NACA-TN-1449

Abstract

INTRODUCTION <br>Recent development in airfoil theory for supersonic speeds (references 1 to 3) indicate pronounced effects of sweepback and aspect ratio on the drag. In reference 3, a method based on thin-airfoil theory for a frictionless fluid (reference 2) was applied to calculate the supersonic wave drag at zero lift for a series of wings having thin symmetrical biconvex parabolic-are sections with untapered plan forms and various angles of sweepback and aspect ratios. The results in reference 3, however, are limited to those cases in which the Mach line lies ahead of the wing leading edge, or to a range of Mach number from 1.0 to the value equal to the secant of the angle of sweepback. The term "Mach line" as used herein refers to the Mach wave that originates at the leading edge of the center section, unless specified otherwise. <br>The present paper extends the calculations of reference 3 for the same series of wings in order to present wave-drag results for cases in which the Mach line lies behind the wing leading edge. These data are obtained for wings of rectangular and sweptback plan forms and cover an extensive range of Mach number beginning with the value at which the Mach line coincides with the wing leading edge. In order to present a more complete picture, the results of reference 3 that cover the lower range of Mach number are reproduced herein together with additional curves computed from formulas given in reference 3. The results of the entire investigation are presented in a unified form similar to that given in reference 3 so that the wave drag for this family of wings may be determined directly from a single chart over an extensive range of sweepback angle, Mach number, aspect ratio and thickness ratio. In the Tenth Annual Wright Bros. Memorial Lecture given on December 17, 1946, Dr. von karman indicated that at zero lift the total wave drag for a sweptforward wing is identical with that obtained for the same wing having a corresponding amount of sweepback. The results of the present investigation for the total drag of sweptback wings, therefore, are applicable to the same family of wings having a corresponding amount of sweepforward. The distributions of section drag, however, will differ in the two cases. Although the calculations have been made for the biconvex parabolic-are profile, the data may be applied to indicate corresponding results for profiles similar to the biconvex parabolic-are profile.