The ultimate fluid mechanics tier list

[@ThomasRintoul]

Loved this! Though I'm not sure I can forgive putting the Rayleigh-Taylor instability in D tier. Turbulent flow is cool!!! We don't need analytical solutions!!!

[@JCisHere778]

There are a few analytical results and "solutions" for turbulent flows :) .

[@mastershooter64]

@@JCisHere778 woah really??? can you give some examples?

[@JCisHere778]

@@mastershooter64 There are some results like the Betchkov (I hope that was the name :) ) invariants that are disconnected from the Navier-Stokes equations and others like the law-of-the wall (and many other turbulent scaling laws) which can be rigorously derived through symmetry analysis of the governing equations. However, the latter should be taken with a grain of salt as they are more of a prototypical solution than an actual solution.

[@abyssaljam441]

An Analytical solution would make designing fluid systems so much easier though. You wouldn't have to spend weeks doing a CFD runs or tunnel tests to work out the best configuration of a thing. Just Excel and goal seek.

[@harris8462]

@@abyssaljam441 Hi! Highschooler here, trying to make a CFD of a Pulsating Heat Pipe. Any resources I could use to learn how to build a CFD model?

[@jhawar-ji]

Laminar Flow in C tier! I have seen everything in my life. My will to live has left my body.

[@kaudsiz]

🤘☹️🖤🌈

[@aminsabir7902]

Destin from Smarter Everyday, leaves the room in rage 🥲

[@juanmairal7048]

Mostly agree but I can't allow Turbulent Flows to be left in the F tier. A problem that scared both Feynman and Heisenberg deserves a much higher position imo. Seriously, as a PhD student of CFD myself I loved the video and I appreciate how a tough topic like fluid dynamics is made very approachable. This is some top tier science communication and I am definately returning to this for inspiration for my next talk.

[@nikospud860]

Amazing stuff. For the first time I am convinced that Kat is a mathematician and not a physicist based on these rankings. #Justice4Laminar

[@KatDoesMaths]

It was the only way to convince people

[@dougdimmedome5552]

But she ranked smoke and even bubble rings so low, not forgivable.

[@juanfelipecespedes6704]

You would think that a mathematician would put turbulence, the most important unsolved problem in classical physics, up in the tier list due to the challenge of its complexity. #MillenniumProblem

[@vigilantcosmicpenguin8721]

Perhaps it's simply fear of the unknown.

[@jordanpipeke]

@@vigilantcosmicpenguin8721 yeah, im scared to look at my asshole

[@rondrajaeev2957]

You answered your own question. It's important in classical physics and engineering. But the maths is just on another level of complex. Approaching it from an engineering or physics perspective turbulence and shocks and compressibility effects are some of the coolest ones based on aesthetics and usefulness but maths is seeking of knowledge for knowledges sake and in that turbulence and instability are just extremely scary. If you have a look at some of the equations you will not have a clue where even to start. The whole point of turbulence is that it is near impossible to mathematically model accurately.

[@MrSam2450]

I’m happy there was no Fog fiasco in this great tier list. Fog is S tier

[@ThomasRintoul]

I dunno, from the comments it would appear that Turbulence Gang is rising

[@ibonitog]

I will never forgive you for your Turbulence-F-tier choice!! :D chaotic systems and the mathematical process of (seemingly) random behaviour arising simply from the non-linearity of deterministic systems is so deeply fascinating and beautiful to me!

[@yoavshati]

0:08 no way! I'm not the author of Firmament: The Hidden Science of Weather, Climate Change and the Air That Surrounds Us too!

[@vigilantcosmicpenguin8721]

I'm not saying I'm the author of Firmament: The Hidden Science of Weather, Climate Change, and the Air that Surrounds Us, but nobody has seen me and the author of Firmament: The Hidden Science of Weather, Climate Change, and the Air that Surrounds Us in the same room.

[@Nartinan]

Fire is arguably another multi-layered fluid phenomenon. Combining interesting fluid dynamics with chemical reactions, phase changes and (somewhat limited) self-sustainability. Considering its beauty and utility, but also the relentless chaos and violence is causes, it's an easy S Tier for me. Also, I can't believe you put the Crabby Nebula in D Tier.

