Just found a Nasa paper on circular wings. Don't worry about all the differential equations, the math is good.
http://naca.larc.nasa.gov/reports/1925/ ... tn-228.pdf
Honestly i think anyone really interested in lift should read sailing theory books.
Angle of Attack
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The spoon into water demo is a good example of Bernouli, (in order for it to be a dipole interaction the spoon would have to be charged, sorry RSC).
You are also right when you say that the air flowing over the top of the wing does not reach the trailing edge at the same time as the air flowing under the wing. This is what my prof. once called 'a useful lie'. The important thing is that there is a speed differential, and this leads the pressure differential. Calculating the magnitude of both is not important for developing a basic understanding of the topic.
Newton's 3rd law does play a big role in the production of lift. By setting the wing at an angle to the oncoming air, (giving it an angle of attack), we cause the wing to push the air down, and by Newton's 3rd law the air pushes the wing back up. As the AOA increases so does the amount of air pushed down. This results in greater lift. You can test this out for yourself by placing a completely flat object into an airstream, ie stick you hand out the window of a car while SOMEONE ELSE drives, and playing with its angle.
When AOA gets to large the air flowing over the top gets sucked into the low pressure area from the rearward sections of the wing. This destroys lift, hence you are stalled.
You are also right when you say that the air flowing over the top of the wing does not reach the trailing edge at the same time as the air flowing under the wing. This is what my prof. once called 'a useful lie'. The important thing is that there is a speed differential, and this leads the pressure differential. Calculating the magnitude of both is not important for developing a basic understanding of the topic.
Newton's 3rd law does play a big role in the production of lift. By setting the wing at an angle to the oncoming air, (giving it an angle of attack), we cause the wing to push the air down, and by Newton's 3rd law the air pushes the wing back up. As the AOA increases so does the amount of air pushed down. This results in greater lift. You can test this out for yourself by placing a completely flat object into an airstream, ie stick you hand out the window of a car while SOMEONE ELSE drives, and playing with its angle.
When AOA gets to large the air flowing over the top gets sucked into the low pressure area from the rearward sections of the wing. This destroys lift, hence you are stalled.
One only needs to be a spectator at a baseball game or a glofer to realize that spinning a ball causes it to lift. It then only stands to reason that spinning a cylinder would cause the same effect. Since the wings of our aircraft do not spin it is not helping in the explanation of lift in that both the upper and lower surfaces are being moved at the same velocity through the air. The shape then of the two surfaces is what causes the change of velocity near the surface, which brings us back to the original discussion of what causes the acceleration of the air over the upper surface.
Let us not forget that once we introduce an angle of attack we also increase the pressure under the wing and thus cause a slowing of the airflow there. Slower airflow equals higher pressure, as Bernoulli stated. That one is a no brainer. Any kid who has held his hand out the window of a moving car and tilted it up slightly has felt that force.
In the case of the spinning cylinder, in part, the explanation comes from the difference in coefficient of friction which is greater for sliding than rolling, or, the side of the cylinder that has the greater velocity to the relative wind would have the lowest coefficient of friction.
This should apply to an airfoil as well.
Free air which flows by the side of a building will swirl around the corner of the building causing what appears to be a relative vacuum behind the building that would pull back on the building. (ie. wind that is blowing parallel to the wall). This air which is in motion should have a lower pressure than the still air behind the building, so why does the air swirl behind the building?
The lower pressure air draws air from behind the building as it passes thereby creating a circular flow which in turn draws some of the free flowing air back behind the building. This effect is similar to the effect of upwash.
The effect of downwash is to cause a "backing up" of the airflow so as to cause a greater height(poor choice of terms) to the lift "wave" over the upper wing surface.
Upwash and downwash work together to form a partial vacuum over an airfoil. When the vacuum becomes too great (high angle of attack) the air flow collapses (from behind) as the flow takes up the appearance of the swirl stated above around the back of a building.
How does that strike you?
Slightly harder on the slower moving, I would venture.
Let us not forget that once we introduce an angle of attack we also increase the pressure under the wing and thus cause a slowing of the airflow there. Slower airflow equals higher pressure, as Bernoulli stated. That one is a no brainer. Any kid who has held his hand out the window of a moving car and tilted it up slightly has felt that force.
In the case of the spinning cylinder, in part, the explanation comes from the difference in coefficient of friction which is greater for sliding than rolling, or, the side of the cylinder that has the greater velocity to the relative wind would have the lowest coefficient of friction.
This should apply to an airfoil as well.
Free air which flows by the side of a building will swirl around the corner of the building causing what appears to be a relative vacuum behind the building that would pull back on the building. (ie. wind that is blowing parallel to the wall). This air which is in motion should have a lower pressure than the still air behind the building, so why does the air swirl behind the building?
The lower pressure air draws air from behind the building as it passes thereby creating a circular flow which in turn draws some of the free flowing air back behind the building. This effect is similar to the effect of upwash.
The effect of downwash is to cause a "backing up" of the airflow so as to cause a greater height(poor choice of terms) to the lift "wave" over the upper wing surface.
