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A wing is a type of
fin A fin is a thin component or appendage attached to a larger body or structure. Fins typically function as foils that produce lift or thrust, or provide the ability to steer or stabilize motion while traveling in water, air, or other fluids. Fin ...
that produces
lift Lift or LIFT may refer to: Physical devices * Elevator, or lift, a device used for raising and lowering people or goods ** Paternoster lift, a type of lift using a continuous chain of cars which do not stop ** Patient lift, or Hoyer lift, mobile ...
while moving through air or some other
fluid In physics, a fluid is a liquid, gas, or other material that continuously deforms (''flows'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear ...
. Accordingly, wings have
streamlined Streamlines, streaklines and pathlines are field lines in a fluid flow. They differ only when the flow changes with time, that is, when the flow is not steady. Considering a velocity vector field in three-dimensional space in the framework of ...
cross-sections that are subject to
aerodynamic force In fluid mechanics, an aerodynamic force is a force exerted on a body by the air (or other gas) in which the body is immersed, and is due to the relative motion between the body and the gas. Force There are two causes of aerodynamic force: ...
s and act as
airfoil An airfoil (American English) or aerofoil (British English) is the cross-sectional shape of an object whose motion through a gas is capable of generating significant lift, such as a wing, a sail, or the blades of propeller, rotor, or turbine. ...
s. A wing's
aerodynamic 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 dyn ...
efficiency is expressed as its
lift-to-drag ratio In aerodynamics, the lift-to-drag ratio (or L/D ratio) is the lift generated by an aerodynamic body such as an aerofoil or aircraft, divided by the aerodynamic drag caused by moving through air. It describes the aerodynamic efficiency under give ...
. The lift a wing generates at a given speed and
angle of attack In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is m ...
can be one to two
orders of magnitude An order of magnitude is an approximation of the logarithm of a value relative to some contextually understood reference value, usually 10, interpreted as the base of the logarithm and the representative of values of magnitude one. Logarithmic dis ...
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 syst ...
to propel the wings through the air at sufficient lift. Lifting structures used in water include various foils, such as
hydrofoil A hydrofoil is a lifting surface, or foil, that operates in water. They are similar in appearance and purpose to aerofoils used by aeroplanes. Boats that use hydrofoil technology are also simply termed hydrofoils. As a hydrofoil craft gains sp ...
s.
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) and ...
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 lightweigh ...
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 pairs ...
s,
bat Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most bi ...
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 to ...
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 fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines ...
, or the inverted airfoil on a
race car Auto racing (also known as car racing, motor racing, or automobile racing) is a motorsport involving the racing of automobiles for competition. Auto racing has existed since the invention of the automobile. Races of various sorts were organi ...
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 dyn ...
, 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 bio ...
. 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) an ...
. 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 In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is m ...
. 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 variety (linguistics), varieties of the English language native to the United States. English is the Languages of the United States, most widely spoken lan ...
) or ''aerofoil'' (
British English British English (BrE, en-GB, or BE) is, according to Lexico, Oxford Dictionaries, "English language, English as used in Great Britain, as distinct from that used elsewhere". More narrowly, it can refer specifically to the English language in ...
) is the shape of a wing, blade (of a
propeller A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...
,
rotor Rotor may refer to: Science and technology Engineering *Rotor (electric), the non-stationary part of an alternator or electric motor, operating with a stationary element so called the stator * Helicopter rotor, the rotary wing(s) of a rotorcraft ...
, or
turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating e ...
), or
sail A sail is a tensile structure—which is made from fabric or other membrane materials—that uses wind power to propel sailing craft, including sailing ships, sailboats, windsurfers, ice boats, and even sail-powered land vehicles. Sails may ...
(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) **Ab ...
). Wings with an asymmetrical cross section are the norm in
subsonic flight 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 dyn ...
. Wings with a symmetrical cross section can also generate lift by using a positive
angle of attack In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is m ...
to deflect air downward. Symmetrical airfoils have higher stalling speeds than cambered airfoils of the same wing area but are used in
aerobatic Aerobatics is the practice of flying maneuvers involving aircraft attitudes that are not used in conventional passenger-carrying flights. The term is a portmanteau of "aerial" and "acrobatics". Aerobatics are performed in aeroplanes and glid ...
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 transoni ...
), 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 airfoil A supercritical airfoil (supercritical aerofoil in British English) is an airfoil designed primarily to delay the onset of wave drag in the transonic speed range. Supercritical airfoils are characterized by their flattened upper surface, highly ...
s, are flat on top and curved on the bottom.


