Talk:Lift (force)

What interactions cause the increase of energy of the air when producing lift (and drag)?

Using the air as a frame of reference, after a wing passes through a volume of air, the affected air ends up with an increase in energy, a downwards (lift related) and somewhat forwards (drag related) non-zero "exit" velocity where the affected flow's pressure returns to ambient.

Using a 1500 lb glider with 60:1 glide ratio at 60 mph as an example, (a Nimbus 4T with an 80 foot wingspan does this at 68 mph), in a steady 1 mph descent, the gravitational power applied to the glider is 1500lb x 1 mph = 4 horsepower. The glider in turn applies this power to the air, adding 2200 lb ft of energy to the air every second.

Most of the energy is in the form of an impluse wave that transmits the 1500 lb weight of the glider through the air and eventually onto the earth's surface.

Clearly Bernoulli is violated by this increase of energy of air (work is peformed). What are the interactions between a wing and air that are responsible for this increase in energy? In real world situation, such as assuming a finite wingspan of 100 feet or less, is there a lower limit to the minimal amount of energy that must be added to the air in order to produce lift for a 1500 lb glider at some range of speed, perhaps 35 mph to 70 mph?

Jeffareid (talk) 20:18, 23 February 2010 (UTC)

Viscosity? When anything moves through the air you get molecules hitting the surface and they inevitably bounce off faster, they then hit each other and similar things happen there. The net upshot is that the thermal energy of the air around the object increases. If you think about it, drag has to involve heating because energy is force times distance, in any second the object has moved a distance against the drag force, and that energy has to go somewhere.- Wolfkeeper 01:56, 24 February 2010 (UTC)

In this case of a glider, the temperature increase of the affected air is small, and the amount of change in velocity of the air in the direction of flight, related to drag, is also small. Most of the change in velocity (from zero relative to the air, to the "exit velocity" speed) is in the direction of lift, and most of the increase in total mechanical energy is related to the increase of "exit velocity" in the direction of lift. Since the wing is at an effective angle of attack, it could be possible to estimate work done in the direction of lift as the average force of the wing times the average component of distance the wing surfaces move perpendicular to the direction of flight, as a wing moves through a cross-sectional plane perpendicular to the direction of flight, but I don't know how to take the pressure differential effects into account. Jeffareid (talk) 03:31, 24 February 2010 (UTC)

There's a handy formula for relating fluid velocity to pressure - it's called Bernoulli's principle :-) If the temperature increase of the affected air is small, it will provide good answers. But, there's no work done in the directin of lift for straight and level flight. (No distance travelled in the dirction of the force = no work.) The propulsion system does the work in overcoming drag.69.1.23.134 (talk) 02:54, 14 March 2010 (UTC)

I agree that no work is done by the lift vector, but it isn't only in straight and level flight. Providing the frame of reference is the one in which the atmosphere has zero velocity, lift is the component of aerodynamic force that is perpendicular to the vector representing the velocity of the airfoil (or wing or aircraft) and so zero work is done, regardless of whether the aircraft is in straight flight or turning, level flight, climbing or descending. Thrust, drag and weight are all capable of doing work on the airfoil (or wing or aircraft) but lift does no work when using this particular reference frame. Dolphin51 (talk) 11:32, 14 March 2010 (UTC)

True for an airfoil, but not for a wing or aircraft. Turning, climbing and descending all involve work in the direction of lift on the wing/body resulting in energy storage/release by the wing/body. 214.4.238.180 (talk) 18:11, 12 May 2010 (UTC)

True for an airfoil, but not for a wing ...? What is a wing if it isn't an airfoil? Climbing and descending involve work, but it is work done by the weight and thrust. Turning flight doesn't involve work. If we choose the reference frame attached to the atmosphere, lift never does work because lift is defined to be the component of aerodynamic force that is perpendicular to the relative velocity, and any force that acts perpendicular to the displacement or velocity vector does zero work. See the definition of Work (physics). Dolphin (t) 21:56, 27 October 2010 (UTC)

For a two-dimensional airfoil or an "infinitely rigid" body there would be no work. But in the case of a real wing/aircraft the wing is displaced in the direction of lift (relative to the center of gravity) during maneuvers. This does real mechanical work on the wing. This is easily visible on the wings of large body aircraft during takeoffs and significant maneuvers. 69.1.23.134 (talk) 01:31, 14 November 2010 (UTC)

69.1.23.134 has written the wing is displaced in the direction of lift ... This is incorrect. Lift is defined to be the component of the aerodynamic force that is perpendicular to the direction of motion, therefore any displacement is perpendicular to the lift. Wherever force and displacement are perpendicular, no work is done - for example a centripetal force is perpendicular to the direction of motion and so centripetal force does no work and the body continues in circular motion with no change in kinetic energy. Dolphin (t) 07:04, 14 November 2010 (UTC)

You are correct that lift is the component of the aerodynamic force that is perpendicular to the direction of motion of the airflow. The work done by the force is the dot product of the force vector and the motion of the wing, so in the case of an airplane flying at a steady altitude, the motion of the wing is perpendicular to the force vector and thus the lift force does no work. By way of contrast, look at a sailboat - the motion of the sail is not perpendicular to the lift force and the lift force does do work (ie transfer energy to the foil). So, sometimes the lift force does work on the foil, sometimes it does not. In particular, when an airplane is climbing, the wings move in the direction of the lift force and the lift force does work on the wings. Mr swordfish (talk) 02:38, 15 November 2010 (UTC)

