![Prof. Van Buren](/img/default-banner.jpg)
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Prof. Van Buren
Добавлен 15 май 2019
Swimming and flying [Aerodynamics #21]
In this video, we cover the aerodynamics of how animals swim and fly. This includes the entire range of shapes and sizes of animals, from whales down to bacteria. We use physical intuition of the Navier-Stokes equations to decompose the forcing mechanisms into (1) added mass; (2) momentum injection; (3) drag-based; (4) lift-based; and (5) viscous-based strategies. We pay special attention to lift-based thrust due to it's widespread use in nature. In addition, we cover how the drag behavior of big fast animals are different from small, slow animals. Swimmers and flyers often do clever strategies for manipulating and interacting with the wake of itself and others through interesting flow fe...
Просмотров: 2 841
Видео
Hypersonics [Aerodynamics #20]
Просмотров 3,8 тыс.2 года назад
In this video, we cover Hypersonic flow, a new regime of high-speed aerodynamics that literally breaks our fluids/thermo analysis. We go so fast that the gas is impacted on a molecular, and even atomic level. This results physically in very thin, aggressive shock layers; thick boundary layers; entropy layers; and low density effects that lead to lack of a continuous gas assumption. It is an ext...
What causes lift [Aerodynamics #13a]
Просмотров 6 тыс.2 года назад
The origin of lift is complex and often questioned. Some misguided explanations include the equal transit time or air "pushing" the foil. While they are attractive, simplified explanations they do not capture the entire truth. Here, we try our best to explain the source of Lift, the "why", from fundamental principles. We will see that Lift is a balance of conservation of mass, momentum, and ene...
Compressible flow [Fluid Mechanics #18]
Просмотров 8 тыс.3 года назад
In today's video we introduce the complicated and vast world of compressible flows. Until now in this series, we have assumed density was constant. Now, we allow density to change, due to the flow, and lots of interesting things happen. We will go over what compressible flow is physically, how to tell if flow is compressible via the Mach number and comparing Kinetic and Internal fluid energy, h...
CFD - Computational Fluid Dynamics [Fluid Mechanics #17]
Просмотров 2,4 тыс.3 года назад
In this video, we take a break from the theory and visit a new way to try and approach and analyze flow problems. Generally, you can learn more about flows through either Theoretical Derivation, Experiments, and now Computational Simulation. Here, we explore the basics of Computational Fluid Mechanics, also known as CFD, which is the process of using a computer to solve discretized linearized v...
Pressure gradients and separation [Fluid Mechanics #16]
Просмотров 6 тыс.3 года назад
In this video, we zoom in on lifting surfaces. Curved surfaces in fluid mechanics generally lead to streamwise pressure gradients in the flow, which adds to the flow complexity. Pressure gradients can be favorable (accelerate the flow) or adverse (decelerate the flow). If an adverse pressure gradient is strong enough, flow separation can occur on the surface, leading to a loss in aerodynamic pe...
Lift and drag [Fluid Mechanics #15]
Просмотров 5 тыс.3 года назад
In this video, we zoom out from the flow itself and start to consider the impact of a fluid on a body moving through it. We are constantly travelling through air/water, and many vehicles are designed to more easily move through and manipulate the fluid. This is the field of aerodynamics (air) and hydrodynamics (water). The primary body forces are Lift and Drag. Forces on a body come from pressu...
Turbulent boundary layers [Fluid Mechanics #14]
Просмотров 6 тыс.3 года назад
In this video we continue our exploration of External Flows with the Turbulent Boundary Layer. Fluid moving near a wall slows down in a velocity deficit region known as the boundary layer due to viscosity. At high enough Reynolds numbers, this flow becomes turbulent and, although there is still a boundary layer, it is much different in behavior and structure. We will explore the physical charac...
