Welcome to session one of understanding containers. We're gonna be breaking down Docker, container technology in general, and how you can use it, how you can use it to run cool things, and how to get comfortable with it. We're gonna kind of jump right in because we have a lot of concepts to talk about in the first video, but I did want to mention before we get started that there is a blog post that will be linked in Discord that you should go check out that will describe some getting started things. We've got recommended stuff you should check out before this video, especially if you're unfamiliar with the command line, and also some getting started, make sure you have a reclaimed cloud account. And once you do have one of those accounts, we can give you credit for the course. Credit in reclaimed cloud so that you can run stuff during the course and beyond to get started. I'm gonna also kind of lay out a couple things for the course right here and say that we've kind of two main objectives. We really wanna make sure that you get some foundational understanding of what containers are and what Docker is and why they're used for hosting applications like this because that's a common thing that comes up of like, hey, why can't I do this in a lamp environment in shared hosting and domain of one's own? And the answer there is pretty simple of like, hey, sometimes applications require different software to run. And many times right away, containers is the answer of how do we make that software manageable? So we're gonna talk a lot about that throughout the series, but that's objective one is getting you some foundational understanding of what they are and why we use them. And the second one, a second major objective is just to get you in there trying some stuff. So we're gonna, throughout the next couple weeks, have you run a couple different applications alongside us, but I would also mention if there's applications that you are interested in running, especially as we get to the later weeks and you wanna try them out yourself and share how that's going in Discord or maybe get help or advice, please do that, this is what this is about is just trying to get some stuff running and working and talking about what we need to do as we go. So with that kind of preliminary stuff out of the way, I'm gonna pull in Jim here and he's gonna get us started with what are containers? What are we even talking about? Yeah, that's so you know that you're in trouble if I'm getting you started. So one of the things I've been obviously trying to think through and work through containers because I do think they're valuable for higher ed and I am excited about what they could mean. And I do wanna actually give me a second. I'm gonna just go to perfect and then watch this as a little trick. You can't do this necessarily with containers. This is not, you know, this is not included but this is beyond, this is the next workshop, ready? You can shrink yourself, right? And there is something to do with scale in containers and we will talk about that. But for right now, I will want to talk a little bit about what I think is so compelling about the world of containers. And it's not so much the technology although it definitely is that too, but it is the metaphor because when you think about containers, I don't know about you. The first thing I think about is this, shipping containers. I think about the shift probably in the 70s and 80s where you had a whole industry go through a radical shift in how they moved goods and services around the world. And in fact, books have been written about this phenomenon. For example, Mark Levinson wrote a book called The Box which talks explicitly about the shift in the 60s and 70s that took shipping into a whole new era of kind of efficiency, global networks, et cetera. And there were a couple of points he made that I think are interesting. And amongst them and probably the most important was the broad standardization of a shipping container. That means they were all essentially the same size. They all essentially had the same hookups and they worked across a vast amount of kind of infrastructure. That would be everything from cranes to high lows to ships to wagons to trains to trucks. They worked across all of that infrastructure for transport and hence made it far more next point flexible, right? You could run and put them anywhere but also ship just about anything you wanted whether it's services, goods, commodities, refrigerated stuff, it was a kind of predefined space that you could fill with what you wanted, right? And by that nature, it had this economy of scale where you could do things cheaper. Because you had the infrastructure already built, it was more efficient, it was faster, it excluded a certain amount of labor. The stevedores that traditionally would load and unload these infrastructural containers were no longer needed. So it changed the whole very logic of labor and transportation. And finally, a big thing about shipping containers is you couldn't really get inside of them. So the people who would go and pack and unpack didn't actually access the container. It was accessed on the back end by the person who was receiving it. And what this meant was you had far less loss, spillage and theft. So in many ways it was a lot more secure. Now that's a kind of interesting shift. It took decades for this shift to be realized but by the 80s and 90s, pretty much all global shipping was happening via containers. But what does that have to do with doctor containers? Well, I think everything, because Docker understood that shift in the 60s and 70s with shipping containers and actually used it as a metaphor for us to understand the shift that's happening in server infrastructure for probably the last decade now. And so one of the things that I'm kind of really compelled by is the container itself, like the shipping container is a lightweight predefined package for an application. Basically ship whatever you want within it. And so I think this kind of definition helps you metaphorically understand that what we talked about with standardization for the shipping container is actually also standardization that it would run across various operating systems, Windows, Mac, Linux, you name it, flexible. Pretty much you can run any application you want within a container. It doesn't really care, right? And that makes for the brave new world of there's so much to do, what do I do? The other thing is costs. And with every advantage, there's always a disadvantage, but containers by the way in which they work more efficiently on the server allow for it potentially to be cheaper to scale bigger. Whether it's always cheaper to run an application in a container versus on a lamp stack or something else is certainly a question that will come up and it's not always one to one, but in general to scale an application larger, it's cheaper. And finally security. The idea of a container for a server infrastructure is that it's isolated, it's containerized, right? And so by that logic, it protects itself from potentially a malware or some sort of breach affecting other containers on that same server. So in some ways, just like with the shipping container the actual server container is safer because of that isolation and because it's locked down usually to a single application. So hopefully my metaphor didn't break down too much but I think that for me is what got me fascinated about containers was the way in which Docker which didn't invent the container but I think in some ways they brought the idea of the container to a broader public into a broader server admin audience by understanding it in relationship to a historical move of shipping containers and what that meant for infrastructure and deploying and shipping not only goods but now applications. So I hope that worked. Taylor, back to you. Sorry, yeah, that was messing up my video stuff here. Yeah, I really love that metaphor too because unlike honestly a lot of tech metaphors it has a lot of valid levels to it, right? Like in one of the things you said early on was that there's a standardized outside. Well, obviously the implication to that is that the inside is not standardized, right? Because you can put whatever you want into it and so that is exactly what we're doing. That is exactly not only what we're doing with containers but that's the problem we're trying to solve is by saying, hey, applications on servers nowadays can be almost anything, right? Dependency and language and whatever wise. So in order to make this manageable at all we have to take that infinite possibility and wrap it in something that's standardized on the outside. So, absolutely. And the other thing, no, the labor at the point but I love it, so. Your point is well taken and I think the other point there is Mark Levinson's book came out in 2006. We released in 2016 and again that was to explain the phenomenon of global shipping but I think in some ways why we're doing this course and why we're excited about Reclaim Cloud is we're trying to help folks wrap their head around the phenomenon that's happening with containerization of applications and what that means more broadly. So there is a one to one but it usually takes decades for us to fully understand that shift unless you're at the cutting edge of implementing it. So I really think that's another primary objective like Taylor you pointed out at the beginning. So I'm excited about that just for myself because I'm still trying to wrap my head fully around this to teach more people more about containers. Awesome. Yeah, so I kind of want to shift gears here a little bit and talk about Reclaim Cloud and the interface of Reclaim Cloud a little bit just to get everyone kind of situated and comfy in their cloud, in their cloud living room, let's call it but a couple of things, like I said earlier there is a post up on ReclaimEd.tech and LinkedIn Discord as well that outlies a few things. We want to make sure you have a cloud account ready to go ahead of time but let me kind of walk you through a few things here. Anytime we're accessing Reclaim Cloud we can go right to Reclaim.Cloud that's the URL and there's of course the login button at the top right so that'll get you set up. And I did want to mention as you're using Reclaim Cloud and other things like this main landing page is worth a look. Some of the container stuff we're talking about is here there's some pricing information that breaks down scaling and all that kind of stuff. And if you have questions about that you can always throw that in the Discord but there's a lot of good stuff here that I would also recommend checking out. So once you get logged in and I'm already logged in of course but once you get logged in you will have something like this. So if you already had an account and you are already running things you may have stuff listed in here. I mean an environment group here to kind of have it be a fresh start like is likely for you is it where you're set up at but yeah so a few things that you'll need to know the right away. In this interface there is there is kind of a few main buttons here at the top left. There is import which lets you like import installer scripts for Reclaim Cloud we're probably not gonna use that it's more of an advanced option. New environment is for creating environments from scratch that are honestly more for developer folks who want to like hey I need a bare Python environment so that I can run my Python app. We