Shock Wave Formation in Transonic Flight
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- Опубликовано: 12 сен 2024
- Formation of a shock wave above the wing of a Boeing 737.
The aircraft itself isn't going supersonic, but it's going fast enough (probably around Mach 0.8) that the local airflow over a portion of the top of the wing is supersonic. This is called "transonic," and results in the formation of a shock wave at a right angle to the surface of the wing. The air in front of the shock is supersonic, and the air behind it is subsonic. The shock wave marks the transition between these two regions.
The shock wave is visible because of the abrupt change in the density of the air. The change in density causes a change in the refractive index of the air, and so the scenery behind it is optically distorted, and it also casts a shadow on the wing surface due to the sun being overhead. It helps that I was sitting so that I could view it nearly edge-on... if I had been a couple of rows further forward or back, it might not have been visible.
Further information for the curious:
• Understanding Shock Wa...
en.wikipedia.or...
en.wikipedia.o...
en.wikipedia.o...
• Shell Oil "Transonic F...
history.nasa.go...
It's easy to forget just how fast the wing is moving through the air.
Why is this so true
Well, you have gotta remember that Mach 1 decreases the higher you go so it’s not actually going that fast for a plane
In the case of a shockwave, it's the other way around
For those of you wondering, this is due to flow accelerating to mach 1 over the airfoil creating the shock even though airspeed is only around mach 0.7-0.8. This phenomena is known as the critical mach number.
Close, this is where the air decelerates to Mach 1 at the end of the supersonic zone. You may have meant this, I'm just being more specific.
well but the wing is a swept wing, so the value of crit mach number will be way higher. Theoretically it should not be possible
Vaccuum accelerated air speed?
@@Frrn1gaaa Your statement is not correct, suppose the M_cr for this infinite airfoil is 0.7, and the swept angle is at 20 deg (very generous estimation), the new M_cr is M_cr/cos(angle) = ~0.81. While swept angle helps to delay M_cr and the drag that comes with it, swept angle too high and you destroy the plane's L/D ratio.
If you are not clacking, your slacking
Hi! Great video!
Would it be ok if I used this video as an example, with links to your video, in an upcoming video I am planning for Mentour NOW? Let me know.
Not a problem.
I love watching your detailed videos. Please sharing a link explaining this further in ur videos. Thanks @MentourPilot
There's a few of these videos up, and this one's my favorite because you can see the refraction projected not just on the top wing surface, but also in the free air between the camera and the forward no-step line just a bit inboard from the wingtip. And the winglet fillet section leading edge.
Beautiful! Thank you! I observed this once myself, and cursed that I didn't have a camera to record it. Thank you so much for sharing!
Mr. Sunrise 1961 - u can always do it again
I saw the very same thing on a Canadian airlines B767 on a flight from Toronto to Vancouver 30 years ago. Everyone I have described this to told me I was wrong, "airliners can't fly supersonic!"
Thank-you for sharing!
It was a common sight, if you looked for it, on the older faster transports. The 727 cruised at M.82 but could do M.86 when running late. The L1011 cruised at M.85 and I've seen M.89. I only got to see it when deadheading. Sitting in line with the wings it was usually there.
Modern airliners can cruise at mach .85
@@jaffacalling53 True. Generally, the very long-range jets (B-747SP, B-777 & A350) are engineered for higher Mach numbers. M.80 vs. M.85 doesn't matter much if you're going from KSTL to KATL but from JFK to Johannesburg can be an hour shorter for the faster jet. What they can do and what they flight plan for are often very different. Flying faster than LRC would make some destinations out of reach.
I witnessed this phenomenon on my flight today, a 787. I had no idea what I was witnessing on the wing and began searching all over the internet. Glad I found this, so I know I'm not going crazy!
Where the hell am I supposed to look?
I've seen this on some airline flights and on our corporate aircraft. Sometimes the lighting conditions make this more obvious since it's always there during high speed flight.