Laminar boundary layers [Fluid Mechanics #13]
Просмотров 4,1 тыс.3 года назад
In this video, we pivot from enclosed flows (pipes/channels) to external flows like boundary layers. A boundary layer is a thin region of flow near the wall that is slowed down due to viscosity and the no-slip condition at the wall. It is critical in our understanding and prediction of many real world flows. We will try and solve the boundary layer theoretically, arriving at the famous solution...
Fluid measurement [Fluid Mechanics #12]
Просмотров 1,6 тыс.3 года назад
In this lecture we take a short break from the theory and start to think about fluid measurement. Whether we are dealing with laminar or turbulent flows, we need observations to confirm our theoretical derivations. Sometimes, these observations come as measurements. Here we cover: (1) what do we need to measure? - velocity [u v w] and pressure [p]; (2) what are measurement resolution and error?...
Reynolds decomposition and Reynolds Averaged Navier-Stokes (RANS) [Fluid Mechanics #11]
Просмотров 9 тыс.3 года назад
In this video, we take a deep dive into the Reynolds Averaged Navier-Stokes equations (a.k.a. RANS). In practice, RANS is a valuable tool to have in your toolbelt when approaching real-world flow scenarios. To get these equations, we need to apply Reynolds Decomposition, separating a time-varying signal into the mean and fluctuating components, to the Conservation Equations and then average the...
Turbulence [Fluid Mechanics #10]
Просмотров 2,7 тыс.3 года назад
With this video, we introduce Turbulence, my favorite topic in fluid mechanics. A flow state characterized by chaos and mess that's literally everywhere in the world. With laminar flows we could make assumptions like steady, fully-developed, two-dimensional, etc. With turbulence, there are no available assumptions to make the Navier-Stokes equations easier to work with, and as a result are not ...
The fluid mechanics of robotic locomotion
Просмотров 2203 года назад
This video is a special topic that I used for a guest lecture in a Soft Robotics course. In the video, we take a crash course on the forces that fluids generate and physically review the famous Navier-Stokes equations. When traversing through fluids, robots need to consider the drag they will feel and the thrust they will produce to overcome that drag. We cover how to estimate your drag by usin...
Practical flow quantities [Fluid Mechanics #9b]
Просмотров 1,4 тыс.3 года назад
Here, we find out how we can make use of our new velocity fields we've learned to solve for in the past videos. While having (u, v, w, P) is nice, it's really not practically useful. We learn how to generally solve for the average velocity of a flow, the maximum velocity, the volumetric flow rate, shear stress, and wall force or drag. These quantities will be useful for fluids analysis and we d...
Laminar pipe flow [Fluid Mechanics #9]
Просмотров 1,9 тыс.3 года назад
The study of laminar pipe flows. Like enclosed channel flow, we will solve the conservation of pipe flows but in cylindrical coordinates. Specifically, we will focus on pressure driven pipe flow. The conservation of mass and momentum-x will get us the velocity fields, and we will go a bit further and explore the pressure field with the other two momentum equations.
