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Lift (force) (English Wikipedia)

Analysis of information sources in references of the Wikipedia article "Lift (force)" in English language version.

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3331web.archive.org
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97nasa.gov
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76doi.org
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54semanticscholar.org
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22scitation.org
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22fiu.edu
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11arvelgentry.com
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11alphatrainer.com
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11planeandpilotmag.com
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11jove.com
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11raskincenter.org
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11telegraph.co.uk
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11mit.edu
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11flugmodellbau.de
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11youtube.com
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11aerospaceweb.org
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11calstatela.edu
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aapt.org (Global: low place; English: low place)

tpt.aapt.org

  • a. "Lift from Flow Turning". NASA Glenn Research Center. May 27, 2000. Archived from the original on July 5, 2011. Retrieved June 27, 2021. Lift is a force generated by turning a moving fluid... If the body is shaped, moved, or inclined in such a way as to produce a net deflection or turning of the flow, the local velocity is changed in magnitude, direction, or both. Changing the velocity creates a net force on the body.
    b. Vassilis Spathopoulos. "Flight Physics for Beginners: Simple Examples of Applying Newton's Laws The Physics Teacher Vol. 49, September 2011 p. 373". Retrieved June 29, 2021. Essentially, due to the presence of the wing (its shape and inclination to the incoming flow, the so-called angle of attack), the flow is given a downward deflection. It is Newton's third law at work here, with the flow then exerting a reaction force on the wing in an upward direction, thus generating lift.{{cite web}}: CS1 maint: deprecated archival service (link)
    c. Langewiesche. Stick and Rudder, p. 6. The main fact of all heavier-than-air flight is this: the wing keeps the airplane up by pushing the air down.
  • "Unfortunately, this explanation [fails] on three counts. First, an airfoil need not have more curvature on its top than on its bottom. Airplanes can and do fly with perfectly symmetrical airfoils; that is with airfoils that have the same curvature top and bottom. Second, even if a humped-up (cambered) shape is used, the claim that the air must traverse the curved top surface in the same time as it does the flat bottom surface...is fictional. We can quote no physical law that tells us this. Third—and this is the most serious—the common textbook explanation, and the diagrams that accompany it, describe a force on the wing with no net disturbance to the airstream. This constitutes a violation of Newton's third law." Bernoulli and Newton in Fluid Mechanics Norman F. Smith The Physics Teacher November 1972 Volume 10, Issue 8, p. 451 "Browse - the Physics Teacher". Archived from the original on March 17, 2012. Retrieved August 4, 2011.

adsabs.harvard.edu (Global: 14th place; English: 9th place)

ui.adsabs.harvard.edu

  • a. Chris Waltham. "Flight without Bernoulli" (PDF). The Physics Teacher Vol. 36 Nov. 1998. Archived (PDF) from the original on September 28, 2011. Retrieved August 4, 2011. Birds and aircraft fly because they are constantly pushing air downwards: L = Δp/Δt where L= lift force, and Δp/Δt is the rate at which downward momentum is imparted to the airflow.
    b. Clancy, L. J. Aerodynamics. Pitman 1975, p. 76. This lift force has its reaction in the downward momentum which is imparted to the air as it flows over the wing. Thus the lift of the wing is equal to the rate of transport of downward momentum of this air.
    c. Smith, Norman F. (1972). "Bernoulli and Newton in Fluid Mechanics". The Physics Teacher. 10 (8): 451. Bibcode:1972PhTea..10..451S. doi:10.1119/1.2352317. ...if the air is to produce an upward force on the wing, the wing must produce a downward force on the air. Because under these circumstances air cannot sustain a force, it is deflected, or accelerated, downward. Newton's second law gives us the means for quantifying the lift force: Flift = m∆v/∆t = ∆(mv)/∆t. The lift force is equal to the time rate of change of momentum of the air.
  • Auerbach, David (2000), "Why Aircraft Fly", Eur. J. Phys., 21 (4): 289, Bibcode:2000EJPh...21..289A, doi:10.1088/0143-0807/21/4/302, S2CID 250821727
  • Wille, R.; Fernholz, H. (1965), "Report on the first European Mechanics Colloquium, on the Coanda effect", J. Fluid Mech., 23 (4): 801, Bibcode:1965JFM....23..801W, doi:10.1017/S0022112065001702, S2CID 121981660
  • "...if a streamline is curved, there must be a pressure gradient across the streamline..." Babinsky, Holger (November 2003), "How do wings work?", Physics Education, 38 (6): 497, Bibcode:2003PhyEd..38..497B, doi:10.1088/0031-9120/38/6/001, S2CID 1657792
  • Williamson, C. H. K.; Govardhan, R. (2004), "Vortex-induced vibrations", Annual Review of Fluid Mechanics, 36: 413–455, Bibcode:2004AnRFM..36..413W, doi:10.1146/annurev.fluid.36.050802.122128, S2CID 58937745

