Goose flying upside down is simply showing off, say experts(wgme.com)
wgme.com
Goose flying upside down is simply showing off, say experts
https://wgme.com/news/offbeat/goose-flying-upside-down-is-simply-showing-off-say-experts
120 comments
Your story reminds me of this video of a snowboarding crow: https://m.youtube.com/watch?v=3dWw9GLcOeA
Thanks; that sent me on yet another YouTube rabbit hole around crows and their zany behavior.
I've seen crows do that near a corner house with L-shaped roof. The wind was going from the backyard, hitting the sloped roof and blowing straight up in that corner and a lot of crows were jumping from the roof, hovering on the wind for a few minutes and returning to the roof when they couldn't keep in the stream.
Plenty of birds of prey do this before going in for the dive
A Goose flying upside down:
https://www.youtube.com/watch?v=7AeJ3aLm0UY
https://www.youtube.com/watch?v=7AeJ3aLm0UY
And more geese flying upside down one-upping or me tooing each other: https://www.youtube.com/watch?v=amhgFdyW1Q8
Okay, but the real question here: What'd he shoot it with?
(Old photographer joke: You're shooting by a lake on a cloudy day and you happen on someone drowning, and have to choose between dropping your gear to run to the rescue and getting a shot to sell the local paper. So - what f-stop do you use?)
(Old photographer joke: You're shooting by a lake on a cloudy day and you happen on someone drowning, and have to choose between dropping your gear to run to the rescue and getting a shot to sell the local paper. So - what f-stop do you use?)
f/8.
I'd be more concerned about shutter speed. If the drownee is flailing their arms, dragging the shutter slower might yield a more dramatic look with the motion blur. Too high of shutter speed so the action is frozen might look more like someone rehearsing their part in a synchronized routine.
Keeping the subject in focus is more important as a decent telephoto will get you an out of focus background. Unless you're just a dick and use a wide angle but wade out into the water to get a decent framing.
I'd be more concerned about shutter speed. If the drownee is flailing their arms, dragging the shutter slower might yield a more dramatic look with the motion blur. Too high of shutter speed so the action is frozen might look more like someone rehearsing their part in a synchronized routine.
Keeping the subject in focus is more important as a decent telephoto will get you an out of focus background. Unless you're just a dick and use a wide angle but wade out into the water to get a decent framing.
With f/8 on a cloudy day you might get problem getting sharp image of the arms or have to settle on grainy image, regardless of the lens.
I would use fastest aperture I can that is still sharp and just shot a bunch of frames very quickly in hopes I can get arms in just the right, dramatic position.
As to whether to shoot wide or tele, if you feel you have enough time try to get subject to fill the frame first, while he still looks lively, and then quickly change the lens to get some additional shots with the background.
I would use fastest aperture I can that is still sharp and just shot a bunch of frames very quickly in hopes I can get arms in just the right, dramatic position.
As to whether to shoot wide or tele, if you feel you have enough time try to get subject to fill the frame first, while he still looks lively, and then quickly change the lens to get some additional shots with the background.
You're both wrong. There won't be much motion at all because drowning people don't splash.
Actually, I am a skipper and because of that I had to go through quite thorough training of which large part is focused on saving people in Man Over Board situation.
I estimate full 1/3rd of entire training was devoted exclusively to getting a person back on the ship if they happened to fall into water while underway.
It is said "people do not splash" because if you are focused on looking for flailing hands and splashing water and shouts for help then your are missing most people that drown.
But it doesn't mean people don't shout and don't flail. They do. Just not most of the time.
I estimate full 1/3rd of entire training was devoted exclusively to getting a person back on the ship if they happened to fall into water while underway.
It is said "people do not splash" because if you are focused on looking for flailing hands and splashing water and shouts for help then your are missing most people that drown.
But it doesn't mean people don't shout and don't flail. They do. Just not most of the time.
>It is said "people do not splash" because if you are focused on looking for flailing hands and splashing water and shouts for help
conclusion: The drowning person is a project manager.
conclusion: The drowning person is a project manager.
I'm definitely not sacrificing my gear for a PM. They can send an email requesting a meeting about being saved, and then get upset that nobody accepted the meeting
Depends on which stage of drowning they are in. If they've just fallen in, they might still be flailing away. If they've been flailing for a minute already, then, yeah, thy might be tired. Plus, it's hard to shout when your lungs are full of water. I can't do it with a mouthful of water let alone lungs. My ventriloquist dummy on the other hand won't shut up while I'm drinking water.
"Directly behind them, not 10 feet away, their 9-year-old daughter was drowning…
How did this captain know—from 50 feet away—what the father couldn’t recognize from just 10? Drowning is not the violent, splashing call for help that most people expect. The captain was trained to recognize drowning by experts and years of experience. The father, on the other hand, had learned what drowning looks like by watching television."
2013 Slate article: https://slate.com/technology/2013/06/rescuing-drowning-child...
How did this captain know—from 50 feet away—what the father couldn’t recognize from just 10? Drowning is not the violent, splashing call for help that most people expect. The captain was trained to recognize drowning by experts and years of experience. The father, on the other hand, had learned what drowning looks like by watching television."
2013 Slate article: https://slate.com/technology/2013/06/rescuing-drowning-child...
someone in the process of drowning, as in exhaustion and/or panic causing ineffective motions that do not get the head far enough above water to take an adequate breath won't be able to splash or yell.
Someone who is not exhausted and not technically drowning yet but who will be if left for another 10,15,60 or whatever minutes does have the ability to yell and splash.