Navier-Stokes in cylindrical coordinates [Fluid Mechanics #9a]
Просмотров 11 тыс.3 года назад
Navier-Stokes in cylindrical coordinates [Fluid Mechanics #9a]
Laminar closed-channel flows [Fluid Mechanics #8]
Просмотров 2,6 тыс.3 года назад
Laminar closed-channel flows [Fluid Mechanics #8]
Buckingham Pi theorem [Fluid Mechanics #6]
Просмотров 4,9 тыс.3 года назад
Buckingham Pi theorem [Fluid Mechanics #6]
Non-dimensional numbers [Fluid Mechanics #5]
Просмотров 3,2 тыс.3 года назад
Non-dimensional numbers [Fluid Mechanics #5]
Dimensional homogeneity [Fluid Mechanics #4]
Просмотров 4,6 тыс.3 года назад
Dimensional homogeneity [Fluid Mechanics #4]
Common assumptions in fluid mechanics [Fluid Mechanics #3b]
Просмотров 4,6 тыс.3 года назад
Common assumptions in fluid mechanics [Fluid Mechanics #3b]
Oblique shocks and expansion fans [Aerodynamics #19]
Просмотров 10 тыс.3 года назад
Oblique shocks and expansion fans [Aerodynamics #19]
Conservation of momentum (a.k.a., Navier-Stokes) [Fluid Mechanics #3]
Просмотров 9 тыс.3 года назад
Conservation of momentum (a.k.a., Navier-Stokes) [Fluid Mechanics #3]
Material derivative [Fluid Mechanics #3a]
Просмотров 5 тыс.3 года назад
Material derivative [Fluid Mechanics #3a]
Conservation of mass (a.k.a., continuity) [Fluid Mechanics #2]
Просмотров 16 тыс.3 года назад
Conservation of mass (a.k.a., continuity) [Fluid Mechanics #2]
How we study fluid mechanics [Fluid Mechanics #1]
Просмотров 13 тыс.3 года назад
How we study fluid mechanics [Fluid Mechanics #1]
Normal shock waves [Aerodynamics #18]
Просмотров 11 тыс.3 года назад
Normal shock waves [Aerodynamics #18]
Intro to compressible flow [Aerodynamics #17]
Просмотров 7 тыс.3 года назад
Intro to compressible flow [Aerodynamics #17]
Lifting line theory [Aerodynamics #16]
Просмотров 22 тыс.3 года назад
Lifting line theory [Aerodynamics #16]
you're the best
I want to learn so much about Aerodynamics 🎉😮
Thank you very much this and your other Videos help so much 😮🎉❤
Bad handwriting too hard to read. Use a computer, not a pen
Bad handwriting, use a computer. There are about 5.4 Billion people using the Internet now. Step up your presentations to match, not down to a hypothetical or organization driven "captive class room". Your visualization are decent, but lack substantially because your drawing skills are not that great. Start with energy and the models, then talk about phenomena with data in hand. Not dribble it in vaguely when you happen to remember while talking. You use words too much where real world images would be better. Even Wikimedia images are better than writing words in English. Animations can be standard symbols of things, once learned and easy to generate, they become tools and reminders of what is possible. There are thousands of languages in the world, and hundreds written and used on the Internet. Most anyone might have seen the images, and never heard or seen the thousands of names people use. You did not link to the background. Like writing a book or paper with no references or index. When you seriously face billions of Internet users, do it consciously and professionally, or at least with some serious intent to talk to and show billions, not thousands. The world has changed and you can be a drag, throwing minds in many vague directions, or you can at every moment and movement reduce momentum, energy and acceleration losses. Turbulence is intimately tied to invisibility and inability to see and anticipate. So show everything, clearly and succinctly, and have everything at hand to bring to bear whatever might be lacking or wanting. It is possible. In many cases it is the difference between dying and survival in conflicts or complex pathways. Hypervelocities are already with us, but you are teaching methods that barely work for steam engines and fossil fuels. Filed as (The world needs complete, dynamic, anticipatory tools and methods, where speed matters) At 10,000 subscribers, RUclips and many other sites will monetize. Add $Thanks and make it easy for people to thank you. You are good, but with effort and intent you could be better. Richard Collins, The Internet Foundation
fascinating job! Very intuitive. What's the next step to go beyond and be prepared to work on aeronautics? Engineering College gives the background, but what can one do by self-learning to expertise at aeronautics?
I'm a high school student and I want to be an Aerospace Enginner, I know fluid mechanics and aerodynamics are important, I have the basic knowledge in math and physics and understand a higher level a bit, how can I learn and understand Fluid Mechanics and Aerodynamics well? Thanks for the video Prof!
The recaps at the end are a real strengthening tool.
I think so too!
Thank you so much for a great effort in explain.
Most welcome!
Your videos are amazing, man!!!! Congrats!! Your explanations are very clear and make the subject even more interesting!
Aw thanks!
great video, but how does the starting vortex take shape in this line of reasoning?