are gonna do almost everything in the marketplace and honestly that's how most of the time how things go. So if I click on the marketplace here there's categories of preconfigured applications and server setups and things like that but you're gonna wanna go right to Dev and Admin tools and in the list should be Docker engine CE and you can click the little star button to favorite that and then it'll show up in your favorites category. I would recommend doing that because we're gonna be using this container quite a bit to run stuff in Docker. The basically what this will do is this will give us an environment in Reclaim Cloud that has Docker set up and ready to use so you don't have to install Docker and Docker compose things on your own. So if you go into your marketplace and now we'll hit install on that it's gonna ask what version of Docker. This is the latest version that's available in Reclaim Cloud right now so we can just leave that. All of these options we're not gonna need. So the main things we'll wanna look at is the environment, display name and region. For environments, this will affect the URL that you can view your applications you're running at. Basically one nice cool thing that Reclaim Cloud does for you is you get before you even map a domain name to anything you get a URL through what's called the shared load balancer that you can use to view your application and this is super nice because it allows you to give nice names of things and not have to worry about IP addresses. So you can name this whatever you want. It is not something that you can change after you've deployed, excuse me, after you've deployed a environment in Reclaim Cloud. The only way to change it is to clone it. So and that's pretty easy to do but generally you wanna give this some name that you can reuse. Sometimes I'm honestly if I'm gonna be mapping a domain to something anyway, I honestly just leave the automatically generated name. It kind of doesn't matter but in my case, I'm gonna call this Docker test and it looks like that's already used. So I'm gonna name it Docker test three. Oh my gosh, that's already used too. How about Docker test 100? Maybe test is not allowed in there. Docker Taylor, great. Then display name. Yeah, the pressure's on, you know. The display name. This is really just for you. This doesn't matter. This can be changed at any time. This will, I'll show you what this looks like but I'm just gonna call this Docker Taylor test. Test is fine in there. And then finally the region. There's several regions in Reclaim Cloud to be perfectly honest, unless you are doing something that is scaling across multiple regions for like high availability or you're doing something that's extremely latency sensitive, you're gonna be fine with any of these regions for just about any web application in my experience. But we are gonna avoid US East right now and that's simply because at the time of this recording we're dealing with a low availability of IP addresses and we're getting that worked out with some of our vendors but basically there's a good chance that if you, if we all in this course deploy to the US East data center and request an IP address for our environments which is what this will do, we may be out. So I'm gonna advise, let's just use US West. We can all standardize on that. Like I said, it's really not going to matter for whatever purposes we need here but yeah, that'll make things easier. So finally I'm gonna hit install and that will get it going. So basically it's setting a container up for us and it's installing Docker inside of that container and getting things ready. So I'm gonna click this little arrow button and that will send this down to the bottom right and I can close my marketplace. That's gonna keep running even if I closed this tab it's gonna keep doing its thing in the background. So while this is going, I'm gonna take a chance to just mention a few other options here that you should know about. So there's the balance button in the top right of Reclaim Cloud. This button will, it should make this stuff a little bit bigger. This button will allow you to do things with your account, put credit on it or set up automatic billing. There's, if you are just started with the Reclaim Cloud account there'll be an upgrade button in here that lets you add a payment method. If you have that upgrade button in Reclaim Cloud that means you're in trial mode so you're gonna wanna get out of that because after two weeks trials are over so we don't want you to have your environment stop working for you at that point. So, but this balance screen is really cool. There's some shortcuts to information on quotas like how much does do things cost by unit of compute or cloud lit is what those are called in Reclaim Cloud. Like I said, you can mess with payment methods, you can view billing history. All kinds of stuff is available in there. Again, I'm not gonna go super far into it but I just wanna mention that that's where that stuff is and if you have questions, definitely feel free to ask. We can discuss that in the Discord. The other thing is this settings tab. So you won't need to be in here a lot but there are a couple of things I wanted to mention while we're waiting on our Docker engine to deploy here. So the first one is SSH keys. We're gonna do everything in Reclaim Cloud for this workshop all in the web interface. And you can do pretty much anything you'd ever wanna do all in the web interface but I wanted to mention that if you are a person who likes to use a local terminal, you can connect to Reclaim Cloud using that local terminal. You just need to generate a public private key and you would add it in here. And the other function in here I wanted to mention is sharing. Environments in Reclaim Cloud can be shared kind of like Google Docs. So you can put in the email address of someone who has a Reclaim Cloud account and they will get access to your environment and then you can manage what level of access they have. Do they have access to the file system and SSH or just to see things and billing? So that's one kind of really cool thing about Reclaim Cloud. Again, I'm not gonna go into all that right now. Just know that you can do that. You can even change ownership so you can take an environment you've built and move it to somebody else after the fact. So all of that's really cool and that kind of stuff can happen right in this settings panel. All right, so the environment Docker-Taylor test is here, this little icon here and this little green with blue squares. That's the environment in Reclaim Cloud for, sorry, that's the icon for a environment. There's a lot of drop-down stuff happening in Reclaim Cloud. So it's good to point this stuff out because it's easy to miss things. So first of all, you can take an environment and collapse it and these nodes and nodes in Reclaim Cloud are the individual containers that make up an environment. So in a lot of cases, we may have more than one node. So basically more than one container doing different things in one environment. A good example is sometimes you may have a large application that has a container that's running the application and another one that's doing the database and another one that's handling load balancing to do HTTPS and stuff. And you might say, why would you do that in multiple containers? Well, sometimes that's the way application is written. It wants it to be that way, the developer intended it that way. Sometimes it's a way to manage scale for really high traffic things. But in our case right now, we just have one node, my Docker engine node, inside this one environment. So I can also do more drop-down stuff in here. You'll notice that there's this node ID. And if I click on that, this is where you can find the IP addresses for your environment. This is really handy, especially if you wanna map domains later on. We'll do a whole session that includes that, but I just wanted to mention here that whenever you see an arrow pointed to the right, you may want to reveal it. That's like an old like 90s UI term, like reveal disclosure triangle. Is that what it's called? Yeah, all this needs is, I think someone, do they call them frames? And it's perfect. Yeah, it all needs to be HTML frames with the blink tag. But okay, so there's a couple of things. And again, to point out the difference between environments and nodes, you'll notice as I'm hovering over stuff, different buttons show up and they apply differently if I'm on a node or an environment. So in an environment, there's a few different buttons here, but the big one you're gonna want to know about right away is this change environment topology. When I click on that, you get a window that lets you adjust the scaling of a environment. So this is essentially how much resources an environment is allowed to request and use. So right now, our environment's use is allowed to use up to four gigabytes of RAM and 12.8 gigahertz of CPU. That's kind of a weird number because it's actually multiple cores in a CPU, but it's running all the numbers together. So, but the reason it does it this way is this matches up more closely with billing with how that works. You get some estimated costs over here and you can view it by hourly or monthly. Again, we can talk about that, but note that this $80 number is only if it was using all of the resources it had available to it every second of the month, which is basically never the case for anything you're gonna run in Refinem Cloud. I don't wanna say never. I'm sure there's some things that will do that, but that's very, very uncommon. You can change how much disk speed space you're allowed to use or an environment, sorry, an environment is allowed to use it or in the individual node, you can allow it to have an IP address or not. IP addresses do cost money. A lot of the, for most of the stuff we're gonna be doing in Docker, we are gonna need an IP address. So, that's gonna be on by default, so. And yeah, and we'll do more with this screen later on in terms of adding more nodes to the environment, but wanted you to be able to see that this is the environment topology and any changes you make in here, you can then apply or cancel. I didn't change anything, so I'm just gonna cancel. You can also stop an environment from here and that will stop everything. You do not get billed for the RAM and CPU of a container when it's not running. You can delete things from here. You can clone them, so this is a great way to make a backup. If you've got an application that's running and it's doing well and you wanna test like upgrading it, this simple is just cloning this, running the upgrade, and if that works well, doing it on the production one and the same thing on the production one and you're ready to go, or maybe even swapping the domain over to the new one. So, that's because we're doing this in containers, that's like dead simple to do. There's also settings for the entire environment. We're not gonna get real far into this right now, but just to mention that the environment has a settings panel as well.  