aerospaceweb.org (Global: low place; English: low place)

aip.org (Global: 2,273rd place; English: 1,697th place)

scitation.aip.org

  • "The airfoil of the airplane wing, according to the textbook explanation that is more or less standard in the United States, has a special shape with more curvature on top than on the bottom; consequently, the air must travel farther over the top surface than over the bottom surface. Because the air must make the trip over the top and bottom surfaces in the same elapsed time ..., the velocity over the top surface will be greater than over the bottom. According to Bernoulli's theorem, this velocity difference produces a pressure difference which is lift." Bernoulli and Newton in Fluid Mechanics Norman F. Smith The Physics Teacher November 1972 Volume 10, Issue 8, p. 451 [permanent dead link]
  • "This classic explanation is based on the difference of streaming velocities caused by the airfoil. There remains, however, a question: How does the airfoil cause the difference in streaming velocities? Some books don't give any answer, while others just stress the picture of the streamlines, saying the airfoil reduces the separations of the streamlines at the upper side. They do not say how the airfoil manages to do this. Thus this is not a sufficient answer." Klaus Weltner Bernoulli's Law and Aerodynamic Lifting Force The Physics Teacher February 1990 p. 84. [permanent dead link]

alphatrainer.com (Global: low place; English: low place)

  • "The lift on the body is simple...it's the reaction of the solid body to the turning of a moving fluid...Now why does the fluid turn the way that it does? That's where the complexity enters in because we are dealing with a fluid. ...The cause for the flow turning is the simultaneous conservation of mass, momentum (both linear and angular), and energy by the fluid. And it's confusing for a fluid because the mass can move and redistribute itself (unlike a solid), but can only do so in ways that conserve momentum (mass times velocity) and energy (mass times velocity squared)... A change in velocity in one direction can cause a change in velocity in a perpendicular direction in a fluid, which doesn't occur in solid mechanics... So exactly describing how the flow turns is a complex problem; too complex for most people to visualize. So we make up simplified "models". And when we simplify, we leave something out. So the model is flawed. Most of the arguments about lift generation come down to people finding the flaws in the various models, and so the arguments are usually very legitimate." Tom Benson of NASA's Glenn Research Center in an interview with AlphaTrainer.Com "Archived copy – Tom Benson Interview". Archived from the original on April 27, 2012. Retrieved July 26, 2012.

arvelgentry.com (Global: low place; English: low place)

  • Arvel Gentry Proceedings of the Third AIAA Symposium on the Aero/Hydronautics of Sailing 1971. "The Aerodynamics of Sail Interaction" (PDF). Archived from the original (PDF) on July 7, 2011. Retrieved July 12, 2011. One explanation of how a wing . . gives lift is that as a result of the shape of the airfoil, the air flows faster over the top than it does over the bottom because it has farther to travel. Of course, with our thin-airfoil sails, the distance along the top is the same as along the bottom so this explanation of lift fails.{{cite web}}: CS1 maint: numeric names: authors list (link)

av8n.com (Global: low place; English: low place)

calstatela.edu (Global: low place; English: low place)

instructional1.calstatela.edu

doi.org (Global: 2nd place; English: 2nd place)