Someone who is not exhausted and not technically drowning yet but who will be if left for another 10,15,60 or whatever minutes does have the ability to yell and splash.
Isn't someone not yet drowning but will be if left for another 60 minutes just someone swimming in a pool?
dragging the shutter slow enough to get motion blur would also make up for any difference in light loss. would require some sort of stabilization though. if you don't have a tri/monopod, you can set it on the ground and use some rocks or sticks (you're near a lake) to prop up the lens. also, i'd suggest using a 1 second shutter release delay to not have any bounce from you pressing the buttons on such a slow shutter.
also, digital cameras could just compensate slower f-stop with higher ISO if necessary
also, digital cameras could just compensate slower f-stop with higher ISO if necessary
For film, I'd go with "cloudy 11" and lose a stop or two of shutter speed, but I haven't shot film in thirty years, so who knows if I'm full of it or not.
(And thank you all for bringing the back half of the joke in such inimitable style!)
(And thank you all for bringing the back half of the joke in such inimitable style!)
Only film I ever shot was disposable 35mm and the older 110mm. Nothing to be adjusted to get your Cloudy 11 or Sunny 16. The one I do use in dslr world is Rule of 500 for astro stuffs. I'd say now to just ensure shooting RAW so you can adjust the white balance in post. Camera defaults for cloudy are just too cool to me.
(I'm never one to shy away from answering obvious rhetorical questions in a joke)
(I'm never one to shy away from answering obvious rhetorical questions in a joke)
> also, digital cameras could just compensate slower f-stop with higher ISO if necessary
Actually you can do the same with film. You just push it in processing.
Whether film or digital it results in grainy image, that's why I actually mentioned it.
Pros don't bring grainy images of drowning people.
Actually you can do the same with film. You just push it in processing.
Whether film or digital it results in grainy image, that's why I actually mentioned it.
Pros don't bring grainy images of drowning people.
I don't know about all that. It's not like shooting in the dark at ISO 32000. It's a sunny day that you've stopped the aperture down a couple of stops. Which means you're probably already shooting at low ISO100. Cameras can easily push to ISO800 with no noise being introduced. Newer sensors can easily go higher than that. Hell, my BMD camera's base ISO is 1600.
So I'm just going to come out and say claiming that pushing the ISO and introducing noise during a daytime (albeit cloudy) shoot and pushing the ISO a few stops to counter stopping down is fake news and scaremongering.
So I'm just going to come out and say claiming that pushing the ISO and introducing noise during a daytime (albeit cloudy) shoot and pushing the ISO a few stops to counter stopping down is fake news and scaremongering.
Apparently people drowning don't actually flail their arms (never seen anyone drowning though).
There's videos of lifeguards: https://www.youtube.com/watch?v=L0KTqPloUiU&list=PLgqwWmjSsN...
Can be pretty hard to see, but no absolute about flailing
Can be pretty hard to see, but no absolute about flailing
Apparently, some people will take the fun out of anyone joking around on an internet forum
I learned from other responses that a drowning person won’t necessarily splash about. See the other comment about how a father couldn’t spot that his daughter 10 feet away from him was drowning - he’d been conditioned by television that a drowning person would splash.
And this is why I carry a GoPro around in my bag.
As always, do your refresher: http://spotthedrowningchild.com/
(On iPad I had to stop loading before page would show the random video, YMMV).
(On iPad I had to stop loading before page would show the random video, YMMV).
“f/8 and be there” is a common expression that describes these situations.
https://en.wikipedia.org/wiki/Ƒ/8_and_be_there
https://en.wikipedia.org/wiki/Ƒ/8_and_be_there
This was my dad. This very last weekend.
Though to be fair, he would not have been able to rescue the said individual.
Though to be fair, he would not have been able to rescue the said individual.
"Once young geese have mastered flying, they start to see what is possible and how far they can go, pulling in random JavaScript libraries and changing the testing framework for no reason."
>pulling in random JavaScript libraries and changing the testing framework for no reason."
Offenders will be hoisted up by the toes with yarn and beaten into unconsciousness with an organic carrot.
Signed: Quality Assurance
Offenders will be hoisted up by the toes with yarn and beaten into unconsciousness with an organic carrot.
Signed: Quality Assurance
Trying to find more photos of this phenomenon [1][2]
[1] https://www.nikoncafe.com/threads/wow-canada-goose-flying-up... [2] https://www.telegraph.co.uk/news/earth/wildlife/5353933/Goos...
[1] https://www.nikoncafe.com/threads/wow-canada-goose-flying-up... [2] https://www.telegraph.co.uk/news/earth/wildlife/5353933/Goos...
[deleted]
I saw this exact thing a couple of months ago not so far from Arhnem. (I thought it might be a crane, but it was moving very fast... so I could be mistaken.)
This bird was diving at about 30-45 degrees from fairly high, and it suddenly inverted, stayed inverted for a second or so, and then righted itself. It was moving very fast, and you could actually hear the sound (and the changes of sound) of the air as it was moving through it.
There were no other airborne birds of that size that I could see anywhere near it, so I initially thought it was dying or otherwise out of control. But then it descended below view, and I never heard a thump.
I searched for inverted bird flight immediately after and learned that there are a number of observed cases where birds may do that. One theory is that they sometimes do it because they enjoy it. Other theories of course involve chasing prey, observing things, showing off, etc. But I like the idea that a bird might just be having fun. I mean, if I could fly, I think I would screw around all the time just because I could. After all, children will just run around wildly just because they can run.
