Sixty Symbols - 2017-07-14
Additional video on how the experiment works at: https://youtu.be/mf_143gkKSQ More links and info below ↓ ↓ ↓ This video features Professor Mike Merrifield from the University of Nottingham. Stripey Clouds: https://youtu.be/rOdRbUQzajo Cloud video on Objectivity: https://youtu.be/C6Fws5kiOI0 A nice pic here: https://cloudappreciationsociety.org/the-kelvin-helmholtz-wave-cloud/ Pic in video courtesy of James Rowley-Hill: https://twitter.com/chunder10 To look at our slow motion videos in detail: https://youtu.be/8foMwq2yJPo Visit our website at http://www.sixtysymbols.com/ We're on Facebook at http://www.facebook.com/sixtysymbols And Twitter at http://twitter.com/sixtysymbols This project features scientists from The University of Nottingham http://bit.ly/NottsPhysics Patreon: https://www.patreon.com/sixtysymbols Sixty Symbols videos by Brady Haran http://www.bradyharanblog.com Animation in this video by Pete McPartlan Email list: http://eepurl.com/YdjL9
I'd suggest a video on lift generated by wings. Because everywhere i look i see contradictory arguments on how it works.
+featherdice "You could also do it by creating a vacuum above yourself and using air pressure to push you upwards."
You might want to think about it before building a prototype of your vacuum creation machine that is supposed to support a real-world aircraft. What are you going to hold up this vacuum-creation machine with? Is it vacuum creation machines all the way up? The Earth already has a partial vacuum creation machine, its gravity. The air pressure on the top surfaces of the plane is already going to be lower than the air pressure on the lower surfaces. But that is not sufficient to generate any significant lifting force since we are talking about denser-than-air aircraft.
The second part of your sentence is exactly what I said. You have to change the momentum of the air. That requires, by necessity, accelerating the air molecules downwards.
This is 17th century physics of the Newtonian 3rd Law of Motion variety.
+Mike Meyer Aircraft propellers do not cavitate. I was speaking of boat propellers. Wings on the keel do not generate enough of a pressure drop to cause cavitation.
+Markle2k and I was speaking of sailboats, not power boats. Since the keel and rudder don't undergo cavitation, it's not an analogue for airplane wings stalling on those craft.
Mike Meyer keels rarely cavitate, but centerboards and rudders on planing boats will happily do so if not very well designed.
+Mike Meyer And the conversation was of aircraft, not sailing vessels before you chimed in and complicated things with your tacking, keeled boats. Heal thyself.
Analogies do not have one-to-one correspondence, those are called "examples".
0:26 - "OK. Call them what you like"
lmao
3:30 the reactions are so typical for people in any lab set up, hahahah
I like how she looks over at him and he nods his head.
Excitement in the lab is always quite calm.
The guy on the right especially seems to be enjoying the experiment.
Makes me sad to hear you guys repeat the equal transit/bernoulli lift fallacy.
Make a video about airfoil lift!
Ironically, the animation even shows why airfoils generate lift: you can see the air being displaced downwards behind the wing...
3:31 "LOOK AT IT, JUST LOOK AT IT!"
-"I'M LOOKING AT IT!"
A good question to ask would be "Yes, but why does it appear to occur at such regular intervals?"
and what factors affect its periodicity
eqlipse333 you can prove this mathematically. There is an equation, called the Taylor-Goldstein-equation, which can have real or complex solutions. The imaginary part will lead to instability (google Richardson number). The real part is a wave, so just sines and cosines. This gives you periodicity. The instability causes the wave to break.
I was thinking the same thing. I don't think the Taylor-Goldstein equation answers it, the question is, why is the wavelength a specific size, not why is there a wave at all.
Last time i was this early the electro-weak force was still around
Wait, has there been a huge discovery I am not aware of ?
Yeah,the weak force and electromagnetism can be unified into the electroweak force.Discovery of this won a Nobel prize a few decades ago in 1979.
I am replying to Hector comment.What do you think he was saying then ?
lol "cloud people"
But why do they appear at regular intervals? Shouldn't the spacing be more random if it's growing from surface fluctuations?
That is a very difficult question to answer, and there are still papers being published on it. Basically, some wave modes are more unstable than others, and their stability (plus a few other experimental parameters), determines how fast they grow. You could think of all possible perturbation ripples happening at once, but only the very fastest growing waves reach the size you can see. Some waves also get an extra initial "kick" from surface and compression waves initiated while setting up the experiment, which then get a head-start, so to speak.
What do you mean by appear to regular intervals?
And I'd guess the answer is because the effect self-initiates itself. That is, one minor perturbation creates a pattern of oscillation.
