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A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expressed as its lift-to-drag ratio. The lift a wing generates at a given speed and angle of attack can be one to two orders of magnitude greater than the total drag on the wing. A high lift-to-drag ratio requires a significantly smaller
thrust Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that ...
to propel the wings through the air at sufficient lift. Lifting structures used in water include various foils, such as hydrofoils.
Hydrodynamics In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids— liquids and gases. It has several subdisciplines, including ''aerodynamics'' (the study of air and other gases in motion) a ...
is the governing science, rather than aerodynamics. Applications of underwater foils occur in hydroplanes,
sailboat A sailboat or sailing boat is a boat propelled partly or entirely by sails and is smaller than a sailing ship. Distinctions in what constitutes a sailing boat and ship vary by region and maritime culture. Types Although sailboat terminology ...
s and
submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...
s.


Etymology and usage

For many centuries, the word "wing", from the Old Norse ''vængr'', referred mainly to the foremost
limb Limb may refer to: Science and technology * Limb (anatomy), an appendage of a human or animal *Limb, a large or main branch of a tree *Limb, in astronomy, the curved edge of the apparent disk of a celestial body, e.g. lunar limb *Limb, in botany, ...
s of
bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
s (in addition to the architectural aisle). But in recent centuries the word's meaning has extended to include lift producing appendages of
insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...
s, bats,
pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 ...
s,
boomerangs A boomerang () is a thrown tool, typically constructed with aerofoil sections and designed to spin about an axis perpendicular to the direction of its flight. A returning boomerang is designed to return to the thrower, while a non-returning b ...
, some sail boats and
aircraft An aircraft is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or by using the Lift (force), dynamic lift of an airfoil, or in ...
, or the inverted airfoil on a race car that generates a downward force to increase traction.


Aerodynamics

The design and analysis of the wings of aircraft is one of the principal applications of the science of
aerodynamics Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dy ...
, which is a branch of
fluid mechanics Fluid mechanics is the branch of physics concerned with the mechanics of fluids ( liquids, gases, and plasmas) and the forces on them. It has applications in a wide range of disciplines, including mechanical, aerospace, civil, chemical and ...
. In principle, the properties of the airflow around any moving object can be found by solving the Navier-Stokes equations of
fluid dynamics In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids— liquids and gases. It has several subdisciplines, including ''aerodynamics'' (the study of air and other gases in motion) a ...
. However, except for simple geometries these equations are notoriously difficult to solve and simpler equations are used. For a wing to produce ''lift'', it must be oriented at a suitable angle of attack. When this occurs, the wing deflects the airflow downwards as it passes the wing. Since the wing exerts a force on the air to change its direction, the air must also exert an equal and opposite force on the wing."The cause of the aerodynamic lifting force is the downward acceleration of air by the airfoil..."


Cross-sectional shape

An ''airfoil'' (
American English American English, sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. English is the most widely spoken language in the United States and in most circumstances ...
) or ''aerofoil'' (
British English British English (BrE, en-GB, or BE) is, according to Oxford Dictionaries, "English as used in Great Britain, as distinct from that used elsewhere". More narrowly, it can refer specifically to the English language in England, or, more broadl ...
) is the shape of a wing, blade (of a propeller, rotor, or turbine), or sail (as seen in
cross-section Cross section may refer to: * Cross section (geometry) ** Cross-sectional views in architecture & engineering 3D *Cross section (geology) * Cross section (electronics) * Radar cross section, measure of detectability * Cross section (physics) **Abs ...
). Wings with an asymmetrical cross section are the norm in subsonic flight. Wings with a symmetrical cross section can also generate lift by using a positive angle of attack to deflect air downward. Symmetrical airfoils have higher stalling speeds than cambered airfoils of the same wing area but are used in aerobatic aircraft as they provide practical performance whether the aircraft is upright or inverted. Another example comes from sailboats, where the sail is a thin membrane with no path-length difference between one side and the other."...consider a sail that is nothing but a vertical wing (generating side-force to propel a yacht). ...it is obvious that the distance between the stagnation point and the trailing edge is more or less the same on both sides. This becomes exactly true in the absence of a mast—and clearly the presence of the mast is of no consequence in the generation of lift. ''Thus, the generation of lift does not require different distances around the upper and lower surfaces.''" Holger Babinsky ''How do Wings Work?'' Physics Education November 2003
PDF
/ref> For flight speeds near the speed of sound (
transonic flight Transonic (or transsonic) flow is air flowing around an object at a speed that generates regions of both subsonic and supersonic airflow around that object. The exact range of speeds depends on the object's critical Mach number, but transonic ...
), airfoils with complex asymmetrical shapes are used to minimize the drastic increase in drag associated with airflow near the speed of sound. Such airfoils, called supercritical airfoils, are flat on top and curved on the bottom.