  • a. Chris Waltham. "Flight without Bernoulli" (PDF). The Physics Teacher Vol. 36 Nov. 1998. Archived (PDF) from the original on September 28, 2011. Retrieved August 4, 2011. Birds and aircraft fly because they are constantly pushing air downwards: L = Δp/Δt where L= lift force, and Δp/Δt is the rate at which downward momentum is imparted to the airflow.
    b. Clancy, L. J. Aerodynamics. Pitman 1975, p. 76. This lift force has its reaction in the downward momentum which is imparted to the air as it flows over the wing. Thus the lift of the wing is equal to the rate of transport of downward momentum of this air.
    c. Smith, Norman F. (1972). "Bernoulli and Newton in Fluid Mechanics". The Physics Teacher. 10 (8): 451. Bibcode:1972PhTea..10..451S. doi:10.1119/1.2352317. ...if the air is to produce an upward force on the wing, the wing must produce a downward force on the air. Because under these circumstances air cannot sustain a force, it is deflected, or accelerated, downward. Newton's second law gives us the means for quantifying the lift force: Flift = m∆v/∆t = ∆(mv)/∆t. The lift force is equal to the time rate of change of momentum of the air.
  • Auerbach, David (2000), "Why Aircraft Fly", Eur. J. Phys., 21 (4): 289, Bibcode:2000EJPh...21..289A, doi:10.1088/0143-0807/21/4/302, S2CID 250821727
  • Wille, R.; Fernholz, H. (1965), "Report on the first European Mechanics Colloquium, on the Coanda effect", J. Fluid Mech., 23 (4): 801, Bibcode:1965JFM....23..801W, doi:10.1017/S0022112065001702, S2CID 121981660
  • "...if a streamline is curved, there must be a pressure gradient across the streamline..." Babinsky, Holger (November 2003), "How do wings work?", Physics Education, 38 (6): 497, Bibcode:2003PhyEd..38..497B, doi:10.1088/0031-9120/38/6/001, S2CID 1657792
  • Williamson, C. H. K.; Govardhan, R. (2004), "Vortex-induced vibrations", Annual Review of Fluid Mechanics, 36: 413–455, Bibcode:2004AnRFM..36..413W, doi:10.1146/annurev.fluid.36.050802.122128, S2CID 58937745
  • "...whenever the velocity field is irrotational, it can be expressed as the gradient of a scalar function we call a velocity potential φ: V = ∇φ. The existence of a velocity potential can greatly simplify the analysis of inviscid flows by way of potential-flow theory..." Doug McLean Understanding Aerodynamics: Arguing from the Real Physics p. 26 Wiley "Continuum Fluid Mechanics and the Navier–Stokes Equations". Understanding Aerodynamics. 2012. p. 13. doi:10.1002/9781118454190.ch3. ISBN 9781118454190.

fiu.edu (Global: 1,561st place; English: 1,512th place)

allstar.fiu.edu

  • Anderson, David; Eberhart, Scott (1999), How Airplanes Fly: A Physical Description of Lift, archived from the original on January 26, 2016, retrieved June 4, 2008
  • "There is nothing wrong with the Bernoulli principle, or with the statement that the air goes faster over the top of the wing. But, as the above discussion suggests, our understanding is not complete with this explanation. The problem is that we are missing a vital piece when we apply Bernoulli's principle. We can calculate the pressures around the wing if we know the speed of the air over and under the wing, but how do we determine the speed?" How Airplanes Fly: A Physical Description of Lift David Anderson and Scott Eberhardt "How Airplanes Fly". Archived from the original on January 26, 2016. Retrieved January 26, 2016.

flugmodellbau.de (Global: low place; English: low place)

corsair.flugmodellbau.de

  • "A concept...uses a symmetrical convergent-divergent channel, like a longitudinal section of a Venturi tube, as the starting point . . when such a device is put in a flow, the static pressure in the tube decreases. When the upper half of the tube is removed, a geometry resembling the airfoil is left, and suction is still maintained on top of it. Of course, this explanation is flawed too, because the geometry change affects the whole flowfield and there is no physics involved in the description." Jaakko Hoffren Quest for an Improved Explanation of Lift Section 4.3 American Institute of Aeronautics and Astronautics 2001 "Archived copy" (PDF). Archived from the original (PDF) on December 7, 2013. Retrieved July 26, 2012.{{cite web}}: CS1 maint: archived copy as title (link)

gsu.edu (Global: 2,981st place; English: 3,158th place)

hyperphysics.phy-astr.gsu.edu

  • "You can argue that the main lift comes from the fact that the wing is angled slightly upward so that air striking the underside of the wing is forced downward. The Newton's 3rd law reaction force upward on the wing provides the lift. Increasing the angle of attack can increase the lift, but it also increases drag so that you have to provide more thrust with the aircraft engines" Hyperphysics Georgia State University Dept. of Physics and Astronomy "Angle of Attack for Airfoil". Archived from the original on October 14, 2012. Retrieved July 26, 2012.
  • "It requires adjustment of the angle of attack, but as clearly demonstrated in almost every air show, it can be done." Hyperphysics GSU Dept. of Physics and Astronomy Archived July 8, 2012, at the Wayback Machine

iop.org (Global: 1,046th place; English: 1,608th place)

iopscience.iop.org

  • "...the important thing about an aerofoil . . is not so much that its upper surface is humped and its lower surface is nearly flat, but simply that it moves through the air at an angle. This also avoids the otherwise difficult paradox that an aircraft can fly upside down!" N. H. Fletcher Mechanics of Flight Physics Education July 1975

jove.com (Global: low place; English: low place)

