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Camber is a complex property that can be more fully characterized by an airfoil's camber line, the curve Z(x) that is halfway between the upper and lower surfaces, and thickness function T(x), which describes the thickness of the airfoils at any given point. The upper and lower surfaces can be defined as follows:
For this reason, on a cambered aerofoil the zero-lift line is better than the chord line when describing the angle of attack. [2] When symmetric aerofoils are moving parallel to the chord line of the aerofoil, zero lift is generated. However, when cambered aerofoils are moving parallel to the chord line, lift is generated. (See diagram at right.)
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 ...
An airfoil with camber compared to a symmetrical airfoil. The maximum lift force that can be generated by an airfoil at a given airspeed depends on the shape of the airfoil, especially the amount of camber (curvature such that the upper surface is more convex than the lower surface, as illustrated at right). Increasing the camber generally ...
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.
Thin airfoil theory assumes the air is an inviscid fluid so does not account for the stall of the airfoil, which usually occurs at an angle of attack between 10° and 15° for typical airfoils. [20] In the mid-late 2000s, however, a theory predicting the onset of leading-edge stall was proposed by Wallace J. Morris II in his doctoral thesis. [ 21 ]
Pitching moment coefficient is fundamental to the definition of aerodynamic center of an airfoil. The aerodynamic center is defined to be the point on the chord line of the airfoil at which the pitching moment coefficient does not vary with angle of attack, [ 1 ] : Section 5.10 or at least does not vary significantly over the operating range of ...
The definition becomes = ′, where is the reference length that should always be specified: in aerodynamics and airfoil theory usually the airfoil chord is chosen, while in marine dynamics and for struts usually the thickness is chosen. Note this is directly analogous to the drag coefficient since the chord can be interpreted as the "area per ...