Check this out
哈哈哈 是不是超棒 这就是流体力学悬浮
Hahaha, isn’t that awesome? That is hydrodynamic levitation
Check it out!
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
那看起来好像说不通啊 即使你把水流挡了一下 球还悬浮在空中 你看
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
Isn’t that cool?
How can it be stable like this? How can this be a stable configuration?
That is what we’re gonna explain
This is my friend Blake
He is a toy inventor, and he actually came up with this and he brought it to me
我就说 “太棒了 肯定有什么物理原理在里头”
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
That’s actually what we’re showing here
We’ve brought this stream down so it’s going at a very low velocity
这样就形成了层流 而且你可以看到 看着球
So it’s pretty much laminar flow, and what you can see, if you look at the ball, is it’s entirely
是不是已经完全被水附着啦 这样水流升起 顶起这个球
enclosed in water, so that water stream comes up, goes around the ball and
just as with the ping-pong ball
如果它移动到水流的一侧 就会慢慢从水柱顶端降下 那么根据伯努利原理
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.
这是我找到的最大的聚乙烯泡沫球 我并不认为还能悬浮 好啦 我们来试试看
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
Should I go higher?
Oh! It’s happening!
难以置信 它在上面悬浮 我的天呐
That is incredible! Look at it dance on there man!
就好像这种不稳定性被克服了 真不可思议你看水以漩涡状散开 真棒
It’s like got this instability, but it corrects. It’s incredible! You should see the way the water is spiraling off there.That is awesome!
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
它推着球向上 但水流也会将球往外推 使其偏离水流
It pushes it up, but it also pushes the ball out, away from the stream
所以我想 球仍然会待在空中 真的难以置信它处于一种稳定的结构中
so what I think is remarkable is that the ball actually will stay there. It is in a stable configuration and
从高速镜头来看 球之所以能保持在水上是因为球旋转时 把水抛向四周了
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
which keeps it right in that stream
It’s because there’s a bit of adhesion between the water here and the styrofoam. Starts to go a little slower
That pulls all that water over the ball
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
如果球移出的太远 增加了水流 也会增加将球推回的动力
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
但对光盘来说却很重要 如果你试图使光盘悬浮 就需要保持正确的方向
But it certainly is important for the disc. If you try to levitate a disc you need to keep it in the right orientation
噢 成功了 让光盘悬浮明显要比球更困难因为他们必须要保持方向垂直
Oh, yes! Getting the discs to levitate is significantly harder than the balls because they have to maintain their vertical orientation
才能实现悬浮 即使只有微风 也会使光盘悬浮变的困难
In order for this to work. Even a slight breeze makes this very difficult
嘿 快看 你能过来看看这是为什么吗
HEY! Check that out! Can you come in and get it?
Oh my goodness
This is a clear demonstration
其中不仅仅是伯努利定理 对吧 主要是因为光盘的旋转实际上承载了水向下喷射
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
Not only is this an awesome experiment
it’s also pretty fun to play around with in the summer, and it was invented by my friend Blake
So come over my channel Innovinci
我会告诉你如何 在一个简单的家庭仓库操作它 你可以在自家后院制一个
and I’ll show you how, with a simple Home Depot run, you can build this in your own backyard
视频下面有我的链接 如果你也想制作这个 点击即可查看
I’ll put a link to that video right here. So if you want to make this, go check it out