Supercritical airfoil
Encyclopedia : S : SU : SUP : Supercritical airfoil
A supercritical airfoil 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 (curved) aft section, and greater leading edge radius as compared to traditional airfoil shapes. The supercritical airfoil was created in the 1960s, by then NASA scientist Richard Whitcomb. The supercritical airfoil shape is incorporated into the design of a supercritical wing.
Supercritical airfoils have four main benefits: they have a higher critical mach number, they develop shock waves further aft than traditional airfoils, they greatly reduce shock-induced boundary layer separation, and their geometry allows for more efficient wing design (e.g., a thicker wing and/or reduced wing sweep, both of which may allow for a lighter wing). The aircraft airspeed at which air flowing over the top of the foil reaches the speed of sound is referred to as the critical Mach. When the airflow over a foil reaches this velocity a shockwave develops and airflow begins to separate from the surface of the foil aft of the shockwave. Both the shockwave itself and the resulting airflow separation have negative effects on the airfoil's performance.
In figure 1, the critical mach is denoted as Cp-crit, the shock is evidenced by a sharp drop in the pressure coefficient, and the position of the shock relative to the chord is indicated by the shock's position along the x-axis. The position of this shockwave is determined by the geometry of the airfoil; a supercritical foil is more efficient because the shockwave is minimized and is created as far aft as possible thus reducing drag.
See also
External links
From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.