# Airfoil Explained for 16-Year-Old Confused By It

• Hoophy
In summary, Airfoils generate lift by bending the air downward. You can't really look at upper and lower regions separately and get the right answer, but it should help with understanding what is going on.f

#### Hoophy

Go easy on me I'm only 16 ;) I am utterly confused with the concept of "Airfoils", I have been doing some research on the web and so far all I have found is confusing descriptions that I do not understand and people arguing over which aerodynamics model for Airfoils is correct. The arguing and such only seem to increase my confusion. What I have taken from this so far is that the the Equal Transit Theory is incorrect, can somebody please explain to me how an Airfoil actually generates lift? Also I am confused about planes flying upside-down and flat Airfoils still managing to provide lift. Thank you for your assistance!

Hoophy
So if I'm understanding this correctly lift is generated when air is deflected downwards? Here's my problem, does the air on top get deflected downward and if so how (structurally) does this happen, or is air on the bottom getting deflected and if so how? Is it air on the top and bottom? Is it something completely different?

All of that air in the vicinity of an airfoil gets bent downward (in the case of positive lift, anyway).

For the air on the bottom, you can (sort of) imagine it like the air is hitting the bottom and being deflected downward, though this is only partially true, as it doesn't take into account the influence of the upper half (as mentioned in the article with the skipping stone fallacy). Still, it may be useful to visualize.

For the top, consider that if the air flew over the top of an airfoil with positive angle of attack and did not bend downward, there would be a void created. This void would be at zero pressure, while the free stream is at some higher pressure, so it would tend to push the air flow back down against the wing. In reality that void never forms in the first place and the air "simply" bends down to follow the contour of the surface.

Those are the simplistic, half-truth answers that ought to help with visualizing what is actually occurring. The truth is, though, that the flow over and under the wing affect each other. They are one system where changes to one will affect changes to the other. In other words, you can't really treat the upper and lower regions separately like I just did any get the correct answer, but it ought to help with qualitatively understanding what is going on.

russ_watters and Hoophy
Thank you so much for taking the time to help me out, I really appreciate your answers they were well constructed and clear. You have answered my question.