Much of what Mr swordfish has written is correct. However, his statement So, sometimes the lift force does work on the foil, sometimes it does not. In particular, when an airplane is climbing, the wings move in the direction of the lift force and the lift force does work on the wings is incorrect. Yes, work is the dot product of the force vector and the displacement vector; lift is defined to be the component of aerodynamic force that is perpendicular to the vector that represents the relative velocity of the airfoil and the freestream, therefore the dot product of these two vectors is always zero. Whether an airplane is climbing, descending or flying level, and we are using the reference frame attached to the atmosphere, the wing does not move in the direction of the lift force so the lift force does no work. (When an airplane is flying level or climbing, and its kinetic energy increases, it is the thrust that does work, not lift. When an airplane is descending and its kinetic energy increases it is the weight that does work.) If we use a reference frame other than the frame attached to the atmosphere, lift will usually not be perpendicular to the displacement so lift will do work. For example, when using the reference frame attached to the Earth's surface the airplane's velocity will be its ground speed and that will sometimes change due to work done by lift, such as when an airplane accelerates while turning downwind, or when it decelerates when turning upwind, and the horizontal component of lift during the turn does work on the airplane. Dolphin (t) 10:45, 15 November 2010 (UTC)

But if you define a single velocity vector (forward) and a single lift vector (up) for a non-rigid body, you will have wing displacements along the "up" axis resulting from the internal torque of the "real" lift at each wing. You cannot establish infinitely many inertial reference frames and discount each contribution to torque individually. If you have one frame for a flexible body, there is real work occuring in that frame. 214.4.238.180 (talk) 16:49, 18 November 2010 (UTC)

This discussion is about airfoils, wings and airplanes. They are being considered as rigid bodies. The comment above by 214.4.238.180 is unclear but in referring to a non-rigid body and a flexible body he appears to be describing the dynamics of wing bending. If so, it is off the current topic. 214.4.238.180 has written You cannot establish infinitely many inertial reference frames ... True, but nobody has done that. Dolphin (t) 22:08, 18 November 2010 (UTC)

Perhaps a rename to "Lift (Thin airfoil theory)" or "Lift (Two-dimensional flow)" is in order. The work performed by lift on any real air vehicle (or even any rotating rigid body) cannot be analyzed from a single 2-D inertial reference frame. 214.4.238.180 (talk) 17:58, 20 January 2011 (UTC)

So may I presume that Dolphin now agrees that wing bending in the case of a real wing/aircraft is a displacement in the direction of lift (relative to the center of gravity) which does real mechanical work on the wing? And that what 69.1.23.134 has written is actually correct? (albeit outside the two-dimensional flow model used in the article - I failed to grasp that the article covered only thin-airfoil theory) 69.1.23.134 (talk) 03:13, 22 March 2011 (UTC)

You asked what interactions cause the increase in energy involved in lift and drag. I don't know if this really answers your question, or just leads to another question, but here is a stab.

(Hope we are indirectly supporting the article here, since Wikipedia policy forbids discussions for other purposes.)

Each tiny patch of wing collides with air molecules. Each collision imparts a change in momentum of the particle (and the glider). For some of those patches, for example at the forward stagnation point, the collisions increase the magnitude of the momentum of the particles, increasing their kinetic energy (by one half the square of the increase, divided by the mass). For others, they decrease it, as on the top surface aft. A patch there is receding from the particle, which dulls the rebounds like a snowball hitting a moving car from behind. The power transfer from a given patch is the sum of those energy changes per unit time, which smooths out to a constant value if all else is steady. For some patches that power is positive, for others negative, But the sum of the powers from all the patches is positive. These are the interactions that cause the increase in energy, I think.

Mark.camp (talk) 16:05, 27 October 2010 (UTC)

@Mark.camp:A body experiences drag and leaves behind a wake where previously there was no movement. The kinetic energy in the wake is the result of work done by the drag force. Lift does no work because it is perpendicular to the direction of motion. Dolphin (t) 11:33, 22 March 2011 (UTC)

• there's no work done in the direction of lift for straight and level flight. (No distance travelled in the direction of the force = no work.) - For straight and level flight, the wing isn't moving in the direction of lift, but the air is being accelerated in the negative direction of lift, and as mentioned in the original post, the wing applies a downwards force on the air, and the surfaces of a wing are angled downwards, so there is some vertical component of the displacement of the surfaces of a wing as it passes through any cross sectional area of air. Rcgldr (talk) 15:44, 26 September 2011 (UTC)

@Rcgldr: Lift is defined to be the component of the aerodynamic force that is perpendicular to the vector representing the relative motion between an airfoil and the atmosphere. So lift is always perpendicular to the direction of motion, regardless of whether the airfoil is moving straight and level or performing aerobatic maneuvers. Consequently, when we are using a reference frame attached to the atmosphere, the lift on an airfoil is always perpendicular to the direction of motion and the lift does no work on the airfoil. This explains why lift can't be used to increase the kinetic energy of an airfoil - that requires either thrust or loss of gravitational potential energy. Dolphin (t) 22:36, 26 September 2011 (UTC)

lift can't be used to increase the kinetic energy of an airfoil - that requires either thrust or loss of gravitational potential energy.

Then how do you explain how a sail accelerates a sailboat? It's not gravity, and it's not some external thrust as from an engine. Mr. Swordfish (talk) 14:56, 27 September 2011 (UTC)

@Mr swordfish: An excellent question! I haven’t grappled with that one before so it has exercised my brain. The answer focuses on the choice of reference frame.

Lift is defined to be the component of the aerodynamic force that is perpendicular to the vector representing the relative motion between the atmosphere and the airfoil. If we choose an inertial reference frame attached to the atmosphere (or even one attached to the airfoil) lift is incapable of doing work. But if we choose any reference frame other than these two, lift is no longer perpendicular to the motion between atmosphere and airfoil, and it is capable of doing work and altering the kinetic energy of the airfoil.

When thinking of a sailboat I instinctively use a reference frame attached to the ocean. I see the wind (the atmosphere) coming from one direction with speed W, and the sailboat initially stationary and then accelerating in a different direction to the wind. However, in doing so I am not using an inertial reference frame attached to the atmosphere or the airfoil so I must expect that the lift on the sail will be responsible for increasing the kinetic energy of the sailboat.

