Name: ハイドロダイナミックレヴィテーション! (Hydrodynamic Levitation!)
Uploaded: 2021-01-14T10:25:41.000Z
Duration: 6 min 9 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

Hahaha, isn't that awesome? That is hydrodynamic levitation

This styrofoam ball is levitating on this stream of water

And it's doing so in a very stable way. The set up it's so stable you can play Frisbee through it

Which is weird to me because the water is off to one side of the ball

And that doesn't seem to make any sense, cause you can block the water for a second and the ball will still levitate, have a look

How can it be stable like this? How can this be a stable configuration?

He is a toy inventor, and he actually came up with this and he brought it to me

And I was like "That is awesome, there's some really cool physics going on here."

Juggling with water. I can't believe it will

just allow you to switch balls like that. They can even hit each other as they go down

It doesn't take the other one off the stream. So how does this effect work?

Well a lot of people might think of the hairdryer ping-pong ball effect. Which works basically based on Bernoulli's principle

We've brought this stream down so it's going at a very low velocity

So it's pretty much laminar flow, and what you can see, if you look at the ball, is it's entirely

enclosed in water, so that water stream comes up, goes around the ball and

If it moves to one side of the stream it slows down the flow of fluid, and according to Bernoulli's principle

This increases the pressure relative to the faster flowing fluid on the other side

So it pushes the ball back into the middle. That is what provides the stability for this ball.

But I think what we're seeing with the bigger balls is something different.

This is the largest styrofoam ball I could find, so I don't expect it to work, but hey we're gonna give it a shot

That is incredible! Look at it dance on there man!

It's like got this instability, but it corrects. It's incredible! You should see the way the water is spiraling off there

So I've been thinking a lot about the physics that makes this possible

What I think is happening is as the stream contacts the ball

It pushes it up, but it also pushes the ball out, away from the stream

so what I think is remarkable is that the ball actually will stay there. It is in a stable configuration and

From looking at the high-speed footage what I really think is going on is this water is getting thrown over and down by the ball

and since the ball is putting a force over and down on the water that water is putting a force up and in on the ball

It's because there's a bit of adhesion between the water here and the styrofoam. Starts to go a little slower

And that's the start of how you get the ball to spin

And how you get that sprayed down on the right-hand side which provides more lift and keeps forcing the ball back into the stream

once the ball is levitating it remains stable because if it drifts too far into the stream that decreases the flow of water around the

Ball reducing the force pushing it into the stream

And if it drifts too far out that increases the water flow over the ball increasing the force pushing it back into the stream

That's what makes the equilibrium position so stable. Any slight perturbation creates a restoring force that moves the ball back to equilibrium

The rotation I think is also nice because that gives it that angular momentum

Providing a little bit of stability side by side, that's not so important for these balls

But it certainly is important for the disc. If you try to levitate a disc you need to keep it in the right orientation

Getting the discs to levitate is significantly harder than the balls because they have to maintain their vertical orientation

In order for this to work. Even a slight breeze makes this very difficult

HEY! Check that out! Can you come in and get it?

that that is not just about the Bernoulli effect, right? It's due to the rotation of the disc that actually carries the water

over and sprays it down which pushes that back into the stream. That's amazing

it's also pretty fun to play around with in the summer, and it was invented by my friend Blake

and I'll show you how, with a simple Home Depot run, you can build this in your own backyard

I'll put a link to that video right here. So if you want to make this, go check it out