Search results
Results From The WOW.Com Content Network
For example, the NACA 2412 airfoil has a maximum camber of 2% located 40% (0.4 chords) from the leading edge with a maximum thickness of 12% of the chord. The NACA 0015 airfoil is symmetrical, the 00 indicating that it has no camber. The 15 indicates that the airfoil has a 15% thickness to chord length ratio: it is 15% as thick as it is long.
For symmetrical airfoils =, so the aerodynamic center is at 25% of chord measured from the leading edge. But for cambered airfoils the aerodynamic center can be slightly less than 25% of the chord from the leading edge, which depends on the slope of the moment coefficient, . These results obtained are calculated using the thin airfoil theory so ...
For a thin airfoil of any shape the lift slope is π 2 /90 ≃ 0.11 per degree. At higher angles a maximum point is reached, after which the lift coefficient reduces. The angle at which maximum lift coefficient occurs is the stall angle of the airfoil, which is approximately 10 to 15 degrees on a typical airfoil.
Schemes have been devised to define airfoils – an example is the NACA system. Various airfoil generation systems are also used. An example of a general purpose airfoil that finds wide application, and pre–dates the NACA system, is the Clark-Y. Today, airfoils can be designed for specific functions by the use of computer programs.
Camber is usually designed into an airfoil to raise its maximum lift coefficient C Lmax.This minimizes the stalling speed of aircraft using the airfoil. An aircraft with wings using a cambered airfoil will have a lower stalling speed than an aircraft with a similar wing loading and wings using a symmetric airfoil.
Angle of attack of an airfoil In fluid dynamics , angle of attack ( AOA , α , or α {\displaystyle \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 moving. [ 1 ]
This angle is 17.5 degrees in this case, but it varies from airfoil to airfoil. In particular, for aerodynamically thick airfoils (thickness to chord ratios of around 10%), the critical angle is higher than with a thin airfoil of the same camber. Symmetric airfoils have lower critical angles (but also work efficiently in inverted flight).
NACA experience provided a model for World War II research, the postwar government laboratories, and NACA's successor, the National Aeronautics and Space Administration (NASA). NACA also participated in development of the first aircraft to fly to the "edge of space", North American's X-15. NACA airfoils are still used on modern aircraft.