If I use a reference frame attached to the atmosphere, the entire ocean is moving in a straight line with speed W. Similarly, the sailboat is initially moving at speed W. (All counter-intuitive!) The sailboat of mass M initially has kinetic energy half*M*W squared. The lift on the sail is perpendicular to the apparent direction of movement of the sail so it acts as a centripetal force and the sailboat appears to follow a circular path, still with speed W and kinetic energy half*M*W squared. Using this reference frame, the sailboat began with speed W and ended up with speed W, but in a different direction, so the lift on the airfoil has changed the direction of movement of the sailboat but hasn’t changed its kinetic energy.

I suspect some high-speed sailboats can actually move faster than the wind speed. That is a complicating consideration! I will have to think about it. Dolphin (t) 22:56, 27 September 2011 (UTC)

Ummmm... I don't know where you got that from, but the idea that lift can't do work is completely false. That's precisely how windmills work; the air flows over an aerofoil, this generates lift force perpendicular to the axis and it turns the rotor, doing work (force times distance). Also, when an aircraft lowers its nose, it loses altitude... and gains horizontal speed. That horizontal speed increase is entirely due to the lift vector being tilted forwards to the horizontal, literally pulling the aircraft forwards and gaining it kinetic energy.- Sheer Incompetence (talk) Now with added dubiosity! 22:59, 16 January 2012 (UTC)

Hi SI. Thanks for taking an interest in this subject. You are correct in saying the lift force on a windmill does work. (There are actually many examples where the lift force does work, but it all depends on choice of reference frame.)

In my edit dated 27 Sept (immediately above yours) I wrote:

If we choose an inertial reference frame attached to the atmosphere (or even one attached to the airfoil) lift is incapable of doing work.

Notice the emphasis on choice of reference frame! When contemplating a windmill it is challenging to use any reference frame other than one attached to the Earth. The frame attached to the Earth is clearly not one attached to the atmosphere (unless the atmosphere is stationary, in which case the windmill won't be turning.) As an exercise in basic aerodynamics, try drawing the blade of a windmill using the reference frame attached to the atmosphere. Be sure to include all the forces acting on the blade. You will see what force is responsible for the work on the mill, and you will probably be surprised. (Let me know if this one stumps you and I will be happy to explain.)

The purpose behind this topic of discussion is to reinforce the idea that lift is not a stand-alone force, as many people think. The stand-alone force is the aerodynamic force. Mankind chooses to resolve the aerodynamic force into two components - lift and drag. Mankind defines these two to be the components perpendicular to, and parallel to, the vector representing the relative velocity between the airfoil and the atmosphere.

When a pilot lowers the nose of his aircraft in order to accelerate, it is the weight of the aircraft that does work on the aircraft and causes its kinetic energy to increase; not the lift. Dolphin (t) 01:58, 17 January 2012 (UTC)

Um. Careful here. Although energy is to a degree frame dependent, changes in energy occur in all frames in a pretty similar way. The lift force does work in all inertial reference frames on the windmill blades. Lift force is not an ultimate source of energy of course, in the case of a windmill that's the sun, but that doesn't stop the lift force doing real work. In the case of the aircraft, the potential energy is the ultimate cause of the acceleration, but the lift force does do work by accelerating the aircraft when the lift force is tilted forwards. If you think about it gravity can't accelerate a vehicle forwards, since it acts always downwards, and $work = \vec force \cdot \vec distance$ giving always zero work done for any horizontal distance when the force is purely vertical, as with gravity, and yet the aircraft gains horizontal speed, work has been done. It's the lift force that actually does the work to accelerate the vehicle laterally.- Sheer Incompetence (talk) Now with added dubiosity! 02:31, 17 January 2012 (UTC)

What I'm saying is, both the aerodynamic force as well as the lift force can and do do work.- Sheer Incompetence (talk) Now with added dubiosity! 02:31, 17 January 2012 (UTC)

┌────────────────────────────────────────────────────────────────────────────────────────────────────┘You have written If you think about it gravity can't accelerate a vehicle forwards, since it acts always downwards. If a person is riding a bicycle down a hill, he or she can take their feet off the pedals and accelerate forwards, at least until arriving at the bottom of the hill. How can that happen? Dolphin (t) 04:52, 17 January 2012 (UTC)

Gravity doesn't do that either, and for the same reason. It's the reaction to the gravity that accelerates the bicycle down the hill. The gravity pushes the bicycle downwards, but the hill pushes back, perpendicular to the surface, which is at an angle. The component of that reaction force that faces forwards down the hill accelerates the bicycle laterally. Gravity itself CANNOT accelerate a bicycle sideways, it points 90 degrees- it's in the wrong direction.- Sheer Incompetence (talk) Now with added dubiosity! 05:55, 17 January 2012 (UTC)

Let me see if I have got it right. The reaction from the hill pushes upwards, perpendicular to the surface. The component that faces down the hill accelerates the bicycle. So the force that is perpendicular to the hill has a component that faces down the hill. Have I got it right? Dolphin (t) 07:11, 17 January 2012 (UTC)

Yes, that's pretty much right, the reaction isn't entirely upwards, it's perpendicular to the surface, which is tilted and that does the work.- Sheer Incompetence (talk) Now with added dubiosity! 17:05, 17 January 2012 (UTC)

I agree that the reaction isn't upwards. It is perpendicular to the surface, and the surface is the side of the hill, which is sloping. You wrote:

$work = \vec force \cdot \vec distance$

The reaction is perpendicular to the side of the hill, and perpendicular means ninety degrees. The dot product of two vectors at ninety degrees is zero, suggesting the work done by the reaction force would be zero. Where are we going wrong? Dolphin (t) 21:49, 17 January 2012 (UTC)

You can pick the distance vector in any direction you want. A horizontal vector is parallel to the horizon. The lift force in the case of the aircraft and for the reaction to the weight of the bicycle both do work in that direction. In a sailing boat, the lift vector also does work horizontally and in a windmill it does work as a torque. For a kite, the lift can be have a vertical component and if the kite rises then it has done work vertically (note that for a kite the drag vector cannot do work if the wind is lateral). The idea that the lift vector cannot do work is false. Of course if you deliberately pick a vector that is at 90 degrees to the lift vector, then it can do no work, but otherwise it will do work.GliderMaven (talk) 01:16, 18 January 2012 (UTC)

GliderMaven is absolutely correct when he writes Of course if you deliberately pick a vector that is at 90 degrees to the lift vector, then it can do no work

Lift is just a component of aerodynamic force. It is defined to be the component of the aerodynamic force that is at 90 degrees to the vector representing the relative motion between the airfoil and the atmosphere. That is the same as saying lift is deliberately picked to be at 90 degrees to the motion.

