64:
460:"...the motion of objects in air and in water obeys identical laws until their speed approaches the speed of sound."(page 41) "... air too can be regarded as incompressible as long as flow speeds remain reasonably low. This assumption is roughly valid as long as airplanes fly slower than... about one-third of the speed of sound."(page 61)
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The weight a foil can lift is proportional to its lift coefficient, the density of the fluid, the foil area and its speed squared. The following shows the lifting ability of a flat plate with span 10 metres and area 10 square metres moving at a speed of 10 m/s at different altitudes and water depths.
215:
height 11 km: lift 1.0 (datum for comparison) 5 m 3.4 in ground effect 4.1 water surface-planing 1,280 just submerged 1,420 depth 5 m 2,840 10 km 2,860
544:"A flat plate held at the proper angle of attack does generate lift, but also generates a lot of drag. Sir George Cayley and Otto Lilienthal during the 1800s showed that curved surfaces generate more lift and less drag than flat surfaces."
83:. This "turning" of the fluid in the vicinity of the foil creates curved streamlines which results in lower pressure on one side and higher pressure on the other. This pressure difference is accompanied by a velocity difference, via
358:"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"
133:
of a boat or aircraft. When designing a rudder a key design factor is the minimization of drag in its neutral position, which is balanced with the need to produce sufficient lift with which to turn the craft at a reasonable rate.
98:. And since the effects of the compressibility of air at low speeds is negligible, these simplified equations can be used for airfoils as long as the airflow is substantially less than the speed of sound (up to about
342:"...the effect of the wing is to give the air stream a downward velocity component. The reaction force of the deflected air mass must then act on the wing to give it an equal and opposite upward component." In:
75:. When oriented at a suitable angle, the foil deflects the oncoming fluid, resulting in a force on the foil in the direction opposite to the deflection. This force can be resolved into two components:
480:"...the low-speed flow of air, where V < 100 m/s (or V < 225 mi/hr) can also be assumed to be incompressible to a close approximation." in Anderson, John D. Jr.
208:
It uses the lift at an altitude of 11 km as a datum to show how the lift increases with decreasing altitude (increasing air density). It also shows the influence of
110:– with air penetrating along the strut from the water surface to the foil – may occur. Both effects may have a substantial influence on the foil's lift.
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91:
129:
Since even a flat plate can generate lift, a significant factor in foil design is the minimization of drag. An example of this is the
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87:, so for foils generating lift the resulting flowfield about the foil has a higher average velocity on one surface than on the other.
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Other types of foils, both natural and man-made, seen both in air and water, have features that delay or control the onset of
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will result in a lift force on the plate. However, while it does generate lift, it also generates a large amount of drag.
522:
489:
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209:
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102:
0.3). For hydrofoils at high speeds, of the order of 50 knots (26 m/s) according to
Faltinsen,
384:"The cause of the aerodynamic lifting force is the downward acceleration of air by the airfoil..."
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408:...if a streamline is curved, there must be a pressure gradient across the streamline...
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122:) to the flow the plate will deflect the fluid passing over and under it, and this
35:(force generated perpendicular to the fluid flow) is substantially larger than the
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Lifted_Weight_as_a_Function_of_Altitude_and_Depth_by_Rolf_Steinegger
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http://quest.nasa.gov/aero/planetary/atmospheric/aerodynamiclift.html
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and then the effect of increase in density going from air to water.
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The simplest type of foil is a flat plate. When set at an angle (the
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Streamlines around a NACA 0012 airfoil at moderate angle of attack
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39:(force generated parallel to the fluid flow). If the fluid is a
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is a solid object with a shape such that when placed in a moving
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A more detailed description of the flowfield is given by the
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24:
509:, {Cambridge University Press}, pp. 169–173, 208–209,
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A foil generates lift primarily because of its shape and
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636:
phillipines thresher shark swim towards scuba divers
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363:. NASA Glenn Research Center. Archived from
507:Hydrodynamics of High-Speed Marine Vehicles
386:Weltner, Klaus; Ingelman-Sundberg, Martin,
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495:
411:
62:
464:Wegener, Peter P. Springer-Verlag 1991
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348:, John Wiley & Sons, p. 378
16:Solid object used in fluid mechanics
346:Fundamentals of Physics 3rd Edition
58:
13:
592:https://doi.org/10.21256/zhaw-4058
412:Babinsky, Holger (November 2003),
344:Halliday, David; Resnick, Robert,
92:simplified Navier–Stokes equations
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47:or aerofoil, and if the fluid is
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203:Lifted ability in air and water
94:, applicable when the fluid is
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1:
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389:Physics of Flight - reviewed
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641:Swimming with Wild Dolphins
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114:Basic design considerations
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441:10.1088/0031-9120/38/6/001
462:What Makes Airplanes Fly?
515:10.1017/CBO9780511546068
484:4th ed McGraw-Hill 2000
361:"Lift from Flow Turning"
43:, the foil is called an
621:Effect of Shape on Lift
606:Lift from Flow Turning
482:Introduction to Flight
68:
626:Incorrect Lift Theory
85:Bernoulli's principle
66:
51:the foil is called a
616:Bernoulli and Newton
414:"How do wings work?"
314:Spoiler (automotive)
433:2003PhyEd..38..497B
551:2011-10-27 at the
189:Leading edge slats
69:
421:Physics Education
267:Flipper (anatomy)
185:Leading edge slot
179:(close-coupled),
139:lift-induced drag
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572:on March 9, 2009
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288:Lift coefficient
262:Drag coefficient
247:Chord (aircraft)
193:Wingtip vortices
173:Vortex generator
59:Physics of foils
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566:"What is lift?"
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553:Wayback Machine
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666:Aerodynamics
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574:. Retrieved
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369:. Retrieved
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293:NACA airfoil
257:Diving plane
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242:Centerboard
153:Bird flight
108:ventilation
655:Categories
533:2005006328
371:2011-06-29
331:References
232:Bilgeboard
181:Blown flap
124:deflection
104:cavitation
298:Propeller
237:Boomerang
53:hydrofoil
549:Archived
505:(2005),
227:Aircraft
220:See also
169:Tubercle
576:July 5,
449:1657792
429:Bibcode
197:Winglet
161:Airfoil
45:airfoil
564:NASA.
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492:pg 114
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177:Canard
147:, and
131:rudder
445:S2CID
417:(PDF)
195:(see
151:(see
149:stall
49:water
25:fluid
578:2011
529:LCCN
519:ISBN
486:ISBN
466:ISBN
324:Wing
309:Skeg
303:Sail
282:Keel
106:and
100:Mach
81:drag
79:and
77:lift
37:drag
33:lift
31:the
21:foil
511:doi
437:doi
199:).
157:Fin
41:gas
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19:A
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