  • "The pressure reaches its minimum value around 5 to 15% chord after the leading edge. As a result, about half of the lift is generated in the first 1/4 chord region of the airfoil. Looking at all three angles of attack, we observe a similar pressure change after the leading edge. Additionally, in all three cases, the upper surface contributes more lift than the lower surface. As a result, it is critical to maintain a clean and rigid surface on the top of the wing. This is why most airplanes are cleared of any objects on the top of the wing." Airfoil Behavior: Pressure Distribution over a Clark Y-14 Wing David Guo, College of Engineering, Technology, and Aeronautics (CETA), Southern New Hampshire University https://www.jove.com/v/10453/airfoil-behavior-pressure-distribution-over-a-clark-y-14-wing Archived August 5, 2021, at the Wayback Machine

mit.edu (Global: 476th place; English: 340th place)

web.mit.edu

  • Flow Visualization. National Committee for Fluid Mechanics Films/Educational Development Center. Archived from the original on October 21, 2016. Retrieved January 21, 2009. A visualization of the typical retarded flow over the lower surface of the wing and the accelerated flow over the upper surface starts at 5:29 in the video.

nasa.gov (Global: 12th place; English: 73rd place)

grc.nasa.gov

  • "There are many theories of how lift is generated. Unfortunately, many of the theories found in encyclopedias, on web sites, and even in some textbooks are incorrect, causing unnecessary confusion for students." NASA "Incorrect lift theory #1". August 16, 2000. Archived from the original on April 27, 2014. Retrieved June 27, 2021.
  • a. "Lift from Flow Turning". NASA Glenn Research Center. May 27, 2000. Archived from the original on July 5, 2011. Retrieved June 27, 2021. Lift is a force generated by turning a moving fluid... If the body is shaped, moved, or inclined in such a way as to produce a net deflection or turning of the flow, the local velocity is changed in magnitude, direction, or both. Changing the velocity creates a net force on the body.
    b. Vassilis Spathopoulos. "Flight Physics for Beginners: Simple Examples of Applying Newton's Laws The Physics Teacher Vol. 49, September 2011 p. 373". Retrieved June 29, 2021. Essentially, due to the presence of the wing (its shape and inclination to the incoming flow, the so-called angle of attack), the flow is given a downward deflection. It is Newton's third law at work here, with the flow then exerting a reaction force on the wing in an upward direction, thus generating lift.{{cite web}}: CS1 maint: deprecated archival service (link)
    c. Langewiesche. Stick and Rudder, p. 6. The main fact of all heavier-than-air flight is this: the wing keeps the airplane up by pushing the air down.
  • "The actual velocity over the top of an airfoil is much faster than that predicted by the "Longer Path" theory and particles moving over the top arrive at the trailing edge before particles moving under the airfoil." Glenn Research Center (August 16, 2000). "Incorrect Lift Theory #1". NASA. Archived from the original on April 27, 2014. Retrieved June 27, 2021.
  • "The problem with the 'Venturi' theory is that it attempts to provide us with the velocity based on an incorrect assumption (the constriction of the flow produces the velocity field). We can calculate a velocity based on this assumption, and use Bernoulli's equation to compute the pressure, and perform the pressure-area calculation and the answer we get does not agree with the lift that we measure for a given airfoil." NASA Glenn Research Center "Incorrect lift theory #3". August 16, 2000. Archived from the original on July 17, 2012. Retrieved June 27, 2021.

www1.grc.nasa.gov

  • "What is Lift?". Glenn Research Center | NASA. NASA Glenn Research Center. Archived from the original on February 9, 2023. Retrieved February 9, 2023.
  • "...when one considers the downwash produced by a lifting airfoil, the upper surface contributes more flow turning than the lower surface." Incorrect Theory #2 Glenn Research Center NASA https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/foilw2/ Archived February 9, 2023, at the Wayback Machine
  • "The theory is based on the idea that the airfoil upper surface is shaped to act as a nozzle which accelerates the flow. Such a nozzle configuration is called a Venturi nozzle and it can be analyzed classically. Considering the conservation of mass, the mass flowing past any point in the nozzle is a constant; the mass flow rate of a Venturi nozzle is a constant... For a constant density, decreasing the area increases the velocity." Incorrect Theory #3 Glenn Research Center NASA https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/venturi-theory/ Archived February 9, 2023, at the Wayback Machine

planeandpilotmag.com (Global: low place; English: low place)

raskincenter.org (Global: low place; English: low place)

jef.raskincenter.org

scitation.org (Global: 5,891st place; English: 4,891st place)

