![]() ![]() ![]() The primary reference volume for all the NACA subsonic airfoil studies remains: Abbott, I.H., and von Doenhoff, A.E., Theory of Wing Sections, Dover, 1959. It is not unusual to neglect the camber line slope, which simplifies the equations and makes the reverse problem of extracting the thickness envelope and mean line for a given airfoil straightforward. The equations which describe this procedure are: x u = x − y t x ()sinθ y u = y c x () + y t x ()cosθ (A-1) and x l = x + y t x ()sinθ y l = y c x () − y t x ()cosθ (A-2) where y t (x) is the thickness function, y c (x) is the camber line function, and θ = tan −1 dy c dx (A-3) is the camber line slope. The NACA airfoils are constructed by combining a thickness envelope with a camber or mean line. Taken together, this literature provides a means of obtaining a rather complete understanding of the ways in which airfoils can be shaped to obtain desired performance characteristics. A number of references have been included to allow the reader to study both the older NACA literature and the new airfoil design ideas. Although a new generation of airfoils has emerged as a result of improved understanding of airfoil performance and the ability to design new airfoils using computer methods, the NACA airfoils are still useful in many aerodynamic design applications. Most of the airfoils were based on simple geometrical descriptions of the section shape, although the 6 and 6A series were developed using theoretical analysis and don't have simple shape definitions. A.1 Airfoil Geometry The NACA Airfoils The NACA airfoils were designed during the period from 1929 through 1947 under the direction of Eastman Jacobs at the NACA's Langley Field Laboratory. Section A.1.1 gives some other sources for airfoils. This appendix provides the detailed definition of many of the classic shapes frequently specified in aerodynamics. Aerodynamicists control the flowfield through geometry definition, and are always interested in possible geometric shapes that would be useful in design. ![]()
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