Why Do Boats Make This Shape?
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- Опубликовано: 28 сен 2024
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This video is about the "Kelvin wake" shape of water wakes behind boats - we talk about mach angle, dispersion, superposition of many waves, and how these all lead to the pattern of a wake. We don't get into Froude number though...
REFERENCES
Boat Wake Wikipedia Page: en.wikipedia.o...
Interactive Boat Wake Simulation: observablehq.c...
Feynman Lectures on Water Waves: www.feynmanlec...
Building up a Boat Wake from V-Shaped Wakes: editor.p5js.or...
Wave Dispersion: en.wikipedia.o...
Mach angle shock waves:
www.sciencedir...
Ship Wakes - Kelvin or Mach Angle? Rabaud and Moisy Paper: journals.aps.o...
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Minute Physics provides an energetic and entertaining view of old and new problems in physics -- all in a minute!
Created by Henry Reich
It’s amazing to see those waves come together to make the recognizable wake pattern. I didn’t know it would be that complicated but it’s really interesting to think about
Hello
Can gravitational waves make similar or really different yet beautiful patterns from which we can do some awesome science?
@@pulkitmohta8964 no dispersion for gravitational waves, I guess: they travel at a constant speed _c_ - or at least only a *very* dense matter can change that noticeably…
@@pulkitmohta8964 no because gravitational waves travel at the speed of light and u would have travel faster to create this phenomenon.
I think it is time to colloborate man
Awesome video. Way more complicated than I thought!
high there
Yes visualization makes easy to understand.
Omg
Sup Derek
Just 4 replies? last time I was this fast when I was a sperm.
Appreciating the fact that i get content like this for free.
This
not really, you are paying with your time spent on ads, still its not too much I think :)
@@ignacyn5346 be quiet
Internet bills, your PC, electricity bills, your internet router
@@creativecreepyturtle1562 the content itself is free
0:31 "In this video, we are gonna explain exactly where this shit comes from."
can't unhear it.
I don't even know what he really says. All I hear is shit
@@l.w.1014 i think it's shape
Lol, I was going to post this too but I think he said "shape".
bruh sammmeee
shift, maybe
I just noticed that for some time these videos aren't actually hand drawn like the older ones. It took me a while to notice, which means that you managed to imitate the look quite well, but I miss the drawing a bit.
Are you sure? I think they still draw some stuff like the boat, water waves and "dispersion" text.
@@2KOOLURATOOLGaming I think it’s tablet drawn with some imitation of a marker. It clearly isn’t hand drawn (if you only include paper in that) when you look at 0:40. They animated the sound waves, and there is no hand moving around like they used to have
On the other hand, this means we get more videos on a more regular basis! There's always a tradeoff.
It allows for more complex visuals.
If you look at 3:21 you can't tell that that isn't hand drown
Years ago when I was riding a boat, I thought about a way to know the speed of the ship I was riding in. I got the idea because I knew that the angle of the shockwave of a supersonic thing relates to its speed, so I looked outside expecting a fine, singular wave. I got surprised about what I found and asked myself why. Thank you for finally answering this
It's a bit late at night, but they posted, so I'm now a *wake*.
Bruh over here it’s 9 A.M
@@Cumgguzzler same
Coolest dad joke I heard in a while
This isnt MinuteEarth.
Edit: All puns belong to MinuteEarth.
Mood
i love learning things i never knew i wanted to know
0:39 this is a bit misleading, because light waves also disperse when not in a vacuum (which is always)
I appreciate you changing the thumbnail and title to make it more clear what you are explaining here
I had no idea he changed the title. Its only been 10 hours.
Lets appreciete the hours of investigating, animating, drawing... all this for free. Thank Minute of Physics
“Free” as in ads + paid promotion but yeah the gratitude is still there, it works for all.
@@yungmurakami6002 you dont pay sh*t for this quality content, that means its free.