Can someone point it out like where to look I watched 3x can’t see anything
Sorry but those aren't shockwaves. You can also observe this at the wingtips or flap edges during landing. Those are simply "transparent" air vortices.
I'm sorry, but they are in fact normal shock waves. Modern Airliners have swept wings because they are transonic airplanes, designed to be flown at high Mach # where local flow is in fact at mach 1 due to the acceleration of the flow around the wing and fuselage. These shocks are visible when the sun is high overhead and the change in density refracts the incident light.
I was first informed about this visible phenomena in my introduction to aerodynamics course at Cornell University, taught by William Sears, who incidentally was the Chief Aerodynamicist at Northrop during the heady days of the XB-35 and the XB-49 flying wings. Great guy, Great teacher.
Vortices are another set of visible flow phenomena, but completely different.
awesome video, great to actually see a shockwave!
there are not much of these on youtube, fortunately I found this one :)
I've told people I saw a shock wave on an airliner and they didn't believe me. HA!
They are haters
they probably thought something much larger in scale when you used the word shockwave.
maybe the way u said it, wasn't shocking enough
Wtf is this o cant see shit
i actually see two. the one in the middle, and one ahead of it. the one in front can be seen out on that black tape about 10 feet from the wingtip.
Nice! Flying at about the speed of pistol bullet makes fun things happen lol...
I don't think we get too many of them formed by our little piston-driven island-hoppers 🤣
Hmm...
Is that propeller plane? The helix thing... (sry, not English, not sure how you call them exactly).
If so, I'd suggest stroboscope.
Or more research, since it's probably very well documented SOMEWHERE ;-)
@@huyxiun2085 I didn’t suggest that it _was_ a piston-driven aircraft, lol
My point stands, 😉
@@huyxiun2085 …Oh, and the ‘helix thing’ is known as wingtip vortices, lol
@@huyxiun2085
*Piston, turboprop, whatever, lol 🍻
Where should i look and what should i look out for ?
Very cool! Never thought to look for this on a plane - I’ll keep it in mind on my next flight.
Would a passenger jet like this begin to function normally again if it was mach 1.1 or more so the shock wave isn't occurring over the ailerons/elevators
I. Would. Totally stare at that the entire flight. So cool
Amazing! Thank you for letting us see the unseen.
Good video! Thanks for posting it.
I'm still studying this but I think the shockwave forms, because the air that gets accelerated over the wing reaches the speed of sound. This type of shockwave does is not dangerous for the plane, it just creates a little bit more drag.
It creates a lot more drag. When that shock wave first forms it is called the critical mach number (and the shock is very weak and probably not visible in normal conditions). A very small increase in speed past that point is called the drag divergence mach, because the drag then climbs like the plane hits a wall (actually called the transonic drag wall). That phenomenon is what dictates the top speed of commercial aircraft.
There is also a phenomenon called shock buffeting, when the normal shock wave is moving back and forth across the wing surface. That causes strong vibrations and aeroelastic stresses and has to be taken into account when designing the plane, otherwise it is dangerous, and is also another limiting factor in commercial planes' top speed.
Creates a lot more drag. Look into critical mach number and drag divergence
Increased Drag is one part.
Behind the Shock wave, Pressure , density & temperature will be higher resulting in reduced Lift fore besides higher Drag . In other words,
Flow on the upper surface of the Wing should not encounter Shock wave to get maximum Lift. This is also sometime referred as Stall.
Well, after 2 years and a couple fluid dynamics courses later, I have to say you are right. Although the stall is the result of the boundrylayer seperation due to the shock, if I remember that stuff correctly :D
@@SydamorHD Clarification,
Boundary layer Separation occurs both during High speed as well as Low speed of the Aircraft.
When Aircraft is cruising at Tran-Sonic/Sonic Speed, Shock wave occurs on top surface of the wing resulting in higher Pr, density, temp behind the Shock wave which in turn causes Boundary layer separation.