[@TheOllieJackson]

As someone currently doing their PhD in Vortex Ring dynamics... I think they're neat

[@mikefochtman7164]

Nice stuff. I remember learning about 'Taylor bubbles' when we were studying boiling water in power plants. The vapor formed when boiling water has to travel up the tubes inside where it was heated. Small bubbles with a large amount of liquid flowing wasn't a problem. But as you add more and more heat, the bubbles coalesce and eventually 'fill' most of the tube. Now you have a wholly different flow behavior that impacts the heat transfer with the tube wall. Fluid flows are so wonderfully complex, even for something as 'simple' as water. :)

[@dubious_potat4587]

3:17 Destin is not gonna be happy about that

[@dougdimmedome5552]

It’s a crime for a mathematically oriented fluid mechanics person to put smoke rings in E tier.

[@dungeonseeker3087]

Here's an interesting one, in Chemistry there's a thing called the Briggs-Rauscher oscillating reaction, not only does it look kinda gorgeous but I have to imagine there's some funky stuff happening inside the reaction material too.

[@p_mouse8676]

The thing with laminar flows is not about its simplicity, but how rare pure natural laminar flows are. They barely exist. One tiny bump can ruin your perfect flow completely, some taking the whole thing to the other extreme.

[@user-xsn5ozskwg]

I adore living in an age where I get to see scientists and mathematicians share their interests and studies in such an accessible and fun way. I can't help but feel the call to explore each example in depth and find out even more. I won't stand for the train slander though.

[@IndustrialBonecraft]

"There was a story about the quantum theorist Werner Heisenberg, on his deathbed, declaring that he will have two questions for God: why relativity, and why turbulence. Heisenberg says, “I really think He may have an answer to the first question." - James Gleick, Chaos

[@hansolo9892]

Yeah, it's a real shame how it got the lowest ranking here.

[@IndustrialBonecraft]

@@hansolo9892 For real, though, I understand the low ranking. Not as a 'this is awful' but more just the collective frustration of a million scientists going "Are you fucking serious!?"

[@hansolo9892]

@@IndustrialBonecraft haha agreed

[@mudgetheexpendable]

Not that it matters, but I completely agree with your higher placement of the ring bubble on grounds of coolth. Fun video, thank you and Simon for it.

[@TheMorris360]

I disagreed with almost every pick, but I still loved this video. Great work!

[@vblaas246]

Suggestion: Some planetary flows could be included, like coriolis effect, saturns hexagon and jupyters towering cloud bands? Awesome video. Rayleigh instability in a water tap should be higher tier for being so commonly overlooked.

[@declansalisbury5698]

as an engineer student we need turbulent flows, but I see why a mathematician doesn't like it, as the models are very hard to do via computation, we usually use wind tunnel data to analysis turbulent flows.

[@Respectable_Username]

I love how vibes based the actual rankings are alongside being shown super cool phenomena. Great video! ❤

[@lad4694]

If you've ever seen some weird spirals around some long smoke stack, tower or chimney (or those old car antennas), they're to mitigate the effects of the Von Karman Vortex sheets. I came across it after googling something F1 related and now can't stop seeing it everywhere on my way to work

[@icskatingqn]

That was really cool, thanks for sharing Kat, and for elevating her work, Simon!

[@pablo_CFO]

I almost die when I saw "Turbulent flow" ranked in the F tier and "Vortex rings" in the E tier... and i understand that this ranking was based on different types of fluid flows rather than specific techniques. However, for me, Lagrangian Coherent Structures represent the most beautiful way of visualizing fluid flows. ❤

[@JCisHere778]

I find turbulence especially beautiful from a mathematical perspective. Especially the fact that the phenomenon is governed by a linear functional equation always baffles me... Also, there are a few really nice analytical results for turbulent flows that are rather surprising

[@olivier8223]

how are the equations linear? the NS-equations are nonlinear

[@JCisHere778]

@@olivier8223 They are, but the evolution of a statistical ensemble is governed by the Navier-Hopf functional differential equation. This is derived from the Navier-Stokes equations but is indeed linear :). P.S. you kinda exchange non-linearity for infinite dimension. So it doesn't do you much good

[@adolfobahamonde2358]