@@kirabey8946 yes, I know I don’t pay for shit. I’m perfectly aware of that. But the channel is funded through ads and paid promotion. If that wasn’t the case, the quality and time put into the videos wouldn’t be the same, or they’d be far less frequent. You’re underestimating the fact that RUclips is a legit money-making platform. 🤡
@@yungmurakami6002 You're focusing on the creator's perspective. From the user/viewer perspective it is without any cost, especially if you have ad blocker, which means it is free. If OP said, "let's appreciate Minute Physics releasing this for free", you'd be correct, but with their wording, you are not.
the progression in the video is just so satisfying... you get a buncha video clips, all these simple concepts, lines, wavelengths, and then BOOM you get a 3D rendering that looks EXACTLY like the clips at the start.
won't be long before we get a supercomputer to render all the particles on earth in real time.
I absolutely love fluid dynamics.
Now I wanna do physically accurate wake shader !! Thx minutephysics you're always amazing and straight to the point and leaving us with just enough to dig through if we want to get deeper, but with the proper terms.
Ayy you are uploading much more frequently now, it's great to see!
Excellent video and awesome graphics to illustrate a complex topic in an intuitive manner! I’m an engineer who sometimes does navigation studies (including wake generation studies), and while I’m familiar with the math, this presentation makes the concept much easier not only to understand the physics but also connect the dots between textbook drawings of waves to what you actually see in real life. Well done!
Very impressive! One little clarification for 0:43 : The speed of sound in an ideal gas varies only by temperature and not e.g. by pressure. Specifically, it is proportional to the square root of absolute temperature, which is the result of particle speeds in a Maxwell-Boltzmann distribution.[1]
It varies by altitude because temperature does, but you can't really say it's 343 m/s in dry air at sea level because sea level does not imply a specific temperature.
[1] en.wikipedia.org/wiki/Maxwell%E2%80%93Boltzmann_distribution
that is an approximation
This is brilliant science communicating: Very interesting topic explained in an engaging way. Thanks, as usual, Henry!
really really good explanation! well done
I've always wondered about this and spent any boat ride just looking at these waves trying to figure them out. Thank you for this clear and beautiful explanation.
You do a great job at explaining complicated things in a way that is understandable. Good job!
Kelvin's ship wake can be computed using the Chester, Friedman & Ursell Method of asymptotic theory (and hence the wake is described in terms of the Airy function and its derivative). The semi-angle of the cone is sin^{-1}(1/3) independent of the velocity of the ship/duck (for the deep water dispersion relation omega²=g|k|).
I always wondered about this ever since I was a child.. Thanks for making this.
I knew about dispersion in optics for ages and was still surprised by water wave dispersion.
as a graphics programmer, i will definitely apply it somewhere, and this explanation gave me the exact idea how to do it.
might be overall one of the best short videos on physics out there.
i actually always wondered why the wake does not look like a mach cone, and i assumed that it had something to do with dispersion, but this explanation made it clear why it looks exactly the way it does.
Look , RUclips notifications does work !
Noice!
This was just... Beautiful.
I miss these types of videos that explain simple yet unique phenomenon.
yeah me too.
I am watching this while having a online physics class with exactly this discussion going on
you have class on sundays?
Bangl;adeshi>:?
@@tommihommi1 He's probably just catching up, but I had lab work every Sunday for the duration of my engineering course.
@@_John_P my condolences. Only people putting in crunchtime for their thesis do stuff on weekends here, and the university buildings are closed on the weekend
@@tommihommi1 yeah in our country we have holidays only in Fridays
So that spawns an interesting question: if dispersion of waves of different speeds exist, are all the differing speeds emitted from the motion simultaneously, or are the water particles accelerating and thus creating the wider waves longer after contact? That would explain why the wake feathers outward more further from the boat instead of closer to it
It'd be cool if you'd link to the Nebula version of the video. At first I was going to comment about a qr code in video but really that's crazy overkill. A link in the description would be awesome though. I subscribed to nebula but don't want to unsubscribe from you here, but bouncing over to the other version would be useful.
Monday's are quite dull in my subscriptions so a new Minutephysics video makes the whole day much, much better. 😀
i really enjoy the pacing in your videos. and going back to put all the components into one concept really makes for a smooth finish. love it
Nice quick simplification of general principles Maybe on Nebula you explain why an object moving smoothly and continuously through a fluid creates waves at all. How discontinuity develops even if continuous movement. Complex fluid dynamics with Reynolds number, dual fluid interface etc.
The single lines combining to the complete shape is magical!
Hey V-Shape! Minutephysics here.
your animations are great in this video, would you care to tell me how they are made?
