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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.
There is an awful lot of bad information regarding lift on the internet - posted by aero dynamists and physicists. Some of them may be teaching in accredited institutions of higher learning.
It makes one pause when considering why NASA is going to use 50 year old technologies and calculations for the future moon launches.
Last edited by SmoothOnTop : 03-20-2008 at 06:15 PM.
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.
Quote:
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.
Quote:
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
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Last edited by Cubdriver : 03-20-2008 at 08:07 PM.
My head hurts after reading other 'experts' and the link you provided in p
Many US patented airfoils have curved upper and lower surfaces, with the general airfoil having a more pronounced upper surface camber.
The expert's hypothesis (from the link from post # 3 'NPR's Lift') is that because airshow pilots fly upside down we should be suspicious of Bernoulli's Principle (BP).
In the same light, other 'experts' dismiss BP because a rubber band powered, flat-winged balsa wing airplane flies just fine.
Both theory of flight gurus seem to forget about angle of attack.
At increasing angles of attack, the relative lower pressure deepens until flow separation.
The balsa wood rubber band airplane's fuselage wing slot is angled up (positive angle of attack) with respect to the relative wind created while it's propeller pulls it through the air.
The flat wing is an airfoil, just not a very efficient one.
If the airshow pilot's plane does not have a symmetrical airfoil, he/she must fly at a greater angle of attack* when inverted than right side up at a given airspeed to maintain level flight.
I'm not ready to 'diss' BP. Think about all the naca airfoil patent paperwork nightmare that would ensue.
* when inverted pushing the nose higher above the horizon.
ps- I just didn't want anybody to attempt a split S close to the ground.
Smooth-
Angle of attack and Bernoulli are valid, no one is leaving those out. And I confess, I made a variety of statements in the other thread, some quite accurate and some pretty far from correct. Like air hitting the bottom of the airfoil or wing and deflecting down is innaccurate. But the idea in the same post about circulation was correct. I get rusty and have to refresh. The topic started because Ira Flato came on Science Friday and said the bottom of a wing has no effect or role in creating on lift, which is too innaccurate to tolerate. I felt the subject needed some review, and admit that I too need an occasional review.
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Last edited by Cubdriver : 03-21-2008 at 09:14 AM.
I do too and I have done a lot of study and coursework on the subject. It can be challenging, but studying and discussing aerospace topics makes professional and personal life more rewarding. I design aircraft systems for a living and enjoy talking about, studying, flying, and designing airplanes. Aircraft are sufficiently complex now that one can spend a lifetime on them without exhausting the subject. Airplanes are objects of practicality, beauty, science, symbolism, history, and are a key component in the advancement of a nation. One of the first things to obtain funding when a nation tries to move forward or protect its assets is aircraft. As such, they are one of the more interesting things to spend time on if you ask me.
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Turn the heat O-F-F!
Last edited by Cubdriver : 03-21-2008 at 04:47 PM.
I do too and I have done a lot of study and coursework on the subject. It can be challenging, but studying and discussing aerospace topics makes professional and personal life more rewarding. I design aircraft systems for a living and enjoy talking about, studying, flying, and designing airplanes. Aircraft are sufficiently complex now that one can spend a lifetime on them without exhausting the subject. Airplanes are objects of practicality, beauty, science, symbolism, history, and are a key component in the advancement of a nation. One of the first things to obtain funding when a nation tries to move forward or protect its assets is aircraft. As such, they are one of the more interesting things to spend time on if you ask me.
Now I know why I appreciate your posts. Both my parents are retired school teachers. My dad, PH.D, Math Education, MSU circa 1974!!! Mom - MS in Education--FAU, 1968. Between 3 sisters and 1 brother.........1 Ph.D.; 2 MS degress; 1 MBA and 5 BS degrees.
Education is the foundation for just about everything. Not to drift too far from the thread on aerodynamics and lift... but my father was an academician and he went for not one but two PhDs, one in psychology and a second in business accounting. I will probably go for a masters since it seems to be something I really enjoy doing and could see spending a lot more time on. For now I am working in industry and paying down student loans. If I did not have to pay for my own education I already would have gone to graduate school, but money matters and there is no way around being responsible for ones debt.
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Last edited by Cubdriver : 03-22-2008 at 05:28 PM.
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