aapt.scitation.org

  • "Most of the texts present the Bernoulli formula without derivation, but also with very little explanation. When applied to the lift of an airfoil, the explanation and diagrams are almost always wrong. At least for an introductory course, lift on an airfoil should be explained simply in terms of Newton's Third Law, with the thrust up being equal to the time rate of change of momentum of the air downwards." Cliff Swartz et al. Quibbles, Misunderstandings, and Egregious Mistakes – Survey of High-School Physics Texts The Physics Teacher Vol. 37, May 1999 p. 300 Archived August 25, 2019, at the Wayback Machine
  • Thus a distribution of the pressure is created which is given in Euler's equation. The physical reason is the aerofoil which forces the streamline to follow its curved surface. The low pressure at the upper side of the aerofoil is a consequence of the curved surface." A comparison of explanations of the aerodynamic lifting force Klaus Weltner Am. J. Phys. Vol.55 No.January 1, 1987, p. 53 Archived April 28, 2021, at the Wayback Machine

semanticscholar.org (Global: 15th place; English: 8th place)

api.semanticscholar.org

telegraph.co.uk (Global: 40th place; English: 27th place)

uba.ar (Global: 5,981st place; English: low place)

df.uba.ar

  • "Both approaches are equally valid and equally correct, a concept that is central to the conclusion of this article." Charles N. Eastlake An Aerodynamicist's View of Lift, Bernoulli, and Newton The Physics Teacher Vol. 40, March 2002 "Archived copy" (PDF). Archived from the original (PDF) on April 11, 2009. Retrieved September 10, 2009.{{cite web}}: CS1 maint: archived copy as title (link)
  • a. Chris Waltham. "Flight without Bernoulli" (PDF). The Physics Teacher Vol. 36 Nov. 1998. Archived (PDF) from the original on September 28, 2011. Retrieved August 4, 2011. Birds and aircraft fly because they are constantly pushing air downwards: L = Δp/Δt where L= lift force, and Δp/Δt is the rate at which downward momentum is imparted to the airflow.
    b. Clancy, L. J. Aerodynamics. Pitman 1975, p. 76. This lift force has its reaction in the downward momentum which is imparted to the air as it flows over the wing. Thus the lift of the wing is equal to the rate of transport of downward momentum of this air.
    c. Smith, Norman F. (1972). "Bernoulli and Newton in Fluid Mechanics". The Physics Teacher. 10 (8): 451. Bibcode:1972PhTea..10..451S. doi:10.1119/1.2352317. ...if the air is to produce an upward force on the wing, the wing must produce a downward force on the air. Because under these circumstances air cannot sustain a force, it is deflected, or accelerated, downward. Newton's second law gives us the means for quantifying the lift force: Flift = m∆v/∆t = ∆(mv)/∆t. The lift force is equal to the time rate of change of momentum of the air.
  • " This happens to some extent on both the upper and lower surface of the airfoil, but it is much more pronounced on the forward portion of the upper surface, so the upper surface gets the credit for being the primary lift producer. " Charles N. Eastlake An Aerodynamicist's View of Lift, Bernoulli, and Newton The Physics Teacher Vol. 40, March 2002 PDF Archived April 11, 2009, at the Wayback Machine
  • "...do you remember hearing that troubling business about the particles moving over the curved top surface having to go faster than the particles that went underneath, because they have a longer path to travel but must still get there at the same time? This is simply not true. It does not happen." Charles N. Eastlake An Aerodynamicist's View of Lift, Bernoulli, and Newton The Physics Teacher Vol. 40, March 2002 PDF Archived April 11, 2009, at the Wayback Machine
  • "This answers the apparent mystery of how a symmetric airfoil can produce lift. ... This is also true of a flat plate at non-zero angle of attack." Charles N. Eastlake An Aerodynamicist's View of Lift, Bernoulli, and Newton "Archived copy" (PDF). Archived from the original (PDF) on April 11, 2009. Retrieved September 10, 2009.{{cite web}}: CS1 maint: archived copy as title (link)
  • "Analysis of fluid flow is typically presented to engineering students in terms of three fundamental principles: conservation of mass, conservation of momentum, and conservation of energy." Charles N. Eastlake An Aerodynamicist's View of Lift, Bernoulli, and Newton The Physics Teacher Vol. 40, March 2002 "Archived copy" (PDF). Archived from the original (PDF) on April 11, 2009. Retrieved September 10, 2009.{{cite web}}: CS1 maint: archived copy as title (link)

web.archive.org (Global: 1st place; English: 1st place)