At first I thought this topic would be way too hard for me to understand, but this explanation made it so simple! Thanks.
that's so complicated as well as beautiful
Wonderful! This was the most comprehensible explanation for wave dispersion I've ever seen!
Thanks! Over time I'd gotten lost in doing calculations and forgotten what a dispersion relation *really* is. These visual really help remind me of the physics underlying all of the math.
This is good stuff. Appreciate your efforts, Henry.
Woah Woah Woah, I wasn't expecting 3D stuff from this channel
2:56
Man I love this channel.
simply fantastic
Very interesting, informative and worthwhile video.
I’m loving these videos! Thanks for the effort. Always very nice illustrations. May I suggest something? It would be great if you did videos with black backgrounds and white drawings. That would be much better for the eye and the battery of the device too ;)
Omg, dispersion relations are so cool! In Computational Aeroacoustics, there's a whole method whose goals is to preserve a constant dispersion relation! That way, sound waves propagate correctly. (It's kinda tricky to explain in a brief YT comment, but super useful)
What a fantastic demostration of how physics is done! I mean, is incredible how a basic result like dispersion yields this apparently convoluted phenomenon. That's what a good physicist finds out!
I really liked the 3D animation, good job on the visualisation.
screw school, screw physics classes - this guy here provides all you need to know
0:30 I did a double take when it sounded like you swore lol
I would be happy to watch the extended version on Nebula. I pay for the subscription, but the app doesn’t work half the time. I can’t see your video there yet.
~ 1:00 - Light also disperses, just not in vacuum. Hence, say, chromatic distortion in lenses.
We're not worthy. Nice teaser with the caveat at the end. I'm intrigued.
the pattern is interesting.
now, here the hard question:
other than speed and the density and depth of the water, what causes the period of the waves? in other words, what is MOST attributed to long period, fast moving waves versus short period, slow moving waves. remove the speed of the boat, and accept that density and depth of water are moot. What actually creates the frequency of the wave?
hint: displacement
spoiler: consult a naval hydrodynamic engineer before guessing.
for another clue: examine pressure waves from submarines and inspect the differences above the hull versus the difference below the hull..
if you are thinking about "lift"...you are getting close....
if you are now thinking that the layer between water and atmosphere contains clues, you are even closer.
have fun with this one.
wow this is so cool!! when all those lines added up my jaw dropped
It's wonderful how someone can explain shortly and easily something that looks obvious or complicated ❤️
0:32 I see what you did there
@minutephysics Can you make a video about beamforming, while on the topic about waves?
thats why we love fluido dynamics
Sounds and light experience dispersion too!
There are actually some mistakes in this video:
1. Water waves do not travel as depicted and it is not the water that moves in some direction. You can best imagine water waves by imagining someone moving up and down a rope fast. (Wave length there depends on how fast the rope is being moved up and down, the faster - the more waves can be seen on the rope. That is different with water waves. I forgot how sound and light waves work exactly, but I believe light waves actually travel (duality is a word that comes to my mind, but it is too long ago that I have learned this.))
2. The waves of any water vessel can never be faster. So the person in the kayak will never see any waves moving in his forward direction. There is no bow way moving forward. Vessels always stay ahead of any of their waves (unless they slow down. You have to actually consider that, when you pass under a bridge, where there is little room at the top. You don't want your own waves to lift you against the bridge.)
3. The waves along the side of the vessel travel exactly at the speed of the vessel. It is only when they put distance between them and the ship or boat, they will start to slow down. The further away from the vessel, the slower the waves and the lower the amplitudes of them.
I am not sure, but I believe that the Kelvin wave pattern has been refuted. Don't know, if there is a newer model. Real wave systems from vessels are extremely complicated.
The animation is amazing
This video reminded me of why I love Physics. Thank you so much.
Awesome and very well explained. I work in 3D and would love to hear more about how you generated this 3D image 3:00. Thanks!
Just a minor note on dispersion: just as with water, there isn't really a single speed of light either. The fact that different wavelengths travel at different speeds is exactly what gets us the dispersion you might see in a prism.
Very good video, the reason is purely mathematical but you can see clearly this patterns of nature c: and I imagine you can also associate this with hyperbolic functions and get the beaulty of this kind of study, frequently just abstract
I kind of not agree with your statement in 0:39 .