​@@JCisHere778 But also shouldn't dissipation impose a cutoff and the effective dimension of the attractor generated by the dynamics should be finite but super high-dimensional? Like a finite dimensional structure embedded in an infinite-dimensional space 🤯

[@charliemw333]

As a CFD engineer I see no problem with turbulence, it's easy to work with, just slap a RANS model on top and pretend it's another passive scalar. Turbulence is clearly S tear 😢

[@fg8557]

Approximating the effect of the turbulence shear stress tensor by one or two scalars 💀💀

[@saifmukadam5261]

Hey I wanted to start studying CFD I wanna know what topic pick up on like research paper and stuff

[@Dragrath1]

Dismissing turbulence as F tier because it involves non analytical solutions automatically is a red flag for a scientist after all in the absence of friction or another comparable constraining force all fluid flow or any other 3+ dimensional system of partial differential equations are turbulent and or otherwise nonlinear and chaotic. We have a strong bias against nonlinear mathematics which is probably a consequence of our brains not having evolved to handle such things but that says more about us than the universe. Again chaos is the norm not the exception, dismiss turbulence and good luck finding away to not violate conservation laws.

[@hansolo9892]

"Chaos is the dark side of nature that we aren't ready for yet."- I remember my non-linear dynamics professor saying this quote once.

[@bruceelder208]

I refuse to accept that laminar flow is C tier. There is no other type of flow that I get more hyped for than when I read the words "assume Laminar flow".

[@CarFreeSegnitz]

9:47 That’s a vapour cone not a sonic boom. Vapour cones are caused by water vapour traversing a rapid pressure change. The air in front of the aircraft is compressed and able to hold on to more gaseous water. There’s a rapid transition to low pressure along the body of the aircraft which has less capacity for gaseous water so the water transitions to visible droplets. Very quickly behind the aircraft air pressure returns to normal and the visible droplets return to invisible gaseous water. Sonic booms are seen briefly during rocket launches between the cloud layer and space. It’s the layer that’s too thin to hold much water vapour but still thick enough to host sound waves. Not as much footage out there and not as impressive as vapour cones.

[@likebot.]

"... turbulence is often where a lot of our _current_ models will break down". Why did I find that funny?

[@neonbricks8182]

I did my final project in undergrad on bouncing droplets/walking droplets and took long(and 3 vibration generators breaking) to actually get the set up work and still have questions about the results we achieve, very frustrating but also very fun once set up correctly.

[@lilcrowlet1802]

bro I'm just hydrology student, that's too many fluids that aren't water

[@jamesbobrob]

How about some love for the Richtmyer-Meshkov instability, or what you get if you combine a supersonic shock with a Rayleigh-Taylor like density difference

[@Thoran666]

My favorite part of the morning: Study the fluid interaction of hot coffee and cold milk as well as the chemical effects of the fluids on the human nervous system.

[@baksatibi]

Kelvin-Helmholtz instability can also occur in the air, creating beautiful repeating wave-shaped clouds.

[@theresalwayssomethingtobui944]

Cool idea! Yet, as an environmental engineer, I would order this completely different! Turbulent flow is amazing for the environment, otherwise e.g. water bodies would die due to Oxygen loss! A tier! And Taylor Instabilities are so cool too - at least C tier!

[@kayleejade7227]

this is literally my favorite video on all KZbin

[@ThePrimevalVoid]

NGL, I didn't know what I was going to see when I clicked on this video, but I enjoyed it a lot!

[@thospe-f8x]

A lot of these lower tier entries remind me of subjects in my field where I tell my colleagues "that's really cool or would be very useful - I really hope someone else gets on that"

[@Refract3d]

@SmarterEveryDay would probably disagree with your placement of Laminar flow!

[@anindyaguria6615]

You could have added plasma and MHD as well. They are pretty neat😂

[@ma5t]

Really enjoyed this, although I disagreed with a lot of the placements! To me, it's the difficulty and chaos of turbulence that makes it so beautiful.

[@trs5127]

Laminar flow deserves S tier just for how satisfying it is.

[@mh1593]

Good call on the Pi ear rings!

[@trevinbeattie4888]

I can see how the rankings would change a lot depending on whether you are looking at just modeling the behavior or only at its aesthetics.

