5 ms·
The obvious follow-up question is : why does a wing deflect the air down?
by o_nate 7y ago
The obvious follow-up question is : why does a wing deflect the air down?
- Sharlin 7y agoWhy it deflects air below the wing downward is trivial: it is an inclined plane (the angle of attack is nonzero) Why it also deflects air above the wing downward – pulling the air down so to speak – is more complicated.
- o_nate 7y agoI guess it works as a very high level explanation. However, as a practical guide to designing an actual working airplane wing, it's probably too high level to be helpful. For instance, if Newton was a complete explanation, then a flat wing at a 45 degree angle should work well. A more complete explanation would also explain why airplane wings typically have the shape they do.
- frank2 7y agoA flat wing at 45 degrees produces massive turbulence above and behind the wing, which in turn greatly increases the drag-to-lift ratio compared to a standard airplane wing. Also I suspect that ailerons and other control surfaces become much less useful in turbulent flow.
- o_nate 7y agoSure, but now explain drag and turbulence using Newton's laws.
- mannykannot 7y agoVia the Navier-Stokes equations, which are the application of Newton's laws to viscous fluids.
- renox 7y agoI don't know if 45° wings provide good lift or not, but what I know is that they would induce a lot of 'drag'. And that the goal is to maximize lift while minimising drag.. So it isn't that complicated why the wings are the shape they are: if there is a 'gentle slope' the air will be redirected downwards without inducing too much drag.
- lutorm 7y agoIt may appear trivial, but thinking about it like a bunch of bullets bouncing off the wing on the bottom (the "particle regime") does not explain why it deflects air (the "fluid regime"). A fluid is governed by fundamentally different physics than a bunch of particles, so just because a bunch of particles hitting an inclined plane also would generate lift does not explain why air hitting the same plane does. For example, in the particle analog, the upper surface of the wing is totally immaterial. You could make it look however you want without affecting the generated lift. In reality, the amount of lift generated is much more sensitive to what happens on the upper surface than on the bottom.
- p_l 7y agoAn inclined plane provides enough force... at ridiculous speeds - generally you need to start with either very, very light vehicle, or supersonic speeds. The angle of attack is important in kickstarting and keeping running various phenomena that ultimately result in pressure differential between both sides of the lifting body (be it wing or other shape).