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Airfoil
*** Shopping-Tip: Airfoil
An '''airfoil''' (in
American English, or '''aerofoil''' in
British English) is the shape of a
wing or blade (of a
propeller or ship's
screw or
sail) as seen in cross-section. It is passed through a
fluid in order to provide either
lift (force) lift or
downforce, depending on its application. Subsonic-flight airfoils have a characteristic shape with a rounded leading edge, followed by a sharp trailing edge, and often with
Camber (aerodynamics) camber.
Image:Aerofoil.png right
Image:Airfoil Evoultion.jpg right|thumb|180px|The historical [[evolution of airfoil sections,
1908 -
1944,
NASA]]
Image:Lift_drag_graph.JPG right|thumb|180px|Lift and Drag curves for a typical airfoil
To understand lift itself, see
lift (force) lift. As well as the wing, an aircraft's horizontal and vertical stabilizers are airfoils. Airfoils are also found in
propellors,
Fan (implement) fans,
Gas compressor compressors and
turbines.
Sails are also airfoils, and the underwater fins of sailboats, such as
centerboards, are similar in cross-section and operate on the same principles as airfoils. Swimming and flying creatures and even many plants and
sessile organisms employ airfoils; common examples being bird wings, the bodies of fishes, and the shape of
sand dollars.
An inverted airfoil will create a downward pressure on an
automobile or other motor vehicle, improving its traction and keeping it on the ground. The term "lift" can mean a force generated in any direction in any medium. Any thin object with a positive
angle of attack, such as a flat plate or the deck of a bridge, will generate lift. Airfoils though are more efficient, generating lift with the least
drag (physics) drag and maintaining lift at higher angle of attack. A lift and drag curve obtained in
wind tunnel testing is shown on the right.
Airfoil design is a major facet of
aerodynamics. Various airfoils serve different flight regimes. A
supercritical airfoil, with its low camber, reduces
transonic drag divergence, while a symmetric airfoil may better suit frequent inverted flight. Supersonic airfoils are much more angular in shape and can have a very sharp leading edge. Moveable high-lift devices,
flap (aircraft) flaps and
slats are fitted to airfoils on most aircraft. New airfoil design techniques continue to develop.
Various systems have been devised to describe and characterise airfoils — the most common and prevalent is the
NACA airfoil NACA system. Before this, various ad-hoc systems were used. An example of a general purpose airfoil that finds wide application, and predates the NACA system, is the
Clark-Y.
image:denney.kitfox.g-foxc.arp.jpg thumb|right|250px|An airfoil section is nicely displayed at the tip of this Denney Kitfox aircraft (G-FOXC), built in 1991.
See also
*
Lift (force)
*
Angle of attack
*
Coefficient of lift
*
Stall (flight)
*
Supercritical airfoil
*
Foil (fluid mechanics)
*
NACA airfoil
*
NACA 0015
External links
-
UIUC Airfoil Coordinates Database
Category:Aerodynamics
af:Vlerkprofiel
de:Profil (Strömungslehre)
es:Perfil alar
fa:ماهیواره
fr:Profil d'aile
nl:Vleugel (vliegtuig)
ja:翼型
pl:Profil lotniczy
*** Shopping-Tip: Airfoil