I agree. But this one's a yellow icon and that one's a gray icon. But you're not bitter. You agree but you're not bitter, right? Yeah, it's a tricky thing and if I was designing this myself, I'd probably make all kinds of other mistakes but this is something I think I would make the right choice on and I would name them differently, but whatever. All right, so now into an individual node. Some nodes have add-ons that allow you to add simple FTP access and schedule the starting and stopping environment or maybe do automatic HTTPS for you, something we'll talk about later. You can restart a node. There's a log viewer, there's redeploy. You really wanna be careful because redeploy is essentially re-downloading container and putting it in place. So depending on how you have things set up, that may overwrite files for you and we'll talk about what that would or would not do for the thing but just be careful about that option. There's a bunch of other more advanced stuff in here, some of which we will get into later but ones that you'll need right away first is the config panel. So config allows you to browse the file system of a Reclaim Cloud node. So right now I'm at the root here. If I go click on this top here and I can go into maybe the root folder, the root users folder, I can use this little thing to make new files or folders. You can edit stuff within here. So now I'm editing text and you can save it. It's a little file manager. You can download stuff and upload stuff from here although you're limited in size. I can't remember off the top of my head what the limit is. I wanna say it's like 10 or 20 megabytes. It's not real huge. Yeah, it's not very big. If you're doing things like video, you will probably wanna use SFTP to do that. And again, I can link to instructions on how you do that. If anyone needs to do that, you won't really need to do that for this workshop. Because we're gonna be dealing with texts, all texts. So, all right, so that's the file manager. And then this one, we're gonna be doing a lot in here, the web SSH panel. So if I click on that on a node that gives us a terminal session inside of the container that we clicked on. Again, it's really important that you're opening a terminal for a node, right? An individual container. Later on we'll be doing things where we have an environment that may have more than one node. So it's really important that you know what terminal you're in. The cool thing is it does label them. So right here it says engine node. Yep, that's the name right there. If I was to change this name, and you can change the name, it would reflect that name change when I opened a new terminal. So, yeah, so the web SSH gives you a terminal.  We're gonna be using this to do various things with Docker and stuff like that. But just to quick demo before we get out of Reclaim Cloud and kind of wrap up the session pretty soon here. I'm gonna run a quick command in this terminal. I mentioned before that this container comes with Docker pre-installed. That's the advantage of it. So we'll just use the Docker's own Hello World container. Real quick, and this will pull down the container and run probably one of the smallest container programs that we will run. So there we go. Docker works. So we'll do a lot more with this in upcoming sessions, but I would recommend for next week's session getting logged in, deploying a Docker engine container like I did and running Docker run Hello World just to make sure that you got everything right. And if you have any questions with that, let me know. When you're done with that, you can either shut this environment down or delete it if you want to because we'll start a new one fresh next time. But yeah, that'll be a good test. It's not real exciting, but I don't know. It's exciting to me. We're emerging on a journey. So... Oh, it's exciting, Taylor. Let's not miss that. It's very exciting. And you did a very good overview of what they need for Reclaim Cloud to get up and running because one of the things, it's kind of almost the logic will start to get a little tricky in some ways, but like all of Reclaim Cloud is containers. Every node is a container and the environments are made up of containers, as you said, Taylor. And so like it's a completely containerized environment. So getting a kind of account there gives you an interface like for you to start playing with applications and getting your hands dirty. So that would be step one. So I really like that we started there. The last thing I want to do here is quickly run through our glossary. So we are going to have a glossary for the course that we'll be posting to Reclaim EdTech. I've got it here as some slides, but I think we'll list it out as a better format like on the actual webpage. I'm just going to go through a couple of terms in it that are relevant for today. There's already more stuff in the glossary and we'll be adding to it as it goes on. But I want you to be aware of it. If you want to peek at what's ahead, you could look at future terms in the glossary. But yeah, so we're going to be adding to this. It'll be hopefully a really helpful resource for you because so much of this stuff is really terminology heavy. So here is our glossary here. The first one is containers. We've been talking a lot about containers. We've been talking about containers the whole time. But one thing I wanted to make a distinction of is that, yes, there are containers in Reclaim Cloud and then Docker containers are also containers. So we're talking about running containers inside of containers. This can get really confusing really fast if we don't set some context and ground rules. Reclaim Cloud. So these are containers that you can deploy. They're customizable. They're always Linux based application containers. You can get root access to these containers. You can install whatever software. It's very similar to using a virtual machine. If you have done that maybe in a different cloud or something like that, you have the same type of access basically as a virtual machine. You can install software. You can treat it like any Linux server if you've worked with Linux servers before. One of the things you can do in them is run Docker engine. And that's what we're gonna be doing. Docker containers. These are containers that are built by developers. Often the developer of whatever application you are trying to run, but not always. Sometimes someone will develop an application and then get someone else or someone else will take it upon themselves to containerize the application. That way it's easier for others to run. So these are built by developers to run a specific thing. That you can technically install software in them if you know what you're doing, but you never would want to because one of the things that happens with containers is when they update any changes you make to the base application container, get overwritten. And we'll talk more about, okay, what does that mean for my data and stuff in future sessions? But typically you're not making major customizations inside of these containers, unlike Reklind Cloud ones. These containers can be run on your local computer technically. If you wanted to, you could install Docker desktop and try containers out, although some networking stuff gets tricky. And I think we'll touch on that at a certain point. Probably next week already. But that is technically possible. We are gonna focus on running them in Reklind Cloud because that gives everyone the same environments. Not everyone's gonna have the ability even install Docker on their machine, depending on how locked down their machine is and if it's owned by a corporate or education IT. Sometimes that won't be an option. So we're gonna do this all in Reklind Cloud and it also makes a lot of the networking stuff very simple. But yeah, you can run these Docker containers on a computer or anywhere you can install the Docker engine like a Reklind Cloud container. Some Reklind Cloud specific terminology. Environment and node. I already talked about this a little bit, but environments are groups of containers. So in this case down here, I've got a container called hedge or an environment called HedgeDoc. And it has two nodes in it. In my earlier thing, my environment was called Docker Taylor Test, right? So these can have multiple containers in them. A node is a single container in Reklind Cloud. In some cases, you may need more than one node, like I said, in the environment. So it's important to know the distinction. When you're doing things like changing editing files using the config panel or the web SSH terminal, you're doing that in a node. You're doing that in an individual container. From now on, I'm gonna do my best to only refer to them as nodes, which is what Reklind Cloud calls them. That way we can try to avoid confusion between the word container and reference to Docker containers and container and reference to Reklind Cloud nodes. I'm surely going to mess this up. Like that is gonna happen, but I'm gonna try to make sure that I use the word node just to make sure that that distinction is clear. But yeah, long story short, environment, bunch of containers, node, single container, an environment contains many nodes, potentially. And then the final thing for Glossary this week, and this is a bad Glossary, right? Because Glossary should have the word at the top and in my case, I haven't done that, but whatever, is the concept of pulling a container. And I mentioned this, we did this. When I did the Hello World, we technically pulled down a container from a registry and ran it. So you will see a Docker pull command someplace on the web, and that's what this is referring to is pulling a container. So you're getting a preconfigured application container from a registry, and it also allows you to update that container. So you can pull new versions and you get new versions of the application. Lastly here, I think I said three slides and I totally lied, we're gonna do four, but I want to allude to Docker Hub. So you might have said in the last slide, well, what's a container registry? And that's just simply a place where people upload containers for others to use. And Docker Hub is the main one. It's the default one in Docker. It's the one we're gonna be using all the time. To be perfectly honest, I'm not even aware of other container registries. I know they exist, but I haven't used them, is my point. So this is the one we're gonna be using. We'll explore in the next session a little bit around Docker Hub and what's there and what you wanna look at when you're evaluating containers. But that's your teaser, basically, because good teaching needs cliff hangers, right? Is that, that's a thing, right? Or no? I think so, no, you're right. Tune in next week for, but I really like the idea of your glossary. I'm loving that and I'm loving seeing that get built over time as we do this class because it's really useful to go back and find those tools. And I like that you're kind of using it as like a cultural, almost phraseology, like pulling a container, like where you have it in quotes and giving people a kind of definition for the concepts they're gonna hear. So it's very much a conceptual work through with some of the things that are gonna be new because that's really what we're gearing this towards.  And so this means getting up and running with Reclaim Clouds to have a place to work, working through some of the very basic ideas that have been talked about in the glossary, reading the post for week one so that you can kind of play with that. And then like Taylor said, reaching out to us in Discord, we'll have a channel there and we'll be interacting with you, questions, concepts we wanna build out from this weekend. So, and also keep tuned if we do any live events or share stuff we're doing with Docker on the fly, that will happen there or elsewhere in Discord as well. So stay tuned.