I'm not sure what you mean. Are you referring to the vortex initiated at the start of the flow---as in when the airfoil first accelerates?
@@prof.vanburen yes, exactly that
How does the airfoil shape produce rotation?
Do you mean generally how a foil might turn the flow downwards, producing the circulation that is the footprint of lift? Or how in reality the no-slip boundary leads to a boundary layer full of rotational flow?
@@prof.vanburen the latter. I think this validates the Kutta condition
Great video thanks for sharing
Thank you for watching!
I'm not a student and i want to study aerodynamics for my rocket thank's
You're welcome, good luck in your studies!
I absolutely loved watching your video. You're an amazing teacher 👍🏻
Ah thank you so much!
thanks for your extraordinary labor, it was perfectly helpful to understand the main concept. But fortunately, ı couldn't get the point when it comes the similarities. İs there any more precise definition about why Cp are equal for different scaled shapes. Or is there any resource that may help me in that subject. Thx again
My pleasure! I looked through the video again because I wanted to be sure, I am not sure where Cp (which is sometimes pressure coefficient) pops up, but I suspect you mean Cl instead, as in the lift coefficient? If so, I should say first that Cl does not *perfectly* stay the same at different scales. Other concepts like turbulence and Reynolds number come into play here. However, for the most part, it is sufficiently equal across a wide range of different scales. This is because take into account all the variables that impact lift when we scale the problem. A bigger airfoil would produce bigger force at the same air speed, but lift coefficient takes that into account by scaling with the area. Does this help at all? Otherwise, I think the text by Anderson might be helpful here. Otherwise, my video in fluid mechanics on non-dimensional numbers more completely goes over these concepts in a way that is not restricted to aerodynamics.
What a brilliant video, thank you very much!
Thank you!
Thank you so much I’m a new student in aero space engineering and this helps me a lot I watched all of this whilst completing some assignments
Hey hi , I'm also doing aerospace engineering ( first year) and the college starts July 10 . I'm more passionate to learn about space shuttles , and i want to self learn . Is you can suggest me on how to self learn ? Thanks a lot ❤
I am glad they helped!
@TITAN_2608 Rocket science! I am not sure of any good references in this specific area---it's not really my area of expertise. I know NASA has a ton of good online resources, that's probably where I would start.
@@prof.vanburen thanks a lot
Explanation at 10:30 is a bit wrong. We are riding on the wave front, fluid on the right seems to move towards us with speed a and on the left, it seems to move away from us with speed a-dv.
Thanks for clarifying!
There is an error in integral calculation in 15:28. Bounds of integral must be from pi to 0 otherwise lift force will be negative.
Thanks for clarifying!
fantastic. thanks for your effort to explain the concepts
Thank you, I really appreciate you going through the videos so closely and catching my (many) goofs!
You explained lots of misconceptions but forgot one which is Venturi effect. This effects is also wrong according to Nasa glenn research center but you base your idea on this concept. Anyway it is a good try.
Thanks, but we will have to agree to disagree on this one. While I think the folks at NASA can be brilliant, I have seen the explanation you are referring to you and I don't find their rebuttal of the idea complete. And I think that's okay, because this is a very hard problem that doesn't get a simple answer! If flow passes by curvature---like one wall with a hill or the leading edge of an airfoil---it needs to react. If things are slow, the fluid just entirely (up to effectively infinitely away from the surface) moves up and over the curve and it is happy. This does not lead to the Venturi effect which is generally used to explain contracting enclosed systems. However, if it is moving rapidly by this curvature, shifting upwards takes time, and the flow might not have that time to react due to compressibility. So, if it can't get out of the way in time (and conservation of mass needs to be obeyed otherwise the world explodes) the flow can can do things like increase in density or speed up in this 2D approximation. Why is speeding up not an option for mass conservation? Would this not be a "virtual" contraction, where the "top wall" of the Venturi is really just reaction time? I know NASA in that reference discusses the flat plate as evidence, but the flat plate also leads to flow fields with curved streamlines that behave like more curved surfaces. Also, it talks about the bottom-side of the airfoil but there curvature is not nearly as rapid. Furthermore, the speed up explanation in this video is specifically attributed to traditional airfoil shapes and is only a smaller part of the big picture. It is this effect in combination with the others that lead to the supreme lift of airfoils. I am not sure my explanation is any more convincing, but I also don't see where in the aeronautics series from NASA that they explain the acceleration of flow around the curvature at the top of the airfoil, which certainly happens. It seems that course online just leads to "Euler equations are complicated". Yes they are. I have seen other explanations that include consideration of angular velocity and centrifugal things, but they didn't resonate with me (or perhaps I just didn't understand them well enough). Anyway, thanks for getting me to think about it more deeply!
