025 – Aerodynamic Lift Explained
This episode is a bit different. I produced it together with Joe D’Eon from the wonderful Fly With Me podcast. Together, we explored the question of how aerodynamic lift really works – in other words: why airplanes fly. He went out and asked a fellow pilot about what he thinks how lift works. I went to the University of Stuttgart’s Intitute for Aero- and Gasdynamics and talked with Thorsten Lutz. He explained the details of how it works. If his explanation still doesn’t do it for you, take a look at Wikipedia. They have a couple of nice illustrations.
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It seems to me that the definitive answer to this question would come from computational fluid dynamics (CFD). CFD should answer the questions “How much is the lift is due to impulse ?” and “What do the flow streamlines around the airfoil look like ?”. It also seems to me that somebody has by now used CFD to inquire about this. DO CFD results exist that answer this question ?
Hi, your suggestions certainly sounds reasonable. but I guess Thorsten would have known about that. So I am not sure :-)
Gibt es die Folge bzw. das Interview mit Torsten Lutz auch in deutsch ?
Die Folge gibt’s nicht in Deutsch. Das Interview muss ich mal kucken. Meldest Du Dich mal per Email bei mir (email@example.com)?
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I’d also like to hear back about if CFD analysis has tackled this.
There is a small imprecision: It is true that the flow above the wing does not have to reach the trailing edge of the wing contemporaneously to the flow below the wing. Indeed the flow above the wing is so much faster that it comes earlier to the trailing edge than the flow below! (The podcast claims the opposite at 16:46)
On a plane flying at 100 km/h at high angle of attack, the velocity of the flow backwards relative to the plane can be over 200 km/h above the wing and below 50 km/h below.
This is explained and simulated for instance in this wonderful explanation about lift and airfoils:
Lift works because the air is accelerated strait down, or tangential to the wing. See the book “Understanding Flight” by Anderson and Eberhardt.
For a helo, it seems natural. A wing is like a helo blade going strait, and accelerating a lot more air slower, but the principle is the same.
Google “coud cutting” for some videos where the wake is visible. Most of the air is pulled down by the upper surface of the wing, rather than pushed by the lower surface.