That is why it is true to say that in the reference frame attached to the atmosphere, lift is incapable of doing work, but in almost every other reference frame lift is capable of doing work. Dolphin (t) 02:05, 18 January 2012 (UTC)

"in the reference frame attached to the atmosphere, lift is incapable of doing work" NO, that is WRONG, because the reference frame attached to the atmosphere is NOT the relative wind reference frame, the lift vector is perpendicular to the relative wind NOT the reference frame attached to the atmosphere!!!!- Sheer Incompetence (talk) Now with added dubiosity! 07:40, 19 January 2012 (UTC)

The relative wind is a vector, not a reference frame. You are writing about the relative wind reference frame.

You have also written the lift vector is perpendicular to the relative wind ... Yes!, we both agree on that point

You have also written the lift vector is ... ... NOT the reference frame attached to the atmosphere. Correct - the lift vector is not a reference frame. In fact, no vector is a reference frame.Dolphin (t) 12:27, 19 January 2012 (UTC)

Basically, the relative wind reference frame and the atmosphere's reference frame are only the same when you're in level, constant speed flight, and yeah, in that case there's no work being done. But as soon as the wing is accelerating, they're different reference frames, and in general, the relative wind reference frame is a non inertial one, and can generate power. That's how windmills work, the blades' relative wind is constantly changing direction and the lift force is very definitely generating power!!!- Sheer Incompetence (talk) Now with added dubiosity! 07:40, 19 January 2012 (UTC)

There it is again - the relative wind reference frame. Relative wind is a vector, not a reference frame. Dolphin (t) 12:27, 19 January 2012 (UTC)

Reference frames have an origin and a speed, which is a vector. You can align a reference frame with the relative wind, this is commonly done to analyse a jet engine in flight for example. In that frame of reference the air will approach the engine along the x-axis.- Sheer Incompetence (talk) Now with added dubiosity! 17:53, 19 January 2012 (UTC)

When we talk about aligning the relative wind with the axis of a jet engine we are constructing a Cartesian coordinate system. For an explanation of what I mean by a frame of reference have a look at Frame of reference#Examples of inertial frames of reference. Dolphin (t) 22:04, 19 January 2012 (UTC)

Look you said: " If we choose the reference frame attached to the atmosphere, lift never does work because lift is defined to be the component of aerodynamic force that is perpendicular to the relative velocity". But I'm not sure which reference frame you mean by "reference frame attached to the atmosphere". Do you mean the reference frame in which the atmosphere is (upstream) stationary and the wing moves or the one in which the wing is momentarily stationary with the wind approaching (say) aligned along one of the reference frame's axes?- Sheer Incompetence (talk) Now with added dubiosity! 17:53, 19 January 2012 (UTC)

Imagine the wind is blowing at 10 knots and an aircraft is flying upwind at 200 knots TAS (190 knots GS). Using the frame of reference attached to the atmosphere, the air is stationary (except in the immediate vicinity of the aircraft), the aircraft is moving at 200 knots and the Earth's surface is moving at 10 knots. Another way of describing the frame of reference attached to the atmosphere is to say As seen by an observer in a hot air balloon ... Dolphin (t) 22:04, 19 January 2012 (UTC)

If the former, then the relative wind points in different directions depending on what the wing does and the force can certainly do work, as in a helicopter or a windmill. If the later, then it's correct to say that at the moment the wing is stationary that the wind is generating no power (since work=force.distance, so power=force.speed, but speed is zero since it's momentarily stationary. BUT, and it's a big but that acceleration can still be non zero, as in a helicopter or a windmill and so it will not be zero a moment later unless the wing is moving at completely constant speed, which in general it WON'T be.)- Sheer Incompetence (talk) Now with added dubiosity! 17:53, 19 January 2012 (UTC)

If that's what you're talking about, then the wing can't be guaranteed to be stationary unless you're using an accelerated reference frame, but those get even more complicated and don't change the underlying physics. And if it's not stationary then the wing can generate power.- Sheer Incompetence (talk) Now with added dubiosity! 17:53, 19 January 2012 (UTC)

What you're saying is very obviously wrong in general, although is true in restricted situations like level flight. The physics is that lift can and does do work, if it didn't no aircraft would be able to takeoff. I mean what other force operates to lift a helicopter?- Sheer Incompetence (talk) Now with added dubiosity! 17:53, 19 January 2012 (UTC)

┌────────────────────────────────────────────────────────────────────────────────────────────────────┘This is a very interesting discussion but it has drifted away from improving the article Lift (force). I have transferred the latest discussion to my Sandbox2 and I will post my reply there. Dolphin (t) 02:09, 20 January 2012 (UTC)

Fundamental physics

Comment here only, I am not going to edit the actual W. page. The fundamental generator of force is inertia, the acceleration of a mass (remember the old unit named Slug?), air in this instance but is the same for a liquid. A brick can fly but aerofoils are about how to achieve least energy loss for whatever regime they are designed to operate in. Hence I am amused at the hand waving, the detail processes surrounding the elephant. — Preceding unsigned comment added by Tchannon (talk • contribs) 14:18, 28 May 2011 (UTC)

Welcome to this talk page. You say The fundamental generator of force is inertia. I haven't heard that before, and I disagree with it. Who, or what source, are you quoting when you say that?