warriors and welcome back to my channel. And yes, this background is very different than normal. I am back at home with my family. I'm not living back in my old room, but that's currently where I am at this moment.  I do want to first say that it was a very hard decision for us to make, was to decide whether or not we were going home. The only reason, well the reason that we did choose to go home was because Brennan was able to get all of work off from the week before Thanksgiving, all the way until the middle of January. And so we are here for more than two months. So we've been here for more than two months. We got tested before and after we traveled. Both tests came back negative, but then when we got home we wore masks around everyone and we kept our social distance. And actually we spent Thanksgiving in a completely different room than the rest of my family in order to keep safety and distance. So I just want to put that out there as like, I am still taking this seriously. I do, I still kind of feel a little bad about traveling because I know we're not supposed to. Yeah it's just kind of what happened and so we're gonna be here until like I said a little over halfway through January. And then we'll go back to our lonely isolated apartment. Anyway, now for the point in this video.  I can't do much about it. But I'm making this video because it is a super exciting video and I'm making it at home because it just came out. So Ariana from The Enchanted Reader tagged me in one of her new original tags that she had just released and I was like oh my word I really want to do this. So I, now here I am in a random like room of our house. I don't have very many books with me but I'm going to do this tag and this tag is the Wonder Book Tag. And this is a tag that she created based off of the new Shawn Mendes album that recently came out and so for every song there will be a question. She tagged me to do it and I'm so honored that she tagged me. And so I'm really excited to do it. And yeah so with that I'm just gonna get right into the video then. So the first book is for the song Wonder, obviously, a book you can't stop thinking about and the book I chose for this was called We Were Liars by E. Lockhart and this book I read forever ago I think as a freshman in high school which was five, six, six and a half years ago. Oh geez six and a half years ago I was a freshman in high school. And so I read it based off of a recommendation of a classmate who I didn't know very well but we were in a writing class together and so I trusted her opinion and it just always was a book that stuck with me because it was the first time for me reading like a non fantasy book that was not required by school because I just did not read a lot of contemporary. I didn't read a lot of realistic fiction like I just know. So basically there was this, there's this family and like I said it was six and a half years ago so it's been a while since I read it but it's about this family who goes on vacation over the summer to like their family home. Some huge event happened like a year or two ago or a couple years ago and the main character kind of doesn't remember it or like has suppressed the memories or something like that and so she goes back with family vacation and endures a bunch of family drama to try and figure out or try to remember what happened, what did she do, what did her friends do, there was something about a fire like I don't know. I barely remember it and I'm pretty sure the character didn't remember it so it would be perfect for me to reread the story especially since I'm pretty sure I like didn't even understand what was going on at the time. It's a book that I always think about because it was such like like I said it was the first non-school required non-fantasy or sci-fi book that I read so it was like a really big deal for me and every time I see it I'm like oh my word that just triggered so many emotions for me I want to read it again and so I just I'm constantly I always get drawn back to it and I've never done anything but I definitely want to buy it and read it again I just I'm also a little afraid to do so. The next song is Hire a sequel that was better than the original. This is a really good one because I so the sequel I chose for this was Thunderhead by Neil Shusterman it's the second book in the Scythe trilogy. The thing is is that I always almost always believe that the first book is always the best book in any kind of series trilogy duology I just I always love the first book because there's so much world-building and explaining that has to happen and that's what I enjoy I enjoy that creativity but I do think that Thunderhead was a really good sequel if not better than the first one because it not only continues on the plot from the first book and it keeps with the characters it also adds in a bunch of new elements to the story adds in new characters and the plot just really takes off in the second one so while I do believe the first one is obviously necessary to be introduced to the story I do think the second one is where the major plot of the trilogy does pick up and like I said you they mentioned like the Thunderhead in the first book but it's not as much of a thing as it is in the second book so it's almost like a new element that was added without it without it being strictly new so I really do think that the Thunderhead was probably better than Scythe if not on the same level at the very least which is not something I always believe in books. The third one is 24 hours a book that you can read in 24 hours and there are quite a few books that I can read in 24 hours as I've done many or readathons or you know even 24 hour readathons so the book I am choosing for this is Once Upon a Time and it's a Disney Twisted Tale I believe it is by Liz Braswell and the thing is is that I could theoretically say any twisted tale book because I feel like all of them are ones that I could read within 24 hours no matter on like the length like some of them are longer than the others but they're all a very similar like easy to understand writing like I don't know if it's quite middle grade but it almost could be just in terms of the style of the writing of both Liz Braswell and Jen Calanetta books because they are two authors that are taking turns kind of like writing the twisted tales so I'm just saying Once Upon a Dream because that's the one that I did read in 24 hours but I think that any Disney Twisted Tale would be one that I could if I just sat down and read it it could happen moving on to the next song is Teach Me How to Love and this is a book with a steamy romance now I do not read a lot of romance I've said this so many times on my channel I'm just not a big romance person per se but I did go with a book for this question and I decided to go with the kiss cushion by Helen Huang this book I read last February when I was attempting to read romance and I chose this one because like yes it's steamy but not necessarily for the sake of things it's a theme in the book it's not just events it's of this girl who asks burgers it's this girl who is not comfortable with touch and so she has been having a hard time finding a life partner because of the sexual aspect of having a relationship she has a hard time with people touching her in that way and so she decides to go out and hire a male escort to help her figure it out and it's so it's steamy but not in the sake for being steamy like there's a whole story there's like a reason for it and that's like the only reason I would ever want to read a steamy book there's just not my preference it's not my type yeah so that's what I chose and this next one is based off the song Call My Friends and is what is your best friend's favorite book now this is an interesting one because not a lot of my friends read and the ones that do they don't read a lot so I decided to go with Brennan who is technically my husband but he really is like my best friend like actually and the thing is is that he has a very different reading taste than I do and he said it's his favorite is a hundred years of solitude he read it for school but it was a project that he could choose and he just he always talks about it he loves it he was he ever since that book he's like I want to read more magical realism and I'm like okay have fun I'm good so his favorite book is a hundred years of solitude and that is by Gabrielle Garcia Marquez so fun right next one is dream a book with a long-distance relationship now there are two books that I debated on going with for this prompts because one of them is like a romantic relationship and it's red white and royal blue by Casey McQuiston and I debated on not going with this one because I talk about it so much on my channel because it was the one romance I thoroughly enjoyed like I loved it completely and so like that's one that would fit the prompt but I've talked about it so much so I'm gonna go with another one that fits the prompt but not quite in the same way so I decided to go with snow flower and the secret fan and this is by Lisa see this book takes place it's a fictional book of back in ancient China and so the long-distance relationship is not a romantic relationship it's a best friend and so because it's ancient China women's lives look very different than how they do now and so this girl who never really gets to leave her house you know her duties are to cook clean be like the woman of the house she gets paired by a matchmaker not only to a husband but also to allow Tom her best I'm a best friend so it's someone who's very similar to her that would get along well with her and they are set up to be best friends but she lives in a different city and then when they both end up getting married off they continue to live in different cities and so the book it's more so about her friendship with her allow Tom over the course of both of their lives so it starts very early when they are going through footbinding to getting matched with the allow Tom to getting matched with the husband to getting married to having children like it's an entire lifetime but it's a very small book and so that's the one that I really wanted to choose for this prompt because it is a long-distance relationship but not in the way that the prompt they suggest sorry but it's just a book that I want to talk about more because it was it was so good then the next one is song for no one a character breakup that destroyed you I struggled with this one so hard because in most of the books I've read there haven't really been much of like a breakup it's always characters getting together there's never really like a breakup or a long lasting breakup and so I don't really remember a lot of character breakups and a lot of them did not affect me in the way I think the author intended so the book I chose for this one is like it fits the prompt but I chose an absolutely remarkable thing by Hank Green the main character is dating a girl it is a same-sex relationship and she breaks up with her at some point in the book and I was like okay it didn't affect me that much but it honestly was a book that had a breakup in it that was like okay that was a main thing that happened in the book moving on so alrighty then we have monster your favorite villain oh good question I never have the answer that I want so like when I'm like oh there are so many good villains out there and then I never remember who they are what they are like I'm so bad at remembering villains unless I just read them so there are plenty of really good villains but for this one I chose the house of sultan sorrow and I'm not gonna talk too much about the villain just because that is a standalone book it's a 12 dancing princesses retelling but I think I don't know if it's necessarily a villain per se but just like the cause of the trouble was so cool so creepy I loved it so while there are probably so many other amazing villains and books that I loved would probably fit this prompt better I just can't think of them so I'm going with the ending of house of sultan sorrow by Erin a Craig just just go read it then you'll understand 305 an unexpected romance between characters now the book I've chosen for this takes me back so long ago way back when I read the mortal