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.