This bird was diving at about 30-45 degrees from fairly high, and it suddenly inverted, stayed inverted for a second or so, and then righted itself. It was moving very fast, and you could actually hear the sound (and the changes of sound) of the air as it was moving through it.
There were no other airborne birds of that size that I could see anywhere near it, so I initially thought it was dying or otherwise out of control. But then it descended below view, and I never heard a thump.
I searched for inverted bird flight immediately after and learned that there are a number of observed cases where birds may do that. One theory is that they sometimes do it because they enjoy it. Other theories of course involve chasing prey, observing things, showing off, etc. But I like the idea that a bird might just be having fun. I mean, if I could fly, I think I would screw around all the time just because I could. After all, children will just run around wildly just because they can run.
We often assume non-human animals are totally focused on the logical business of survival. But we aren't, and I don't see why they would be any different
Watch any number of animal documentaries. Animals (particularly mammals) of all kinds engage in play, whether children or adults. I find it odd that anybody questions the idea.
That's more evidence that playing is part of the logical business of survival than evidence that animals aren't spending their time in the logical business of survival.
If we dial into any number of our "higher level behaviors", you can often go all the way back to "survival". Play is an important part of skill acquisition, and the easiest way to incentivize it is to make it "fun". Naturally, having fun as an evolved trait will lead to behaviors that don't necessarily have an obvious survival benefit.
I'd be more surprised to see a mammal that doesn't at all engage in behaviors purely out of enjoyment.
I'd be more surprised to see a mammal that doesn't at all engage in behaviors purely out of enjoyment.
Corvids are totally playing. There's a video of a young crow which has discovered that it can stand on a small object and "snowboard" down a snow-covered roof. Fun! Gets to the bottom, picks the object up, flies to the top, goes again. That's almost exactly what a human child would do. And it's exactly as much "part of the logical business of survival" ie none.
> it's exactly as much "part of the logical business of survival" ie none.
This is just an assertion, and it's actively contradicted by huge piles of evidence. Why do you believe it?
This is just an assertion, and it's actively contradicted by huge piles of evidence. Why do you believe it?
What evidence is there?
My guess would be that it's a side-effect of evolution, in that play is helpful for the young and is driven by it being fun. Doesn't seem like adults playing is necessarily beneficial to survival, I'm curious what the evidence to the contrary would be.
My guess would be that it's a side-effect of evolution, in that play is helpful for the young and is driven by it being fun. Doesn't seem like adults playing is necessarily beneficial to survival, I'm curious what the evidence to the contrary would be.
One non-inconclusive piece is the massive number of productive, but opaquely so, behaviors that animals have. In this case, my guess would be that their "play" is closely intertwined with their intelligence, and that "play" is actually an evolutionary mechanic to explore potentially unoccupied niches in the environment. I.e. if "crow snowboarding" was somehow an exploitable niche, this crow might have just found it, and over generations, crows that are specialized to do just that would evolve.
This is a bad example, because I don't see a niche to exploit. As a more appropriate example, New Caledonian Crows use shaped pieces of twigs to dig bugs out of trees because their beaks are too short to reach. I could absolutely see that having evolved out of a young crow messing around with a twig. Older crows see what's happening and decide to try it themselves, and you end up with crows specialized to use twigs like that.
Imo, it's hard to find truly purposeless activities in the living kingdom. Millenia of natural selection have favored creatures that do purposeful things. The squirrels that liked to do nothing or romp around in the trees for no reason didn't spend their time stashing away nuts for winter, and they died. Humans largely being the exception, since our use of technology has created such a large ecological niche that we're not really at threat of being outcompeted or starving during the winter.
This is a bad example, because I don't see a niche to exploit. As a more appropriate example, New Caledonian Crows use shaped pieces of twigs to dig bugs out of trees because their beaks are too short to reach. I could absolutely see that having evolved out of a young crow messing around with a twig. Older crows see what's happening and decide to try it themselves, and you end up with crows specialized to use twigs like that.
Imo, it's hard to find truly purposeless activities in the living kingdom. Millenia of natural selection have favored creatures that do purposeful things. The squirrels that liked to do nothing or romp around in the trees for no reason didn't spend their time stashing away nuts for winter, and they died. Humans largely being the exception, since our use of technology has created such a large ecological niche that we're not really at threat of being outcompeted or starving during the winter.
Here's a fun example https://www.youtube.com/watch?v=EGaSHDmuAPg
There's an interesting comment in that video that says the bird thinks it's an egg and it's trying to break it open.
I don't know if that's true but I wanted to point it out to hopefully get some answers here.
I don't know if that's true but I wanted to point it out to hopefully get some answers here.
Initially sounds possible. Only question I'd have is...how adept is that kind of bird at slurping up splattered egg innards? That's a _lot_ of force it's using if it thinks it's an egg. If it's trying to eat it, wouldn't it either squish it in its beak or stab it a bit to just break the top?
This is one of my favorite ted talks, on animal behaviour: https://www.youtube.com/watch?v=GcJxRqTs5nk
The examples of animals doing things the way they do are both funny and entertaining.
The examples of animals doing things the way they do are both funny and entertaining.
say experts who are flightless and honestly a little jealous ;)
>> This aerial acrobatic resembles a falling leaf and may be used to avoid avian predators or a long, slow descent over an area where hunters for sport or food are present.
Reminds me of a description I heard from a DEA pilot of the combat landings they would pull in Colombia.
https://www.businessinsider.com/a-c-130-pilots-view-of-a-com...