Boundary layer separation also occurs on Aircraft wing at very low speed when Angle of Attack is very high. It can be seen during Aircraft take off and Landing, the Wing position with respect Relative Air flow will be very high.
Stall literal meaning is STOP. In other words, Stopping of Lift Force.
Without Boundary layer separation, Reduction in Lift Force will not happen or STALL will not happen.
Different Text books write the same definition differently
Last time I looked out the window, I saw a grotesque fur laden creature fly out of the clouds and land on the wing.. I pulled up one of the panels.. .. I saw a sky Marshall's gun and took it from him and shot the creature, saving all the lives on board the plane.. Thank you.
Nice catch! I've spotted this myself.
that is far more visible than I thought it was going to be
That is so cool!
It's a subsonic flight but the air pressure travelling over the wings is either transonic or supersonic.
That’s just the sun reflecting on the wing
If im not wrong the maximum Mach speed of the 737NG is 0.82
Very nice and instructive video!
Yes, the aircraft is travelling slower but the air that travels above the wings and some other parts of the airplane are much faster, almost hitting Mach no. This is perfectly normal
If that's true, the plane must be traveling under 13 to 14 kilometers of height. Above 14 kilometers, the planes speed would get dangerously near Mach 1(since the speed of sound at an altitude of around 14,81 kilometers is the same as the aircrafts maximum speed).
@@mandernachluca3774 below 40000 feet
that works out to 629 mph if im not mistaken
Dang!! I blinked and missed it!! 😂
It's shock wave or its flow of wind ......Which show some loop at surface on edge
Wht you guys looking? ?
Yeah I've seen this specifically on the 737 before they operate that equipment on the margins
I never had a window clean enough to observe that...
Where am I supposed to be looking at?
Amazing!
Need some help here, I saw the title and thought it’d be cool to check out but I’m not sure what I’m supposed to be looking at?? I see a wing and that’s it.
It's subtle. Look for the shadow of the shock wave about halfway between the leading and trailing edges. It shifts forward and backward a bit. Once you see this, look higher along the leading edge of the winglet... there is a small optical distortion there that moves around a bit as well. We're looking through the shock wave edge-on, and the sudden change in air density causes the optical distortion.
Russell Croman nice! I see it
There is part of the airflow on the wing going supersonic and causing optical disturbances, see that in the middle of the wing? That's not a scratch on the window, it's a Shockwave.
The schlieren effect!
It is a rather subtle linear shadow that dances fore and aft . The line runs out the wing. It is easier to see if you zoom the video in a bit. It is a shadow resulting from the cataclysmic change ib density of the air refracting the light falling on the wing. It is enhanced by increasing the contrast of the picture/video. I have taken my own photographs of this and have shared them for years.
This shockwave causing a drag?
some airbus planes actually have a warning for this, like the a330
Been watching cgi animations, but here is the math in the flesh . . . in the obvious line dancing on cord. SCIENCE!!!!!!🤓
Cant see it. Its air.
Am i the only one who see nothing ?
I See Line Shock waves moving Tiny there😑😑
Very fuel consuming at the air speed.
Didn't see anything....
Is it a normal shock wave?
Yes, it is! The oblique shock wave only forms if the airfoil has sharp angle ramp.
No its definitely oblique. The surface would have to be perflectly flat for a normal shock and there is curvature on the upper surface of the wing
@@stillnotspicy Nope its a normal shockwave. The air is accelerated until reaching Mach 1 and decelerated again below, which is the definition of a normal shockwave. Oblique Shockwave fomrs when the air behin the shockwave is still above Mach 1 and creating a cone.
44 seconds completed wasted watching that
?????
Wow a wobbly line haha 😂
so the air going over the wing is at transonic speed not at Mach 1?
Sort of: “transonic” means there is a range of speeds of airflow, both below, at, and above the speed of sound. en.m.wikipedia.org/wiki/Transonic
Derek Wall part of the air going over and after the wing's leading edge is supersonic.
