I wanted to ask a question regarding airfoils. When looking at videos online about them, the instructors say that airfoils work because the top of the wing turns air down due to the coanda effect and the downturned air also turns the air under the wing down to create lift. I think I understand the law applied here to be with every action there is an equal and opposite reaction however, with the explanation they gave, it seemed like they were saying that the air on the top that was turned down was the only thing that is turning the air under the wing down. I that true? I would assume that, even though that does happen, the lift generated from the bottom of the actual wing deflecting the air down was more and more important than the coanda effect on the top. The video also said that disrupting the flow on top of the wing through too high of angle of attack would cause it to stall, but wouldn't the actual reason being that the bottom of the wing converts too much lift into drag by changing the opposing force that is lifting it from mostly up to mostly back? There was another source that said that there was a vortex at the back of the wing that pushed the air at the bottom of the wing so that the net force would cancel out a bit, slowing the air down and making a pressure difference to lift the wing. What is that about? Please help.
Answers (1)
First you want to remember that it took a hundred years to learn that stuff, so it might take you a while to understand it. For a long time they thought the Bernoulli effect was the only source of lift.
When talking about this air versus that air you need to remember that the air was all together before the wing hit it, and it all has to come together again somehow after the wing has passed. All that coming together is measured as lift or drag or turbulence.
If you raise the angle of attack you eventually have only drag, no lift. You are trying to visualize several interacting effects. Keep plugging away and eventually you will start to feel like you have seen this before.