Upwash and downwash work together to form a partial vacuum over an airfoil. When the vacuum becomes too great (high angle of attack) the air flow collapses (from behind) as the flow takes up the appearance of the swirl stated above around the back of a building.
How does that strike you?
Slightly harder on the slower moving, I would venture.
Pilots get higher, SCUBA Divers do it deeper!
Hey OW a rolling tire has MORE friction than a sliding tire.
Does anyone remember the two Velocities that crashed after getting into a deep stall. The canard and the wing were producing vortex lift as the airplane fell straight down (in a level attitude) at about 10 mph. One of the pilots actually opened up the canopy and tried rocking the nose down. I don't know what would have happened if he would have succeeded.
ahramin
Does anyone remember the two Velocities that crashed after getting into a deep stall. The canard and the wing were producing vortex lift as the airplane fell straight down (in a level attitude) at about 10 mph. One of the pilots actually opened up the canopy and tried rocking the nose down. I don't know what would have happened if he would have succeeded.
ahramin
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Right Seat Captain
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I never said anything about magnetic forces, OW. That's a different issue completely. I was speaking of dipole forces, where one side of the water molecule has a slight positive charge, from the Hydrogen atoms loosing their electrons to the Oxygen, and the Oxygen having 2 extra electrons gives it a slight negative charge. Overall, the charges are balanced, but still one side of the molecule is slightly more positive than the other. This is not a magnetic effect whatsoever. In terms of having something being charged, you' be hard pressed to find anything that is completely neutral, including a metal spoon. Specifically when it comes to metal, you have atom neucleuses surrounded by a sea of electrons, collected from all the atoms. The surface of the metal, tends to be unbalanced, since the atoms at the surface are not surrounded completely by the sea of electrons, and have slightly positive charge. If you have a plastic spoon, this happens to a greater effect, from the hydrogens all along a polymer chain having a slightly positive charge.OW wrote:Now that I would have a tough time grasping. If I put a magnet on the faucet would that change it?
Does being drawn toward a speeding train when you are standing close also have to do with magnetic charges?
Do you wear a bimetal band on your wrist?
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justplanecrazy
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I think that this is the key to the post, the NASA article states:
"The upper flow is faster and from Bernoulli's equation the pressure is lower. The difference in pressure across the airfoil produces the lift.} As we have seen in Experiment #1, this part of the theory is correct. In fact, this theory is very appealing because many parts of the theory are correct."
It is saying that the Bernoulli's equation as a whole is actually false. There are many parts that are correct, but as a whole it doesn't stand up. I guess the most obvious example to confirm this, is a wing that has a symetrical upper and lower shape. In this case, Bernoulli's theory would suggest that there would be the same pressure formed on both sides of the wing. In the example on the Nasa website, we can see that this is not true.
"The upper flow is faster and from Bernoulli's equation the pressure is lower. The difference in pressure across the airfoil produces the lift.} As we have seen in Experiment #1, this part of the theory is correct. In fact, this theory is very appealing because many parts of the theory are correct."
It is saying that the Bernoulli's equation as a whole is actually false. There are many parts that are correct, but as a whole it doesn't stand up. I guess the most obvious example to confirm this, is a wing that has a symetrical upper and lower shape. In this case, Bernoulli's theory would suggest that there would be the same pressure formed on both sides of the wing. In the example on the Nasa website, we can see that this is not true.
We have no effective screening methods to make sure pilots are sane.
— Dr. Herbert Haynes, Federal Aviation Authority.
— Dr. Herbert Haynes, Federal Aviation Authority.
Put the bong down and read through all the stuff at nasa, including the discussion of Bernoulli vs Newton. Not just the pretty pictures for the grade 3s. 
It is not saying that Bernoulli's theorem is false. It is saying that the thoery of lift (which is not Bernoulli's) under discussion is false. When it says "this part of the theory" the theory in question is the theory of lift being discussed, not bernoulli's theorem.
Bernoulli was not an aeronautical engineer. His theory is not on how lift is produced. It simply states that as the speed of a fluid increases it's pressure decreases. Which is true or i would have lost my last sailboat race. He cannot possibly be wrong in his theory of lift because he never made one.
A symmetrical airfoil at 0 AOA will produce the same pressure on the top than on the bottom. That is why you need a positive angle of attack to produce lift with one. But that wing at a positive angle of attack still produces an increase in the speed of the air over the top of the wing, hence decreasing the pressure and producing lift.
ahramin
It is not saying that Bernoulli's theorem is false. It is saying that the thoery of lift (which is not Bernoulli's) under discussion is false. When it says "this part of the theory" the theory in question is the theory of lift being discussed, not bernoulli's theorem.
Bernoulli was not an aeronautical engineer. His theory is not on how lift is produced. It simply states that as the speed of a fluid increases it's pressure decreases. Which is true or i would have lost my last sailboat race. He cannot possibly be wrong in his theory of lift because he never made one.