instrument series I know I never talk about the mortal instrument series that's because I don't remember majority of the mortal instrument series I read it in middle school and the other problem is that I read the series right as like one of the last books or so was like coming out to complete the first series that Cassandra claire wrote and I sat down one week in the summer and I read the entire series over the span of a week I just sat there and I read that book because you know it was middle school I didn't have summer homework and I didn't have anything better to do with my time because what are friends right what's a social life for a middle schooler so I sat down and I read it and I did not predict and if you haven't read the more mortal instrument series spoiler the relationship between Alec and Magnus I I love it I love that it happened but I just didn't see it coming again I was in middle school so I never saw anything coming but yeah so forever ago when I read mortal instruments that happened and I was like this is very interesting video I just it's so hard filming in this room because it's like echoey and plain because no one is living in this room but there was also no good spot to film so I'm just kind of like the next prompt has always been you and that is a couple that is endgame slash your fictional ultimate OPT OTP couples alike the ultimate couple and for this one I chose Jude and Cardin from the airfolk trilogy I know I know it took me I was when I read that trilogy and I have read all three and I'm gonna try and keep this spoiler free but when I was reading the books like even the first one the second one I was like no there's no way I'm supporting Jude and Cardin no I refuse I'm not hopping on that boat no I refuse I refuse and then all of a sudden I read the Queen of Nothing and I was like oh my gosh Jude and Cardin oh my heart it has to happen it must be and I just completely flipped my my opinion just absolutely 180 turn around just like Jude and Cardin yes please and I haven't even read any of the extra books outside of the trilogy well I've read I've read one I read the Lost Sisters but that was in between books one and two but I haven't read any of the airfolk books that are like Cardin's background or his stories reason why he is where he is I haven't read those yet and I want to but I get the feeling once I read those I'm gonna be even more like oh I want Jude and Cardin and mmm but like for the longest time I was refusing to hop on that train and now I'm like so then the next front is a piece of you a book you would never lend out this one's a hard one because I actually love lending my books out the problem is no one ever wants don't let my books out to people because no one ever like asks me for them and there have been so many times I'm like you should read this book I have it do you want to borrow it and people are like maybe and then they never do but I will share a time when I did lend a book to my husband and he destroyed it and I was so mad at him I got so mad because he dog-heared like every other page every couple of pages it was just dog-eared it was flapped it was oh I got so mad at him for doing that and so I I really hate for him to borrow my books but I also want him to read so I still let him but we have now had a talk of how to treat books especially books that are not your own because like seriously who takes someone else's book and then just destroys every single corner in the book who does that seriously people so I am perfectly fine with lending out my books to people as long as they know to like respect the book respect me in my books but to choose a book for this prompt I would probably say spend the dawn just because the copy that I have is a soft cover and I got it on our honeymoon so it's like special to me so that's probably a one why wouldn't I prefer not to lend it out but I don't feel very strongly like this specific book must never leave my sight or you know none of my books can be lent out it's just yeah that's fine already we are almost to the end we've got look up at the stars a book set in another planet slash in another world and for this one I am choosing vintage which is the first book in a trilogy I read it for my class and I really I loved it for a couple of reasons one it is based off of a different world and it's very creative but to it's like a huge commentary on society even though it's like sci-fi it's really cool because it's about this girl who is from an African tribe and they cover themselves in the red dust of the earth and she really wants to leave and go to this prestigious Academy but her community is like no that's not how we roll what are you doing but then she ends up getting accepted into the Academy and so she goes and she is the only person like her who goes to this Academy in space and it's about her facing like keeping her own traditions facing who is she like why is she doing what she's doing and it's just really but then also the commentary of how other people treat her when they see someone who's different than they are did they treat her nice do they put her down and it was just it was a really good book and I think a lot of people should read it and it's also like very short so it's really like there's no excuse for you not to read it I haven't read the rest of the trilogy for it yet but I really want to so yeah based in another planet is binti but it's based off of our planet then the last song slash prompt for this tag is can't imagine a book you can't live without and this is a really good prompt um so the book that I have chosen it's another first book in a trilogy and that would actually be in cart I own this book on my Kindle because it's a book that I love to read when traveling and it's one of those rare books that I will read over and over again without like being annoyed or hating it and it's always one of those books that when I'm going through a slump will encourage me to read because the book itself is based off of books and stories it's about this girl who lives with her dad in Europe and her dad is a bookbinder but little does she know that her dad has a special gift he is a silver tongue meaning that when he reads aloud he reads things out of the book characters objects you know if he sits there and reads a paragraph about it it's coming out however that also means that something goes in and so that is exactly how Maggie and her father lost their mother is he accidentally read out a villain of a book when he was reading a story to his family and the wife went in so sad so tragic but that villain that he read out is now causing horror to the world and the and the father has to set things right and so he and some other book characters have to take down this evil and figure out how to send him back into the book considering he has no idea how to target who goes into the book obviously if he knew how to do it his wife wouldn't have gone in the book but yeah so I don't think I could live without ink heart it's a book that I listen to with my mom and then it's a book that I take with me everywhere when I travel and I read it all the time so well that was the wonder book tag thank you so much for an enchanted reader for tagging me to do this I had so much fun sitting there and like puzzling over the prompts like oh I have so many good books for this or I know absolutely nothing and so it was really fun to come up with this list of books to talk about so I cannot thank her enough for tagging me to do this and but with that let me know in the comments below what any of your answers to this tag would be also if you're interested in it the original video will be down below as well as a link to enchanted readers channel just in general so you can check out more of her videos because she makes some pretty awesome videos and she's made quite a few tags in the last couple of weeks based off of music that was coming out and I think that's just so cool how she is incorporating music and books because sometimes for some people so go hand in hand and for some people they don't and so yeah definitely check her out also feel free to subscribe to my channel if you're new here I will be posting videos every Thursday feel free to give this video a thumbs up comment down below anything you want answers to this tag questions explanations your favorite book I don't know feel free to go ahead do what you like and with that I will leave you guys wishing you all a happy reading


Good afternoon everybody. I've been running so much for the last three days that I haven't had a chance to say hello and Haven't had a chance to hear all of the wonderful things that The solution winners have brought but I have read about the individual projects And I will get further briefed in the next couple of days by having the chance to be with you We're moving it for me my calendar is now moving into the SDSN phase because it's been the General Assembly And going back and forth to the UN and We're on the west side and they're on the east side and so it's been a lot of transport In in the last three days. Let me just say a little bit about what I've seen during the General Assembly basically Global society Global academia, that's a lot of us and global business is way ahead of the politicians in general and Maybe I got the worst dose of politicians in the morning Yesterday because the General Assembly opened with two of the worst politicians on the planet both scenario first Who gave a perfectly awful talk? and then If you can imagine worse we have a Trump Who gave an even worse talk? Although I have a sneaking suspicion that both talks were written by the same person actually And I think that that may literally be true because there were certain nasty themes that permeated both speeches about national sovereignty and nations and Anti-globalism and a bunch of nonsense But the day ended well with the opening of impeachment proceedings against President Trump Which he richly deserved for that awful speech that he gave and I Felt pretty good about that and what I've also felt quite good about is How many solutions are being developed? right now you are doing wonderful work in solutions across many different fields and Many different local realities and this is also very important because local context culture ecology geography affects the kinds of solutions that make sense and this is At the essence of the whole notion of a global network of Solutions that you're finding them sharing them and making it possible for others to learn and We've had a wonderful day also of businesses Talking about solutions and that is very very exciting for me I just arrived from a Fantastic discussion with the Swedish company Scania Which makes big trucks? and they're completely committed to Decarbonizing their fleet and Even though I do almost nothing but talk about this subject morning noon and night every day seven days a week Fifty-two weeks of the year I learned a lot in the last few minutes from what this company is doing I'm going to show you a picture actually I maybe this is so obvious to you, but I've never seen it before, you know One of the big puzzles is how do you make large? trucks Zero emission we know for vehicles light-duty vehicles that electrification is almost surely the right way But for large trucks the problem is that the size of batteries right now given the Battery performance takes up too much room and it's non-economical And so there's a problem of electrification of large vehicles that is basically solved for light-duty vehicles and So I was asking and they have a perfectly sensible solution that I've never actually thought about which is You can't quite see it, but it's a giant truck being like a city trolley with the over over highway Grid we don't have that anywhere in the United States as far as I know Anywhere tried and it's only at the beginning in Europe, but what a smart straightforward idea which is you don't need the batteries if you have the green electricity powering the highway system and what the CEO of Scania was explaining to me is that 80% or so of their heavy freight is on a very small proportion of The roads which is basically the highway system So if you just devote one lane of the highways you can actually create a A Corridor