inch thick, the air undergoes large changes in pressure, density, and temperature across this minute boundary. These effects are far-reaching, even extending to the ground in the form of sonic booms. Aerodynamic theory has been developed that enables the characteristics of these shock waves to be precisely calculated.

 

At higher supersonic speeds, the shock waves continue to increase in strength, bending back to form an acute angle with the aircraft surfaces. The equations of supersonic flow at this point no longer apply, and many interactions between shock waves and flow field are evidenced. One major effect is a loss of lifting effectiveness of the wings and tail surfaces, because the shock waves attenuate the aerodynamic forces. Of more significance, the friction of the air flowing along any surface raises air temperature to many times that of the surrounding atmosphere. Airflow is now in the hypersonic-flow region, and the science of thermodynamics is added to aerodynamics. Though not exactly defined, it is generally accepted as applying to speeds above about Mach 5. It is an area of multiple shock waves and interference effects. The difficulty for the aerodynamicist arises from trying to unterstand the effects of flow that is discontinuous at each shock wave. Each new geometric shape calls for reorganization of theory.

[Tolmosoff]

Nope thats not it at all.

 

The shock wave was over a half mile behind the jet and traveled just as fast as the jet.

 

Could it been an after shock wave trailing the jet ?.

 

Maybe something the air Force would like to know.

[iNow]

It wasn't a shock wave, then. Probably more related to some sort of turbulent air.

[Tolmosoff]

I don't think turbulent air rippleing against the underside of clouds that travel as fast as a supper sonic jet can be.

 

Can you write to some airforce and see if they can make some heads or tails from my info.?.

[iNow]

Can you write to some airforce and see if they can make some heads or tails from my info.?.

Yes, I sure can, but I'm not going to.

 

 

How about you take the onus on yourself to find us a picture of what you're talking about so... well... so we know what you're talking about?

[Kyrisch]

Awhile back I saw a diagram that I can't seem to find on google images that tried to explain the phenomenon of the sonic boom. I seem to remember the wavefront of the sound being likened to the wake of a boat in the water. When the boat travels faster than the propagation velocity of the water waves, the wave front actually recedes from the rear of the boat and appears to follow the craft a ways off the aft in a manner similar to what the OP describes. Anyone know anything about this?

[iNow]

Probably not what you're thinking of, but here's something along those lines:

 

 

 

http://quest.nasa.gov/aero/planetary/atmospheric/drag1.html

 

 

 

From that same site, another cool image (but it required the plane to be flying through smoke):

 

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Tolmos - How about this (same phenomenon as above, but more natural):

 

Schlieren image of the shock waves generated by an F-18 aircraft flying at Mach 1.4. The Mach cone generated by the head and tail shocks can be seen as well as the shocks generated by the leading and trailing edges of the wings. (NASA Dryden Flight Research Center)

 

 

More to Kyrisch's point, it sort of looks like this:

 

[insane_alien]

Nope thats not it at all.

 

The shock wave was over a half mile behind the jet and traveled just as fast as the jet.

 

Could it been an after shock wave trailing the jet ?.

 

Maybe something the air Force would like to know.

 

i already explained this to you, its where the shockwave hits the cloud layer. and of course it hit half a mile behind the plane, it takes time for the wave to hit the cloud layer and by that time the plane has moved on(about half a mile on in this case)

 

it wasn't an after shock, after shocks are a purely earthquake phenomenon, not a supersonic flow phenomenon.

 

the airforce know about it dince they know about shockwaves