A wing accelerates air on top of itself. Does this cause any forward thrust? I would think so because the air is accelerating backwards which should create an equal and opposite reaction forward.
$\begingroup$
$\endgroup$
1
-
$\begingroup$ We've only known how wings work for about a century, so maybe the news hasn't gotten around. Here is my favorite explanation. $\endgroup$– Mike DunlaveyCommented Mar 24, 2017 at 20:29
Add a comment
|
2 Answers
$\begingroup$
$\endgroup$
For a normal wing in normal flight, there is some forward force on the front part of the wing.
Unfortunately, there’s a larger rearward force on the aft part of the wing that more than cancels this, so the net effect is the induced drag, not a positive thrust.
Perhaps interestingly, large turbofan engines use this effect to get a significant amount of their forward thrust from their carefully-shaped intakes. Since the air is given additional energy in the engine and the outlet nozzle doesn’t have to generate (radially inward) lift, just thrust, everything works together.
answered Apr 23, 2019 at 3:09
$\begingroup$
$\endgroup$
1
Sailboat sales act like a plane in a dive. It gains forward speed because the wings are pointing down. As they go down through the air, it pushes them forward by a camming action like a windmill. The only forward thrust in level flight is just behind the tip, where most of the losses from the backward force on the tip are returned. The air is not being accelerated backwards. It goes slightly faster over the top surface because it has a bit further to go in about the same time. See diagram.
-
$\begingroup$ "It goes slightly faster ... because it has a bit further to go in about the same time. " - this is B.S. $\endgroup$ Commented Apr 23, 2019 at 4:06