that is zero emission with existing technologies and it's a wonderful solution And I said oh and if you've got that one quarter they can also be autonomous and Glint in his eye. Yes, that's part of the plan to so that we can move to autonomy of vehicles at the same time and Along that corridor can also be what you need for that which is 5g a heavy Concentration of access so suddenly you've made the transport corridor wonderfully Efficient and green and the technologies are obviously within reach and I confess I Hadn't thought about that as a solution I imagined that it would have to be a hydrogen fuel cell solution or Further advances on batteries and then I asked what do you do within the cities and he answered well within the cities? We're already all electric. This is basically the answer even for freight because it's a local Transport but then he explained that To make the cities work better You could cut down Tremendously on the number of trucks within the cities because most of the trucks are carrying a very small fraction of their potential load and with digitization of the Information about which freight is going where it's possible to make a perimeter around the city that the big trucks are coming in and they're transferring The freight into a very small number of electric vehicles because that's what the digital information will allow And I asked well could that be automatic also? He said yes, that's what we're doing so that can be autonomously done because they have a modular design of How the freight is going to be Built on top of the the transport Infrastructure so Fantastic things can be done Once we have the determination and the knowledge to do it we heard earlier today at the conference from Another fantastic company. I don't know if any of you was at the discussion with Pat Brown of impossible foods but He had the very bright idea that given the extraordinary burden of beef consumption on the planet to make What is surely a new term and that is plant-based meat Every plant yeah plant-based meat, so he just calls it meat But they're making meat products out of plants and I For impossible foods The breakthrough that they've had with the beef is to get an extremely strong Taste of beef into this plant-based food by Heem protein Which was the result of their research work that the heme protein gives a lot of the taste to beef and it can be Produced by yeast in fact, I think it is for impossible foods and then put into a plant-based protein and the Implications of that for easing the burden on the physical environment are absolutely startling I only had a small part of the imagination of all of the different Dimensions of ecological pressure that will be relieved from this Including an obvious point that we should remember that I would have forgotten on a first pass through this Which is that the amount of antibiotics being used in beef production is so high that it is one of the absolutely dire risks of creating mass resistance to large classes of antibiotics and that the pressure therefore of moving to a Plant-based meat diet would also have implications such as vastly reduced industrial uses of antibiotics and therefore vastly prolonging the usefulness and life of the antibiotics But that was just one of the many aspects of the solution that he offered We also had the vice president of sustainability of 3m Which is a major materials company in the United States about all of the different ways that Their products are being redesigned and reconfigured to be sustainable So we should feel quite optimistic actually I Technological solutions plus impeachment will get us the sustainable development goals. So I think we're getting very very close Thank you for organizing this wonderful Solutions group. I know in each country how happy The response was so congratulations to all of you for the fantastic work that you're doing your really heroes of the SDG We will make your solutions known and spread That's a core part of our network and thanks to all of you for your leadership


We will now look at solutions to the similarity temperature boundary layer equation. By way of remainder, the equation is theta double prime equal to Prandtl number into m plus 1 by 2 f theta dash minus gamma f dash theta plus 2 e c f double prime 0 square equal to 0 with the boundary conditions that at the wall theta 0 will be 1 and in the infinite state theta n pretty will be 0. We are interested in developing solution so that we look at effect of Prandtl number, we look at effect of pressure gradient and of course, also the suction of blowing parameter which is embedded in the solutions for f f dash and f double prime. We look at effect of wall temperature variation gamma and we look at effect of viscous dissipation on the nature of the solutions of things. Remember, I obtain already solution for Prandtl equal to 1, m equal to 0, gamma equal to 0 and e c equal to 0. That is the solution I presented in the last lecture. Now, I want to look at effect of very high and very low Prandtl numbers and this is what you see. For liquid metals, the value of eta, remember at 0.005 which is very low Prandtl number, the value of theta max or the value of delta star is nearly 53.3 whereas, for Prandtl number equal to 1, it was 4.92 as you remember. So, as the Prandtl number is reduced, the thermal boundary layer thickness goes on lower and lower temperature gradient. If I were to correlate this theta prime 0, it would be correlated reasonably well by this correlation n u x is equal to 0.564 Reynolds x Prandtl to the half. On the other hand, on the oil side, you will see Prandtl equal to 1 gives you this which is the reference solution about 4.92 as the temperature boundary layer thickness. But for 500, 500 and 1000, you see the temperature boundary layer thickness goes on reducing and I have given some values here. For 1000, it is as low as 0.495 which is 10 times smaller than the velocity boundary layer thickness which was about 5 and this is 0.6 and at Prandtl number of 100, it is just one-fifth of the boundary layer thickness for Prandtl equal to 1 and minus theta preserve goes on increasing with Prandtl number and a good curve fit which is 0.339 Reynolds x to the power 5 Prandtl to the third. But we will discuss both these solutions a little later. We want to study effect of m first of all and for which we will assume that there is no suction or blowing. We will assume that the wall temperature is constant. We will assume that there is no viscous dissipation included. We are only including the effect of m along with that of the Prandtl number. So, the governing equation as you will see for gamma equal to 0 and E c equal to 0 would simply be that theta double prime Prandtl m plus 1 by 2 f theta dash equal to 0 which I can write as d theta dash over d theta dash because theta double prime is simply d theta dash and that would equal minus Prandtl m plus 1 by 2 f. If I integrate this equation once, I will get ln theta prime from 0 to eta equal to minus Prandtl m plus 1 by 2 which is a constant into 0 to eta f d eta. Another way of saying it is theta prime at any eta would be equal to theta prime at 0 exponential of minus Prandtl into m plus 1 by 2 0 to eta f d eta. If I integrate this equation once again, then I get theta equal to minus theta prime 0 0 to eta exponential of this quantity into d eta plus a constant of integration C 1 which I discover firstly from the boundary condition theta 0 is equal to 1. So, if I set theta 0 which means 0 to 0, therefore, this contributes nothing and theta 0 being 1, I get C 1 equal to 1. Now, I impose the boundary condition at infinity. So, theta infinity is 0. This integration will become 0 to infinity and therefore, I will get theta prime 0 which is of interest to me because that represents the Nusselt number equal to 0 to infinity exponential of all this raise to minus 1. Now, we will see some special cases of f. Since velocity solution f d eta is known, we can evaluate this integral. The solutions that I show here have been evaluated for moderate Prandtl numbers 0.75, 10 and 25 allowing for M negative. Remember, I cannot go below M equal to minus 0.091 because that is where the separation occurs. So, I begin with M equal to minus 0.085, minus 0.065, minus 0.04, 0.331 and 4. These are the axial rating flows. Now, remember H x will be function of x M minus 1 by 2, the heat transfer coefficient. Remember, N u x is H x x by k is equal to some constant into Reynolds x to the half and this constant is a function of Prandtl number. So, what do we get? H x will be equal to k by x into u infinity x by nu raise to half into or proportional to that. What is u infinity? It is equal to C x. So, I get this as C nu by half into x into M plus 1 by 2, which is nothing but proportional to k C by nu raise to half x raise to M minus 1 by 2. Remember, heat transfer coefficient, the pressure gradient has this effect on heat transfer coefficient. If M is equal to 0, H x will simply decrease with x. So, for M less than 1, H x will decrease with x, but for M greater than 1, you could also get H x relatively increasing with x. This is something very, very important. This is for M greater than 1 H x versus x and for M equal to 1, H x will be constant M equal to 1. Now, this is a very, very important point to remember that for stagnation point flow, heat transfer coefficient is essentially constant. You will recall that we had also seen that delta 2 star and delta 1 star etcetera, all the thicknesses are also constant for stagnation point flow. So, let us look at the solutions for showing the effect of M at any one Prandtl number. Let us take Prandtl number 0.7 and then you will see that when M is equal to 0 for flat plate, the thickness is 0.5.6, but when you have decelerating flow, the thickness goes on increasing like the velocity boundary layer thickness. When you have accelerating flow, the temperature boundary layer thickness also decreases as shown here. This state of affairs prevails at all Prandtl numbers that I have listed here. Now, let us look at the effect of Prandtl number at any pressure gradient. Let us look at stagnation itself. You will see that for Prandtl number 7, minus theta prime 0 is 0.49. It increases to 1.03 at Prandtl 5, 1.32 and 1.81. What have we seen? As the value of M increases, the heat transfer coefficient increases. As the Prandtl number increases, the heat transfer coefficient increases. We have captured both these effects in the solution. Of course, it would be possible to develop a correlation of the form N u x is equal to C times N u x. R e x to the half, where C is now a function of Prandtl number and M for Prandtl number between 0.7 and 25 and minus 0.085 M 4. You will see that this will take the form of an experimental correlation, which can be used for further design work at any time we wish and one need not generate new solutions every time by means of a computer. I now want to look at the effect of very high and very low Prandtl numbers in the presence of pressure gradient. Remember, for Prandtl number very much greater than 1, delta would be much less than 0. Therefore, you will have a situation of a velocity boundary layer like that and a temperature boundary layer just like that. In other words, delta is much, much smaller than delta. For all practical purposes, I can say that the velocity profile is really linear in the temperature boundary layer equation and that we have seen many times in our earlier solution. In other words, f dash eta within the temperature boundary layer will simply be equal to f dash 0 for that value of M into eta. Integration will give me f eta is equal to f double prime 0 M, which is a constant eta square by 2 plus a constant. But f 0 is equal to 0 and therefore, c is equal to 0. So, essentially I get f dash eta equal to f double prime 0 into eta square by 2. That is what I have shown here. f eta would be approximately equal to f double prime 0 M eta square by 2. If I now include this solution in this here, which is an approximate solution to the velocity in this, I can readily evaluate minus theta prime 0 and that is what I have done. If I substitute f double prime 0 M eta square by 2 for f, then I get that. This would simply transform to minus Prandtl M plus 1 f double prime 0 M divided by 12 into eta cube because this is equal to eta square is eta cube by 3. 