Design features

Aircraft wings may feature some of the following: * A rounded leading edge cross-section * A sharp trailing edge cross-section * Leading-edge devices such as slats, slots, or
extension Extension, extend or extended may refer to: Mathematics Logic or set theory * Axiom of extensionality * Extensible cardinal * Extension (model theory) * Extension (predicate logic), the set of tuples of values that satisfy the predicate * Ext ...
s * Trailing-edge devices such as flaps or flaperons (combination of flaps and ailerons) * Winglets to keep wingtip vortices from increasing drag and decreasing lift * Dihedral, or a positive wing angle to the horizontal, increases ''spiral stability'' around the roll axis, whereas ''anhedral'', or a negative wing angle to the horizontal, decreases spiral stability. Aircraft wings may have various devices, such as flaps or slats that the pilot uses to modify the shape and surface area of the wing to change its operating characteristics in flight. * Ailerons (usually near the wingtips) to roll the aircraft clockwise or counterclockwise about its long axis *
Spoiler Spoiler is a security vulnerability on modern computer central processing units that use speculative execution. It exploits side-effects of speculative execution to improve the efficiency of Rowhammer and other related memory and cache attacks. ...
s on the upper surface to disrupt the lift and to provide additional traction to an aircraft that has just landed but is still moving. * Vortex generators mitigate flow separation at low speeds and high angles of attack, especially over control surfaces. * Wing fences to keep flow attached to the wing by stopping boundary layer separation from spreading roll direction. * Folding wings allow more aircraft storage in the confined space of the hangar deck of an aircraft carrier * Variable-sweep wing or "swing wings" that allow outstretched wings during low-speed flight (i.e., take-off and landing) and swept back wings for high-speed flight (including
supersonic flight A supersonic aircraft is an aircraft capable of supersonic flight, that is, flying faster than the speed of sound (Mach number 1). Supersonic aircraft were developed in the second half of the twentieth century. Supersonic aircraft have been use ...
), such as in the
F-111 Aardvark The General Dynamics F-111 Aardvark is a retired supersonic, medium-range, multirole combat aircraft. Production variants of the F-111 had roles that included ground attack (e.g. interdiction), strategic bombing (including nuclear weapons ca ...
, the
F-14 Tomcat The Grumman F-14 Tomcat is an American carrier-capable supersonic aircraft, supersonic, twinjet, twin-engine, two-seat, twin-tail, variable-sweep wing fighter aircraft. The Tomcat was developed for the United States Navy's Naval Fighter Experi ...
, the
Panavia Tornado The Panavia Tornado is a family of twin-engine, variable-sweep wing multirole combat aircraft, jointly developed and manufactured by Italy, the United Kingdom and West Germany. There are three primary Tornado variants: the Tornado IDS (inte ...
, the MiG-23, the MiG-27, the Tu-160 and the B-1B Lancer warplanes * Strakes to improve flight characteristics * Chine, which may blend into the wing *
Leading-edge droop flap The leading-edge droop flap is a device on the leading edge of aircraft wings designed to improve airflow at high pitch angles (high angle of attack). The droop flap is similar to the leading-edge slat and the Krueger flap, but with the differenc ...
, a high-lift device * Fairings, structures whose primary function is to produce a smooth outline and reduce drag. For example, flap track fairings Wings may have other minor independent surfaces.


Applications and variants

Besides fixed-wing aircraft, applications for wing shapes include: *
Hang glider Hang gliding is an air sport or recreational activity in which a pilot flies a light, non-motorised foot-launched heavier-than-air aircraft called a hang glider. Most modern hang gliders are made of an aluminium alloy or composite frame covered ...
s, which use wings ranging from fully flexible (
paraglider Paragliding is the recreational and competitive adventure sport of flying paragliders: lightweight, free-flying, foot-launched glider aircraft with no rigid primary structure. The pilot sits in a harness or lies supine in a cocoon-like ...
s, gliding parachutes), flexible (framed sail wings), to rigid * Kites, which use a variety of surfaces to attain lift and maintain stability * Flying model airplanes *
Helicopter A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attribu ...
s, which use a rotating wing with a variable pitch angle to provide directional forces * Propellers, whose blades generate lift for propulsion. * The
NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...
Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program n ...
, which uses its wings only to glide during its descent to a runway. These types of aircraft are called
spaceplane A spaceplane is a vehicle that can fly and glide like an aircraft in Earth's atmosphere and maneuver like a spacecraft in outer space. To do so, spaceplanes must incorporate features of both aircraft and spacecraft. Orbital spaceplane ...
s. * Some racing cars, especially Formula One cars, which use upside-down wings (or '' airfoils'') to provide greater traction at high speeds. *
Sailboat A sailboat or sailing boat is a boat propelled partly or entirely by sails and is smaller than a sailing ship. Distinctions in what constitutes a sailing boat and ship vary by region and maritime culture. Types Although sailboat terminology ...
s, which use flexible cloth sails as vertical wings with variable fullness and direction to move across water. * Hydrofoils, which use rigid wing shaped structures to lift a vessel out of the water to reduce drag and increase speed.