Reminds me of a description I heard from a DEA pilot of the combat landings they would pull in Colombia.
https://www.businessinsider.com/a-c-130-pilots-view-of-a-com...
Haha, real /r/nottheonion vibes here :) Would love to see a video
I first saw this news on that exact sub. :)
Very interesting... website is pretty terrible though. Here's a link to a translated local source with the same info:
https://www-rtlnieuws-nl.translate.goog/editienl/artikel/524...
https://www-rtlnieuws-nl.translate.goog/editienl/artikel/524...
The original source is some strange indie news wire service I've never heard of before, "Zenger news."
"Because I was inverted."
https://www.youtube.com/watch?v=ump0N5yOpkM
https://www.youtube.com/watch?v=ump0N5yOpkM
I assumed this was the goose they were talking about.
A+
A+
Sigh. That was Maverick in the (we prefer the term) inverted dive. Goose was just along for the ride.
My memory is weird!
As I was reading this link, i suddenly thought of the movie 'Top Gun' - which I have'nt watched or discussed this decade!!
And then a few minutes later, it dawned on me!
There is this character called 'Goose'!
As I was reading this link, i suddenly thought of the movie 'Top Gun' - which I have'nt watched or discussed this decade!!
And then a few minutes later, it dawned on me!
There is this character called 'Goose'!
If only you'd read the comments thread before posting this...
Cue the conversation on how wing works.
One of my favourite pointless internet arguments! I usually just point to this link and walk away:
https://www.scientificamerican.com/article/no-one-can-explai...
Answer: because a surface of a certain geometry produces a force perpendicular to fluid flow as per the Navier-Stokes equations. But that's not a good explanation to give a room full 2nd graders, therefore your pet-explanation will have to make a compromise somewhere. You are all equally right and wrong at the same time. Unless you say "equal transit theory". Then you are just wrong.
https://www.scientificamerican.com/article/no-one-can-explai...
Answer: because a surface of a certain geometry produces a force perpendicular to fluid flow as per the Navier-Stokes equations. But that's not a good explanation to give a room full 2nd graders, therefore your pet-explanation will have to make a compromise somewhere. You are all equally right and wrong at the same time. Unless you say "equal transit theory". Then you are just wrong.
That sounds like the problem of explaining how magnetism works. Engineers and scientists understand very well how airfoils generate lift. It is not some kind of mystery like the article implies.
It is true that most of the popular simplified explanations are incorrect. Flat plate airfoils generate lift if they have positive angles of attack. Airplanes can fly upside down. At fractional mach numbers, pressure above and below the wings is essentially equal.
If you are not flying near the speed of light, Newton's laws apply. So, if you want simple explanation, the wing deflects air downwards and that pushes the airplane up. If you put your hand outside the car window at an angle, you will feel a force. Should be simple enough for 2nd graders.
It is true that most of the popular simplified explanations are incorrect. Flat plate airfoils generate lift if they have positive angles of attack. Airplanes can fly upside down. At fractional mach numbers, pressure above and below the wings is essentially equal.
If you are not flying near the speed of light, Newton's laws apply. So, if you want simple explanation, the wing deflects air downwards and that pushes the airplane up. If you put your hand outside the car window at an angle, you will feel a force. Should be simple enough for 2nd graders.
The article does specify that "nobody can explain how wings work", not that "nobody knows how wings work". It also tries to go into "but WHY do the Navier-Stokes equations work like this", which is just not how physics works.
But yeah, there is just not an explanation that is both simple and complete and journalists have a pretty rough time dealing with that.
But yeah, there is just not an explanation that is both simple and complete and journalists have a pretty rough time dealing with that.
The article doesn't imply it's a mystery, only that simple one-liner explanations are insufficient. The headline is reasonably clickbait-y.
The momentum theory of lift is simple, intuitive, but unfortunately incomplete (just as the differential pressure explanation). It's covered in the article.
> But taken by itself, the principle of action and reaction also fails to explain the lower pressure atop the wing, which exists in that region irrespective of whether the airfoil is cambered. It is only when an airplane lands and comes to a halt that the region of lower pressure atop the wing disappears, returns to ambient pressure, and becomes the same at both top and bottom. But as long as a plane is flying, that region of lower pressure is an inescapable element of aerodynamic lift, and it must be explained.
Also I want to address this:
> At fractional mach numbers, pressure above and below the wings is essentially equal.
Surely you mean density? Air pressure is certainly not the same above and below, as differential pressure integrated over the surface is equal to the lift force generated by the wing. So no, while the Newton's explanation is a great explanation for a second grade classroom, it is not complete.
The momentum theory of lift is simple, intuitive, but unfortunately incomplete (just as the differential pressure explanation). It's covered in the article.
> But taken by itself, the principle of action and reaction also fails to explain the lower pressure atop the wing, which exists in that region irrespective of whether the airfoil is cambered. It is only when an airplane lands and comes to a halt that the region of lower pressure atop the wing disappears, returns to ambient pressure, and becomes the same at both top and bottom. But as long as a plane is flying, that region of lower pressure is an inescapable element of aerodynamic lift, and it must be explained.
Also I want to address this:
> At fractional mach numbers, pressure above and below the wings is essentially equal.
Surely you mean density? Air pressure is certainly not the same above and below, as differential pressure integrated over the surface is equal to the lift force generated by the wing. So no, while the Newton's explanation is a great explanation for a second grade classroom, it is not complete.
> Surely you mean density?