  • "What is Lift?". Glenn Research Center | NASA. NASA Glenn Research Center. Archived from the original on February 9, 2023. Retrieved February 9, 2023.
  • "There are many theories of how lift is generated. Unfortunately, many of the theories found in encyclopedias, on web sites, and even in some textbooks are incorrect, causing unnecessary confusion for students." NASA "Incorrect lift theory #1". August 16, 2000. Archived from the original on April 27, 2014. Retrieved June 27, 2021.
  • "Most of the texts present the Bernoulli formula without derivation, but also with very little explanation. When applied to the lift of an airfoil, the explanation and diagrams are almost always wrong. At least for an introductory course, lift on an airfoil should be explained simply in terms of Newton's Third Law, with the thrust up being equal to the time rate of change of momentum of the air downwards." Cliff Swartz et al. Quibbles, Misunderstandings, and Egregious Mistakes – Survey of High-School Physics Texts The Physics Teacher Vol. 37, May 1999 p. 300 Archived August 25, 2019, at the Wayback Machine
  • Arvel Gentry Proceedings of the Third AIAA Symposium on the Aero/Hydronautics of Sailing 1971. "The Aerodynamics of Sail Interaction" (PDF). Archived from the original (PDF) on July 7, 2011. Retrieved July 12, 2011. One explanation of how a wing . . gives lift is that as a result of the shape of the airfoil, the air flows faster over the top than it does over the bottom because it has farther to travel. Of course, with our thin-airfoil sails, the distance along the top is the same as along the bottom so this explanation of lift fails.{{cite web}}: CS1 maint: numeric names: authors list (link)
  • "The lift on the body is simple...it's the reaction of the solid body to the turning of a moving fluid...Now why does the fluid turn the way that it does? That's where the complexity enters in because we are dealing with a fluid. ...The cause for the flow turning is the simultaneous conservation of mass, momentum (both linear and angular), and energy by the fluid. And it's confusing for a fluid because the mass can move and redistribute itself (unlike a solid), but can only do so in ways that conserve momentum (mass times velocity) and energy (mass times velocity squared)... A change in velocity in one direction can cause a change in velocity in a perpendicular direction in a fluid, which doesn't occur in solid mechanics... So exactly describing how the flow turns is a complex problem; too complex for most people to visualize. So we make up simplified "models". And when we simplify, we leave something out. So the model is flawed. Most of the arguments about lift generation come down to people finding the flaws in the various models, and so the arguments are usually very legitimate." Tom Benson of NASA's Glenn Research Center in an interview with AlphaTrainer.Com "Archived copy – Tom Benson Interview". Archived from the original on April 27, 2012. Retrieved July 26, 2012.
  • "Both approaches are equally valid and equally correct, a concept that is central to the conclusion of this article." Charles N. Eastlake An Aerodynamicist's View of Lift, Bernoulli, and Newton The Physics Teacher Vol. 40, March 2002 "Archived copy" (PDF). Archived from the original (PDF) on April 11, 2009. Retrieved September 10, 2009.{{cite web}}: CS1 maint: archived copy as title (link)
  • Ison, David, "Bernoulli Or Newton: Who's Right About Lift?", Plane & Pilot, archived from the original on September 24, 2015, retrieved January 14, 2011
  • a. "Lift from Flow Turning". NASA Glenn Research Center. May 27, 2000. Archived from the original on July 5, 2011. Retrieved June 27, 2021. Lift is a force generated by turning a moving fluid... If the body is shaped, moved, or inclined in such a way as to produce a net deflection or turning of the flow, the local velocity is changed in magnitude, direction, or both. Changing the velocity creates a net force on the body.
    b. Vassilis Spathopoulos. "Flight Physics for Beginners: Simple Examples of Applying Newton's Laws The Physics Teacher Vol. 49, September 2011 p. 373". Retrieved June 29, 2021. Essentially, due to the presence of the wing (its shape and inclination to the incoming flow, the so-called angle of attack), the flow is given a downward deflection. It is Newton's third law at work here, with the flow then exerting a reaction force on the wing in an upward direction, thus generating lift.{{cite web}}: CS1 maint: deprecated archival service (link)
    c. Langewiesche. Stick and Rudder, p. 6. The main fact of all heavier-than-air flight is this: the wing keeps the airplane up by pushing the air down.
  • a. Chris Waltham. "Flight without Bernoulli" (PDF). The Physics Teacher Vol. 36 Nov. 1998. Archived (PDF) from the original on September 28, 2011. Retrieved August 4, 2011. Birds and aircraft fly because they are constantly pushing air downwards: L = Δp/Δt where L= lift force, and Δp/Δt is the rate at which downward momentum is imparted to the airflow.