Your final sentence suggests you think lift should be explained only in simple, basic terms. Many people are very happy with simple, basic explanations of things. I think we cater for those people in the article Lift (force). Wikipedia aims to reflect the sum of knowledge to be found in reliable, published sources. On the subject of lift, reliable published sources go far beyond a simple, basic explanation so it would be inappropriate for Wikipedia to omit the more comprehensive, science-based explanations found in those sources. Dolphin (t) 00:57, 29 May 2011 (UTC)

'The fundamental generator of force is inertia.' is i suppose a confusing way of stating Newton's second law, 'force is the rate of change of the momentum.' — Preceding unsigned comment added by 81.141.165.139 (talk) 19:50, 29 October 2011 (UTC)

Planing lift

An editor recently added discussion of Planing to this article. What's the consensus about this change? My take is that it's a separate topic that should be covered in it's own wiki article. I definitely don't think it belongs in the overview, as it's only somewhat related to the main thrust of the article. Introducing the term "Submerged Foil Lift" seems like it would confuse the reader.

I'm going to undo the edits pending consensus here on the talk page. Mr. Swordfish (talk) 20:08, 28 October 2011 (UTC)

I obviously think youre mistaken as LIFT is the topic and planing is obviously a type of lift wherein: "A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction.[1] ." There are obviously a LOT of shared aspects. The omission of planing lift and discussion of its relation to submerged lift are simply an omission due to the fact that aero guys are largely editing the copy. Please revert the page.Juanguzman1967 (talk)LOTS of examples of obvious, visible "flow-turning" here: http://www.google.com/search?rlz=1C1_____enUS424US424&gcx=w&q=surfing&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&biw=1440&bih=815&sei=%20URerTs_zNc7MrQfIkpjWDAJuanguzman1967 (talk) 20:59, 28 October 2011 (UTC)

Hopefully you'll take the occurrences of Lift in discussion of planing hulls in numerous books as evidence that planing hulls do exist and Lift per the definition above absolutely belongs in the article here. If I need to cite particular works I will, however it would be in bad faith to disregard the truth of the matter. Certainly we could situate the sub-discussions of both submerged and planing lift under respective headings though. Please refer : http://www.google.com/search?tbm=bks&tbo=1&q=planing+hull+lift&btnG=

Juanguzman1967 (talk) 00:59, 29 October 2011 (UTC)Further: http://www.scribd.com/doc/39037195/3/Savitsky-MethodJuanguzman1967 (talk) 01:59, 29 October 2011 (UTC)

@Juanguzman1967 - You have written If I need to cite particular works I will ... Of course you need to cite your sources. We all have to cite our sources. No-one contributing to Wikipedia should ever ask if it is necessary to cite sources. Please read, very carefully, WP:Verifiability. Dolphin (t) 03:56, 29 October 2011 (UTC)

Oh please Miss, Ms or Mrs "Dolphin," pray don't scold me. I am but a novice wikinerd. But the fact is, the existence of planing lift is common knowledge. Vastly more people have caused, played with, and otherwise experienced planing lift than the much more complicated submerged flow-turning lift which overwhelms this article. You should research how many people have actively caused planing lift for recreation by skipping stones, surfing, skimboarding, waterskiing, wakeboarding, windsurfing, sticking their hand out car windows, flying kites, for that matter, vs. how many have piloted an aircraft, driving submerged foils. In fact, planing lift is the most elemental and common type of lift man deals with and as it's strictly Newtonian, it's quite arguably a much better starting point for understanding lift than discussing foils. (And by the way, in fact, billions of animals worldwide do far more -- exponentially, galactically more lifting with foils than we do. You gave them short shrift here, too. This article was a joke when I arrived.) You can force me to start a new article I suppose as there's really no accountability on the likes of you two around here, but a Planing Lift article will trample all over this one as it is the most elemental lift.Juanguzman1967 (talk) 04:57, 29 October 2011 (UTC)

I'm not scolding you. I'm asking you to read WP:Verifiability. On Wikipedia, when someone writes It is a known fact or Everybody knows or It is common knowledge it will be assumed that they believe it to be true but can't actually cite a source to allow independent verification. Material that is unsourced is likely to be removed. That is the way encyclopedias operate. Dolphin (t) 05:40, 29 October 2011 (UTC)

> In fact, planing lift is the most elemental and common type of lift man deals with and as it's strictly Newtonian, it's quite arguably a much better starting point for understanding lift than discussing foils.

That's an interesting opinion, and I'm not going to argue that it's incorrect. But even if I agreed with you, wiki is not the place to air our opinions; we're here to present a summary of the published sources and I'm unaware of any treatment that proceeds from planing to "submerged lift" as a pedagogic method. So what would be the justification for doing it here?

There's already an article on planing sailboats. Much of what you have written could go there. Perhaps a more general article on the phenomenon of planing lift (as applied to motorboats, surfboards, skipping stones, etc ) would be in order as well. Mr. Swordfish (talk) 14:33, 29 October 2011 (UTC)

┌────────────────────────────────────────────────────────────────────────────────────────────────────┘ Planing lift is Lift itself -- the most elementary phenomenon of Lift. It's the lift youre talking about when you talk about foils, but without foil-side attachment, flow-turning, turbulence, stalling etc. "There's already an article on planing sailboats. Much of what you have written could go there." It's the lift of kiteflying. Would you have it subsumed to the "kite-flying" page because it "crowds" this article inconveniently? Wiki articles don't have a word-limit -- why impose this argument on an honest, good-faith contributor? I don't have a monetary or cynical interest here. Planing lift simply belongs in an article on the broader subject "Lift (force)." Consider the complexity and controversy around how lifting foils work. Consider how elemental planing lift is. They are two heavily- (and hierarchically-) related phenomena of Lift that are studied and practically utilized by two different groups, but it seems to me encyclopedias cover broad fields that have sub-aspects that don't talk to each other much, often. In my opinion Webster's definition of Lift itself in the most general terms and then a discussion of planing lift should lead the article, with the vastly more complicated and controversial subject of foils following. It should be included and this is the proper hierarchy, which positions the simple form above discussion of the complex. Planing is Lift exactly per the definition at the top of the page. Juanguzman1967 (talk) 00:01, 30 October 2011 (UTC)

