How do you get a PhD in fluid mechanics?

thanks to curiosity stream and nebula for sponsoring this video stick around to the end for a whopping 26 discount it's actually a different effect that I'm getting on my screen because of the oh that's so cool refresh rate science lots of people follow this YouTube channel because of the Vlogs I made during my PhD in atmospheric physics at the University of Exeter unfortunately however I had to graduate at some point and that necessarily meant the end of my videos showing what doing a PhD was like however there are lots of people out there doing interesting PhD projects and so in this video series I'm spending a few days with a new researcher each episode showing you what that life is like learning a bit about them and learning about the topic of their thesis this episode I'm spending some time with Kat who's studying for a PhD at the University of bath and unusually is a regular streamer on Twitch inspiring the next generation of math students it's freshers week here at the University of bath but I'm not here for any of these freshers behind me I'm here for a PhD student someone who is studying something that's actually very similar to what I was doing my PhD on fluid mechanics but whilst I was looking at the big scale stuff in the atmosphere she's looking at something a lot smaller I'm Katie Phillips but I go by Kat I am a second year PhD student at the University of bath but I'm in my third year of the samba CDT here which is the statistical Applied Mathematics at Bath Center of doctoral training and my PhD research is in theoretical fluid dynamics of impacting droplets so picture I'm going to call it a bath but just a very large body of water with a small droplet above it and the droplets falling so you can think of rain in a puddle you can think of in the bath splashing big body of water and then droplet a lot of current models so whenever they look at this in for other reasons you have a droplet that falls if it has enough speed it bounces so you get you've seen rain bounce and it disappears and the models at the minute just kind of only focus on the droplet and the water because if you are someone what am I looking at they would say those two things but we don't live in a vacuum so we have air as well and the air is actually like incredibly crucial to the system because the air is the thing that is stopping those two bodies of water from coalescing mixing because as soon as they touch it disappears and it joins the bath so what my research is is kind of considering this air layer like actually putting it into the equations like looking at what happens how the pressure moves through the air does the air like jettison out of the way does it stay there and you actually end up with this very thin band of air this entire process and I'm trying to use theoretical and numerical like modeling to figure out what happens there this Probably sounds rather abstract but cat had a low-tech demonstration of what this looks like practically and some interesting things that can happen when you mess with that bath so in our normal system we have just a falling droplet there you go um but that is quite boring so what we can do is stick our bath on top of a car speaker so we put it on top of a car speaker because we want to control the frequency of it being shaken vertically so I've attached it to an app on my phone that has a frequency modulator and that allows me to crawl how um much we're shaking and how fast we're shaking the bath there's a critical frequency at which we can generate surface waves so we can start seeing the effect of shaking the bath but below that so we're subcritical we get enough energy to keep the droplets bouncing but not so much to massively affect their behavior as we increase the frequency we start getting more chaos in the system and we can get moving droplets and then be on that again when we hit critical frequency where we generate Faraday waves on the free surface obviously we could keep going and if we actually go well beyond um critical frequency we actually get so much energy in the system that it can generate droplets so they are called um Faraday generated bouncing droplets the thing that's really interesting about this is the fact that you have um what's called pilot wave phenomena happening so you have the droplet which is essentially a particle and you have this um the free surface acting as a wave field that's kind of dictating the movement and behavior of the droplet so as the droplet bounces it's interacting with the waves that it's generated previously or the waves generated by other droplets and that dictates where it goes next what more serious experimental setups have been able to do is recreate Quantum phenomena such as the double slit experiment so you can recreate the double slit experiment using this setup by putting two malls submerged underneath the free surface and as the waves on the top of the surface move around they'll interact with the walls underneath and you can yeah get this double slit experiment recreated so my work is trying to describe what happens in the air and the pressure transfer between the droplet and the bath and so hopefully by the end of the PHD I will have a system that but feeds into models that describe the walking and balancing Behavior so I fit in on the micro scale where they model the macro scale at the start of our Theses they're encouraging everyone when they write up to put in a responsible research and Innovation um section to be like why is your research useful you can't just do abstract Maths for no reason anymore it's like what is this going to feed into bigger models it can feed into like oceanography because obviously you've got rain and evaporation happening it can feed into some