The ideal gas law applies, at least nearly enough. So PV = nRT. By saying the density is equal between the top and bottom, you are also saying the pressure is equal. The air around the wing is having it's momentum changed, not it's pressure. At least, at sub mach speeds.
The ideal gas law applies, at least nearly enough. So PV = nRT. By saying the density is equal between the top and bottom, you are also saying the pressure is equal. The air around the wing is having it's momentum changed, not it's pressure. At least, at sub mach speeds.
You're confusing static, dynamic and total pressures. Static pressure is the pressure of a fluid on a body when the body is at rest relative to the fluid. Dynamic pressure is the velocity created pressure. Total pressure is the sum of the two, and is what is used in the ideal gas law. To compute lift force static pressure is what is integrated around the wing surface. Total pressure remains constant in the fluid flow for low Mach numbers. Static pressure can and absolutely does change significantly as it accelerates through a streamline such as in low-speed aerodynamics. I understand the semantics on the different kinds of pressure can be confusing. But you should know that when aerodynamics refers to "pressure" as it applies to lift generation, they are referring to static pressure.
I should also mention that this pressure absolutely does change a lot over the flow field, and is commonly used to experimentally and mathematically quantify lift. The following is an image of the pressure distribution of a NACA 2412 airfoil at low speeds.
https://www.chegg.com/homework-help/questions-and-answers/n-...
Just to explain the chart a little bit, in aerodynamics, pressure is usually simplified to a Pressure Coefficient (CP) value. A CP of 0 is when static pressure equals atmosphere. A CP value of 1 occurs at the stagnation point (where velocity is 0, therefore static pressure equals total pressure). Note how this type of chart has an inverted y-axis (a common convention so that the wing upper surface is at the top). Notice how the static pressure on the lower surface is roughly atmospheric, while the upper surface pressure suction peak is high. In this case roughly equal in magnitude to the dynamic pressure. This is a typical pressure distribution for most airfoils, with the suction peak increasing in magnitude as angle of attack increases.
This plot can be obtained mathematically using some sort of potential flow scheme (see: XFOIL for 2D airfoils), or experimentally using pressure taps on a wind tunnel model. The area between the upper and lower surface curves is directly proportional to lift. The larger the difference between upper and lower surfaces, the more lift.
I should also mention that this pressure absolutely does change a lot over the flow field, and is commonly used to experimentally and mathematically quantify lift. The following is an image of the pressure distribution of a NACA 2412 airfoil at low speeds.
https://www.chegg.com/homework-help/questions-and-answers/n-...
Just to explain the chart a little bit, in aerodynamics, pressure is usually simplified to a Pressure Coefficient (CP) value. A CP of 0 is when static pressure equals atmosphere. A CP value of 1 occurs at the stagnation point (where velocity is 0, therefore static pressure equals total pressure). Note how this type of chart has an inverted y-axis (a common convention so that the wing upper surface is at the top). Notice how the static pressure on the lower surface is roughly atmospheric, while the upper surface pressure suction peak is high. In this case roughly equal in magnitude to the dynamic pressure. This is a typical pressure distribution for most airfoils, with the suction peak increasing in magnitude as angle of attack increases.
This plot can be obtained mathematically using some sort of potential flow scheme (see: XFOIL for 2D airfoils), or experimentally using pressure taps on a wind tunnel model. The area between the upper and lower surface curves is directly proportional to lift. The larger the difference between upper and lower surfaces, the more lift.
Google Bernoulli's equation, when you change the momentum of the flow, the pressure will change drastically (the energy has to come from somewhere).
> But taken by itself, the principle of action and reaction also fails to explain the lower pressure atop the wing
What? The pressure is lower on top of the wing and higher below because the air is being pushed downwards by the wing. I will happily explain this to any second-grade classrooms you find yourself having trouble with.
What? The pressure is lower on top of the wing and higher below because the air is being pushed downwards by the wing. I will happily explain this to any second-grade classrooms you find yourself having trouble with.
And how is that air moving from the upper surface to the lower surface of the wing? is it magically permeating the wing surface? Keep in mind that the vast majority of the pressure differential comes from upper surface suction rather than a pressure increase on the lower surface. At shallow angles of attack there is often little or no increase in pressure on the lower surface; nevertheless lift is produced. Your simplification does not adequately explain this, as addressed in the section of the article subtitled: "Turning on the Reciprocity of Lift"
> Nevertheless, there are at this point only a few outstanding matters that require explanation. Lift, as you will recall, is the result of the pressure differences between the top and bottom parts of an airfoil. We already have an acceptable explanation for what happens at the bottom part of an airfoil: the oncoming air pushes on the wing both vertically (producing lift) and horizontally (producing drag). The upward push exists in the form of higher pressure below the wing, and this higher pressure is a result of simple Newtonian action and reaction.
> Things are quite different at the top of the wing, however. A region of lower pressure exists there that is also part of the aerodynamic lifting force. But if neither Bernoulli’s principle nor Newton’s third law explains it, what does? We know from streamlines that the air above the wing adheres closely to the downward curvature of the airfoil. But why must the parcels of air moving across the wing’s top surface follow its downward curvature? Why can’t they separate from it and fly straight back?
> Nevertheless, there are at this point only a few outstanding matters that require explanation. Lift, as you will recall, is the result of the pressure differences between the top and bottom parts of an airfoil. We already have an acceptable explanation for what happens at the bottom part of an airfoil: the oncoming air pushes on the wing both vertically (producing lift) and horizontally (producing drag). The upward push exists in the form of higher pressure below the wing, and this higher pressure is a result of simple Newtonian action and reaction.