"Lift occurs when a moving flow of gas is turned by a solid object." - NASA. (Whoever wrote the article does go on to negate all lift not utilizing 3D engineered foils with curved surfaces on top, but that's an error many aero guys make apparently.) A kite is obviously utilizing lift. A kite operates without the benefit of a 3D foil body's upper surface being optimized to enhance flow-turning but the inconvenient fact is that it simply doesnt need it. So the kite, of all things, exists outside the discussion of the Lift article. Because it is so elementary and fundamental --in other words, common knowledge-- planing lift is totally overlooked and omitted even after it's been illustrated. The trees are the forest, gentlemen. Quite so, in spite of my charming demeanor.Juanguzman1967 (talk) 22:27, 3 November 2011 (UTC) http://dictionary.reference.com/browse/planeJuanguzman1967 (talk) 20:21, 5 November 2011 (UTC)

The Oxford English Dictionary definition of "plane" is as follows: verb [no object] (of a bird or an airborne object) soar without moving the wings ; glide: a bird planed down toward the water below

(of a boat, surfboard, etc.) skim over the surface of water as a result of lift produced hydrodynamically. -- http://oxforddictionaries.com/definition/plane?region=us&rskey=AtuBt9&result=1#m_en_us1278560.008. I rest my case, gentlemen and trust I may revert the page with this definition providing all the support anyone should need. Juanguzman1967 (talk) 20:29, 5 November 2011 (UTC) As I believe the material will just be deleted again if I revert the page, I guess I have no choice but to continue providing citations until the body of evidence I'm accumulating here reaches a tipping point sufficient to sway the judges who seem to hold final control of this material, Dolphin51, and MrSwordfish? https://docs.google.com/viewer?a=v&q=cache:YT8S6ziu3DQJ:aerade.cranfield.ac.uk/ara/arc/rm/2998.pdf+&hl=en&gl=us&pid=bl&srcid=ADGEESgFxTWHHivkjuqAdtzGl12eG--9bOkof0gmaK6p4yta_KqIJd_JsBIQuJSISJD9IZSZFTUNrTwPv5RIqMHFZGFENV16jzINuQK_hZh7R7S0IIWDoGFOls7MmCKePJHOq3uZHpeR&sig=AHIEtbTF5gBSfl0v23oyK5yqDOFwvHoAlw&pli=1 Juanguzman1967 (talk) 22:16, 5 November 2011 (UTC) I am looking here http://www.grc.nasa.gov/WWW/k-12/airplane/bernnew.html and here http://en.wikipedia.org/wiki/Aerodynamic_force and conclude that Lift appears to have been completely misappropriated as the page now is completely concerned with the Aerodynamic_force. Lift is the article. Please address this. Juanguzman1967 (talk) 23:18, 5 November 2011 (UTC) NASA video equating hydroplaning with "lift" at http://www.youtube.com/watch?feature=player_detailpage&v=90mj4Fh5MrU#t=37sJuanguzman1967 (talk) 01:10, 6 November 2011 (UTC) NACA study of "planing lift of a flat plate": http://crgis.ndc.nasa.gov/crgis/images/7/77/1957_Investigation_of_The_Planing_Lift_of_a_Flat_Plate_at_the_Langley_High-Speed_Hydrodynamics_Tank.pdf This oughta do it: http://www.waveequation.com/NACA-TN-3233.pdfJuanguzman1967 (talk) 01:26, 6 November 2011 (UTC) http://naca.central.cranfield.ac.uk/reports/1958/naca-tn-4251.pdfJuanguzman1967 (talk) 03:24, 6 November 2011 (UTC) http://www.flyingmag.com/technicalities/technicalities-short-history-airfoilsJuanguzman1967 (talk) 03:26, 6 November 2011 (UTC) http://naca.central.cranfield.ac.uk/reports/1958/naca-report-1355.pdf This page needs to be drastically edited -- obviously Lift has been recanted here and my research bears me out. What this page is currently displaying is a specific realm of Lift, not the thing itself. I feel I've cited the matter sufficiently using NASA and NACA and will revert the [page tomorrow, providing these sources in the proper format. http://naca.central.cranfield.ac.uk/reports/1958/naca-tn-4168.pdf Thanks. Juanguzman1967 (talk) 03:40, 6 November 2011 (UTC) etymology of "plane": http://www.etymonline.com/index.php?term=plane&allowed_in_frame=0Juanguzman1967 (talk) 04:16, 6 November 2011 (UTC) http://en.wikipedia.org/wiki/Wikipedia:Vandalism#What_is_not_vandalismJuanguzman1967 (talk) 04:21, 6 November 2011 (UTC)

@ Juasguzman:

Nobody is disputing the fact that planing lift is a real phenomena worthy of study and inclusion in wikipedia. (FYI, my nym is a reference to the Swordfish - a planing dinghy designed in the 50's by Uffa Fox). However, planing lift where the fluid only contacts one side of the foil is a different but related topic to the much more mainstream "submerged" lift treated in this article. The overwhelming majority of texts on "lift" concern themselves with this phenomena, not planing lift. Where a text addresses planing lift, it almost always includes the modifier "planing" whereas ordinary unmodified "lift" is assumed to be submerged lift.

I understand that you would like it to be otherwise, but wikipedia is supposed to reflect the broader body of published works, not be a place for us to push our own agendas.