really cool theoretical problems and there's like loads and just anything that has a very thin layer of water or any water with anything impacting on it you can have boats impacting on like waves you still get this thin layer of air protecting it for us up to a certain point and my what I'm doing will hopefully better those models and make them more accurate without being too heavy now if you've seen some of my PhD Vlogs or coding streams on twitch.tv4. Simon Clark then you'll know that the atmosphere is described using fluid mechanics in fact it's described using the exact same equation that Cat uses the navier Stokes equation just with different assumptions made and so different terms in the equation ignored so Kat and I geeked out on a whiteboard talking about how you model the atmosphere and how you model a water droplet and what the differences are you know for atmospheric stuff obviously well most of the time you are interested in time dependence yes but like actually a lot of the time you can ignore it and you just find like a balance like a geostrophic balance for example but like that's fair we're both on the same page advection term absolutely important it's something that's been killing me in my own climate model this then becomes the well actually you're also missing a term from atmospheric science which is the Coriolis term so you'd have you know like a um oh God this is where I get the medicine so yeah there's a rotational too there's a rotational term there and and then you'd also have this would be your gradient force in terms of just your overall pressure gradient and that also is probably the most important term in terms of actually forcing you know a domain yeah um and then this is your viscosity term yes so that can get in the bin no that's the atmosphere is invisible there's no imagine if the atmosphere was viscous so in my air layer I would have inviscid flow and in my liquid I now consider small viscosity so obviously if it's too viscous um you don't get necessarily the right surface tension into play right so the crucial thing about this is it's absolutely tiny if you have like a large body impact it it's a different system you'd have um gravity waves taking over but because this happens this is like my millimeters microbe like tiny stuff um it's all capillary wave so it's surface tension that's like the driving force of why you get this bounce right um so that can stay please okay um have you watched any of this art restoration YouTube channels oh yeah restoration this is the mass version so what's interesting to me at least is that like it's the same equations that get used in atmosphere in this kind of context every flow mechanic context but because of the assumptions you make no two field uses the exact same equations because you're binning you know different terms yeah but like the actual universality of the equation is just really beautiful yes and it's one of the things I love about fluids is because you kind of no matter what physical system you're given you start from the same thing and then you can look at it and start just making it nicer and nicer to play with until eventually you have an equation that is solvable by some sort of numerical scheme you hope one day one day one of the things when I was finishing up my undergrad Masters was I was looking through some of my old notes from like when I was a small child in school like year seven eleven or year old or so um and we found this mock interview that we did to like prepare us for big school and it was like what do you want to be when you're older and I put researcher as an 11 year old child I put researcher I want to keep learning and I don't think I ever really lost that I think it definitely moved around a bit as I grew up and you know I think part of it was I wanted to be an archaeologist or I wanted to be Doctor Who and you know the the reason why I wanted to research kind of changed a bit but I really liked learning I find I get very excited whenever something works also stem Ambassador so I do um Outreach stuff targeted towards children and I remember in my training for that they brought up this stat of the number of people interested in maths at different key stages um so you look at like five-year-olds 11 year olds 16 year olds and one thing is there's a noticeable drop I think there's something inherently wholesome about small children if you like do you like this they go yeah they don't know what they're talking about but what was interesting is you hit the 11 year old Mark and suddenly it goes from pretty equal split between the genders to a massive drop and is even more shocking when you hit like 16 year olds and then suddenly by the time you're hitting 18 year olds and like how many of you are going to go do you know stem or maths at University you're hitting the like five percent Mark and I think that's a really big shame and I think it's a it's a societal issue because something is happening along there that is making girls and women feel like they don't they can't go into it I was really fortunate that I had an incredible maths GCSE teacher who was female and she just completely inspired me I love the way that she tackled all the problems she made classes really fun and then again I was very fortunate at University it was actually my third year fluid dynamics lecturer um Dr Katarina Carey who just completely inspired me I just she was so great she was an incredible teacher which is not something you can say about every academic because the teaching and the the lecturing side of things is very different to being an incredible researcher she was so great about the way she spoke about things and I genuinely don't know if I'd have done as much or as well in my undergrad and like wanted to do as much now and