[@benmcreynolds8581]

I love Turbulent flow. Its the most facinating thing

[@AttackSpeed407]

Considering plasma is basically a superheated ionized gas, does that mean it has its own unique fluid mechanics? Or is it something different altogether?

[@zeldovich33]

Oh I notice that combustion, plasma and nuclear is missing, I work with Ritchmyer meshkov instability whit shock flame interactions. Also detonation phenomena. A lot of perturbation methods, pde and so many cool things

[@abyssaljam441]

Can a perfect fluid, like those used in potential flow calculations, be compressible? I asked my lecturer last week and he didn't know of the top of his head.

[@NG_Dropkick]

As an aerospace and mechanical engineering student, I've never been so angry at a tier list lol

[@benmcreynolds8581]

What about the way they make Kodak film? Like layers of different laminar flows of different fluids to make multilayered film?

[@jonathandevries2828]

"TURBULANT FLOW IS BETTER!!" -Some guy outside of Destin's house probably...

[@jessicatymczak5852]

I have written code to solve the Navier-Stokes equations, and talk about pathological. Energy dissipation in turbulent flow is not well done.

[@lazaraza]

Turbulent flow in the F tier?!.. ...but hey, it's your video.

[@JamByPy]

Turbulent Flow in F tier painful 😂

[@pavel9652]

I didn't realize there is a specific fluid dynamic effect in play in the planetary nebula.

[@PolygonAlley]

That Brainiac clip has lived in my head rent free for 15 years.

[@moydodir79]

Great idea, but as aerospace eng, must absolutely disagree on the rankings 🤣🤣🤣. Supersonic flow, turbulence, Von Karman, RT instability, vortex rings - all should be at least C, and more likely B and above 🤣🤣🤣 Thanks for the reminder of how cool is fluid dynamics :)

[@ThePrimevalVoid]

9:45 Wait, do we not already consider air to be a compressible fluid? I feel like otherwise a lot of early thermodynamics doesn't make much sense.

[@JCisHere778]

There is no such thing as an incompressible fluid. However, different flow phenomena can be treated as either compressible or incompressible, governed by the Mach number, Helmholtz number, etc..

[@KatDoesMaths]

In practical terms yes It's compressible, however when you're in 'low speed' regimes, we often treat it as incompressible to make the systems nicer. It's one of those assumptions that if you wanted to include every single fact about the fluids you'd put it in, but the difference in effects is so small it's not needed at the lower speeds and makes the maths simpler.

[@jaylentracey1051]

Air is much happier to just move out of the way rather than compress- think like when you open a door. So you just treat is as incompressible for systems working under the speed of sound

[@Finnspin_unicycles]

@@jaylentracey1051 well, incompressible under mach 0.3 is the general rule of thumb, above that it depends on the exact problem.

[@pavel9652]

Bouncing droplets are overrated. In Ireland rain bounces of everything and even rains sideways. It is called lashing rain ;) July 2023 was the wettest July on record and it was a complete nightmare.

[@mitchhowe2201]

Excuse me! Complex fluids are way more than just shear thickening/thinning - they are any fluid composed of more than one state of matter. The stress-strain moduli can be so unpredictable in their behavior that there isn't even a classification, one simply just has to plot the data. There are also fascinating behaviors like viscoelasticity that are accurate models for so many industrial, environmental, and biological materials and are still not well understood at all. I think complex fluids are pretty cool. Sincerely, a graduate student studying complex fluids.

[@melissamybubbles6139]

The bouncing water droplets are pretty neat. Thank you and Simon.

[@datguy6101]

Great video!

[@kendrajohnson6535]

Very, very cool! Loved the ferrofluids :)

[@benmcreynolds8581]

Could cavitation bubble's be a part of this?

[@gasdive]

When you mentioned dense above, less dense below, I thought i was going to see Rayleigh-Bénard cells. Was also hoping for some Bose-Einstein condensate.

[@johnmartinez2445]

Laminar flow…. IN C TIER!!!! I’m dying. Laminar flow is my baby as a process engineer :(. We gotta get a better ranking for the king of applied fluids, laminar flow!!

[@mikkelkragh1336]

Bonus points for referencing Ghost In The Shell

[@lyrimetacurl0]

I thought it would be CFD models tier list (like k-epsilon, BSL Reynolds Stress etc).

