The ultimate fluid mechanics tier list

hi welcome back wait what hi I'm not Simon Park you might recognize me from places such as not being the author of firmament the hidden science of whether climate change in the air that surrounds us that case tackles nah but they both do maths have very funky hair and very similar names I'm Kat a maths PhD at the University of bath studying fluid dynamics pan-acidental I also stream on Twitch in my spare time doing mass communication and sharing my experience of being a PhD student I often go on tangents on stream about topics that I'm passionate about and just like everyone else those opinions can be completely baseless done mostly on Vibes and very difficult to change my mind about obviously I'm going to share some of those opinions with you now specifically I'm going to talk about my field of research if Simon can rank clouds I can definitely rank fluid dynamics fluid dynamics is the study of flows of fluid meaning liquids or gases under forces or stresses which can cause them to move the behavior of the fluids can vary due to a wild variety of factors how viscous the fluid is meaning how much it sticks to itself how dense the fluid is what type of fluid is it are there multiple fluids interacting with each other or is there a boundary around there acting on the system even just what extra forces are there like gravity when all these different factors combine in different ways the the fluids can behave wildly differently and some of the resulting flows are incredibly cool and some of them are meh without further Ado I introduce you to the fluid Dynamic phenomena tier list we're going from F tier all the way to EST here judging will be done on Vibes sci-fi nurse and mathematical Beauty I study bouncing droplets now when a droplet is Falling Towards a liquid bath one of three things is going to happen it's either gonna Splash it's gonna sit on the surface and coalesce meaning it touches and disappears or and this is the cool one it's gonna bounce when it bounces it means that the speed and size is right so that their layer of air keeping the two liquids apart doesn't deplete doesn't disappear it prevents the droplet from touching the free surface so the free surface has time to kick backwards and basically act like a trampoline now you can start getting really funky with changing the size and the speed of the droplets so that splashes cause bouncing droplets or coalescing causes Cascades or smaller and smaller bouncing drops if you shake the bath itself you can get periodic droplets that will bounce indefinitely and if you want to know more about those go check out the PHD stories video I did with Simon last year so where am I ranking this well it's not just because it's my PhD research it's also because rain bouncing on puddles is one of the best Moody Aesthetics and one of the reasons why anime looks so pretty sometimes so I'm putting this in Nest here so what about the simplest fluid flow when all the fluid streamlines meaning the directions of the velocities all point in the same direction or are parallel to each other or anti-parallel they're very neatly organized this is called laminar flow this phenomena is so smooth that when a jet of it moves through air it can look like glass it looks so still now it's really pretty and it's a fun experiment to try and recreate at home but it's kind of boring but without it us mathematicians would be screwed we oftentimes use laminar flow assumptions for systems to be easier than when we consider them without it we'd have to look at every single particle and how that moves in the fluid and that's just just way too much a good phenomena to have but it's pretty meh so seating what about that messy non-laminous stuff turbulence is perhaps a more accurate model of what happens all around us streamlines interact and the movements become chaotic and unpredictable this can look really pretty however the mathematician in me is screaming because turbulence is often where a lot of our current models will break down you really need heavy machinery like either scientific computations or experiments to understand turbulent flow and all of my assumptions especially completely stop working so turbulence can get in the bin left here laminar and turbulent flows are the two extremes of fluid dynamics and often the building blocks for a lot of the other phenomena we're going to look at the next few phenomena to make the list occur when fluid interacts with very particular boundaries so let's get back into it perhaps one of the prettiest phenomena I'm going to show you next can often be hard to see damn you turbulence these are Von Carmen Vortex streets these are caused by what's called Vortex shedding when a uniform flow moves past a solid body the flow left in the wake after the body is often unsteady and gets pushed from side to side generating these beautiful vortices that align themselves in these periodic patterns and they're compared to lampposts down a street thus the the name for Aesthetics I'm giving this B to you what if instead we move to something 3D instead of just one direction of rotation we expand to a Taurus like a donut shape so the flow is rotating around the cylindry bit of the donut this is called a Vortex ring they occur a lot in nature any way you have an outlet really but they can be really difficult to see the way you visualize the them is by suspending particles in the fluid kind of like a smoke ring which I will beautifully demonstrate in this next clip these are fun to look at but incredibly difficult to see without high-tech equipment or an airzuka which was surprisingly hard to get hold of so this is getting easier moving away from vortices and turbulence imagine a very very laminar flow a flow that is so neatly layered that each layer lies on top of one another nearly touching so they can move one way in the other without interacting that heavily for certain fluids the flow is actually able to be undone this is best demonstrated in a Taylor cuet flow which is a cylinder moving inside of a static cylinder with fluid contained between the two if we rewind and move back exactly the way we moved it you get each point back exactly to its original starting position which just doesn't happen with most flows you can't unpour a glass of water now this definitely feels like it breaks physics but it's incredibly slow and a very scary experiment to do in real life so I'm going to give this a detail up next we have what I'm calling complex fluids and don't worry these aren't using imaginary numbers complex fluids have inherent properties to the fluid structure that makes them behave quite strangely now we start getting into the Sci-Fi stuff this next one is perhaps one of the most demonstrated phenomena in fluid dynamics and all you need is cornstarch and water when corn starch is fully suspended in the water the new fluid has a rather interesting property when left alone it looks like any other liquid and if I pour it gently it will move but when a large force is applied something strange happens under Force the fluid becomes solid-like to put it in proper terms the viscosity is now dependent on the forces applied to the fluid and when the viscosity depends on the force in this way it's called a non-Newtonian fluid if the force makes the fluid more viscous like in this case we call the fluid Shear thickening because it thickens when it's sheared but in