3 ms·

>There is an area of low pressure over the wing where air is taking a longer path than under the wing, but that is only responsible for a small fraction of the

by na85 10y ago

>There is an area of low pressure over the wing where air is taking a longer path than under the wing, but that is only responsible for a small fraction of the lift. The "equal transit time" theory that you appear to be referencing here (air over the top takes a longer path, thus it must go faster and air under the bottom takes a shorter path thus it goes slower) is a complete fallacy. There is no mechanism in physics that requires the air to "meet up" at the trailing edge of the wing.

billforsternz 10y ago
Thanks for this. I read a million explanations of how airfoils worked as a boy and they all said the air had to travel faster over the top surface to catch up. Why does it have to catch up? I would scream internally. I'm stunned to find it was never true.
- rhizome 10y ago
  Probably like the Bohr model in Chemistry, it's an easy way to introduce the concept. Frankly I was under the impression it was true, too, and my dad was a small-plane pilot.
  - halomru 10y ago
    The Bohr model at least has simplicity going for it, and it's close enough to explain most things that are relevant to chemistry. For aircraft lift, "equal transit time" is not easier to understand than "an angled wing pushes air down, because of conservation of momentum that pushes the aircraft up".
  - deleted 10y ago
    [deleted]
- luca_ing 10y ago
  If you're interested in the topic, maybe you'd like to read http://www.allstar.fiu.edu/aero/airflylvl3.htm http://www.allstar.fiu.edu/aero/airflylvl3.htm
- mbrookes 10y ago
  This [1] is one of the most comprehensive examinations of lift, written in layman terms. You can read the HN discussion here [2], since this appeared on the front page a week ago, much to my surprise [3]. [1]1 http://ljjensen.net/Maritimt/A%20Review%20of%20Modern%20Sail%20Theory.pdf http://ljjensen.net/Maritimt/A%20Review%20of%20Modern%20Sail... [2] https://news.ycombinator.com/item?id=13829625 https://news.ycombinator.com/item?id=13829625 [3] https://news.ycombinator.com/item?id=13835243 https://news.ycombinator.com/item?id=13835243

by na85 10y ago

billforsternz 10y ago

Thanks for this. I read a million explanations of how airfoils worked as a boy and they all said the air had to travel faster over the top surface to catch up. Why does it have to catch up? I would scream internally. I'm stunned to find it was never true.

rhizome 10y ago
Probably like the Bohr model in Chemistry, it's an easy way to introduce the concept. Frankly I was under the impression it was true, too, and my dad was a small-plane pilot.
- halomru 10y ago
  The Bohr model at least has simplicity going for it, and it's close enough to explain most things that are relevant to chemistry. For aircraft lift, "equal transit time" is not easier to understand than "an angled wing pushes air down, because of conservation of momentum that pushes the aircraft up".
- deleted 10y ago
  [deleted]
luca_ing 10y ago
If you're interested in the topic, maybe you'd like to read http://www.allstar.fiu.edu/aero/airflylvl3.htm http://www.allstar.fiu.edu/aero/airflylvl3.htm
mbrookes 10y ago
This [1] is one of the most comprehensive examinations of lift, written in layman terms. You can read the HN discussion here [2], since this appeared on the front page a week ago, much to my surprise [3]. [1]1 http://ljjensen.net/Maritimt/A%20Review%20of%20Modern%20Sail%20Theory.pdf http://ljjensen.net/Maritimt/A%20Review%20of%20Modern%20Sail... [2] https://news.ycombinator.com/item?id=13829625 https://news.ycombinator.com/item?id=13829625 [3] https://news.ycombinator.com/item?id=13835243 https://news.ycombinator.com/item?id=13835243