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A supercritical aerofoil (supercritical airfoil in American 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 cambered ("downward-curved") aft section, and larger leading-edge radius compared with NACA 6-series ...
After World War II, NACA research began to focus on near-sonic and low-supersonic airflow.After considering the sudden drag increase which a wing-fuselage combination experiences at somewhere around 500 mph (800 km/h), Whitcomb concluded that "the disturbances and shock waves are simply a function of the longitudinal variation of the cross-sectional area" – that is, the effect of the wings ...
At high-subsonic flight speeds, the local speed of the airflow can reach the speed of sound where the flow accelerates around the aircraft body and wings.The speed at which this development occurs varies from aircraft to aircraft and is known as the critical Mach number.
, is the coefficient of lift of a specific section of the airfoil, t is the airfoil thickness at a given section, c is the chord length at a given section, is a factor established through CFD analysis: K = 0.87 for conventional airfoils (6 series), [4] K = 0.95 for supercritical airfoils.
It is used for near-supersonic flight and produces a higher lift-to-drag ratio at near supersonic flight than traditional airfoils. Supercritical airfoils employ a flattened upper surface, highly cambered (curved) aft section, and greater leading-edge radius as compared to traditional airfoil shapes. These changes delay the onset of wave drag.
The supercritical airfoil is a type that results in reasonable low speed lift like a normal airfoil, but has a profile considerably closer to that of the von Kármán ogive. All modern civil airliners use forms of supercritical aerofoil and have substantial supersonic flow over the wing upper surface.
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. [1] The exact range of speeds depends on the object's critical Mach number, but transonic flow is seen at flight speeds close to the speed of sound (343 m/s at sea level), typically between Mach 0.8 and 1.2.
a=chord, b=thickness, thickness-to-chord ratio = b/a The F-104 wing has a very low thickness-to-chord ratio of 3.36%. In aeronautics, the thickness-to-chord ratio, sometimes simply chord ratio or thickness ratio, compares the maximum vertical thickness of a wing to its chord.