2 into 2 is 4 into 3 is 12 into d eta minus 1. Now, if I use the definition of this and that is what I will show you how to evaluate that integral. It is not a very difficult thing to do, but we will nonetheless do that. So, for the moment, let us say let Prandtl M plus 1 f double prime 0 M divided by 12. Let us say it is equal to a and define a eta cube equal to x, then 3 into eta square 3 a eta square d eta will equal d x. Therefore, d eta will equal d x divided by 3 a eta square. And eta square will be eta cube raised to 2 by 3 and that will equal x by a raised to 2 by 3. I get d x divided by 3 a into x by a raised to 2 by 3. 1 over 3 a into 1 by 3 into d x over x raised to 2 by 3. Therefore, our integral is simply 0 to infinity and exponential of minus a eta cube d eta can be written as 0 to infinity exponential of minus x into 3 a raised to 2 by 3 1 by 3 sorry into x raised to minus 2 by 3 into d x or this is equal to 1 raised to 3 a raised to 1 by 3 integral 0 to infinity x raised to minus 2 by 3 exponential of minus x d x. Now, if you recall the definition of gamma function, it is given as 0 to infinity x raised to n minus 1 e raised to minus x d x. So, in our case n is nothing but n minus 1 is equal to minus 2 by 3 and therefore, n will be equal 1 minus 2 by 3 equal to 1 by 3 equal to 1 by 3. So, essentially we have integration integral itself is equal to 1 over 3 a raised to 1 by 3 is equal into gamma times 1 by 3, but usually gamma functions are plotted for values of gamma greater than or equal to 1 and therefore, we make use of the relationship that gamma n plus 1 is also equal to n times gamma n. So, in other words gamma 1 by 3 can be written as 1 over 1 by 3 into gamma 4 by 3 into that is equal to 3 times gamma 4 by 3. This is gamma 4 by 3 and therefore, you will see our integral can be written as gamma 4 by 3 divided by a raised to 1 by 3. The integral itself will become minus theta prime 0 a raised to 1 by 3 divided by gamma 4 by 3 because this is raised to minus 1. So, this goes into the denominator, the a goes into the numerator and this is the solution. The value of gamma 4 by 3 you can look up the tables of course, it is about 0.893. So, if you look at m equal to 0, if I put m equal to 0 and recall that for m equal to 0 f double prime 0 is 0.33 and use this equal to 0.893 then you will see a correlation is possible for very very high Prandtl numbers n u x 0.339 r e x to the 0.5 Prandtl third. Now, I had curve fitted the solutions exactly in the same manner here for oils as you will see here 0.339 r e x to the Prandtl third. These are numerical solutions and this is obtained from our assumption that the velocity profile is linear. So, this kind of an assumption helps you to evaluate closed form solutions which we can call as correlations, but you can do this for any value of m for which f double prime 0 m has been calculated from the velocity boundary layer solution. Likewise, let us look at the case of very low Prandtl number in which case as I said the velocity boundary layer thickness will be solved and the temperature boundary layer thickness will be solved T b l and this will be the v b l. So, you will see for greater part of the thickness of the boundary layer u is in fact equal to u infinity and therefore, f dash eta in the term is about 1 throughout the boundary layer which gives me f eta equal to eta itself. In this equation for theta prime 0 if I substitute f equal to eta then I will get the relationship as that this will simply become eta square by 2. So, this becomes Prandtl m plus 1 by 4 eta square whole thing is integrated raise to minus 1. If you put this as some y or something like that you can do this carry out this integration quite easily and use the error function definition e r f x is equal to 2 by root pi 0 to x e raise to minus eta square d eta then you will see and note that r f infinity is equal to 1. Then you will it is very easy to show that n u x r e x to the minus 5 which is minus theta prime 0 will simply be equal to Prandtl m plus 1 by pi and that is what you see for again for m equal to 0 you will see this becomes simply Prandtl divided by pi and as a result 0.564 r e x in Prandtl to the half. The great thing about this solution is the following at liquid metals for liquid metals you see both the exponent of Reynolds number and Prandtl number is identical. Now what does that mean r e x and Prandtl that is u infinity x by nu into nu by alpha the thermal. So, nu and nu gets cancelled that means in liquid metals viscosity has no influence and that matches with the idea that viscosity is really if its effect is confined to such a narrow region of the thermal boundary layer thickness that viscosity simply has no effect on the rate of heat. This result is very typical of liquid metal heat transfer whereas, for all other higher Prandtl numbers you will always get a separate effect of Reynolds and Prandtl number. But here incidentally this product this is Reynolds number this is Prandtl number, but the product Reynolds Prandtl is called Peclet number Peclet was a French scientist and Peclet number is of importance in liquid metal heat transfer. Liquid metals as you know I used in very high heat flux heat transfer cooling such as breeder reactors and others. So, these kinds of solutions are great value and the constant is 0.564 if you recall I will go back to the numerical solution that we had obtained. Yes indeed the solutions at very low Prandtl numbers do match this correlation here and that is precisely where it comes from it comes from this assumption that F dash eta is about 1. So, having studied the effect of M the pressure gradient and Prandtl number high and low Prandtl under essentially constant wall temperatures and no suction and blowing and no viscous dissipation. We now move to the case of looking at effect of wall temperature variation again I am going to consider the flat plate boundary layer no suction or blowing and viscous dissipation is neglected. Then the governing equation read something like this now there is no closed form solution possible for this because of this additional extra term and I need to now look at the numerical solution which I have presented here from very moderate Prandtl numbers wall temperature variation gamma positive indicates that the temperature of the wall is increasing with x whereas, this indicates that the temperature is decreasing with x negative value of gamma indicates the temperature is decreasing with x. So, what do we find let us look at results at any one Prandtl number and you will see compared to gamma equal to 0 where wall temperature is constant there is as gamma increases there is a wall temperature increases in the x direction then so does the Nusselt number or the solution which is minus theta prime 0 increase when the temperature decreases with x you in fact the heat transfer decreases and in fact you hit the situation at gamma equal to minus 0.5 where there is absolutely no heat transfer this is called the adiabatic case. If you reduce gamma still further then you will actually get negative heat transfer although the wall temperature is bigger than the free stream temperature you will actually get a negative heat transfer. Now, I have allowed gamma to take any arbitrary value simply because E c is equal to 0 and we did say that gamma is restricted to 2 m only when E c is included we have not included E c and therefore, this is a remarkable result that when the temperature wall temperature decreases with x you could get a situation of adiabatic heat transfer or in fact even negative heat transfer and we did alert right in the beginning that we are interested in looking at situations like this for gamma equal to minus 0.5 temperature gradient at the wall is 0 is an adiabatic case although T w is greater than T infinity. Now, we can explain this why this happens. So, let us take our flat plate and the wall temperature is now decreasing with x this is the wall temperature. So, you can imagine at any x the particles close to the surface would arrive from a region of higher temperature from a region of higher temperature. So, much so that the convicted heat into the layer the temperature here could well become absolutely equal to the temperature of the wall at that point. So, in effect I get a situation where I have a profile which will look like that which will look like that. So, basically although T w is bigger than T infinity T w is bigger than T infinity I could get a situation where it is like that if the slope is still negative this is corresponding to gamma equal to minus 0.5 I could even get a situation which is like that this is gamma greater less than minus 0.5 this is let us say minus 0.6 as I have shown. So, you could get situation where the heat transfer will be heat will going in although T w is greater than T infinity. The situation arises because the fluid particles coming from the upstream region would be a hotter than the value of the wall temperature itself. So, these order fluid may thus inhibit heat transfer from the surface to the cooler free stream by the same reasoning for gamma equal to minus 0.5 theta would increase beyond 1 at some distance close to the surface and heat will flow into the surface even if T w is greater than hence T w heat transfer coefficient will be negative. We verify these in the next slide where I have shown effect of value of gamma on the predicted temperature profile. The curve here shows the constant wall temperature case the frontal number is chosen to be 0.7 therefore, the boundary layer thickness is slightly bigger than 5. Let us look at the acceleration side this is gamma equal to 1, this is 2, this is 4 and you get steeper gradients and near the wall and thinner and thinner temperature boundary layer thickness as wall temperature increasing with x. But on the negative side that is wall temperature decreasing with x you will see you get a shallower gradient near the wall and the boundary layer thickness itself goes on increasing at gamma equal to minus 0.5 you can see very clearly the 0 gradients and for gamma equal to minus 0.6 value of theta here at this point has exceeded the value at the wall which was 1. So, our temperature solution does indeed confirm what we anticipated now we look at the effect of viscous dissipation and viscous dissipation typically is accounted when you have very high velocity gradients d u by d y whole square or when you have very high viscosity which is mu. So, I am taking here the case of pranthole equal to 0.7 and assuming that the velocity gradients near the wall are very very high then the solution would be and the wall temperature is constant there is no suction or blowing and the pressure gradient is 0. Then the governing equation will be this and because the wall temperature is constant E c would be simply this and theta is this. So, E c less than 0 implies that T w is less than T infinity E c greater than 0 implies T w is greater than T infinity. So, here are the solutions to so this is 0.292 for pranthole number 0.7 is the value of theta dash 0 with 5.26 as the temperature boundary level of thickness. When E c is positive that is when T w is greater than T infinity you in fact do find an almost adiabatic situation at E c equal to 1.2 and negative heat transfer when E c becomes 2.4 and 4.8. On the other hand when E c is negative that is if T wall is less than T infinity that is cooling case then you find that the heat transfer rate increases in the presence of effect of it. So, E c equal to 1.2 is a special adiabatic case is a very very special adiabatic case and here are the solutions for different values of E c the a cut number. So, here the solution is for a cut number equals 0 this is theta dash eta and the wall value is 1 you do see that at 1.2 the gradient is 0 and therefore it turns out to be an adiabatic case and for 2.4 the temperature is exceeded value of 1 and it has exceeded value of 1. So, although T w is greater than T infinity you will get negative heat transfer for these two values of a cut numbers. On the negative side you see the temperature gradient becomes sharper and sharper. Because of the viscous