I fully support the creation of an article on planing lift, and linkage to it from this article. I think your energies would be better placed there than trying to fundamentally change the topic of this article. Mr. Swordfish (talk) 16:44, 7 November 2011 (UTC)

I thoroughly disagree. My interests comprise my agenda, but this discussion about topics regarding Lift is not a matter of agenda. It is a discussion of proper hierarchy. Surveying basic Lift phenomena in a reasonable hierarchy from basic to more complex is not "fundamentally changing the topic" which is Lift (force). I and any reasonable user of Wikipedia take the word at the top of the page to be the topic, and we often discover that what we "always think of" is not at all the entirety of the thing -- that is all to the point. I think letting one field's jargon overwhelm the real topic is anti-educational and counterproductive to the goal of any encyclopedia.

As to your argument regarding published works, I would refer you to the NACA papers I cite above and the planing/lift formulae in them.

The article as it stands is completely overwhelmed by discussion of issues, facets, controversies, etc of aerodynamic force relating solely to submerged lifting foils, solely given over to manmade lifting foils at that. I've noted before my exception to the scant-if-any mention of naturally-occurring lifting foils. The topic at the top of this page is "Lift (force)."

Lift's most general definition and phenomena (whence the "flat plate" example?) should be at the top, followed by more complicated phenomena. This is a matter of standard hierarchy.

Most of the foil material on the page now should be moved to "aerodynamic force" and Foil pages. The Wiki guidline I cite above gives me the right to "edit boldly," as long as I cite the NACA and other evidence. I encourage you to move the aero foil material which crowds this parent topic to appropriate subordinate pages.

I've made this case as reasonably as I wish to with you -- who is the higher authority I request review from? Juanguzman1967 (talk) 17:48, 7 November 2011 (UTC)

Again: "A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction.[1] It contrasts with the drag force, which is the component of the surface force parallel to the flow direction.

Furthermore:

"plane (1) "flat surface," c.1600, from L. plantum "flat surface," properly neut. of adj. planus ::"flat, level, plain, clear," from PIE *pla-no- (cf. Lith. plonas "thin;" Celtic *lanon "plain;" ::perhaps also Gk. pelanos "sacrificial cake, a mixture offered to the gods, offering (of meal, honey, and oil) poured or spread"), suffixed form of base *pele- "to spread out, broad, flat" (cf. O.C.S. polje "flat land, field," Rus. polyi "open;" O.E., O.H.G. feld, M.Du. veld "field"). ::Figurative sense is attested from 1850.

The verb meaning "soar, glide on motionless wings" is first recorded 1610s, from M.Fr. planer (16c.), from L. planum on notion of bird gliding with flattened wings. Of boats, etc., "to skim over the surface of water" it is first found 1913.

plane

(2) 1908, short for aeroplane (see airplane).

http://www.etymonline.com/index.php?term=plane&::allowed_in_frame=0Juanguzman1967 ([[User ::talk:Juanguzman1967|talk]]) 17:56, 7 November 2011 (UTC)

Also, I note your terms used here:

"Nobody is disputing the fact that planing lift is a real phenomena worthy of study and inclusion in wikipedia. (FYI, my nym is a reference to the Swordfish - a planing dinghy designed in the 50's by Uffa Fox). However, planing lift where the fluid only contacts one side of the foil is a different but related topic to the much more mainstream "submerged" lift treated in this article. The overwhelming majority of texts on "lift" concern themselves with this phenomena, not planing lift. Where a text addresses planing lift, it almost always includes the modifier "planing" whereas ordinary unmodified "lift" is assumed to be submerged lift.

Please note the generic term in your argument.Juanguzman1967 (talk) 18:18, 7 November 2011 (UTC)

I missed the noun form of Plane, which Oxford defines as

" 1 a flat surface on which a straight line joining any two points on it would wholly lie:

the horizontal plane

an imaginary flat surface through or joining material objects:

the planets orbit the sun in roughly the same plane

a flat or level surface of a material object:

the plane of his forehead

a flat surface producing lift by the action of air or water over and under it.

Juanguzman1967 (talk) 18:21, 7 November 2011 (UTC)

Select "plate:" http://www.grc.nasa.gov/WWW/K-12/airplane/lift2.htmlJuanguzman1967 (talk) 03:47, 8 November 2011 (UTC)

I fully agree with Mr. Swordfish: leave the subject of this article as it is -- lift force on a body (primarily foils) in a homogeneous medium (air, water). The article is long enough (see WP:SIZE). Planing lift can go into a separate article, and be referred to from Lift (and here). -- Crowsnest (talk) 14:02, 8 November 2011 (UTC)

Juanguzman: ...who is the higher authority I request review from?

Editing decisions on Wikipedia are done by consensus of the editors involved, i.e. the people who take the time and trouble to participate in the discussion on the talk page. On this issue, four editors have weighed in so far. Perhaps others editors will also voice their opinions.

The closest thing to "higher authority" I'm aware of is the mechanism at Wikipedia editor assistance. You might want to check out that resource.

BTW, this discussion would be much easier to follow if you adhered to the indentation conventions when you post.

Mr. Swordfish (talk) 14:42, 8 November 2011 (UTC)

Then the title of the article should be changed to disambiguate the subject and specify that it is talking about submerged foils and that this is only one type of fluid-dynamic Lift. NACA and NASA agree, of course, that of course Planing is Lift, as does the Oxford English dictionary. To not more specifically title this article would be misleading.

(I would respect the minutiae of Wikiconventions such as indentation guidelines only if the editors present had dealt with this issue and others relating to it much differently.) Juanguzman1967 (talk) 16:45, 8 November 2011 (UTC)

No one is claiming that Planing lift isn't an example of lift. It's just that it's sufficiently different than the more commonly studied lift-in-a-homogeneous-fluid that it should be broken out into it's own article. Sort of like how an open-face sandwich is sufficiently distinct from an ordinary Sandwich that it deserves separate treatment in a separate article. This is a judgment call about organization and the common usage of language, not something that is "right" or "wrong".

If you want your view to prevail, you'll need to convince some other editors. The best way to do that is to familiarize yourself with the talk page guidelines and try to persuade people to your point of view. Your other recourse is to avail yourself of the resources at Wikipedia:Dispute_resolution. Mr. Swordfish (talk) 20:54, 8 November 2011 (UTC)

The introductory paragraph in Lift (force) is sufficiently generic that it covers planing lift. It would be appropriate to add a new section to the article, dedicated to planing lift. If there is another article dedicated to planing lift, that section could link to that other article.

