How fast moving water “defies” gravity

A powerful jet of water pointing downwards can actually hold up an object against gravity! But how? I think I've worked it out. Let me know what you think of the explanation. Video also features: Hair dryer levitation and hand blender levitation. Are they related? Well it's all fluid dynamics, that's for sure!

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[waxpoetik_]

"Somewhere above absolute zero" is exactly how I want my weather forecasts from now on.

[agb]

Steve Mould, 4am, running naked though the streets of London.

[ethangrazier]

I love your approach to yhese subjects. I find most youtube channels take a basic topic, that all of already know by simply living on earth, and "explain" them as if it's this brand new discovery and that they have all the answers.
And altho science can be fun and interesting, most people aren't that thick.
Your intuitive way of teaching / sharing what you've learnt is exactly the type of content i wish to be invloved with. Thank you for the refreshing videos.

[distantfuture]

Someone shouted "Bernoulli Effect!" at a Shellac gig I was at. Was that you, Steve?

[jordandinodude]

I literally just sent a message to Veritasium last week about this effect asking him to make a video on it!! You beat him to it, but I'm so glad someone actually did a video on this!

[Tony-nlpf]

6:53 You see the water rushing upwards and into the sides of the glass. I'm sure friction alone would have a pretty strong upward force, pulling the cup upwards with the water. Obviously this isn't the only force but you mentioned intuition, that's what I saw for a split second without thinking about it.

[AakashKalaria]

With a blender, Water is creating an "air tight seal" which is not letting the flask fall down.


The blender is held by hand and the rotating blades are thrusting the water towards top hence pushing the blender down which keeps the blade below water most/all the time.


For the flask to fall, AIR from top of the flask needs to reach to the bottom of the flask otherwise it will form a vacuum. And to fill in the vacuum, the flask is being pushed up by the air surrounding it because of air tight seal by water... water is being pushed up by blades and blades are being pushed up by hand.


Water is acting like a giant suction cup.

[oldcowbb]

6:09 "it's just navier-stokes" me explain every fluid phenomenon from now on

[feha]

5:22 you forgot to draw an important force, the one that makes peoples intuition faulty: the force of the hairdryers jet pushing down in the center (before the air is diverted sideways). The pressure difference has to not only overcome gravity, but also that force.

The blender example reminds me of how drones and toy-helis are sucked up onto ceiling if you get too close. And I would argue it is caused (at least in part) by the same effect.
Though it also reminds me of the ground-effect, where drones/toy-helis need less torque to hover than fly, thanks to sitting on the pillow of air achieved by their propellers pushing air downwards. Makes me wonder, did you really try it with the mixers propeller spinning both directions? Or might it perchance not have angled blades? Nvm, saw a shot of the blades, they are mostly flat (even pulling water up from "floor" a bit, like how a drone pulls air down from ceiling), explains that.

7:00 So, you have yet to explain why this effect you are describing/showing only appears when it counteracts gravity (when the jet is pointed downwards), and why, if in the initial example you had held the plastic thing in place like you did when pointing downwards, it still flies off as opposed to sticking to the hose.

finished video. Why were the water example made to have a rim going up past hose, while the air example didn't? Technically you can argue the mixer example had a rim too. Is it needed for this to work with water? Or was it just cause it was easier to make the parts that way, and it potentially actually makes the effect worse/weaker?

[dillbourne]

me: *watches first 3 second* ok, i get it.
1 second later
me: WHAT?

[OceanPictures]

This is what happens on the top surface of an air-foil (like on a wing), you are creating lift through pressure differential. The velocity of the air/water coming from your hair dryer/hose creates a region of lower pressure on the top surface of your styrene/plastic cup than the ambient pressure found below the styrene/plastic cup so you get lift.

[knoodkuhl]

Maybe I'm to late, but I may found a solution for the handblender-effect. If you look at the behaviour of a handblender you will notice, that the blades are designed to suck liquid from underneath and (because of centrifugal force) push it out trough the slots on the outer diameter. Therefore the handblender is acting like a pump. In open space the fluid is circulating but if you get close to the bottom the gap is to tight to provide enough liquid to get trough. because of that pressure decreases and the "pump" sucks to the bottom. I hope this makes sence...

[jaspastritt]

That rolling shutter effect at 7:30 <3

[Jim]

I like shouting Bernoulli as well. Sounds like a Monty Python skit?

[fn]

I think the hair dryer experiment works thanks to the Bernoulli principle (less pressure between the polystyrene surfaces than the outside), while I think the blender and garden hose experiment work differently:
I believe that the water pushes on the inner walls of the container, creating a sort of "internal grip", as if we imagined taking a glass not from the outside but from the inside by spreading the fingers

[ramacoppolaro]

Relatable moments with Steve Mould 1:17

[olegil]

The hose popping off at the end of the demonstration there is classic. These are some really thought provoking problems.

[KaiseruSoze]

When you confine the outward velocity to a layer you get a uniform layer of molecules as opposed to the random motion outside of the confinement. You're basically "stealing" the inner pressure. I.e. if you take a 1mm volume of ordinary thermodynamic particles the average *velocity" is zero. When you think of it in polar coordinates ... your dual plane set up goes from a net 0 velocity to a net outward velocity ( no negative r ) when you turn on the hair dryer. And as a result the pressure outside has the up/down components and the inside does not.


BTW, if you like using JavaScript to do animations, you might take a look at WebGl or three.js. Three.js is easy. WebGl is comprehensive but hard.

[flexico]

Advances in science do not come with Eureka's, they come with, "Huh, that's weird..."

[SpencerPetersen]

I think that the hand blender at the end of the video is the perfect tool for making good hummus, which brings us full circle to the beginning of the video.