wanted to share that as much if it hadn't been for her so I know I was very very fortunate to have those very you know Wonderful female influences in my life um also my mum because I have to say that because she's great we'll put that in now as a matter of fact I actually have some history with the uni here because I grew up about 15 minutes that way and obviously as a kid you don't have much reason to come up to the university but my parents brought me here to learn how to cycle so my very first ride ever on a bike without stabilizers was down this path which is a very shallow incline so I came careening down here at what I thought was tremendous speed and then I collided with a bin that used to be right where that Lamppost is face first into a rubbish bin apparently my parents only fished me out when they stopped laughing and I do know that just over here just behind you there are some signs Wanderer I don't know why those are there as I've already mentioned it was freshers week on campus when I filmed this which meant that there were social events happening everywhere but one social event that was happening every week was in the maths Department every week we have one of the PhD students come in and make a cake or attempt to make a cake and it's just an excuse in the middle of the week to like get away and enjoy a break from work now taking the view of the lay person a gathering of a dramatic PhD students sometimes maths not always we try and have a band until one of the analysts turn up and then suddenly it's pure maths all the way the fact that the tables are actually whiteboards so you can write on the tables is quite fun although if you do that in the pub they get a bit angry at you you wouldn't do a PhD if you didn't love what you do so there is some talk on it but there's also like sports and socials and we're you know we're real people too there's more than just math shocking I know this is the bit that gets me in trouble with my supervisor for not spending nine to five on the PHD I do tutoring for the University so I teach the first year undergrads get them into thinking about calculus and differential equations I then do private tutoring I then also help out at my local yoga studio because when everything moved online for them there was a bit of a panic we hadn't been able to do it over lockdown but there is a group on campus called the mathematicians excellent name I know so they're a group that I kind of use the stem ambassadorship for all my training with that and we are hoping to be able to go back into schools and do Outreach days I then have a Twitch account cat does maths where I kind of take everything that I've learned from my teaching and from my PhD and kind of shove it into the general like public audience and say hey look at this this isn't scary maths is actually quite cool I promise and this is how I originally met cat through Twitch in case you don't know twitch is a website where creators live stream and interact with a chat in real time original it was just used by creators playing video games but now has a community of streamers cooking playing role-playing games and studying we both do educational streams and both believe that twitch can be used to great effect in education such an untapped potential for Academia to kind of bridge the gap like showing my PhD research as I'm doing it it's not scary well it might look scary right now but it's not scary because you can see me sitting there and working through it and you can ask questions you can talk to academics and it removes this like stigma that Academia is this scary building filled with old white men that aren't going to do anything except glare at you you know like maths isn't blackboards and grumpy people there's a lot of that but it's not exclusively and yeah I think Twitches is beautiful like opportunity to actually have honest communication with people on what it's actually like to see how cat went about this I joined her for one of her streams so what are we doing here what stream are we doing okay so I call them maths office hours which is basically my attempt at um shoving as much maths into the public domain as possible so at the minute we've been going through past papers of AI romance one really nice comment I had once from a follower that was just they didn't understand it in school and they hated it in school after watching my stream they finally got it and they really appreciated it and I was like that's that's that's nice it's not just people with like math Stockholm syndrome no no hello there's two of us um can we rotate the screen yeah like I don't do what you like there we go just I'll just cut me off there we go [Music] foreign [Music] my face there we go that's just a bit better okay I fixed it um should we should we do something else oh yeah so the first one that we've got is given that Y is 2x squared minus 5x find dydx from first principles we want to find this gradient so whenever we want to find um alignment we do things we do rise over run so if we introduce the function at this point is f of x plus Delta X okay so that is then wherever there's an X here we now have an X Plus Delta X so that's going to be not plus equals two two times this is now representing our X so that goes in there so X Plus Delta x squared minus five lots of that so X Plus Delta x squared plus 2 x Delta X plus Delta x squared thank you for agreeing with me I can see you nodding yes correct every time we need to divide by something we're getting there and it's minus five would you like to continue so now basically we then have to subtract from this effectively you're taking this expression and assuming that Delta X is zero nearly but you need to subtract on the top fist no no that's what I mean but we're subtracting so