Posted by berkoa on January 29, 2009
Amazing picture. I am showing to my professor as we just had lecture about shockwaves forming on wings due to blunt bodies and bow shock, but this is not what anyone had in mind.
-berkoa@rpi.edu |
Posted by schreiner on January 30, 2009
I recalculated somethings... this is what I think:
The wave waves with the speed of sound, to all directions. The distance from aircraft divided the distance from the nose to the area of the wave is let say 1 5th of the distance. That means it flies approx Mach 0.2.
Just my two cents. |
Posted by Andreas Fast on January 30, 2009
Impressive effect!! |
Posted by Taras on January 30, 2009
Gerard, I guess I also have to admit that I've never seen such a thing in my life. Besides the nose section, I also see the shockwaves forming over the trailing edge of the left wing section and in front of engines 2,3 and 4 |
Posted by Mark Lawrence on January 30, 2009
Incredible catch Gerard! Well done on getting such a rare shot! |
Posted by Marshall F. on January 30, 2009
That's not a shockwave. Looks more like the 74 is flying through a preceding aircraft's vortices. It happens all the time, but the vortices are usually invisible. |
Posted by JavierCL on January 30, 2009
Very very rare condensation, congratulations for this interesting photo. |
Posted by Frederick Miller on January 30, 2009
You were telling me about this and I just could not wait to see it. That shot is eye candy to everyone in aviation as it shows us something that has never been recorded. This will be a shot that is discussed and shown in lectures of aviation as it shows something that is rarely seen and can not be duplicated in a wind tunnel. Absolutely Jaw Dropping!!! BRAVO |
Posted by gerard isaacson on January 31, 2009
To help shed light on this picture, a storm had just cleared the area, I shot this around the same time USAirways #1549 dropped into the Hudson. This 747 cleared the view of the sky in my back yard like the space schuttle. The halo appeared once very faintly which drew my attention, so I raised the camera in case I saw it again, the first halo last like 1/2 a second, then I started to see it again so I depressed the shutter once...just one shot...that's what I got...the halo or shockwave moved with the plane...it did not pass through a vortex donut so to speak...it was 11 degrees on the ground so I think possibly this is light playing off a layer of ice crystals where the air is compressing by the bow wave. I've just never seen this before. I wonder if the crew were able to see it?..j |
Posted by Mmmmmmm on February 1, 2009
Photoshopped, and not very well done at that. Professional airline pilots on another site are having a bit of a giggle. Sorry gerard. |
Posted by gerard isaacson on February 1, 2009
Dear MMMMMMMMMMMM...My talents in photo shop do not exceed my God given talents to capture a good image on film or digital without artificial enhancement...thats why I can make a $$$ living at aviation photography full time as I'm sure you don't, nice try though...Perhaps you should try looking up more often, you might learn something...Gerard Isaacson |
Posted by midiron on February 4, 2009
Just my geeky perspective, but let us look at what seem to be the facts:
1) These patterns APPEAR to have color, which implies something optical. The Prandtl-Glauert Singularity just produces vapor. Such vapor sometimes does produce color, but also tends to appear in a conical shape. Prandtl also predicts a radius much, much smaller than what we see in the photo.
2) P-G concerns the separation and re-attachment of airflow at high Reynolds numbers (which need not be transonic), but the patterns we're seeing do not seem to result from detached flow, especially when you consider the asymmetrical ring around the nose. In addition to the evident color, please also note that this ring around the nose seems to be almost actually TWO rings. The second one, sharper and less cloudy, looks like it is just forming/becoming visible.
3) Just assuming for argument's sake that there is some kind of P-G effect, what about the shapes we're seeing behind the left wing and ahead of the right-wing pods? Seems like a totally different kind of effect, and not at all related to the classic "N" shape shockwave that is predicted and well-observed. Also, we know that transonic waves will creep up from behind the trailing edge, but this airplane is flying much too slowly for that. At approximately 5,000 feet, this airplane is doing probably 0.2 Mach. We sometimes see condensation developing below and behind extended flaps at such speeds, but this aircraft is clean and we know that it was a cold day (-11C), so ice crystal formation (sublimation) is more likely than condensation.
4) We should also consider what is NOT. Maybe the aircraft in the photo is nowhere near the actual phenomena. Looking at it, the Boeing appears to be above the bow shape, yet far below the trailing edge shape. The pod shapes seem to vague to judge, but all three shapes seem to have a similar intensity and coloration.
5) Also missing are the wingtip vortices often visible in high-humidity conditions. If we were dealing with a P-G effect, then we would expect to see tight vortices coming off the wingtips.
6) Related to 4, maybe it is flying THROUGH some kind of ring-shaped vortex created by a factory or a local explosion of some kind (these are well-documented), but the photographer claims to have seen the phenomenon actually repeat itself, which is why he said he raised his camera in the first place. If the effect repeated itself, the aircraft was not flying through an existing vortex. UNLESS it, by some massive coincidence, managed to re-enter or remain in wake turbulence from a preceeding aircraft. Could be, and I've seen it happen.