Mach 1 is part of transonic, transonic ranges from mach 0.8 to 1.2. So the air above the wing's leading edge isn't supersonic, it is still transonic.
the 1k liker
Probably vapor or slipstream, a jumbo jet isn't slim nor powerful enough to hit mach 1
The title is a bit misleading. Let me explain...
When an airfoil (wing) moves through the air, the air moving over the top of the wing is travelling faster than the air below the wing. (This is often used as the explanation of how a wing generates lift, however the actual explanation is much more complex and the fact that the air over the top is moving faster is just part of the whole picture.)
Anyway, since the air on top is moving faster, that means that it will reach the speed of sound, mach 1, before the plane itself. The mach number of the plane at this point is referred to as the "Critical mach Number". Exceeding this speed can cause some serious problems related to controlling the plane, and it can also damage the structure of the aircraft. The critical mach number is then essentially the speed limit of that particular aircraft. Depending on temperature, the actual airspeed in mph may be more or less, but the mach number is a design limit and doesn't change unless the shape of the airfoil changes.
If you look at an airfoil for a 737 jet vs a Cessna 172, you'll notice that the airfoil on the 737 has a cusp at the trailing edge while the 172's airfoil is relatively straight. This cusp on the 737's airfoil increases the critical mach number, allowing the aircraft to fly at higher speeds without the risk of damage or loss of control.
What you're seeing in the video is the shockwave forming over the top of the wing due to the plane reaching its critical mach number. Next time you're on a flight and you have a good view of the wing, take a look out of the window when you reach cruising altitude and you may see this shockwave yourself! The reason you see it is because at mach 1, disturbances in the air can no longer propagate forward faster than the plane, so they get bunched up together and the air becomes compressed. Compressing a fluid changes its density, which affects the refraction index of light passing through. Heat also does this, which is why you can see wavy patterns in the air rising above a hot object.
*Correction: The 737 doesn't have a supercritical airfoil. The Airbus A380 is a good example of a plane that does have one.
Watched this three times..... still don't see anything. 👎
It's pretty subtle, but definitely there. You want to look for this hairline kind of bouncing forward and back. Also, you can see a little "mirage effect" along the black line painted into the wing. Both of these are the transonic shockwave.
What planet do you live on mate? That’s a Subsonic Wing of a B737. They cruise at around .74-.78. Mach. There’s absolutely no way is there going to be any form of shockwave at those slow speeds!! You need to be up around .99 for that to start!!!
Before you start attacking people, check if you are actually correct because I can tell you, that you are wrong in this case. You have become a victim of the Dunning-Kruger effect, so please be humble because it is embarrassing to throw around falsehoods. First of all, I would recommend you to search up "transsonic flight". There is I believe even a neat wikipedia page which explains what it is.
So basically, we have an airliner cruising at around M 0.8, some a bit faster, some a bit slower. They cruise within the transsonic flight regime. What does transsonic mean? A wing has a high-pressure zone underneath and a low-pressure zone above. Airflow is not static, it is highly variable around aerodynamic surfaces. As air gets into the low-pressure zone, it accelerates to supersonic speeds causing the boundary layer above the wing to break off creating turbulent air and making the wing buffer due to those turbulences. This is the reason why airliners of today have supercritical wings and swept wings. It is because they want to increase the speed at which this phenomena happens (called critical Mach number) and decrease drag from flying inside that transsonic flight regime. Having a chaotic boundary layer going into supersonic speeds and creating turbulence is very draggy. Those wings are a tradeoff because such a wing also needs a good Lift-to-Drag ratio.
The Convair 990 was a plane built to fly especially fast inside that transsonic regime. They had such a problem witv supersonic airflow that they had to install huge pods on their wings to keep the airflow attached and reduce drag.
May be that you have heard of WW2 planes getting out of control when picking up speed and diving down. That was because they had straight wings and upon approaching transsonic flight, the wing couldn't handle supersonic airflow at all which caused high-speed stalls and planes tumbling out of control.
It's quite shocking.