14:40 that is not the chain rule, that is the definition of the total differential😊
Haha I have a mathematically talented grad student who also won't let me live this down. You're very correct here...but it certainly looks like a chain rule 🤔
I finally understand! Thank you!
My pleasure!
THIS IS AWESOME man thank you SO MUCH for making these!!
My pleasure!
thank you 🎉🎉
You're welcome!
Can you help me to understand why at 8:13 we have Cd equal to 2 integrals one positive and one negative, and then at 9:10 Cd became a unique integral with minus sign? I do not understand the minus sign. The same happen for Cl.
It has been a while since I looked at this lecture! I think it is because earlier in the video we are considering generalized calculation of lift and drag from the upper and lower surfaces of generic shape. Further down, we consider just a cylinder which has simplified versions of the equations. I will have to re-watch in detail just to make sure that's the case.
Very educational series, nice and to the point, takes you from everything baby steps. Am interested in learning more about how birds fly, is there a book that you can recommend - something along the lines of bionic wings for drones preferably like the one done by festo
This is a heavy question and I am happy it is more in my area of expertise! In this case, I think it would be more valuable to dive into journal articles and not books. While some books might exist, it's still a vastly growing area of our understanding and researchers first publish their findings in journals---which I think is where the coolest stuff is. One such journal you could look into is Bioinspiration and Biomimetics. Otherwise, I tend to try and follow the work of groups I am familiar with. For example, Prof. David Lentink has always been a go to for someone I check out to see where the state of the art is in bird-like drones. And, even if you don't have paid access to the journal, authors are usually more than happy to share a copy of their work for free if you just email and ask.
Thank you very much for the explanation
You're welcome!
Thank You Prof alot! ❤ I'd appreciate it if you made a detailed video about what aspect does F1 Teams Design their frontal and rear wings on
That would be a cool vid!
Good Vid
Hey thanks!
I'm currently writing my bachelors thesis about fluid dynamics and your videos are incredibly helpful for catching up on the basics :D Thank you!
Good luck with your thesis! What topic in fluids are you covering?
Your playlist is underrated
Aw thanks!
Great presentation! It helped me a lot.
Glad it helped!
Aree kuch samaj nhi aa rha kya padha rha hai.
I think this translates roughly to "I don't understand"? Happy to help if you have any specific questions!
Awesome video, thank you! For the X-momentum in the flow between plates example - can you do all the eliminations (steady, fd, 2d, etc) before you decompose and average to have less terms to compute?
Hmm, good question. I haven't done it out the reverse way because I think you might lose important terms if you simplify at the beginning, but I'd have to check. Regardless, if you start with the RANS equations and eliminate from there, isn't it the same amount of terms to compute anyway?
Now that is not fair, this channel deserve more subscribers.
Aw thanks! I am happy with everyone involved, regardless.
önemli hocam
Thanks!
you are insane !!
Thanks, I think!
your going to help me make a missile someday
Definitely the ethics of aerospace education and its inherent integration with human violence (WW1 and WW2 rapidly advanced the field) are something important to consider and discuss
@@prof.vanburen I can’t even understand this
For a project we are working on calculating the influence of wingtips on induced drag. However, we were wondering if the lifting line theory can also be used for a wing which is not flat, but instead has winglets.