You can observe dispersion with light (EM) wave and "sound" (pressure) wave too. Just not as dramatic. The case of a transverse physical wave in a medium as heavy as water makes this phenomenon a lot more observable but doesn't mean that water (or liquids in general) stands out of the rest of the physic of the universe.
Every single medium have some degree of dispersion. The only way of getting no interractions at all is to get no medium at all (absolute vacuum) but even air causes a bit of dispersion.
Real question for @minutephysics, does viscosity have an impact on wave shape or angle?
So insightful! I never knew wakes could be described like this
At first I thought it would be only about how waves cancel each other out but nope, turns out it was quite special. thanks!
As a general comment. Hiding the caveats behind a paywall is of course a good idea but kind of (maybe) leaves a bad aftertaste. I guess if people really would need to know about this topic they should be going to Nebula.
Love how science explains our everyday lives :)
The more you know
This video is amazing but I also kinda want the code they used to make the straight line drawings
Been wondering about this for years now. A masters degree in mathematics later and I still didn't now what's going on. And now it only took you 4 minutes to reveal this mystery. Thank you!
Used this to kill a small amount of time. Fascinating.
Enjoyed the video, though the ad transition read wrong as hell... "this video was filled with inaccuracies, to find out what they were.. pay us".
Brilliant video but a little thing at 0:37 and @ you put the dispersion for deep water waves which is slightly misleading ...
So with dispersion there are 2 types of velocities (group and phase) and you put the formula for phase (Which is fine) but hard to say that is straight up the velocity.
Second better to say the dispersion relation is omega= sqrt(gk) as that's actually what the dispersion relation is and implies the formula for phase velocity shown.
Minor points but I think the channels viewers can handle the subtleness of this topic.
How do you manage to do a video on Kelvin Wake patterns without mentioning that they have a specific name and specific angle?
Thanks, this was great. I was wondering about this last summer, as I was watching boats and the wave patterns from a cliff. My SO doesn't share my appreciation of fluid dynamics for some reason though.
Why does the speed of water-surface waves depend on the wavelength? Is it something about them traveling across the 2D interface of fluids with very different density rather than through a more-or-less homogeneous, 3D medium?
Why do sound waves travel at the same speed regardless of frequency, but water waves don't? I thought fluids and gases behaved essentially the same. What other wave mediums display this dispersion effect?
In fact, it was a false statement. There is (variable) dispersion in every medium for every kind of wave. Except in absolute vacuum (that we could describe as "no medium").
Once again, nailed it.
you could get a V-ish shape from diffraction too no? Sorta the opposite situation as the typical diffraction example (barrier with narrow slit -> just a narrow barrier). But that alone wouldn't look anything like a boat wake, other than the general V-ish boundary lol. Completely different situation as the boat, different pattern within the V.. this would be like tossing a rock into a pond, and there's a branch protruding through the surface somewhere. Here, the waves are already there independent of the boat (branch) and the boat-analog is obstructing them. Whereas in the wake-situation the water (ideally) is initially wave-free and the boat's motion creating waves continuously.
Love 💝 your amazing work
From Curious Physics 🔥
I wonder if there's some sort of stealth hull shape that could make a wake with self canceling waves that would basically make it have no visible wake.
How is the wake and wave patterns related to the angles seen in newly created vineyards rows when passed by in your car?
This is amazing, thank you.
Amazing video!
How much does surface tension play into the physics here?
It seems quite important to me "on the surface" lol....
I would love to see a comparison of really small scales to the very large ones depicted here....
Thanks for this, water is the most fascinating substance on the planet!
0:31 "We're going to explain exactly where this sh*t comes from"
I totally heard it
Wonderful! I have often thought of this but never figured out the physics in my head! Now I'm really curious how to calculate this angles and why they're always the same...
I love that you can make a 3d wake by literally making a wake
Absolutely love this channel
Assuming the same thing happens in the air too? Just a bit more inside the 3D object (Air) than on its surface.
This also makes me think about the simultaneous wake in the air caused by the boat.
Understanding Complex science topic in minutes
Looks like a “ship wake” in the “high Seas”. I’ve seen clouds that look similar.
Amazing! Dispersion!