Practical Engineering Hey! It's you!

I think it is difficult to avoid turbulence while increasing the stream diameter.

+

My thoughts exactly. (Actually, I assumed it was gremlins or possibly aliens (perhaps alien gremlins? hmm.). You should listen to the engineer.)

Practical Engineering Good call Grady. I'd be interested in seeing a side by side setup with gradually increasing cross-sectional areas, kind of like a pan flute. Edit: Also, some different viscosity liquids would be neat.

There are two different wave speeds to worry about. There's the speed of the surface waves, but also the much faster speed of the sound waves within the fluid. It's the sound waves that transfer most of the energy and momentum. (Like, consider the bow shock of a boat. Even when the boat's traveling faster than the surface waves, which they often do, you still get a bulge in front of the bow of the boat.) But yeah, I agree that it's probably not just a surface tension effect for this reason.

To me, it just looks like the water it stacking up on itself because it’s incompressible. The flow rate wants to stay the same and the water wants to stay together, so it ripples up to create a longer path.

Wouldn't it be just that the water is slowing at the point of intersection and the ripples are pushed back up the stream? Blow air through your lips and see if you feel the wind on your chin. You introduce and obstacle slowly. Do you start to feel wind on your chin?

To my knowledge, surface tension is the speed of sound. If you had a rod all the way up to the moon, and you move the bit near earth the tip near the moon would not move faster then the speed of light.

I'd imagine it's from the particles/atoms impacting stuff, causing them to bounce back (on an atomic level, on a large scale they just flow to the side) and when they bounce back it sends energy backwards as a wave. Having a constant and mass amount of atoms hitting it like this and reflecting their kinetic energy, probably is whats causing the wave. If you increase the rate of flow by pressurizing it instead of relying on gravity, and I'm right, the wavelength should get shorter. It'd make sense that when you move your finger towards the faucet the length of the visibly wavy area increases as that's getting closer to a source where the energy can get reflected back, ant at some specific length (which you'd calculate using gravity and the mass of water maybe and such) it becomes resonant and most visible/strong, or tuned to the frequency if resonant isn't the right word, like selecting the correct/optimal antenna length for a wavelength where the waves are reflected at the exact right point and none of them cancel each other out. Calculate the "antenna length" for molecules of that weight traveling at that speed (you'd have to know the length to get the speed), and see if it creates the most stable wave even at each octave. I'd consider that reason to call it the cause instead of surface tension (though surface tension is required to get a wave instead of spatter all over the place)

Hahahaha that face cracked me up xD

It was a definite "what am I doing with my life" face. I could relate.

I bet that is what sparked the idea.

JustKeith I dunno. Can't say I've ever managed laminar flow from my pee-pee. Not that I've really tried though.

Every guy watching this knew what he meant though!

How do you only have 7 likes??

still

Don't let Veritasium see this...

I love you videos, sir! thank you for your consistent effort!!

Turbulent! Turbulent! Team Turbulent!

Not all the time, only when your stream is stable and steady or else you're going to give yourself a golden sprinkle.

that part was amazingly funny.. as he wanted to make sure nobody has any strange ideas about where that liquid comes from! :)))

urinals are usually where I make my deposits, their walls and those of bowls have a curve, I utilise that to avoid splashback: pee along the curve

@@frankzaffuto3670 Same. Gotta utilize that curve to avoid splash back. So important. 👍

@@swoop_cheetah Love the kinda scientific discussions that go on in these comments.

Or he could just use different shapes to vary the anti-node. That would hopefully set him on a path to building a relationship between boundary conditions and wave propagation. You could build a law that way.

^ this

He should also try to distillate it with exo-ionic sub atomic particles, to increase the kessleration.

L'effetto coanda si verifica con qualsiasi fluido , anche con l'aria

Reminds me of Feynman. He famously made one of his largest discoveries trying to figure out (if my memory doesnt fail me) why a medalion on a wobbling tray is wobbling with a different frequency than the tray itself.