It would not be appropriate for details of planing lift to be added to the existing introductory paragraph.

At present, Lift (force) is supported by 62 in-line citations related to use of the word lift to mean a component of the force generated by a body submerged in, and moving through, an homogenous fluid. None of those citations use an expression other than lift so there are no good grounds to adopt a new expression such as submerged lift.

If Juan wants to challenge some aspect of the content of Lift (force) he could ask for assistance at Wikipedia:Third opinion. If he wants to challenge the behaviour of any of the Users who created the article, or who contribute to this Discussion page he could ask for assistance at Wikipedia:Wikiquette assistance. Dolphin (t) 06:57, 9 November 2011 (UTC)

I've cited plenty of sources and the whole of naval architecture uses the term in studying planing lift of hulls. Those folks just dont show up here. Wonder why. I've got better things to do than this though. This whole thing -- the blatant bias, the huge omission, and your tyranny of small minds--in the face of my citation of the Oxford dictionary, NASA, NACA... this is exactly why Wikipedia is a joke. And it is a joke. Nobody would cite Wikipedia in seriousness in any venue that mattered at all, and anyone relying on Wikipedia is sanctioned. Because it's full of this kind of ... 'substance.' — Preceding unsigned comment added by 206.16.109.32 (talk) 20:17, 9 November 2011 (UTC)

Here's a Google result that shows pretty clearly that the aforementioned tunnel-vision is simply wrong: association of https://www.google.com/search?q=flat+plate&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a#sclient=psy-ab&hl=en&client=firefox-a&hs=vhJ&rls=org.mozilla:en-US%3Aofficial&source=hp&q=flat+plate+planing+lift&pbx=1&oq=flat+plate+planing+lift&aq=f&aqi=&aql=&gs_sm=e&gs_upl=10291l12318l0l12496l13l9l0l0l0l0l612l1973l3-1.1.2l4l0&bav=on.2,or.r_gc.r_pw.r_cp.,cf.osb&fp=bb50f3788b2ebeea&biw=1200&bih=696Juanguzman1967 (talk) 20:54, 11 November 2011 (UTC)

Here's a very interesting paper that found a "streamlined" airfoil to have worse lift/drag/stall than a flat plate at a variety of AoAs. I was interested in the flat wings of insects. They actually are corrugated, but they are certainly not the airfoils this page has boxed all Lift up with. The paper looks at the effects of the corrugated flat wings too. https://docs.google.com/viewer?a=v&q=cache:6o7zWANicIEJ:www.public.iastate.edu/~huhui/paper/2007/AIAA-2007-0483.pdf+&hl=en&gl=us&pid=bl&srcid=ADGEESg--3Zr8674jhSGEdeXOCBzwzGEK4pjKnHfIaUZG3xD7brOSWE7GluZcOlKAfM89WEcwNrgVGGncyRmEa-jFo792rTsGwi6sIgHurof0s83trWjz9rF9MhgQbKqvShoHMsPp6hv&sig=AHIEtbQhPKShlkE-umy2U-FMcakjxcUklQ Juanguzman1967 (talk) 21:11, 11 November 2011 (UTC)

Airplanes

if lift is 'up' on an airplane, and allows it to fly, why can planes fly upside-down? — Preceding unsigned comment added by 98.69.160.44 (talk) 01:43, 2 January 2012 (UTC)

Lift by Rotors

I would like to see a section of the article dedicated to lift created by rotors, i.e. by helicopter propellors. I've been researching this for, well, almost a day, and so far I haven't been able to find barely anything on the internet, and I've begun to start reading actual books for the information =) If anyone has any resources, or could help me just to gather information and sources to write a section describing lift by rotor, that would be awesome. Thanks. BriEnBest (talk) 08:38, 14 January 2012 (UTC)

Oh and by the way, I'm hypothesizing that the normal "airfoil" approach won't work because (I'm hypothesizing) that the fast-moving propeller blade will change the pressure of the air after a few spins by an as-yet-unknown-by-me amount. BriEnBest (talk) 08:40, 14 January 2012 (UTC)

Agree that this would be a useful addition to Wikipedia. But probably best as a separate article. Mr. Swordfish (talk) 16:47, 16 January 2012 (UTC)

@BriEnBest: A conventional helicopter has two rotors - the main rotor and the tail rotor. The blades on both these rotors are airfoils and they generate lift in the same way as the wing of a fixed-wing aircraft. A helicopter's rotors generate lift by exactly the same process as the propeller of a fixed-wing aircraft generates thrust. In both cases, each blade operates in the downwash from the preceding blade but this has only a very small effect on the lift generation, and this effect can be ignored for most purposes. Dolphin (t) 21:34, 16 January 2012 (UTC)

Picture with dotted stream line

Hello, very nice article. I think that in the picture with the dotted moving streamline there is an error. On the upper surface, the black dots that are near the airfoil shall move faster than those of the free stream, thus resulting on a curve of the opposite direction. The pressure near the upper part of the airfoil is smaller than the pressure of the stream, indicating that the air travels faster. isn't this correct? — Preceding unsigned comment added by Stelios19781111 (talk • contribs) 08:22, 16 January 2012 (UTC)

If you watch the picture carefully, you will see that the dots on the top of the airfoil speed up as they pass over the wing and momentarily exceed the free-stream velocity. However, they first slow down as they approach the wing and the the momentary increase in speed is not enough to compensate for the slowdown as they approach. Thus, all the air in the vicinity of the wing is delayed. Mr. Swordfish (talk) 16:16, 16 January 2012 (UTC)

"Bluff Body" is not explained

I've no idea what this is, either. — Preceding unsigned comment added by 99.41.68.19 (talk) 19:21, 5 February 2012 (UTC)