I could give you a very technical explanation, but it seems you have already read it anyways.
Facts: Air is a fluid. Lift is all about pressure differentials on a wing. You have to have velocity to have lift. You can't avoid drag if you have lift.
In your car, if you get to above 40 mph (to clearly experience the effect)
and stick your hand out the window (forearm PARALLEL the car for better experience) your hand and arm will be pushed UP and BACK. The BACK part of pushing is the induced drag. As simple as that.
The angle between oncoming wind (relative wind) and your arm is the AOA. The more your rotate your arm upward, the greater BACKWARD pressure will become.
It is impossible to have AOA and have all of the actual pressure force act perpendicular (straight up) to the relative wind. The actual pressure force will ALWAYS act at a rearward angle (UP and BACK). The upward part is LIFT that we want. The backward part is INDUCED DRAG that we dont want, but have to have as inevitable by-product of lift generation.
AOA + motion = > pressure increase on the bottom surface of (arm, hand, wing, ironing board, whatever), pressure decrease on the top surface of the same
Pressure increase on bottom/decrease on top => Pressure differential
Pressure differential = > Actual pressure force acting upward and backward
Pressure force => Lift (upward) + Induced Drag (backward)
More AOA => More Lift => More backward acting force => More Induced drag
Keep digging at it, just not while in an airplane!
Originally Posted by
sellener
I would like to understand induced drag a bit better.
I am fully capable of spitting out phrases I have heard in handbooks, and circulers. For instance.... for a checkride oral I might say induced drag is the penalty an airfoil pays anytime its generating lift.
Or
Wing tip vortices are the source of induced drag
Or
Vortices create downwash behind the trailing edge which effectivly increaseing the angle of the relative wind which also directs the lift vector (which acts perpindiculer to the relative wind) back.
Or
Something about upwash in front of the wing which also changes the relative wind a bit bending the lift vector back
bottom line, I dont truly understand what all causes induced drag....
my best understanding to date is.....
air travels high to low from under the wing towards the wingtip and then combines with the air their to impart a rotation to the air (vortice) the spiraling down motion over the trailing edge makes the effective relative wind angle a bit more and thus the drag vector tilts back to stay perpindiculer to the relative wind.
But I think there's a bit more to it than that if thats even an accurate statement.