Wing

A wing is a type of fin that produces lift, while moving through air or some other fluid. As such, wings have streamlined cross-sections that are subject to aerodynamic forces and act as an 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 to propel the wings through the air at sufficient lift.

Lifting structures used in water, include various

• 
  Winged tree seeds that cause

  autorotation

  in descent
• 
  A laughing gull, exhibiting the "gull wing" outline.
• 
  Bat in flight

Aerodynamics

The design and analysis of the wings of aircraft is one of the principal applications of the science of

For a wing to produce "lift", it must be oriented at a suitable angle of attack relative to the flow of air past the wing. When this occurs the wing deflects the airflow downwards, "turning" the air as it passes the wing. Since the wing exerts a force on the air to change its direction, the air must exert a force on the wing, equal in size but opposite in direction. This force manifests itself as differing air pressures at different points on the surface of the wing.^[4][5][6]

A region of lower-than-normal air pressure is generated over the top surface of the wing, with a higher pressure on the bottom of the wing. (See: airfoil) These air pressure differences can be either measured directly using instrumentation, or can be calculated from the airspeed distribution using basic physical principles—including Bernoulli's principle, which relates changes in air speed to changes in air pressure.

The lower air pressure on the top of the wing generates a smaller downward force on the top of the wing than the upward force generated by the higher air pressure on the bottom of the wing. Hence, a net upward force acts on the wing. This force is called the "lift" generated by the wing.

The different velocities of the air passing by the wing, the air pressure differences, the change in direction of the airflow, and the lift on the wing are intrinsically one phenomenon. It is, therefore, possible to calculate lift from any of the other three. For example, the lift can be calculated from the pressure differences, or from different velocities of the air above and below the wing, or from the total momentum change of the deflected air. Fluid dynamics offers other approaches to solving these problems—and all produce the same answers if done correctly. Given a particular wing and its velocity through the air, debates over which mathematical approach is the most convenient to use can be mistaken by novices as differences of opinion about the basic principles of flight.^[7]

Cross-sectional shape

Wings with an asymmetrical cross section are the norm in

• A rounded leading edge cross-section
• A sharp trailing edge cross-section
• Leading-edge devices such as
  extensions
• 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
• Spoilers 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 to help prevent flow separation in transonic flow
• 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
• B-1B Lancer
  warplanes

Applications

Besides fixed-wing aircraft, applications for wing shapes include:^{[citation needed]}

• paragliders, gliding parachutes
  ), flexible (framed sail wings), to rigid
• Kites, which use a variety of lifting surfaces
• 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 airfoils
  ) to provide greater traction at high speeds
• Sailboats, which use sails as vertical wings with variable fullness and direction to move across water

Tensile structures

In 1948, Francis Rogallo invented the fully limp flexible wing, 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.^{[citation needed]}

See also

• Flight

Natural world:

• Bird flight
• Flight feather
• Flying and gliding animals
• Insect flight
• List of soaring birds
• 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 suit

Sailing:

• Sails
• Forces on sails
• Wingsail

References

External links

Wikimedia Commons has media related to Wings.

• How Wings Work - Holger Babinsky Physics Education 2003
• How Airplanes Fly: A Physical Description of Lift
• Demystifying the Science of Flight – Audio segment on NPR's Talk of the Nation Science Friday
• NASA's explanations and simulations
• Flight of the StyroHawk wing
• See How It Flies