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  • [music]

  • Hey it's me Destin welcome back to Smarter Every Day.

  • So some of my favorite things to learn are those things that I've seen for several years

  • and I've made a lot of observations and I kind of think I get it, you know.

  • I mean, like really get it. And then I find out, I don't.

  • So when I first saw what I'm about to show you, it blew my mind because it was

  • so simple I should have seen it my entire life but I didn't. Look at this bird.

  • The muscle that flaps the wing is here toward the center, and he pushes down on the wing.

  • But the feathers going out towards the edge of the wing are overlapping in such a way

  • that they all push together on the down-stroke, but on the back stroke they

  • delaminate, allowing them to open up like louvers and allowing the wind

  • to pass through them. This means there's a lot less resistance on the back stroke.

  • Basically this bird wing is a biomechanical check valve. That's amazing.

  • I've never thought about that, but I saw it in the high speed video in Peru on the macaws

  • for the first time. This is why I've never seen it.

  • Look how fast it happens.

  • There's no way I could have observed that.

  • But watch the macaws on high speed and you can see for yourself, clearly the feathers are delaminating

  • on the back stroke. On the down stroke you can see that all the feathers

  • overlap in such a way that they provide a firm boundary layer that air can't pass,

  • but on the up stroke look what happens. You can see that the wing separates and the feathers turn

  • so that the air is flowing straight in between them. You can even see

  • straight through the wing. I think that's amazing, so he has a lot less resistance on the back stroke

  • than he does the down stroke. Another thing he does to decrease this resistance on the

  • back stroke is he's performing more of an elliptical sweep with his wings instead of

  • just an up and down flap. So what he's doing is, on the back stroke he's pulling that

  • wing in, and he's decreasing the length so he decreases the surface area

  • of the total wing. That's pretty awesome as well. So one of the coolest misconceptions I had

  • is pretty clear to see on this red macaw. I used to think that birds just flap down

  • and they create high pressure underneath them and they push themselves up. But if you look

  • at this macaw something else is happening. Look at the back of his wing here.

  • You can see that the feathers are being lifted up on the down stroke. What that means is we have

  • a low pressure situation there. It's like in engineering when we use something called

  • computational fluid dynamics. Basically what we do is we analyze the flow field and we figure out

  • what pressure situations we have at each location. Now you know

  • that on an airplane wing we have a low pressure situation on top. That's exactly what's happening

  • with this red macaw. So look at his wing and you can see that not only does he have a high pressure

  • situation on the bottom, but the low pressure is so great that it's pulling those feathers

  • off of his wing. That's amazing. So not only is he pushing down but he's

  • being pulled up on the same stroke. That's pretty awesome.

  • Now this green parrot's doing the last thing that I thought was pretty wild. If you notice he is angling the tips

  • of his wings on the back stroke and pushing back behind him, so he's providing

  • thrust, but one thing that's happening that I don't really understand but it looks like it could be

  • true, he's breaking his wing in half between the secondary and primary feathers,

  • and he's angling it and it looks like he's diverting that flow down,

  • almost like a vertical take off Harrier jet. It's pretty cool, and I think it could be

  • happening, but I've never actually thought about a bird being able to provide downward thrust

  • on a backward stroke. That's pretty wild. So I thought I knew

  • how flapping flight works but clearly I didn't. Send this to any of your buddies that like to think critically

  • cause they'll do what I do now. Every time I see a bird against the sky I watch his wing

  • and on the down stroke right at that point where he's pausing to transition back to an up stroke

  • if you watch you can see sunlight pop in between the feathers because he's

  • opened it up for lower air resistance on the back stroke, and I think that's awesome

  • because now I know how bird flight works. Anyway I'm Destin, you're getting

  • Smarter Every Day and I'll leave you with this picture that my daughter made by gluing homing pigeon feathers to a piece of paper

  • to create her own bird. You're getting Smarter Every Day. Have a good one.

  • We are in the middle of a cotton field in Alabama. If you've never seen it, it's a really pretty sight.

  • And what are we gonna do here son? - Let this bird go.

  • - We

  • - We're gonna let this bird go, but before we let the bird go, we're gonna talk about his feathers, aren't we.

  • [ Captions by Andrew Jackson ] Captioning in different languages welcome. Please contact Destin if you can help.


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B1 stroke wing bird pressure smarter resistance

How Bird Wings Work (Compared to Airplane Wings) - Smarter Every Day 62

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    Bing-Je posted on 2013/12/08
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