Design features

Aircraft wings may feature some of the following: * A rounded
leading edge The leading edge of an airfoil surface such as a wing is its foremost edge and is therefore the part which first meets the oncoming air.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 305. Aviation Supplies & Academics, ...
cross-section * A sharp
trailing edge The trailing edge of an aerodynamic surface such as a wing is its rear edge, where the airflow separated by the leading edge meets.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 521. Aviation Supplies & Academics, 1997. ...
cross-section * Leading-edge devices such as
slats Super Low Altitude Test Satellite (SLATS) or Tsubame was a JAXA satellite intended to demonstrate operations in very low Earth orbit (VLEO, below 200 km), using ion engines to counteract aerodynamic drag from the Earth's atmosphere which i ...
, 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 * E ...
s * Trailing-edge devices such as
flap Flap may refer to: Arts, entertainment, and media * ''Flap'' (film), a 1970 American film * Flap, a boss character in the arcade game ''Gaiapolis'' * Flap, a minor character in the film '' Little Nemo: Adventures in Slumberland'' Biology and he ...
s or flaperons (combination of flaps and ailerons) *
Winglets Wingtip devices are intended to improve the efficiency of fixed-wing aircraft by reducing drag. Although there are several types of wing tip devices which function in different manners, their intended effect is always to reduce an aircraft' ...
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. *
Aileron An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement around ...
s (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. Ac ...
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 generator A vortex generator (VG) is an aerodynamic device, consisting of a small vane usually attached to a lifting surface (or airfoil, such as an aircraft wing) or a rotor blade of a wind turbine.Wing fence Wing fences, also known as boundary layer fences and potential fences are fixed aerodynamic devices attached to aircraft wings. Often seen on swept-wing aircraft, wing fences are flat plates fixed to the upper surfaces parallel to the wing ch ...
s to keep flow attached to the wing by stopping boundary layer separation from spreading roll direction. *
Folding wing A folding wing is a wing configuration design feature of aircraft to save space and is typical of carrier-based aircraft that operate from the limited deck space of aircraft carriers. The folding allows the aircraft to occupy less space in a c ...
s allow more aircraft storage in the confined space of the
hangar deck A hangar is a building or structure designed to hold aircraft or spacecraft. Hangars are built of metal, wood, or concrete. The word ''hangar'' comes from Middle French ''hanghart'' ("enclosure near a house"), of Germanic origin, from Frankish ...
of an
aircraft carrier An aircraft carrier is a warship that serves as a seagoing airbase, equipped with a full-length flight deck and facilities for carrying, arming, deploying, and recovering aircraft. Typically, it is the capital ship of a fleet, as it allows a ...
*
Variable-sweep wing A variable-sweep wing, colloquially known as a "swing wing", is an airplane wing, or set of wings, that may be swept back and then returned to its original straight position during flight. It allows the aircraft's shape to be modified in fli ...
or "swing wings" that allow outstretched wings during low-speed flight (i.e., take-off and landing) and swept wing, swept back wings for high-speed flight (including supersonic flight), such as in the F-111 Aardvark, the F-14 Tomcat, the Panavia Tornado, the MiG-23, the MiG-27, the Tu-160 and the B-1B Lancer warplanes * Strake (aeronautics), Strakes to improve flight characteristics * Chine (aeronautics), Chine, which may blend into the wing * Leading-edge droop flap, a high-lift device * Aircraft fairing, Fairings, structures whose primary function is to produce a smooth outline and reduce drag. For example, flap track fairings Wings may have other Wing configuration#Minor independent surfaces, minor independent surfaces.


Applications and variants

Besides fixed-wing aircraft, applications for wing shapes include: * Hang gliders, which use wings ranging from fully flexible (paragliders, gliding parachutes), flexible (framed sail wings), to rigid * Kite types, Kites, which use a variety of surfaces to attain lift and maintain stability * Free flight (model aircraft), Flying model airplanes * Helicopters, which use a rotating wing with a variable pitch angle to provide directional forces * Propellers, whose blades generate lift for propulsion. * The NASA Space Shuttle, which uses its wings only to glide during its descent to a runway. These types of aircraft are called spaceplanes. * Some racing cars, especially Formula One cars, which use upside-down wings (or ''
airfoil An airfoil (American English) or aerofoil (British English) is the cross-sectional shape of an object whose motion through a gas is capable of generating significant lift, such as a wing, a sail, or the blades of propeller, rotor, or turbine. ...
s'') to provide greater traction at high speeds. * Sailboats, which use Sailcloth, flexible cloth
sail A sail is a tensile structure—which is made from fabric or other membrane materials—that uses wind power to propel sailing craft, including sailing ships, sailboats, windsurfers, ice boats, and even sail-powered land vehicles. Sails may ...
s 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 evolution, evolved in insects,
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 to ...
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 lightweigh ...
s), and mammals (
bat Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most bi ...
s) as a means of Animal locomotion, locomotion. Various species of penguins and other flighted or flightless bird, flightless water birds such as auks, cormorants, guillemots, shearwaters, eider duck, 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 (helicopter), autorotation in descent File:Seagull wing.jpg, A laughing gull, 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 invented a kite-like Rogallo wing, 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 * Insect flight * List of soaring birds * Samara (fruit), Samara (winged seeds of trees) Aviation: * Aircraft * 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 * 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)