Oh I hadn't heard of that, really cool. It just shows how looking at the world with a different, curious perspective can help us answer big questions we didn't even know we needed to be asking.

So I'm curious did your parents say this was fascinating which launched you into a physics career or did they just tell you to stop playing with the water which crushed all your scientific curiosity and now you are trying to find yourself? 🙂 Noticing this at the age of 5 is impressive!

I spent ages as a kid at the bathroom sink experimenting with this !!! 😂

Me too! I'm 54 years if age and have been wondering about this since I was a child. Thank you Steve for shedding light on this and helping me understand. Washing up has become interesting, (for a while)!

But what about the vertical offset difference visible on the video that happens between these two kinds of waves? The droplet creating wave has the pinch and bulge points perfectly aligned vertically, if you look at the "left and right side" of that stream. On the other hand, the waves that appear when you put an obstruction in the stream are, what seems like vertically offset, almost snaking, if that's even a word, or maybe even helixing. What I mean is, we didn't see the tridimensionality of the stream in the video, I don't quite understand why the water would make these snaking vertically offset waves given that it would cause more stress on the surface tension, so I think that the stream actually forms a helix. I hope someone understands what I'm trying to say.

I also considered the 3rd dimension aspect of it but it may not be screwy. I figure the target provides an obstruction transmitting a decelerating force up through the column of water and that probably needs a deflection in one polarity from the center and some unclear dynamic between flow and surface tension backpropagates the transversal wave in a single plane. But it's possible there is some spiraling, if the unknown dynamic allows such a standing wave configuration. One premise I like to adhere to is that if you can setup an honest simulation in a computer that produces the observed effect then you might well have explained it adequately. I suspect it would be very difficult to replicate this in a model. I'm guessing the speed of sound in both water and air are in play. While water play might seem frivolous, such a concept of a seemingly static standing wave through flow might turn out to be all important in some forward part of physics.

I think you're right about the wavelength. I also wonder if it's a helix. Might it be related to this effect in high viscosity fluids? kzfaq.info/get/bejne/sOBln6qcqcrPZ2w.html

Completely left field, but this made me wonder what properties water falling at terminal velocity would have. Wonder if that would impact this experiment....also, can water travel at terminal velocity and maintain laminar flow?

Muzkaw That's what exactly what I was/am thinking! Would be interesting to see the effect with different fluids...

That was exactly what I thought of.

Philipp Reiger Oops, I messed up that sentence, please forgive me.

Agreed, that’s what it reminded me of.

Keksdieb I didn‘t correct you, it was really like that. 😂

Thank you!

I was looking for a comment about Hamon

HAMON OVERDRIVE

MOTA MOTA MOTA MOTA MOTA MOTA MOTA MOTA MOTA MOTA

Part 3 didn't have Hamon smh

@@mayabartolabac It has, it was when Joseph Joestar was fighting DIO. He used hamon + hermit purple so he can't get touched by DIO

Thinnestmeteor it will form from down to up, because information travels through materials at the speed of sound in that medium. So the upper part of the stream won't notice instantaneously that an object has been placed under the stream.

Maybe this is one for @theslowmoguys

Yes! Use soapy water and see whether you get the same effect!

I'd guess that it's a scalable effect, i.e. that higher or lower tension will require wider or narrower flow to work, but I'm not sure what way round that would be! I'd guess higher tension would be able to cope with greater flow (as it can do more pulling) so presumably lower tension could work for even finer streams. Viscosity should also play a role, I think. :)

andymcl92 my hypothesis is, that less surface tension should lead to less beading.

Dragon Curve Enthusiast I agree, but since surface area is proportional to radius squared and volume to radius cubed, I suspect the effect would be greater for narrower streams, so lowering surface tension and having a finer flow MAY lead to the same outcome.

What the hell is your profile pic

55Ramius The adhesion of the water to the to an object forces the cohesive properties of water to bend in the most efficient and stable way. Where stable conformations exist, you get standing waves. Liquids with less surface tension have less surface tension because of a decrease in cohesive properties. This means fewer stable conformations resulting in fewer standing waves, particularly when the distance between adhesive endpoints (the faucet and the bowl) decreases. Mix a few drops of dish soup into water and try it out.