effectively we're subtracting 2x squared minus 5x yes from this so that just leaves us with the terms that have the Delta X and I'm going to write it like this okay if you have to it does say find dydx so I'd Mark that wrong if I was marking this one so because you defined so if anything I'd say that's your fault why because you you substituted y for a f yeah so Y is a function of F so write that down anywhere did you what did I just highlight oh sorry this time when I'm defining this is the setup this is the maths this is the so we set d y d x formally to be the limit as X Delta x times zero f of x plus Delta x minus f of x over Delta X which in this case is 4X minus 5. goodbye please end the stream I'm ending it dang it that was chaos it's completely chaos but like it was really fun and like it's one of these things where like if people are enjoying themselves they look they stealth learn yes yeah yeah if it's full time like if say you know something miraculous happens and you know suddenly gain huge numbers of followers and it becomes viable as a full-time thing do you think you'd want to do this over Academia that's difficult because fundamentally I want to do both yeah it's like I feel like Outreach is so so so important and full-time science communicators and content creators are absolutely invaluable to getting people into it but then I also have this like bit of me that loves what I do within Academia but also feels like for representation wise it's all well and good saying you should do this but then I wouldn't be doing it myself yeah and like if I did ever give up Academia for something like this it's because this is easier and I can curate my environment much better and I feel like because I love my research and I love like teaching lecturing as well as messing around for hours on this I don't want to give that up for this and I want like I want to be one of the people when they're like oh you know I have three female lecturers this year like I want to be one of those yeah and I want to be like visible being myself but also in an academic environment because I feel like it's all well and good to promote change outside of it and encourage nude growth through life fundamentally that's how we're going to change the perception on Academia is by the new people coming into it being themselves and being different and being a diverse group of people but that's not good if then everyone leaves at the highest level because all you're left with that is the people have been around for ages so I I love this and I would want to do this at the very least more seriously part-time but I have always said I want to do Academia and Outreach as like a mix of both you're you're becoming the female lecturer that you had at undergraduate yes like a little bit because it was one lecturer can Inspire even if it's two students yeah it's worth it it's expanding the representation yeah definitely that's that's the goal at the very so some some University give me a job oh and in case you didn't pick up on it cat is Welsh and so one of the redeemable rewards on her twitch is well Invasion has redeemed um the Welsh name would you like to give it a go oh is this the full right someone get ready to clip this please what they're nailing uh yeah [Music] it's basically what I said perhaps unsurprisingly when cat and I got in front of a whiteboard we geeked out enormously and I got her to explain her work in way more detail than I could ever fit into a YouTube video if you'd like to see a bonus video of us talking through the equations in her work then that is available on nebula the educational streaming service that I co-own along with dozens of other creators here we upload the videos that we upload to Youtube but with extra content and without any advert at all no pre-roll ads and mid-roll ads no ads in the videos themselves it's just the thoughtful educational part of YouTube with creators like Ali abdal Lindsay Ellis and Jordan Harrod but with a better viewing experience for you you can download videos and watch them offline and by watching a Creator you directly financially support them and help them make more content you can get access by signing up with our partners curiosity stream who curate the finest library of documentaries on the internet such as the beautifully produced Butterfly Effect which includes an episode code on the history of fluid mechanics they have thousands of professionally produced documentaries available at your fingertips to complement the Indie produced content on nebula by signing up at curiositystream.com Simon Clark you get access to all these documentaries extra content from Indie creators like me on nebula and you also get an amazing 26 discount it works out at 14.79 a year or a little over one dollar a month for the version of YouTube that you probably already watch but better and with access to thousands of brain improving documentaries that's curiositystream.com Simon Clark with thanks to curiositystream and nebula for sponsoring this video a massive thank you to cat for being so generous with her time and allowing me to join her on her stream I had a great time making this video and I really hope that you enjoyed watching it if you'd like to see the previous videos in this PhD Story series then check out the playlist on screen right now along with another suggested video if you did enjoy the video please do pop it a like and if you're not subscribed then consider subscribing to find out when I release more in this series thank you for watching and I'll see you in the next one

Channel: Simon Clark

Views: 67,431

Keywords: drsimonclark, dr simon clark, simonoxfphys, simonoxphys, PhD, grad school, studying, PhD vlog

Id: 2hgG4ieFuKw

Length: 23min 47sec (1427 seconds)

Published: Wed Oct 27 2021