> Things are quite different at the top of the wing, however. A region of lower pressure exists there that is also part of the aerodynamic lifting force. But if neither Bernoulli’s principle nor Newton’s third law explains it, what does? We know from streamlines that the air above the wing adheres closely to the downward curvature of the airfoil. But why must the parcels of air moving across the wing’s top surface follow its downward curvature? Why can’t they separate from it and fly straight back?
"how is that air moving from the upper surface to the lower surface of the wing?"
What? Of course it isn't moving from above the wing to below - just that it's being compressed below the wing, and decompressed above it.
"Why can’t they separate from it and fly straight back?"
Because... they are parcels of gas, full of molecules flying in all directions at high speeds, bouncing off one another and things nearby, and if that parcel of air flies straight back it will find itself above a bit of space that contains nothing at all, and the molecules which are going in that direction will find they are able to do so unopposed (until they hit the wing) - so some of them will do so.
As a result, the mass of the gas will spread out into a larger volume, the number of molecules colliding with the surface of the wing per unit of time will drop (as they are more diffuse), and the pressure will drop.
This doesn't seem very mysterious.
What? Of course it isn't moving from above the wing to below - just that it's being compressed below the wing, and decompressed above it.
"Why can’t they separate from it and fly straight back?"
Because... they are parcels of gas, full of molecules flying in all directions at high speeds, bouncing off one another and things nearby, and if that parcel of air flies straight back it will find itself above a bit of space that contains nothing at all, and the molecules which are going in that direction will find they are able to do so unopposed (until they hit the wing) - so some of them will do so.
As a result, the mass of the gas will spread out into a larger volume, the number of molecules colliding with the surface of the wing per unit of time will drop (as they are more diffuse), and the pressure will drop.
This doesn't seem very mysterious.
This doesn't explain why a higher pressure on the lower surface should necessarily equal a lower pressure on the upper. I posted that quote to focus on the person I was addressing who stated that "pressure is lower on top of the wing and higher below because the air is being pushed downwards by the wing". The above commenter was stating that somehow the higher pressure on the lower surface somehow causes the lower pressure above. The quotation I posted refutes that point. Static pressure in a flow is not a conserved value. It does not have to come from anywhere. This can be easily demonstrated with an airfoil shape with a relatively flat bottom such as the NACA airfoil series. Static pressure on these airfoils' lower surfaces tends to roughly equal atmospheric. Yet the upper surface still creates suction. In the majority of airfoils there is way more suction than there is pressure increase on the lower surface. Why? This is not adequately explained by the above commenter's statement.
Also just a minor point of pedantry: wings don't compress air. At least not in low Mach number flows. The static pressure changes as a result of the relationship between pressure and velocity. Compression is when the total pressure (static + dynamic pressures) changes. Total pressure in a low-mach number flow remains constant.
Also just a minor point of pedantry: wings don't compress air. At least not in low Mach number flows. The static pressure changes as a result of the relationship between pressure and velocity. Compression is when the total pressure (static + dynamic pressures) changes. Total pressure in a low-mach number flow remains constant.
Maybe there's a different word than 'compression' that means 'to cause an increase in pressure'. It seemed like the logical choice, but I'd love to know what other word is preferred.
Because I'm pretty sure wings cause an increase in air pressure.
I guess the idea of 'dynamic pressure' is 'pressure that is caused by colliding with air just because you're moving relative to it'. But surely in the moving reference frame of the wing, that looks, locally, quite a lot like compression...
Because I'm pretty sure wings cause an increase in air pressure.
I guess the idea of 'dynamic pressure' is 'pressure that is caused by colliding with air just because you're moving relative to it'. But surely in the moving reference frame of the wing, that looks, locally, quite a lot like compression...
I too would like another word, because I can tell you first hand that the confusion between total, static, and dynamic pressure is the source of many headaches amongst aerospace engineering students. It doesn't help that many textbooks often refer simply to "pressure" and expect the readers to intuit which they are referring to given the appropriate context.
A book will say:
"In low-speed aerodynamic flow, pressure is constant along a streamline"
and then one chapter later say
"Pressure changes with a change in velocity along a streamline"
The first references to total pressure while the second refers to static, but at first glance they seem contradictory.
However I would fully avoid the word "compression" since implies that we are squeezing more air into a fixed volume (a.k.a. an increase in density) which is NOT what is happening in a low-speed air flow. The definition of compression strictly applies to total pressure. Although most people don't learn this, since compression is often used in relation to stationary flows to begin with (such as in pressure vessels) where the dynamic pressure is 0, thus static pressure equals total pressure.
A book will say:
"In low-speed aerodynamic flow, pressure is constant along a streamline"
and then one chapter later say
"Pressure changes with a change in velocity along a streamline"
The first references to total pressure while the second refers to static, but at first glance they seem contradictory.
However I would fully avoid the word "compression" since implies that we are squeezing more air into a fixed volume (a.k.a. an increase in density) which is NOT what is happening in a low-speed air flow. The definition of compression strictly applies to total pressure. Although most people don't learn this, since compression is often used in relation to stationary flows to begin with (such as in pressure vessels) where the dynamic pressure is 0, thus static pressure equals total pressure.
> But why must the parcels of air moving across the wing’s top surface follow its downward curvature? Why can’t they separate from it and fly straight back?
