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In the Ray Kurzweil's book How to create a mind is said that:

The mathematics of how Bernoulli's principle produces wing lift is still not yet fully settled among scientist [...]

What does this statement mean? I have always known that the Bernoulli equations were well known. There is something that I am missing?

Qmechanic
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AntonYellow
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  • See also http://physics.stackexchange.com/questions/290/what-really-allows-airplanes-to-fly. For more try this search. – John Rennie Nov 25 '15 at 16:36
  • When Kurzweil says that, there must be more to what he is saying. As you've quoted it, it makes no sense. I'm trying to guess what he's referring to. Is it the reason behind the Kutta condition, for example? – Mike Dunlavey Nov 25 '15 at 18:00
  • I feel like somebody else has made a comment about this same statement. The reality is, from a physics perspective we all know how lift is made and there is no doubt about it. From a simplified model perspective, we come up with various ways to explain how each model predicts list. And surprisingly many models get it right by looking at things that wouldn't normally make sense -- equal transit, Bernoulli effect, bound circulation, etc.. – tpg2114 Nov 25 '15 at 18:55
  • @tpg2114: equal transit gets it right? – Mike Dunlavey Nov 25 '15 at 18:57
  • @MikeDunlavey Under a very restricted set of cases, I believe it does. But I always dismissed it as confusing and nonsensical so I didn't think about it past when it was introduced in my undergrad aerodynamics course. – tpg2114 Nov 25 '15 at 18:58
  • @AntonYellow -- if you want an pretty big overview for why scientists say "There are many theories of how lift is created," I summarized how we go from what really happens to a model in this answer. But really, there is no dissent among scientists about how lift is created; just about why different models that ignore large parts of the real physics still get it right. – tpg2114 Nov 25 '15 at 19:00
  • I can suppose Kurzweil is talking about the Kutta condition which is "not yet fully settled" mathematically, but there is no doubt that it applies. It has to do with the question: why does the air not snap around the trailing edge of a wing and go to the upper surface? Wing lift fundamentally depends on this. To explain it requires viscosity. – Mike Dunlavey Nov 25 '15 at 19:10
  • @MikeDunlavey Maybe we should talk about this elsewhere sometime, but what about the Kutta condition is "not fully settled" mathematically? It's an imposition to eliminate the slip line downstream of the trailing edge, which is only needed because we dropped the viscous term and now can only impose 1 instead of 2 boundary conditions like the real physics would require. It allows us to select the proper solution from the set of solutions that are possible from the equations. – tpg2114 Nov 26 '15 at 04:38
  • @tpg2114: You clearly know more about it than I do. I was just going by the Wikipedia summation. Maybe you can tell if Kurzweil is mistaken. – Mike Dunlavey Nov 26 '15 at 16:25

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