A symmetrical airfoil at 0 AOA will produce the same pressure on the top than on the bottom. That is why you need a positive angle of attack to produce lift with one. But that wing at a positive angle of attack still produces an increase in the speed of the air over the top of the wing, hence decreasing the pressure and producing lift.
ahramin
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justplanecrazy
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O.k. just wait until Hedrix C.D. endsahramin wrote:Put the bong down and read through all the stuff at nasa, including the discussion of Bernoulli vs Newton. Not just the pretty pictures for the grade 3s.
O.k. explain the theory of lift to me then without involving the Bernoulli theory. I wasn't saying that Bernoulli's theorm is false, but rather how it is applied may be. The theory of lift is made up through several theories such as Bernoulli's.It is not saying that Bernoulli's theorem is false. It is saying that the thoery of lift (which is not Bernoulli's) under discussion is false. When it says "this part of the theory" the theory in question is the theory of lift being discussed, not bernoulli's theorem.
Bernoulli was not an aeronautical engineer. His theory is not on how lift is produced. It simply states that as the speed of a fluid increases it's pressure decreases. Which is true or i would have lost my last sailboat race. He cannot possibly be wrong in his theory of lift because he never made one.
Bernoulli's equation is part of the theory of lift. An imbalanced pressure will cause a movement of the object seperating the two, hence lift. This is one theory on how lift is formed!! After reading the other pages I can see that you are on the right track though. It is actually the "longer path" or "equal transit" theory that is being questioned, not Bernoulli's or the Theory of Lift.
http://www.grc.nasa.gov/WWW/K-12/airplane/wrong3.html
This page explains it more completely than that first one. I guess they are saying that the cambered wing doesn't cause the particles to travel faster because of the longer distance. Rather it is the turning that is important.
Once you read all three false theories, the whole picture is a lot clearer.
http://www.grc.nasa.gov/WWW/K-12/airplane/wrong1.html
http://www.grc.nasa.gov/WWW/K-12/airplane/wrong2.html
I love how people that can only speek out of their ass trying to put down the other posters, can never hold a constructive conversation. Your post told me nothing other than that you don't understand the article either. Go sail your boat.
We have no effective screening methods to make sure pilots are sane.
— Dr. Herbert Haynes, Federal Aviation Authority.
— Dr. Herbert Haynes, Federal Aviation Authority.
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Cat Driver
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Hmmmm
Hmmmmmmmm
There sure is a lot of nit pickin going on here about how lift is produced.
But the question is can you figure out how to actually fly the thing...
Based on a lot of the product that I get to re train there just has to be some sharp guys out there with an awsome understanding of physics that can't fly an airplane good enough to teach students......
Unless I'm getting students from one instructor.
Cat
Hmmmmmmmm
There sure is a lot of nit pickin going on here about how lift is produced.
But the question is can you figure out how to actually fly the thing...
Based on a lot of the product that I get to re train there just has to be some sharp guys out there with an awsome understanding of physics that can't fly an airplane good enough to teach students......
Unless I'm getting students from one instructor.
Cat
The hardest thing about flying is knowing when to say no
After over a half a century of flying no one ever died because of my decision not to fly.
After over a half a century of flying no one ever died because of my decision not to fly.
Bernoulli's theorm is correct. That we can prove through simple experiments, however many of the old text books state that lift is caused simply by the application of Bernoulli's Theorm.
A sail is, for all intents and purposes an airfoil, no arguement there.
I don't know if Bernoulli ever thought if his theory and experiments had anything to do with why birds fly, I didn't get a chance to ask him.
The issue, as I see it, is not that the air over the wing is accelrated and therefore the pressure drops, it is how the air is accellerated.
Bernoulli did it by forcing a fluid through a restriction. The argument that the air above the wing provides the restriction is weak at best because the affected air is relatively close to the airfoil for the amount of force that would be required. This is why much of the recent discussion has focused on the one surface as the significant contributor, instead of explaining it by reference to a restricted flow.
A sail is, for all intents and purposes an airfoil, no arguement there.
I don't know if Bernoulli ever thought if his theory and experiments had anything to do with why birds fly, I didn't get a chance to ask him.
The issue, as I see it, is not that the air over the wing is accelrated and therefore the pressure drops, it is how the air is accellerated.
Bernoulli did it by forcing a fluid through a restriction. The argument that the air above the wing provides the restriction is weak at best because the affected air is relatively close to the airfoil for the amount of force that would be required. This is why much of the recent discussion has focused on the one surface as the significant contributor, instead of explaining it by reference to a restricted flow.
Pilots get higher, SCUBA Divers do it deeper!
To explain lift to a student by Bernoulli's theorm alone is only giving a student a simplified version of a more complex subject. We also have to include Newton's Law and several other theories of lift to give the student the big picture. At this point I don't think anyone can say that it is 20% Bernoulli and 80% Newton or any other combination but the one thing we often forget is all that stuff is THEORY. If they were 100% sure we would be teaching the facts of flight instead of the theory of flight!!!
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Flying Low
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Wow...talk about rising a thread from the dead! Exactly a year and a day later. That's a long long time for formulate a response! 
"The ability to ditch an airplane in the Hudson does not qualify a pilot for a pay raise. The ability to get the pilots, with this ability, to work for 30% or 40% pay cuts qualifies those in management for millions in bonuses."