I’m sure smarter people than I wrote the article, but the way I explain it to myself is that it’s a manifestation of the same basic force or effect where the lower pressure area needs to be filled somehow. Like how the wind blows, cyclones form, etc., except in this case giving the wing lift somehow ends up being part of the most efficient “fill the void” solution.
Like how just behind a driving truck there’s an abrupt region of lower pressure; however, the air obviously doesn’t just keep on going straight forever but rushes in (incidentally, giving a boost to whomever happens to be tailgating). The gradual shape of the wing changes the scale of the effect, so that it happens constantly with tiny air ‘parcels’, each filling in the minuscule lower pressure region. (And, probably not unrelated to the fact that it’s intuitively unnatural for air to flow that way, lifting the wing a little apparently turns out to help even out that void most efficiently.)
It’s interesting to ponder for sure.
I’m sure smarter people than I wrote the article, but the way I explain it to myself is that it’s a manifestation of the same basic force or effect where the lower pressure area needs to be filled somehow. Like how the wind blows, cyclones form, etc., except in this case giving the wing lift somehow ends up being part of the most efficient “fill the void” solution.
Like how just behind a driving truck there’s an abrupt region of lower pressure; however, the air obviously doesn’t just keep on going straight forever but rushes in (incidentally, giving a boost to whomever happens to be tailgating). The gradual shape of the wing changes the scale of the effect, so that it happens constantly with tiny air ‘parcels’, each filling in the minuscule lower pressure region. (And, probably not unrelated to the fact that it’s intuitively unnatural for air to flow that way, lifting the wing a little apparently turns out to help even out that void most efficiently.)
It’s interesting to ponder for sure.
> I’m sure smarter people than I wrote the article
I doubt it. This daft idea that wings are hard to explain is kept alive by pop science writers because it's a reliable source of money for old rope, that's all.
I doubt it. This daft idea that wings are hard to explain is kept alive by pop science writers because it's a reliable source of money for old rope, that's all.
The experts cited in the article are some of the most well-known researchers in the field of aerodynamics. John D. Anderson is the author of 7 reference textbooks, all of which are commonly used in the field. His research took him from the US Airforce Aerospace Research Laboratory to the becoming the Chief of the Hypersonics Group at the US Naval Naval Ordnance Laboratory. He was Chairman of the Department of Aerospace Engineering at the University of Maryland. He is a member of the National Academy of Engineering for aerospace engineering. His name is attached to enumerable scientific journals that I encourage you to search through if you think that an average Hacker News user knows more about aeronautics than him.
The pressures above and below the wing are absolutely not equal, even at idealized incompressible flow (zero Mach number).
Pressure distribution: https://www.researchgate.net/publication/262976779_Aerodynam...
Pressure contour plot: https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.ripubl...
Pressure distribution: https://www.researchgate.net/publication/262976779_Aerodynam...
Pressure contour plot: https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.ripubl...
> That sounds like the problem of explaining how magnetism works.
https://www.youtube.com/watch?v=36GT2zI8lVA
https://www.youtube.com/watch?v=36GT2zI8lVA
[deleted]
It seems similar to explaining monads. If you stick to the math and logic, it's quite clear and hard to confuse. But if you succumb to the common temptation to explain it in a more "intuitive" way, it seems you are doomed to tumble down the stairs in the dark.
That article seems to oddly assume that in the Newtonian explanation, deflection of air is implied to only happen below the airfoil rather than above. At least when I explain lift that way, I gesture air being sent downwards both along the top and bottom of the airfoil.
As to explaining why air above the airfoil has to go downwards it seems pretty obvious that the air gets sucked into the gap left by the airfoil, but more importantly the article left out the Kutta condition that air doesn't wrap around a sharp trailing edge. This is both an intuitive phenomenon and crucial to the estimation of lift.
As to explaining why air above the airfoil has to go downwards it seems pretty obvious that the air gets sucked into the gap left by the airfoil, but more importantly the article left out the Kutta condition that air doesn't wrap around a sharp trailing edge. This is both an intuitive phenomenon and crucial to the estimation of lift.
One of the reasons there is so much confusion on this is that there are at least two different valid ways to look at it, but any given person usually only knows one of them (or rather, a simplified version of a serious misunderstanding of one of them). Different people know a different one of them, and thus argument breaks out whenever the topic comes up.
NASA has a bunch of aerodynamics educational material on their old Glenn Research Center website. Here's a page on these two different ways to look at lift [1].
Very briefly, the gas flow has to simultaneously conserve mass, momentum, and energy.
One approach is to consider conservation of energy. When you work out the implications of that you get different flow velocity over different parts of the wing and different pressure due to those differences. When you integrate the pressure over the whole wing you find that you get lift.
The other approach is to consider conservation of momentum. Working out the implications of that, you get velocity differences in the flow. If you integrate those around the whole wing, you find that there is a net turning of the flow downward. Conservation of momentum requires that the wing gets momentum opposite of that and we have lift.
[1] https://www.grc.nasa.gov/www/k-12/airplane/bernnew.html
NASA has a bunch of aerodynamics educational material on their old Glenn Research Center website. Here's a page on these two different ways to look at lift [1].
Very briefly, the gas flow has to simultaneously conserve mass, momentum, and energy.
One approach is to consider conservation of energy. When you work out the implications of that you get different flow velocity over different parts of the wing and different pressure due to those differences. When you integrate the pressure over the whole wing you find that you get lift.
The other approach is to consider conservation of momentum. Working out the implications of that, you get velocity differences in the flow. If you integrate those around the whole wing, you find that there is a net turning of the flow downward. Conservation of momentum requires that the wing gets momentum opposite of that and we have lift.