In nature

In nature, wings have
evolved Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variati ...
in
insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pa ...
s,
pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 ...
s, dinosaurs (
bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
s), and mammals ( bats) as a means of locomotion. Various species of penguins and other flighted or flightless water birds such as
auk An auk or alcid is a bird of the family Alcidae in the order Charadriiformes. The alcid family includes the murres, guillemots, auklets, puffins, and murrelets. The word "auk" is derived from Icelandic ''álka'', from Old Norse ''alka'' (a ...
s, cormorants,
guillemot Guillemot is the common name for several species of seabird in the Alcidae or auk family (part of the order Charadriiformes). In British use, the term comprises two genera: ''Uria'' and ''Cepphus''. In North America the ''Uria'' species are ...
s, shearwaters, eider and scoter ducks and diving petrels are avid swimmers, and use their wings to propel through water.
;Wing forms in nature
File:PSM V19 D181 Various seeds of trees.jpg, Winged tree seeds that cause autorotation in descent File:Seagull wing.jpg, A
laughing gull The laughing gull (''Leucophaeus atricilla'') is a medium-sized gull of North and South America. Named for its laugh-like call, it is an opportunistic omnivore and scavenger. It breeds in large colonies mostly along the Atlantic coast of North ...
, exhibiting the " gull wing" outline File:PikiWiki_Israel_11327_Wildlife_and_Plants_of_Israel-Bat-003.jpg, Bat in flight


Tensile structures

In 1948,
Francis Rogallo Francis Melvin Rogallo (January 27, 1912 – September 1, 2009) was an American aeronautical engineer inventor born in Sanger, California, U.S. Together with his wife, he is credited with the invention of the Rogallo wing, or "flexible wi ...
invented a kite-like tensile wing supported by inflated or rigid struts, which ushered in new possibilities for aircraft. Near in time, Domina Jalbert invented flexible un-sparred ram-air airfoiled thick wings. These two new branches of wings have been since extensively studied and applied in new branches of aircraft, especially altering the personal recreational aviation landscape.


See also

* Flight Natural world: * Bat flight * Bird flight * Flight feather *
Flying and gliding animals A number of animals are capable of aerial locomotion, either by powered flight or by gliding. This trait has appeared by evolution many times, without any single common ancestor. Flight has evolved at least four times in separate animals: i ...
* Insect flight *
List of soaring birds This is a list of soaring birds, which are birds that can maintain flight without wing flapping, using rising air currents. Many gliding birds are able to "lock" their extended wings by means of a specialized tendon. ;Bird of prey * Buzzards * ...
* Samara (winged seeds of trees) Aviation: *
Aircraft An aircraft is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or by using the Lift (force), dynamic lift of an airfoil, or in ...
* Blade solidity * FanWing and Flettner airplane (experimental wing types) * Flight dynamics (fixed-wing aircraft) * Kite types * Ornithopter – Flapping-wing aircraft (research prototypes, simple toys and models) * Otto Lilienthal *
Wing configuration The wing configuration of a fixed-wing aircraft (including both glider (aircraft), gliders and powered aeroplanes) is its arrangement of lifting and related surfaces. Aircraft designs are often classified by their wing configuration. For examp ...
* Wing root * Wingsuit flying Sailing: * Sails * Forces on sails * Wingsail


References


External links


How Wings Work - Holger Babinsky Physics Education 2003

Demystifying the Science of Flight
– Audio segment on NPR's Talk of the Nation Science Friday


Flight of the StyroHawk wing
{{Authority control Aerodynamics Aerospace technologies Aircraft wing components Bird anatomy Bird flight Insect anatomy Mammal anatomy es:Ala (zoología)