If you've got a bump at one end and it's growing, the stuff in the bump has to come from somewhere, which means that a dip has to get started a little ways away, based on the size and shape of the growing bump. But when a dip is created, it also starts growing, which pulls stuff away from the top a bit further along, starting another bump, and so on. Since the instability is the same in each case, the distance to the next resulting fluctuation is the same in each case. If there are multiple bumps that happen to form before the chain gets established, you get some irregularities, which you can see in the raw slow motion attached to the extra video. Around 1:50 in that video, you can see two smaller, closer-spaced, faster-mixing bumps to the right of the bigger bumps in the rest of the shot.
3:32 my reaction: OMG!!! IT'S SO BEAUTIFUL!! AND THE PHYSICS AND MATH BEHIND IS SO INTERESTING AS WELL!!!
their reaction:......*nod nod*.....cool.....
Shame! Shame! Lift over a wing is not caused by Bernoulli phenomenon! It's the Kutta condition at the trailing edge resulting in circulation that is described by the Kutta-Jukowski Theory of Lift! Please make a correction video!
Anyone for a cup of Insta-Billy-Tea?
Yes, me. Served at triple point, please.
Shouldn't that be "cuppa"?
That might be some of the most beautiful slow mo shots you've taken. Great video as always. Love cool phenomena like this that have a relayively simple explanation!
3:23 this should be a meme
I'd rather call it sweetroll clouds, they look delicious.
I've seen it before
I am so confused,some articles I have read said the Bernoulli effect as the sole explanation for why airplanes have lift is wrong.
the Bernoulli equation is wrong, but effects of pressure and velocity still apply.
How is the Bernoulli equation wrong??
it is correct for the case in which flow is steady, but on a plane it is turbulent, which Bernoulli does not deal with. Should have been more clear on that one, I admit.
Oh I see
Kutta Joukowsky equation
those were the straightest and most parallel looking lines I've ever seen someone draw
Best explanation I've ever seen, excellent job!
Thank you! Very clear explanation!
Great video and explanation. The concept of instability was well pointed out, while some other videos failed. Honored to be your fan.
The music in this video could be sampled into one heck of a jungle track.
OMG THE EQUITRANSIT FALLACY
What?
Kimchi Koalaa the "equal time transit falacy" is stating that the air takes an equal amount of time to go through the top and bottom of the wing, which is wrong. That does not mean that Bernoulli's Principle does not play a role on generating lift, although there's more to it -- it is not wrong to say that Bernoulli's related to lift, it is only wrong to use equal time argument to justify a difference in air speed. The fact that air speeds up when it goes through a narrower cross section is true due to continuity, and that's what he states.
He actually states that the air speeds up because the path over the top of the wing is longer than the path under the bottom, which is definitely wrong.
he said 'travels further', that is not correct, I do recognise that the Bernoulli's principal does play a role in the KZ theory
You are indeed correct, sorry, I had missheard it and only remembered the "travels faster" part. I guess one could argue that he only said it travels further, and not at the same time, but that would be optmistic to the point of foolishness. Quite sad actually.
Beautiful!
3:33 pure gold
Ripples in the sand after the tide has gone out and sand dunes caused by the same thing I suppose.
Why is there such a regular distance between the instabilities?
Why is it happening everywhere (along the interface) at the same time?
Really appreciating the increased production value of these videos
amongst cloud people :D
This going to be one of those things I see everywhere now, isn't it?
That face at 3:33 is what I live for!😂😂😂
0:47 jovian instabilities
ghiribizzi and thousands of years old jovian vortex
This is the principle behind ocean waves formation, am I right?
7/10 Not a waste of my time. Glad I watched this.
Not our best ever review, but solid enough!
A perfect 5/7 from me
A E = mc2 where m is a number greater than 0 and c is 299 792 458 meters per second from me
Thanks for these videos, guys. Makes me wonder why didn't they teach us physics in a fun and interesting manner at school ?
Oh no, not the "air goes faster over the top" theory of aerodynamic lift!
I didn't know I needed a cloud fix until this video.
Airplanes have lift because the wings are inclined planes relative to the plane of thrust.
NO! That is the wrong explanation for lift! Bad physicist!
Well, it's an incomplete explanation of lift.
Hey Brady! I'd love if you could make a sixty symbols video regarding the new study published in nature on quantum communication.
this is beautiful
This is very interesting! I work in a plasma physics laboratory where we look into a lot of plasma instabilities. By treating plasma as a fluid we can get things such as Rayleigh-Taylor instabilities which are very similar to these.
don't you love physics?!
Helmholtz looks like Jeremy Corbyn :D
Awesome video!
As a meteorologist, we were taught those were "Kelvin-Helmholtz clouds".
What explains the regular spacing of the instabilities?
i think i saw this video before
Sixty Symbols - 2017-07-14
Don't miss the extra video I made about the experiment!!!
https://youtu.be/mf_143gkKSQ
chaoslab - 2017-07-14
Always! :-)