[1] https://www.grc.nasa.gov/www/k-12/airplane/bernnew.html
I think it's a classic case of not understanding equality, hiding behind enough complexity that it's a bit more complicated than usual. Many people have a hard time not reading equalities as an implication... if there's a mass and an acceleration, then there's a force. But the equality says, it's the same. It isn't an if-then, it is that whereever there is a mass that is accelerating, that is force. The force doesn't "cause" the mass to accelerate and the mass accelerating doesn't "cause" the force; they're equal, they're the same thing, trying to wedge in between the two of them is a fatal error, and a very common one in physics education.
Both of those approaches are equal. Or, to put it another way, it isn't that the fast moving air and the slow moving air "causing" a pressure differential which then "causes" lift... it's one integrated process. They aren't separable. You can't have different levels of pressure without some effect on air velocity, you can't have forces in the air without some effect on pressure, etc. The whole argument is all "But what causes what?" and the only correct answer is that it's an equality, not an implication. It can only be properly understood as a single whole that can be looked at in several ways.
Both of those approaches are equal. Or, to put it another way, it isn't that the fast moving air and the slow moving air "causing" a pressure differential which then "causes" lift... it's one integrated process. They aren't separable. You can't have different levels of pressure without some effect on air velocity, you can't have forces in the air without some effect on pressure, etc. The whole argument is all "But what causes what?" and the only correct answer is that it's an equality, not an implication. It can only be properly understood as a single whole that can be looked at in several ways.
The point is that it's much easier to intuite which way the air gets deflected (and thus change in momentum) than where the air speeds up or slows down. In fact, the easiest way to know where the air speeds up and slows down is indirectly based on where the pressure will be higher and where it will be lower, since the latter is easier to intuit than the former.
>or rather, a simplified version of a serious misunderstanding of one of them
or both?
or both?
Does this all work for symmetric wing cross sections?
I usually just say “Bernoulli’s principle” with a hand-wave. It’s an ignorant dismissal accompanied by a practical demonstration. Works great at parties inside wind tunnels.
cooling the balls, so to speak
What is this kind of annoying cookie consent dialog? Takes over a minute to disable advertisment cookies, probably just to coerce users into accepting all cookies
This is why I really suggest using uBlock Origin, blocking all of the trackers, and then removing the cookie popups. That would have been blocked by the "EasyList Cookie" and "Fanboy's Annoyances" list(s), with the other default filters in place for trackers.
For the lazy (works for me with uBlock Origin & Chrome):
1. https://easylist.to/
2. Click "add it to your ad blocker" on the relevant list.
3. Click subscribe in the upper right corner
1. https://easylist.to/
2. Click "add it to your ad blocker" on the relevant list.
3. Click subscribe in the upper right corner
I didn't see any of them, page loaded instantly.
Browser is Samsung Internet on my mobile, which has a built in section for ad blocking. I've enabled Adblock for Samsung Internet and Adblock Plus, can't quite remember why I enabled both, but there's a few more too. (Sadly no Ublock Origin, which I run on my desktops).
I am actually quite happy with this, it's very impressive out of the box.
Browser is Samsung Internet on my mobile, which has a built in section for ad blocking. I've enabled Adblock for Samsung Internet and Adblock Plus, can't quite remember why I enabled both, but there's a few more too. (Sadly no Ublock Origin, which I run on my desktops).
I am actually quite happy with this, it's very impressive out of the box.
> This may take up to a few minutes to process.
It did for me. When it got to "applying settings", I scrolled down and started reading. Then, as I was half way through, it scrolled all the way up just to proudly announce that the Sisyphean task of NOT tracking me is done.
> You have successfully updated your Cookie settings.
It did for me. When it got to "applying settings", I scrolled down and started reading. Then, as I was half way through, it scrolled all the way up just to proudly announce that the Sisyphean task of NOT tracking me is done.
> You have successfully updated your Cookie settings.
I closed the page when it popped up. I didn't end up reading anything on the site.
At this point, seeing the TrustArc dialogue evokes a visceral urge to exit whatever page I'm on ASAP. I can't believe they're able to get away with this kind of behaviour.
I'd be quite happy if CA sued them. Or you could add up the 10-20 second time wasted and multiply it by several million californians to get a sense of how many person-years of attention they're stealing to try to trick people into waiving their privacy rights.
If you turn off JavaScript, you get this message:
> Please ensure Javascript is enabled for purposes ofwebsite accessibility
Still waiting on the punchline.
> Please ensure Javascript is enabled for purposes ofwebsite accessibility
Still waiting on the punchline.
This is hilarious. It was literally "loading" for a good few seconds and then "processing" the request for even longer. What in the world...
With the dark pattern they have there, doesn’t seem like “consent” at all anymore.
Just accept everything and either use Cookie Autodelete on desktop or manually delete all your cookies every night when you brush your teeth before bed.
Much more efficient use of time.
Much more efficient use of time.
Took 20s to just accept them.
That page has probably the worst cookie banner experience I've ever seen! 3 pop-ups later, 5 second delay between each, and the page jumping back to the top after each of them, I gave up and decided no article is worth this amount of suffering. I got to read the first paragraph tho, I guess that's something....
I also remember another time watching a sparrow land on a wire fence backwards in a fairly strong wind: it flew with the wind towards the fence, then turned around in mid-air a metre or two before it reached the fence, was blown the rest of the way and landed neatly.