    b. Clancy, L. J. Aerodynamics. Pitman 1975, p. 76. This lift force has its reaction in the downward momentum which is imparted to the air as it flows over the wing. Thus the lift of the wing is equal to the rate of transport of downward momentum of this air.
    c. Smith, Norman F. (1972). "Bernoulli and Newton in Fluid Mechanics". The Physics Teacher. 10 (8): 451. Bibcode:1972PhTea..10..451S. doi:10.1119/1.2352317. ...if the air is to produce an upward force on the wing, the wing must produce a downward force on the air. Because under these circumstances air cannot sustain a force, it is deflected, or accelerated, downward. Newton's second law gives us the means for quantifying the lift force: Flift = m∆v/∆t = ∆(mv)/∆t. The lift force is equal to the time rate of change of momentum of the air.
  • "...when one considers the downwash produced by a lifting airfoil, the upper surface contributes more flow turning than the lower surface." Incorrect Theory #2 Glenn Research Center NASA https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/foilw2/ Archived February 9, 2023, at the Wayback Machine
  • " This happens to some extent on both the upper and lower surface of the airfoil, but it is much more pronounced on the forward portion of the upper surface, so the upper surface gets the credit for being the primary lift producer. " Charles N. Eastlake An Aerodynamicist's View of Lift, Bernoulli, and Newton The Physics Teacher Vol. 40, March 2002 PDF Archived April 11, 2009, at the Wayback Machine
  • "The pressure reaches its minimum value around 5 to 15% chord after the leading edge. As a result, about half of the lift is generated in the first 1/4 chord region of the airfoil. Looking at all three angles of attack, we observe a similar pressure change after the leading edge. Additionally, in all three cases, the upper surface contributes more lift than the lower surface. As a result, it is critical to maintain a clean and rigid surface on the top of the wing. This is why most airplanes are cleared of any objects on the top of the wing." Airfoil Behavior: Pressure Distribution over a Clark Y-14 Wing David Guo, College of Engineering, Technology, and Aeronautics (CETA), Southern New Hampshire University https://www.jove.com/v/10453/airfoil-behavior-pressure-distribution-over-a-clark-y-14-wing Archived August 5, 2021, at the Wayback Machine
  • Denker, JS, Fallacious Model of Lift Production, archived from the original on March 2, 2009, retrieved August 18, 2008
  • Anderson, David; Eberhart, Scott (1999), How Airplanes Fly: A Physical Description of Lift, archived from the original on January 26, 2016, retrieved June 4, 2008
  • Raskin, Jef (1994), Coanda Effect: Understanding Why Wings Work, archived from the original on September 28, 2007
  • "Unfortunately, this explanation [fails] on three counts. First, an airfoil need not have more curvature on its top than on its bottom. Airplanes can and do fly with perfectly symmetrical airfoils; that is with airfoils that have the same curvature top and bottom. Second, even if a humped-up (cambered) shape is used, the claim that the air must traverse the curved top surface in the same time as it does the flat bottom surface...is fictional. We can quote no physical law that tells us this. Third—and this is the most serious—the common textbook explanation, and the diagrams that accompany it, describe a force on the wing with no net disturbance to the airstream. This constitutes a violation of Newton's third law." Bernoulli and Newton in Fluid Mechanics Norman F. Smith The Physics Teacher November 1972 Volume 10, Issue 8, p. 451 "Browse - the Physics Teacher". Archived from the original on March 17, 2012. Retrieved August 4, 2011.
  • "Cambridge scientist debunks flying myth - Telegraph". Archived from the original on June 30, 2012. Retrieved June 10, 2012. Cambridge scientist debunks flying myth UK Telegraph 24 January 2012
  • Flow Visualization. National Committee for Fluid Mechanics Films/Educational Development Center. Archived from the original on October 21, 2016. Retrieved January 21, 2009. A visualization of the typical retarded flow over the lower surface of the wing and the accelerated flow over the upper surface starts at 5:29 in the video.
  • "...do you remember hearing that troubling business about the particles moving over the curved top surface having to go faster than the particles that went underneath, because they have a longer path to travel but must still get there at the same time? This is simply not true. It does not happen." Charles N. Eastlake An Aerodynamicist's View of Lift, Bernoulli, and Newton The Physics Teacher Vol. 40, March 2002 PDF Archived April 11, 2009, at the Wayback Machine
  • "The actual velocity over the top of an airfoil is much faster than that predicted by the "Longer Path" theory and particles moving over the top arrive at the trailing edge before particles moving under the airfoil." Glenn Research Center (August 16, 2000). "Incorrect Lift Theory #1". NASA. Archived from the original on April 27, 2014. Retrieved June 27, 2021.