7) The bow shape resembles a parhelic circle. These usually form at a 22 degree angle between the observer and the object, which is plausible here, but how to explain the non-circular shapes ahead of the right wing and behind the left one? Again, potentially two different effects.
At any rate, congratulations on capturing something really fascinating!
jt |
Posted by gerard isaacson on February 4, 2009
I am in touch with a 747 driver from Kalitta...I'll quote..." As a pilot myself, I have never seen anything like it on a transport catagory aircraft but I know that they exist (shockwaves).Normally at a particular speed, we do have localize airflow go supersonic. When we cruise at mach 0.86, we are already in what's called "transonic region". Max for the 747 is 0.92 Mach. That is an uninterrupted airflow over the pitot tube corrected for compression, etc."...He goes on to say that he feels I had the perfect condition for the phenomenon to be seen with the naked eye and through the lens. Again, the sun was in the right place, temp humidity and density were all just right.
Two weeks prior to this shot after passage of another storm...same type conditions but not as cold, I witnessed an American 767 at about the same altitude cross the spance of my backyard sky, leaving contrails as if it were at 31,000 feet. Not vortices, but contrails from the engine cores. Again I grabbed my camera and sat there till the light diminished and no other incoming transports repeated the event. |
Posted by Burmarrad on February 14, 2009
Well done with this lovely photo Gerard,regards Burmarrad |
Posted by berkoa on February 15, 2009
I'll get my professor's opinion on this one, he teaches compressible flow....either way great shot and congrats from RPI. |
Posted by marlenawitek on February 25, 2009
Hello. I from Poland (sorry for my english). I think it is plasma, name is (i think) the "annular discharge plasma" - variety. i cant translate for english more, sorry.
Foto is fantastic, this is rarity for human eyes in nature!
Greetings. |
Posted by berkoa on February 25, 2009
Its not plasma......I spoke to my professor. Theres two answers.
1. It is a WEAK supersonic wave (not a strong, there is a difference if you take compressible flow or propulsion systems or fluid dynamics), that tore off the sin and caused temperature and pressure differences creating condensation on a high humidity day. Even on very cold days you can have 90% humidty.
2. A new theory being proposed by various professors at my school. A turbulent region separated from the aircraft and continued spiraling, causing a pressure gradient. The water inside the turbulent region reflected light in a new phenomenon that can create the illusion of a vapor cloud.
-berkoa@rpi.edu |
Posted by marlenawitek on February 27, 2009
Plasma exist in nature, like aurora polaris, candlelight, where magnetic fields making this pictures. They are more informations in internet. Atmospheric air ionisation (sorry english), this is any sensation, but hardly ewer we can see that. Thunder this is plasma too! Moore characters. |
Posted by Carlos on March 9, 2009
Gerard it's an amazing picture! never seen before with such a definition.
I teach aerodynamics, and I agree with the idea of a weak pressure wave. It is not a shock wave (speed over the sound one), it is a sound wave (the sound itself). When every object moves in the atmosphere -even at low speeds- it pushes away the particles of air (and moisture) surrounding it at the velocity of sound. In this case the aircraft encountered very cold turbulent flow (a vortex core with "ice" particles inside) and disipated it creating a growing annulus (that grew up at the speed of sound). Look at the spiral it created. Hope you can get more of this!
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Posted by Frank on September 17, 2009
I may be missing something here, bit if you looke very close to the #4 engine, you will see a similar effect, as well as what appears to be a ripple from turbulent air off the trailing edge of the port wing. |
Posted by gerard isaacson on September 17, 2009
Yes, if you look carefully ,the entire airframe has this effect...I'm 54 and have looked up at every aircraft that has past over my head since I was 6 years old...I have never seen this before and was very fortunate to catch this...I had seen an Airbus create even a funkier effect earlier this day which prompted me to get my camera...Unfortunetelly, I was just photodocumenting items for ebay and had the camera set on jpg/med rather than RAW as I typically do. imagine the image in RAW?! |
Posted by Paul on May 16, 2011
This is indeed droplets or ice crystals becoming visible in the sunlight. They seem to prismaticly break the light a bit to give some color. You need not fly supersonic to have a bow wave, but if conditions are just right, these weak waves can also trigger water vapour to form briefly from compression-decompression. I have captured on video a very nice shock wave dancing on the surface of a cruising jetliner going transsonic (as PAX). I could only see it from 1 or two seats right above the centre of the wing. I just had to show it to one of the pilots after landing (was the last get off). He said he knows of the shock waves, but has never seen one in his thousands of hours flying, nor any other phenomena. Those seats in the front are just not a good place for observing these. |
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