contrast is also true if the force makes it more runny then it's called a Shear thinning fluid that's like ketchup it's the reason why we shake the bottle to make it runnier now this is incredibly cool at first glance and quite fun to play with but once you enter the realm of complex fluids the phenomenon is so last year even John tickle from Brainiac already got it covered and that's a throwback and a half it's definitely cool enough to make the list and it does deserve a place there but it's not that exciting detail when an effect is first documented with the words I can offer no explanation for this Behavior you know something really funky is about to happen and that's exactly what Alan K said in 1963 in his nature paper when he first discovered the bouncing stream effect which we now call the K effect this happens when certain Shear thinning fluids are released in a very thin stream on a solid surface initially the fluid builds up in a pile however every once in a while something fantastic happens the jet hits the liquid surface and is rebounded off ricocheting upwards in an unstable stream it was in 2006 that an explanation for this phenomenon was discovered thanks to the use of high-speed cameras it was observed that actually thin layer of air is preventing the jet from joining with the pile of fluid causing it to bounce off just like my bouncing droplets so for having a surprising connection to my research and being incredibly fun to experiment with this is definitely getting a tier have you seen the movie Lucy you know the one with the people only using 10 of their brains so they unlock the rest of Scarlett Johansson's brain turning her into this big black blob monster that's what I always think of when I see this next one stepping fully into the brain of a Sci-Fi author this fluid is wonderfully spooky and breaks all perceived Notions of how fluids are supposed to behave and to top it off it's absolutely fascinating mathematically too in the same way that you can obtain non-Newtonian fluids through suspending particles in a liquid like water What If instead we suspend tiny iron compounds in the fluid making the whole fluid magnetic when it's fully mixed in aptly named ferrofluids interact with magnetic fields causing these wonderful spiky shapes that just don't seem like they could come from a liquid the shape is formed due to the fluid Trying to minimize the energy in the system it doesn't want to be stretched but it's still reacts to magnetic fields this is such a cool phenomenon but the constant reminders of the very strange film do take it down a little bit to Aid here imagine a train with a whistle one of those old steam-powered ones when the whistle blows and it's sat in the station the sound waves travel out at 330 meters per second in all directions generating a sound wave once the train starts moving and the whistle blows the source of the sound wave is also moving along with the Train the train since it's old and inefficient and slowly destroying the planet knew I'd get some climate science in there for you Simon it isn't moving faster than the sound it produces so you end up with this bunching of sound waves in front of the train and a lag behind but what if we go faster if instead we were able to go faster than the speed of sound then suddenly the source of the sound is in front of the wave that it just generated this causes a sonic boom which not only causes an enormous amount of energy but it sounds like thunder and can cause all sorts of interesting things to happen mathematically when we approach the speed of sound suddenly air starts acting as a pressable fluid which can be incredibly fun to study but also a little bit mad the maths of compressible flows and supersonic flight is so cool but personally I hate thunderstorms and I hate when supersonic jets go overhead and allow noises just attached with the field are really stressful so I'd have to move this down to seat here final group of phenomena I want to talk about involve multiple fluids multi-layered flow is a massive field of study as it can be used to understand things from industrial processes to how the layers of the atmosphere interact with each other whenever you have two different things meeting there's always going to be some interesting phenomena occurring draw a wave did it look something like this well it might look like a stylized version of what we see on the ocean it's actually not that far away from reality these types of waves are generated by what's called a Kelvin helmholtz instability and it doesn't just happen on the sea it can happen in clouds or in any too fluid problem and yes there are two fluids in the ocean the air does count it happens when you have a system where there's a lighter fluid it's moving in One Direction directly on top of a denser fluid in this case the air is moving across the ocean the surface between them is free to move and it kills up in this wave pattern it's one of my favorite phenomena to look at because it's what we draw when we're a kid and suddenly that's a real thing in maths that is so fascinating this one gets beatier take the previous system a lighter fluid on top of a denser fluid and flip it on its head you now have a denser fluid sat on top of a lighter fluid and it's no longer stable due to gravity so the denser fluid is going to want to move downwards through the lighter fluid but it can't move all at once so instead these plume-like shapes form personally I think they look like squids but the resulting interface is absolutely gorgeous in certain experiments and under certain conditions you can see these fingers reaching downwards however the motion quickly becomes very very complicated and turbulent detier the astute view will notice that this next phenomenon is actually a very specific type that I've already shown you why does it get its own category why does it get its own ranking if the other one is more General the answer to which is it's my video and I can do what I want but also this one looks cooler I just think it's neat so take a Vortex ring and put it under water now you have air moving in a spiral pattern in a Taurus under the water and you get a ring bubble and that's exactly what I mean it to be it's a bubble that's in the shape of a ring the bubble is very unstable but the faster it spins the more stable it becomes the slower it moves the less stable eventually breaking out into typical bubbles that you see shout out to the plateau raelian stability for that one just really quickly deter because it breaks my fun bubbles arguably a ring bubble and a Vortex ring are the same thing just with different fluids but this one is so much cooler to look at and there are loads of really fun videos of divers beluga whales and dolphins making them underwater so this bums it up slightly to seat here so yeah that's the list there were loads of phenomena that I had to cut out but if you want to hear me talking more about fluid dynamics maths or anything in general come see me over on Twitch at cat does maths if you you want to let me know exactly why and how I'm wrong with my rankings though you can leave them in in the comments down below for Simon to deal with that's it for me I'll see you in the next one or not foreign

Channel: Simon Clark

Views: 21,073

Keywords: drsimonclark, dr simon clark, simonoxfphys, simonoxphys

Id: gF9G7g1nTDk

Length: 13min 3sec (783 seconds)

Published: Wed May 24 2023