Kaedenn My friend is a research fellow working in the field of mathematical modelling of the phenomena involving jets, collision of jets etc.

ya, well my friend has a vagina, but thats not helping any of us rite now is it? @@yashagrawal9309

Anything with viscous fluids is simulated using Navier Stokes. There are many simulation schemes that use it, but surface tension is an additional effect that needs to be added into the momentum equation (the second of the three). I really want to explore this on my free time, but right now I’m having to focus on my plasma research

Thanks!

Wow. You are super smart and stuff.

I also think so. And if you look closely the the "waves" are shifted from the left to the right side of the stream unlike with the droplets. In 3d it would form a spiral, just like if you pour honey for example (just a smaller spiral).

Thats just what i tough. Flow is obstructed with finger, water molecules hit the finger, slow down and need to go around longer way, but another molecules are already hitting them and slowing down again, but there are molecules above them that have greater speed so water is piling up? I also think that this bending is in fact a spiral shaped stream, because curvature on the left doesn't cover curvature on the right side of stream or thats just the point of view.

I just checked with my own tap, and it's definitely a spiral. I don't know what that means for the different theories of why the water bends, but it did bother me that the shape with an obstruction didn't exactly match the shape that causes the breaking into droplets. If this does have something to do with Rayleigh-Plateau instability, then something has to explain the spiral shape. It's still a standing wave, just with one component that's out of phase with the other. And, notably, a spiral should be unable to cause drops of water to break off. The "piling up" hypothesis seems to fit what I'm seeing. All the outermost water is pushed outward, but its hydrogen bonds pull it back inward at the same time. Along with some small random motion to the side, this could cause orbits to form, closely followed by the orbiting water tending to favor whichever orbit happens to be densest, again because of the hydrogen bonds. A lot like the formation of planets from orbiting dust clouds. And since the water is falling while orbiting, it traces out a spiral. I wonder if a high-speed camera would show anything useful. If the water does pile up and start orbiting, I'd expect to see the spiral grow upward over time.

Using high fps camera would be nice. I wonder how long can be the stream to actually form the spiral from obstruction point to source and how fast its growing upwards. Would it be the speed at which the water falls down, faster/slower. Maybe the "frequency" of the ripples as shown in this video depends on the speed of water hitting the obstruction point, the further it is - greater speed caused by gravitation - denser the spiral. I wonder also if the direction of the spiral is always the same, and if its the same as water that you let go through a sink hole.

Could you explain the change in wavelength of the ripples as the obstruction moves further from the source? My initial thought was that the coiling radius might have been related to the velocity of water (an obstruction further from the source blocks faster-moving water, and somehow this translates to tighter coiling). However, this paper (tel.archives-ouvertes.fr/tel-00156591/document, p.24) and my own brief experimentation seems to show the correlation isn't linear. The standing wave hypothesis could explain the change in wavelength, but you would expect the change to be sinusoidal, not linear. Perhaps a tap just doesn't show a large enough sample size?

I think the reason for the tighter coiling is that the column of water, and therefore the spiral around it, is thinner. Thinking again in terms of orbital mechanics, orbiting closer to the center causes the water to orbit faster, which means it doesn't fall as far before coiling all the way around. Also, since there's less water in a slice of a thinner water column, it's less resistant to changing its direction. Of course, faster-falling water would tend to lengthen the coils, but it looks like, at least at the heights we've tested, thinness wins out. I'm no expert on fluid dynamics or orbital mechanics, so I might be wrong about a lot of this. In particular, before looking at that paper, I hadn't thought of considering the water to be like a rope. In that case, the explanation is probably more complex than the orbiting model would suggest. And I'm not really sure how to test what I've proposed.

No no, I'm just saying *if* they worked, this would be how.

PC LOAD LETTER

Thanks for the story! Glad you got someghing from the video :)