Lyman, sir.
`Newton' and `Bernouilli' are both right in their way. `Newton' is couched in terms of conservation of momentum, `Bernouilli' in terms of conservation of energy. Both need to hold.
On a hovering Harrier, where does the lifting thrust act? Outwards and upwards equally at the elbow in the nozzles, where Mr Newton's second legal adviser would recommend his engineers to toughen the structure. The fuselage structure is on the rack, with seven tons pulling up, and seven tons pulling the machine apart abeam. As it starts to move forward, the flow over the wings takes some of the upward load, and the nozzles swivel back, rotating those 45 degree forces at the elbows forward, pulling the Harrier along instead of holding it up, while still trying to rip it apart acrossways.
Owain,
I fully accept your point that linear shear is not rotation, but once you account for the descending slab of air behind the aircraft, with the wingtip vortices to connect it to the non-descending air far from the flightpath, it's not a big stretch.
Close to the wing, I agree that the air that moving downwards the fastest is descending round the flap edge in that 757 picture, but that high-speed flow is part of a tight vortex - it spreads and slows behind, making the large scale dipole flow from the C17 wake picture, also effectively seen in the 747 contrail shot.
If the wing was all the way across a smooth windtunnel section, with no tips, the air behind the wing would have a uniform descending velocity component - there would be lift - and yet no rotation. I suspect almost the same is true for a sailplane wing - the downstream airflow is almost all descending slab, and almost no wingtip vortex.