NACA-RM-A55J28

Abstract

INTRODUCTION <br>The computing method of reference 1 has been effectively used to estimate the zero-lift drag-rise coefficients of various relatively smooth wing-body-tail combinations (refs. 2, 13, and 4). However this original method involves several operations, and the checking procedures, such as were used in reference 3, are time-consuming and check back to only the slopes of the area-distribution curves and not to the area-distribution curves themselves. <br>It is the purpose of this paper to present and to analyze another method for representing the slope of area-distribution curves, which will allow for a more rapid computation of wave drag and will permit the use of an improved method of checking the computations. The basic method for computing the wave drag is fundamentally the same as in reference 1 and is based on the theory of reference 5. The main difference is that Tchebichef polynomials (refs. 6 and 7, also spelled Chebyshev) are used to represent the Fourier sine series defining the slopes of the area-distribution curves. <br>The new method is evaluated by comparison of results with analytical solutions, results from the previous method, and experimental results for mach numbers up to 1.8. The configurations selected, for which experimental data were available, included models of a triangular-wing interceptor-type airplane, a swept-wing interceptor-type airplane, and a body-tail configuration with a scoop-inlet duct.