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
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 ❤
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.
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.
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.
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
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?
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
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
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.
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.
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.
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.
This is an excellent series - you're a fantastic instructor. I hate to be a "choosy beggar", but do you have any homework problems, exams, etc. to complement this course? I'd love to work through some problems to check my understanding.
I could send you some, if you're interested. I do all custom problems in class for quizzes you might find useful. Just shoot me an email vanburen@udel.edu
If you consider that flow redirection is caused by the downwash of the induced vorticity, something interesting happens. Suddenly you have an explanation as to why air flows faster over the top of the wing, as the vortex carries momentum across the upper surface of the wing, keeping the boundary layer energized. Suddenly Coanda and Bernoulli make sense. The vortex takes away lift at the tips to enhance it at the center, an easy trade off to make since it makes lift possible to begin with.
These have been great to go through!! A quick typo note: at 16:50 you have s2-s1 = cv ln(T2/T1) - R ln(p2/p1) when I believe it should be s2-s1 = cv ln(T2/T1) + R ln(v2/v1)
Yes! You're right, there is a typo here which is corrected in the PDF version of these notes on my site. Unfortunately my typo rate seems strongly correlated with the amount of thermodynamics content there is.
