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  • [Engines screaming]

  • Hey it's me, Destin. We're at an airshow.

  • So today I'm going to teach you about vortex shedding.

  • [Music]

  • [Engines screaming]

  • (Man) YEAH!

  • (Destin) Fly... flying our airplanes.

  • [Engine roaring]

  • (Destin) I can't hear you. Why does the smoke come out of the airplane?

  • (Sadie) To help it go better.

  • - Makes perfect sense.

  • [Engine roaring]

  • [Propellers thumping]

  • So on a wing...

  • You know, in layman's terms, the Bernoulli principle -

  • where flow is high, pressure's low. Got it?

  • Where flow is high, pressure's low.

  • So the air has to travel farther over the top of the wing than on the bottom,

  • so it's flowing faster. So we have low pressure on top

  • and high pressure on the bottom.

  • So high pressure pushes the airplane up. That's why the airplane flies.

  • But something you didn't know:

  • if you're on the edge here... if you look at this,

  • we've got high pressure and low pressure

  • and they try to have a discontinuity here,

  • So what happens is that high pressure tries to run around the top of the aircraft,

  • and you get what's called a vortex, or vortex shedding.

  • And you can calculate the vorticity on that.

  • So let's go to the other axis.

  • Okay, so now we're looking at the tip of the wing.

  • So again, you have low pressure on top, high pressure on bottom.

  • So that high pressure runs around...

  • The flow runs around and tries to roll over so that they can meet,

  • because nature abhors a vacuum; it doesn't like discontinuity.

  • So what happens is, as it rolls you get a vortex in this direction here.

  • [Engine roars]

  • Okay, you can see on this wing what they've got on the end

  • is it's kicked up just a little bit.

  • So you've got the high pressure here flowing around,

  • and you've got the low pressure here, but it's also swept.

  • If you come around at this angle and look,

  • you can see that it's swept, and the whole idea is to control the vortices

  • as they shed off the end of the vehicle. So that's it.

  • You reduce drag by getting that off of the vehicle

  • and getting it out and away from you.

  • [Birds chirping]

  • Can you say hello? - Hewow.

  • It's me and my buddy, and we're on a kayak,

  • and we're overlooking a hot air balloon festival.

  • Okay, vortex shedding does not only happen with airplane wings,

  • it also happens with things like paddles.

  • If you have a low pressure and a high pressure side on the paddle,

  • You get the discontinuity right on the edge

  • [Destin laughs]

  • I'm really ruining my canoe trip with my buddies. [Laughs]

  • Anyway, you get vortex shedding and discontinuity on the side, so watch.

  • When you watch the paddle here, you'll see a vortex occur right on the edge.

  • You'll notice it happens where it's rolling from the high pressure side

  • to the low pressure side.

  • (Child) Could you see the flames? (Other child) Yeah!

  • (Destin) I'm going to show you an example of

  • what life is like without asking science questions of yourself all the time.

  • So, Jacob, my friend,

  • why do you say that there's a vortex on the edge of the wing on a fighter jet?

  • (Jacob) Because... - No, you gotta look a the camera!

  • - Oh! It's the camera.

  • Because Tom Cruise was cool in Top Gun when he was the Maverick.

  • That's before he went crazy and needed to go do the loops.

  • - It has been noted.

  • If you don't ask scientific questions of yourself

  • you'll go through life thinking Tom Cruise is cool.

  • [Destin laughs]

  • (Destin) What's this called? (Jacob) Vortex shedding.

  • - How did you know that? - Because I have smart friends.

  • - Whatever.

  • (Woman) We have a rocket scientist... (Jacob) I know a rocket scientist.

  • (Destin) A-10 Warthog. That's where it's at.

  • [Engine screaming]

  • Captioning in different languages welcome. Please contact Destin if you can help.

[Engines screaming]

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B1 INT high pressure pressure vortex destin shedding jacob

Vortex Shedding - Smarter Every Day 23

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    林宜悉   posted on 2020/03/26
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