Originally Posted by
SmoothOnTop
Lift has many factors, but one can't rule out the majority element from Bernoulli's principle (BP).
When a wing tip vortex is formed, a significant portion is due to BP.
Think of air of higher pressure that flow towards lower pressure (wind, for example).
The higher pressure air below the wing spills over the wing tip towards the lower pressure above. As viewed from behind, the left wing tip vortex is clockwise and the right wing's is counter clockwise.
The problem with having discussions on highly technical subjects here is that internet is too limited to allow for an adequate explanation. I do not mind taking a swag at it, but providing short and simple reductions of complex phenomena is impossible when a full treatment takes years to assimilate. A far more fundamental aspect of the phenomenon of lift would be the Newtonian mechanics upon which Bernoulli based his equation. A good desktop reference is Aerodynamics for Naval Aviators. Something more simple is Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25).
Pressure differential between the upper and lower sides of a wing causes air to wrap into rolls at the edges and form into vortices, but it is incorrect to think pressure on the bottom is positive because
all the air surrounding a wing in normal operation is below ambient pressure, except a small region near the leading edge.
There is an awful lot of bad information regarding lift on the internet - posted by aerodynamists and physicists. Some of them may be teaching in accredited institutions of higher learning.
By and large I found teachers in college to be well-informed and well-prepared. Some of them were leaders in their respective fields. Internet is a sort of wild west upon which no one should base their education. Internet sources are not subject to peer review and in most cases are simplified for mass consumption. Whenever I want to know the truth about something I run to my old college textbooks. There is still a lot of quality material on the web but exercise caution and use it only as supplemental to accredited coursework, peer reviewed journals, textbooks, and your own research.
It makes one pause when considering why NASA is going to use 50 year old technologies and calculations for the future moon launches.
In a lecture that I attended by astronaut Bonnie Dunbar she stated that NASA has lost a lot of the knowledge and expertise gained from the original Moon shots. But I do not think that astronautical science has gone backwards since the 1960s, I think it has gone forward such that a manned mission to Mars is now feasible and low-earth orbit may soon be developed for commercial exploitation.
-Cub