NASA-TP-1500

Abstract

A study has been made of the factors which place limits on the theoretical leading-edge thrust, and an empirical method for estimating attainable thrust has been developed. The method is based on the use of simple sweep theory to permit a two-dimensional analysis, the use of theoretical airfoil programs to define thrust dependence on local geometric characteristics, and the examination of experimental two-dimensional airfoil data to define limitations imposed by local Mach numbers and Reynolds numbers. The applicability of the method was demonstrated by comparisons of theoretical and experimental aerodynamic characteristics for a series of wing-body configurations. Generally, good predictions of the attainable thrust and its influence on lift and drag characteristics were obtained over a range of Mach numbers from 0.24 to 1.3. <br>The method is compatible with the Polhamus leading-edge suction analogy for fully detected vortex flow, when the analogy is considered to represent the limiting condition of a gradual rotation of the suction vector as leading-edge thrust is lost. An additional advantage of the method is the possibility it presents for designing wings in an iterative manner to maximize thrust and the attendant performance benefits.