Comment by p_l
2 years ago
And it's an "even more wrong" explanation than the "lies for children" diagram used in school physics class.
For reference, actual "proper" discussion of lift in textbooks on aerodynamics have tendency to start with a sphere/cylinder.
Do you have any recommended reading on this topic? I'd like to brush up.
Understanding Aerodynamics: Arguing from the Real Physics by Doug McLean, a former aerodynamics Technical Fellow at Boeing Commercial Airplanes.
Bill Beaty's site was the one that opened my eyes to these misunderstandings: http://www.amasci.com/wing/airfoil.html
If the diagram shows lift but doesn't show the air being directed downward after leaving the tailing edge of the wing, I basically stop reading. That's the whole thing.
Thank. You. That's exactly what is missing and that's exactly what I have mentioned in my... highly criticised comment. It just shows how pervasive the misconception is.
If you take a step back there is a simple way to think about this. In order for the object to stay up there, there needs to be equal and opposite force from some other body. What is that other body? It is the mass of air that is being directed in the opposite direction of the lift force acting on the plane.
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There used to be a good one from NASA, written for K-12 but 100% adhering to actual science not "lies for children".
EDIT: This is a good starting point for the frankly awesome material from NASA Glenn Research Centre: https://www.grc.nasa.gov/WWW/K-12/VirtualAero/BottleRocket/a...
Unfortunately it partly bitrotted due to using java applets for interactive demos, but I think most of it is still reachable - I'll try to find it later when I'm at the desk.
Personally I learnt from a 1980 book that was still part of mandatory reading for glider pilot course in Poland in 2005.
There is no lift on a sphere or cylinder without rotation dude. The whole point of parent post is that the "proper" discussion does not inlay a good intuitive understanding of lift, which in my opinion, should start with "push air down to go up".
Yes, there's no lift.
But there's quite different flow and drag around it, which was used as opening for for adding rotation (which would add viscosity effects including lift from rotation) and other changed shapes in better way than starting with flat plane.
Why is it wrong?