dissipation see at some point the temperature actually goes below the free stream temperature because it is less than 0. So, just as wall temperature is exceeded for positive E c free stream temperature is exceeded. So, E c less than 1.2 theta is less than 0 at some positions indicating that T eta E can be greater than T infinity within the boundary layer and E c greater than 1.2 minus theta h x is less than 0 even when T w is given. Both these are effects of viscous dissipation due to mu du device square. This kind of viscous heating is of great concern viscous heating effect in reentry vehicles of into the space from the space into the upper atmosphere. When sudden increase in viscosity of the atmosphere would generate and the reentry vehicle is hurtling down at very high velocities of the order of 5 to 6000 meters per second and you get enormous gradients very close to the wall as a result the viscous dissipation term becomes very dominant and you would generate large amounts of heat and if the cut number turns out to be bigger than 1.2 then you could well get heat transfer into the reentry vehicle surface a dangerous and that is why the reentry vehicles are coated with ablating materials. So, that when the heat transfer takes place inside and the surface temperature goes up the material evaporates and carries away the heat of which has been ingress from the outside into the wall of the reentry vehicle. So, study of such effects is of great consequence in practice. Now, we look at finally, the effect of B F the suction and blowing parameter and I am going to consider again the constant wall temperature and ignore viscous dissipation but I will allow for effect of M, I will allow for effect of Prandtl number and B F. So, we are looking at three parameters here B F, Prandtl number and M and I am restricting this to the case of gases because these B F cases are of interest in gas turbine cooling problems. So, you will see in suction case when B F is negative compared to B F equal to 0 which is no suction and I am looking at flat plate solution then when there is suction there is increase in heat transfer but when there is a blowing there is a decrease in heat transfer and you will recall that B F equal to 0.612 was the case where separation occurs. So, we are not interested in B F equal to 1 but we are interested for M equal to 1 in which you will see that again the same thing prevails that the heat transfer increases on the suction side whereas, it decreases on the blowing side and this essentially occurs because the thickening and thinning of the boundary layers associated with suction or blowing. Suction thins the boundary layer and therefore, increases the rate of heat transfer blowing thickens the boundary layer and therefore, lowers the heat transfer coefficient. For M equal to 0, B F equal to 0.612 is a very special case and that is where the separation occurs. You will see on the next slide the graphs these are the flat plate solutions and these are the stagnation point solution. This is B F equal to 0.5, 0.3, 0, minus 0.5, 1 and 2. As I said B F equal to 0.612 is an adiabatic case. You will see on the suction side we get very large temperature gradients and on the blowing side we get shallower temperature gradients compared to M equal to 0. Now, if I were to compute this for potential number of 0.5 or 1, the results are very similar and therefore, not shown here. So, with this I conclude my discussion on the similarity method as a whole and therefore, it is time that we look at the summary of the equations and the boundary conditions. For the velocity boundary layer similarity equation is this F triple prime plus M plus 1 F F double prime plus M 1 minus F times square equal to 0, where M is the pressure gradient parameter. The suction and blowing parameter comes in through the boundary condition F 0. The similarity conditions or the variables are U infinity is equal to C x raise to M. B F V W x U infinity x R e x to the half must be constant and the variable eta must be y under root U infinity by nu x and the similarity solutions are C F x M B F which is a function of M and B F equal to 2 times F double prime 0 R e x to the minus 0.5. Likewise, the temperature equation is theta double prime into Prandtl M plus 1 by 2 F theta prime minus Prandtl into the wall temperature gradient parameter and the viscous dissipation parameter. The boundary conditions are simply this theta 0 is equal to 1 theta infinity is 0. The similarity condition is that the wall temperature can vary only as x to the power of gamma. If a cut number or the viscous dissipation is present however, gamma must remain equal to 2 M and the similarity solutions as a whole are multi-parameter solutions involving pressure gradient M, Prandtl number, suction and blowing parameter, wall temperature and E c that is what I have shown you. We have seen a wide variety of solutions of this type. It is not very difficult to write computer programs both for solving the velocity boundary layer equation as well as the temperature boundary layer and I have already given you the method in the last two lectures. So, I suppose with that I conclude my discussion of similarity method. In the lectures to follow, we will take up integral methods of solving boundary layer equations.


This is Mr. Nagesh Arthambake, Assistant Professor, Mechanical Engineering Department, Valchan Institute of Technology, Sholapur. Today, we are going to discuss the automobile steering geometry, learning outcome. At the end of this session, students will be able to explain automobile steering geometry. In this particular session, we are going to discuss what is steering geometry and different types of steering geometries. Now, before discussing this topic, we will see what is meant by automobile steering geometry. Please think, students, what is steering geometry. We will see, it is the relationship of the angles among the front wheels, front wheel attaching parts and ground. First one, the steering geometry is the camber. Camber is the inward or outward tilt of wheels from vertical when viewed from the front of the vehicle. Camber is measured in degrees on vehicle, positive camber is adjusted initially. So, when vehicle is loaded and rolling along the road surface, vehicle should run straight up and down with zero camber. This puts the full width of the tyre trade on the road surface, which is desirable. However, it is difficult to obtain a zero camber. The camber goes negative when tyre hits the bump and goes positive when falls in a pothole. This is caused by unequal length control arms of the suspension system. In any camber, either positive or negative causes uneven tyre wear. So ideally, camber should be zero, which is somewhat difficult. So initially, negative camber is provided. Now, next one is caster. What is meant by caster? It is the tilt of steering axis towards the front or rear of the vehicle. If the tilt is towards the front, it is taken as negative and when it is towards the rear, taken as positive. Usually, positive caster is provided to the vehicle. Caster is measured in degrees. Caster angle adjustment is for some feasibility. So, first one is to maintain directional stability and control to increase steering returnability and to reuse steering effort. This requirement can be met by providing positive caster. Vehicles with power steering have more positive caster than with manual steering. However, the more positive caster requires more steering effort, which is not filled due to power steering. Any degrees in positive caster then require causes spring sagging. Next one, that is steering axis inclination. That is also called as kingpin inclination. First of all, we will see what is steering axis. It is the line passing through centers of ball joints. It is the axis around which a front wheel swings for steering. It is the angle between vertical line and steering axis. It is the inverted of the steering axis from vertical as viewed from the front. This inverted is desirable because of some of the reason. It helps in returning the steering wheel to straight ahead after completing a turn and keeps the vehicle in stable condition. This is called as steering returnability. It helps in reducing steering effort, especially when vehicle is not moving and also reduces tire wear. Steering axis inclination cannot be adjusted because it depends on geometry of knuckle. Usually it is correct, but when it is not within the specification, the spindle, steering knuckle, ball joint and other dependent parts wear or bend down. This is indication of a wrong steering axis inclination. In this, we will see what is scrub radius. In this particular figure, we have shown a distance between this particular ball joint and the tire. That will give you a scrub radius. The term scrub radius is defined as it is the distance between steering axis and tire contact area centerline as their intersection with road surface. If the steering axis intersects the road surface inside the tire centerline, scrub radius is positive. If that intersection point is outside the centerline of the tire, it is negative. Zero scrub radius means steering axis and tire axis meet at ground surface exactly. Scrub radius is not an alignment angle and usually cannot be directly measured. However, it directly affects steering stability.  While front drive vehicles with macpherson strut from suspension have negative scrub radius. Next one, that is tow in, tow out. What is tow in, tow out? It is the measurement of how much the wheels point in or out from the straight ahead position. It is measured in mm, inches or in degrees. Ideally, running tow must be zero. When the wheel points inwards, it is tow in. And when wheel points outwards, it is tow out. Zero tow means the wheels run parallel. They are at same distance part at in front as well as in rear. Any tow in or tow out tracks the tire sideways as it rolls. The greater the tow angle, faster the tire rear. Next one we will see. In this also we will discuss the suspension height. That is not mentioned over here. What is suspension height? It is the distance measured from some specific point of the body frame or suspension to the ground. It is not adjusted correctly. It can affect wheel alignment. Incorrect height can affect from sagging coil or leaf spring. Incorrect torsion bar adjustment. Now next one we will see that is the turning radius. What is turning radius? It is the difference in the angles of the front wheels in turn. Also called as tow out on turn or turning angle. During a turn, the two front wheels travel on concentric circles. Having common centers, the inner wheel run through greater angle while outer run through a smaller one. So as the distance is greater from outer wheel and small for inner wheel. If turning radius is incorrect, check for the bent in steering arm or a tire rod. Now next one is the included angle. Included angle, it is the addition of camber angle and steering axis inclination. Together it will form an included angle. It is not an adjustable angle. However, an improper included angle often indicates a bent in spindle or strut. Now next one is setback. What is setback? Wheel setback is the difference in vehicle wheelbase from one side to other. It occurs when one wheel is behind the other on same axle. Setback occurs from production tolerances during vehicle manufacturing or from impact damage. It also occurs because of improper placement of engine or subframe. A vehicle with drift or pull towards the side with shorter wheelbase setback more than 19 mm is excessive indicates bent in parts. Now last one is that is the thrust angle. Here you can see in this figure what is the thrust angle. When the wheel is properly aligned, it should move in a straight line. But if rear of vehicle has improper setback, it may not move straight ahead. The direction of travel is determined by three lines. That is run the length of vehicle. Vehicle center line is the line passing through center of the vehicle body. This line should be the same as the geometric center line of the vehicle that connects the midpoints of front wheels and rear wheels. The thrust line is a line from the midpoint between the two rear wheels. Now these are the references. Thank you.