[@mastershooter64]

Now do the ultimate magnetohydrodynamics tier list

[@otsokivivuori7726]

Destin from Smarter Every Day would be horrified with your placing of laminar flow

[@EladLerner]

Laminar Flow C tier? *Destin has entered the chat*

[@deidaburi]

What do you think about Saffman Taylor's problem?

[@KatDoesMaths]

A tier, we love a thin film

[@khernrhun8220]

Some part I known, some I don't. Some I didn't understand but the fact tht KETCHUP is nonnewtonian will stay with me forever :D

[@vigilantcosmicpenguin8721]

First, Simon put cirrus clouds in D-tier. And now you rank laminar flow as C-tier, to the chagrin of Destin-heads everywhere? This channel's tier lists really have a way of rocking the boat.

[@VoidHugger]

This video is just "how many other science KZbinr's videos can we use in a single video"

[@tonywilson4713]

Aerospace engineer here and I hate to break your Sheldon Cooper math bubble but all aerodynamics involves compressible fluids NOT just supersonic flight because air is (that's right) compressible. Its not that compressibility effects magically go away they are simply less significant at lower speeds. Just remember you maths geeks come up with formulas while us engineers learn how to use them. 🤷‍♂🤷‍♂ And before you complain just remember the next time you're in a jet at 35,000ft doing Mach 0.8 it was a smartass like me who designed the wings that are keeping you from falling from the sky. P.S. I did like the video. 👍👍

[@tonywilson4713]

​@professorfrog7181 Since you want to be a smart ass. I actually studied aerodynamics AND PASSED so I kind of know this stuff and am fully aware what terms we drop out of the Nav-Stokes at various conditions. Which is something you clearly don't get. So if I get a cringe award from the math geeks WTF do you clowns get? I know - how about the computer your in front of right now or the electricity that powers it. My kind just makes it possible for M0R0NS to travel safely at 35,000ft rather than trying to figure out how droplets of water land in a puddle. That's the difference between math-geeks and engineers - WE MAKE STUFF WORK!

[@kilmermad3306]

When you say draw a wave and my brain goes to a sine curve 😂

[@AakeTraak]

This must be the best of the Simon Clarks...

[@Istrianprincess]

The fluid dynamics of dihareah severity

[@brucewinningham4959]

THANK YOU for posting this Informative & Interesting Video, Beautiful Lady.

[@xaviergonzalez5828]

Nice video Kat, I'm looking for information about fluid dynamics masters degree programs. This video it's really handy for me! Thank you!

[@tadhgtwo]

Now that's a ranking video. No space give to fog.😂

[@Chris-io2cs]

great video! but I do have to say that mixing in background music without a really good mic is.. a bit difficult on the ears, especially during the intro

[@grg7452]

UPSTREAM CONTAMINATION!!!

[@adnankassem8114]

Fantastic video! But some of those ranking decisions were blasphemous at best and an outright criminal offence in other cases. But I did enjoy the video!!!

[@Henrik26]

I see my ketchup with a completely different set of eyes now.😂

[@catheosto]

So cool!

[@pitsielias483]

You can't put turbulence 😢 at trash tier 😢 its unforgettable 😂😂. Like the fact that it breaks most of mathematics 😊what a beauty

[@rorrt]

What did laminar flow ever do to you?

[@MrMaagaard]

Oh man. No superfluidity. Superfluid helium-4 is awesome. And neutron star cores transitions to a superfluid state at 500 to 800 million Kelvin.

[@alyeanna]

Am I the only one who gave them all S tier?

[@hansolo9892]

This is the worst tier ranking ever, you killed the mathematician in me.

[@Alfa-FSB-Agent]

Cant even believe you put tủbolance in F tier

[@trulybengali]

Turbulence in F tier because your assumptions break down !! Nonetheless, a good four-minute video.

[@KC_G4S]

Laminar flow is S Tier 🤬🤬

[@Agrantar]

Oh come on! Laminar flow in C? For the usefulness it deserves a B at least!

[@RaglansElectricBaboon]

I like your make up more than Simon's. Also I'm trying to place your accent.. South Wales but not at all strong? Can you tell I didn't enjoy the terrible maths lecturers our Engineering department had?

[@user-vc5zt9ci12]

Laminar is our friend! Not C. Surely