Hmm, good question. I'm not sure it would appropriately capture the end effects as it will change things slightly (generally for the better with regards to induced drag). Potentially you might find measurements on induced drag of winglet systems in literature?
@@prof.vanburen It was hard to find an appropriate way to calculate the induced drag of winglets. What we eventually found is that by predicting the downwash profile of a wing (by for instance using computer programs like OpenVSP or XFLR5). An expression can be found for the circulation, resulting in an estimation of the induced drag (as explained in the video). We are however not sure if these estimates come close to the real world. Moreover, we found that using the method of restricted variations that the optimal induced drag is obtained when the downwash is proportional to the local cosine of the dihedral angle. So when having a winglet at for example 90 degrees dihedral, the net sidewash should equal 0. This means that the winglet should not produce thrust, however the winglet causes a upwash on the main wing, reducing the induced drag of the main wing. This way, the winglet mainly helps the main wing perform better, instead of producing thrust itself. Some more considerations can be found in our Aerodynamics Assignment for the University of Twente: dickdekker.jouwweb.nl/induced-drag-of-winglets
Thank you so much for these amazing videos Prof. van Buren! The hill analogy was very useful for understanding the utility of the Reynold's number!
Aw thanks! Turbulence is one of my favorite subjects, I'm glad it resonated with you.
Hi Professor, 1. For a propeller, if we intend to keep Re similarity, we then choose L=D and V=Omega*R as tip speed ratio. However, if we implement blade element momentum, every blade element spanwise will have different Re numbers. Considering downscale 5m Diameter turbine to a 0.8m Diameter turbine and the blade element at 1/5R, meaning 0.5 and 0.16m respectively, do we need to ensure the Re equal among those? 2. Why do we choice V=Omega*R? Looking forward to hearing from you. Thanks. Huy.
Thanks for your patience! Just getting to comments after a short stint away. This is a good question. In these cases, there are multiple velocity scales (tip speed vs forward speed) and it is very hard to preserve all the non-dimensional numbers when scaling down. If you scale down in size, usually you need to increase velocity to compensate. This means, needing much higher rotation angular velocities of the turbine (to preserve tip speed ratio), which introduces all different sorts of problems. Definitely a challenge! Tip velocity is just a lateral velocity component, there is still usually a forward velocity. Typically, you choose based on which one is dominant.
I did not get why the mass flow rate (mdot on the rigth side of the equation) = the change on the cube mass at 06:10
dot indicates "change in time", so it is just the symbolic definition of mass change of the cube.
Why are the pressures on the front and back of the cylinder in opposite directions?
Not sure where specifically you mean, but generally I draw pressure as being normal from the surface with the arrow length correlating to pressure strength.
If the fluid flowing at the top is faster, then why is the pressure there higher? Should it be lower instead? I'm confused, please enlighten me.
Great question, I think I am just confusing with my arrows. In that case, it's really to indicate there is a strong pulling force (low pressure region)
@@prof.vanburen Your videos are great! For this point, I also got confused, since I would expect the top/bottom pressure to be lower, since the velocity is higher. Would it make sense to add a note about that? Thanks so much for your videos.
Thnx prof you saved my day❤
Glad to help!
Can you make a course that explains differentiation and integration
Back to the basics! If I ever am asked to teach the course at Uni, I can get some video lectures for it.
This is LLLLLLLLIIIIITTTTTTTTT
Nice!
Hallo Prof, In deriving the shear stresses, there is a mathematical manipulation carried out, namely multiplying du/dt with dy/dy. My question is why not multiply with dx/dx. It might seem a dumb question but just need to understand the logic behind this manipulation. Thanks
Really great question! I'm guessing it is just because it worked, we found that the skin friction scaled with flow gradient, which in this case is in the y-direction. There might be a more rigorous math reason, or a better explanation---in either case I do not know it.