  • "The theory is based on the idea that the airfoil upper surface is shaped to act as a nozzle which accelerates the flow. Such a nozzle configuration is called a Venturi nozzle and it can be analyzed classically. Considering the conservation of mass, the mass flowing past any point in the nozzle is a constant; the mass flow rate of a Venturi nozzle is a constant... For a constant density, decreasing the area increases the velocity." Incorrect Theory #3 Glenn Research Center NASA https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/venturi-theory/ Archived February 9, 2023, at the Wayback Machine
  • "The problem with the 'Venturi' theory is that it attempts to provide us with the velocity based on an incorrect assumption (the constriction of the flow produces the velocity field). We can calculate a velocity based on this assumption, and use Bernoulli's equation to compute the pressure, and perform the pressure-area calculation and the answer we get does not agree with the lift that we measure for a given airfoil." NASA Glenn Research Center "Incorrect lift theory #3". August 16, 2000. Archived from the original on July 17, 2012. Retrieved June 27, 2021.
  • "A concept...uses a symmetrical convergent-divergent channel, like a longitudinal section of a Venturi tube, as the starting point . . when such a device is put in a flow, the static pressure in the tube decreases. When the upper half of the tube is removed, a geometry resembling the airfoil is left, and suction is still maintained on top of it. Of course, this explanation is flawed too, because the geometry change affects the whole flowfield and there is no physics involved in the description." Jaakko Hoffren Quest for an Improved Explanation of Lift Section 4.3 American Institute of Aeronautics and Astronautics 2001 "Archived copy" (PDF). Archived from the original (PDF) on December 7, 2013. Retrieved July 26, 2012.{{cite web}}: CS1 maint: archived copy as title (link)
  • "This answers the apparent mystery of how a symmetric airfoil can produce lift. ... This is also true of a flat plate at non-zero angle of attack." Charles N. Eastlake An Aerodynamicist's View of Lift, Bernoulli, and Newton "Archived copy" (PDF). Archived from the original (PDF) on April 11, 2009. Retrieved September 10, 2009.{{cite web}}: CS1 maint: archived copy as title (link)
  • "There is nothing wrong with the Bernoulli principle, or with the statement that the air goes faster over the top of the wing. But, as the above discussion suggests, our understanding is not complete with this explanation. The problem is that we are missing a vital piece when we apply Bernoulli's principle. We can calculate the pressures around the wing if we know the speed of the air over and under the wing, but how do we determine the speed?" How Airplanes Fly: A Physical Description of Lift David Anderson and Scott Eberhardt "How Airplanes Fly". Archived from the original on January 26, 2016. Retrieved January 26, 2016.
  • Thus a distribution of the pressure is created which is given in Euler's equation. The physical reason is the aerofoil which forces the streamline to follow its curved surface. The low pressure at the upper side of the aerofoil is a consequence of the curved surface." A comparison of explanations of the aerodynamic lifting force Klaus Weltner Am. J. Phys. Vol.55 No.January 1, 1987, p. 53 Archived April 28, 2021, at the Wayback Machine
  • "You can argue that the main lift comes from the fact that the wing is angled slightly upward so that air striking the underside of the wing is forced downward. The Newton's 3rd law reaction force upward on the wing provides the lift. Increasing the angle of attack can increase the lift, but it also increases drag so that you have to provide more thrust with the aircraft engines" Hyperphysics Georgia State University Dept. of Physics and Astronomy "Angle of Attack for Airfoil". Archived from the original on October 14, 2012. Retrieved July 26, 2012.
  • "It requires adjustment of the angle of attack, but as clearly demonstrated in almost every air show, it can be done." Hyperphysics GSU Dept. of Physics and Astronomy Archived July 8, 2012, at the Wayback Machine
  • Yoon, Joe (December 28, 2003), Mach Number & Similarity Parameters, Aerospaceweb.org, archived from the original on February 24, 2021, retrieved February 11, 2009
  • "Analysis of fluid flow is typically presented to engineering students in terms of three fundamental principles: conservation of mass, conservation of momentum, and conservation of energy." Charles N. Eastlake An Aerodynamicist's View of Lift, Bernoulli, and Newton The Physics Teacher Vol. 40, March 2002 "Archived copy" (PDF). Archived from the original (PDF) on April 11, 2009. Retrieved September 10, 2009.{{cite web}}: CS1 maint: archived copy as title (link)
  • Elements of Potential Flow California State University Los Angeles "Faculty Web Directory". Archived from the original on November 11, 2012. Retrieved July 26, 2012.

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