The bizarre ripples that form in a stream of water

I noticed that when I obstruct a laminar flow of water I get these ripples forming upstream like a standing wave. Here's my attempt to capture them on film and to explain them. It might have something to do with Rayleigh-Plateau instability.

[PracticalEngineeringChannel]

You can try it with larger flow areas where surface tension effects will be less prominent to confirm whether it is related to surface tension. Cool video!

[PracticalEngineeringChannel]

I’ve been thinking about this more and it really has me interested. Water falling from the faucet should be supercritical flow meaning the flow velocity is faster than the wave celerity. So there should be no way to affect the flow upstream with an obstruction. Maybe surface tension travels faster than waves? This is beyond my knowledge of fluids, but a really cool phenomenon.

[labibbidabibbadum]

"Steve - did you finish the washing up?"
"Ahhh, ... well, here's an interesting thing..."

[HebaruSan]

3:30 - "No, I'm not pissing on the wall"

[troseberry]

Hi Steve. You should try this with something that has been coated with a hydrophobic substance. It would be interesting to see if the loss of adhesion to the obstruction would change the effect.

[philoposos]

I remember wondering about this when I was a child. Then I grew up and got dull. Thanks the internet we can enjoy people like him who still kept in touch with his inner curiosity.

[SpencerTwiddy]

Steve it's really refreshing to see how you can find such cool phenomena in ordinary things! Your videos always show the power of science to describe our world, keep up the good work

[XavierXonora]

So often I come on this channel and the video is something I've wondered about since I was a kid, and it sort of validated that I wasn't asking stupid or pointless questions but that my parents were just too worn down to deal with them all

[HunterJE]

I remember being fascinated about this as a kid and playing around with it enough to get yelled at for wasting water

[KijasFX]

Steve holding bottle on wall and eating Pringle are soooo stupid and silly moments BUT it’s what makes your channel unique. Great videos!

[DarkVortex]

I think you're right. These standing waves also explain why the wavelength seems to shorten downstream. The water downstream has been accelerating under gravity for longer so is moving faster, and conservation of mass means the stream has to get thinner (you can see that in the video). This also means that there is less mass per unit length in the stream, and just like with a guitar string, less mass per unit length (a thinner sting/stream) means a higher pitch note with a shorter wavelength. So the natural wavelength of the standing wave smoothly decreases from top to bottom as the width of the stream smoothly decreases.

[Arquimedes_Aram]

I loved how you provoke reactions with your scene 3:20 that plays with the suggestion evoking a life familiar scene, like when we piss the wall when we were kids.... and then right next silently you gives us that look of " Is not what you are thinking" Ha ha ha ha ha is so magnificently well executed!

[pedroscoponi]

You might say that this specific field of study is... untapped.
I'll see myself out.

[TheLoneStreamer]

Dude! I noticed this when I was like 5 and I’ve been wondering why this happens ever since! I’m 23 so a long time lol

[Muzkaw]

If you look carefully, the bubbles arr not aligned. Maybe the effect has more to do with viscous fluid coiling (like honey coiling) since water has some viscosity

[vesvj]

I smoked for about 15 years, but happily quit smoking about 12 years ago. Your candle smoke reminded me of something I saw quite a lot when I still smoked. The column of smoke from a cigarette would sometimes create what appeared similar to laminar flow... sometimes there would appear a kind of ripple in the smoke column and interrupting it would cause the wavelength of the ripples to change. I still don't know why, but think this video might be part of that answer.

[SittunSwayamPrakash]

Your videos deserve way more views, my friend. Incredible how you pull up such new stuff from regular daily life. Love your work <3

[anwarulbashirshuaib]

Steve's videos are the explanations of the things that I found out in my everyday life. I used to turn on the tap very slowly in my bathroom, adjust the flow rate until I got the perfect ripple, and then stare at it. Often this would keep me staying inside the bathroom for an hour or two, my mother would knock on the door at a regular interval of 5 minutes. Often she screamed, "It has been so long, what the hell are you doing? GET OUT NOW!" 😂😂

[bohdanpyzh]

"Bizarre ripples"? Well now Steve had mastered the power of Hamon

[F_L_U_X]

It's surface tension. When you block the flow, it backs up the stream and it buckles. When the droplet separates from the stream, it snaps the end of the stream closed and the stream acts like a rubberband that sends energy upwards which has the effect of a momentary blockage.