Date of Award:

5-2020

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Mechanical and Aerospace Engineering

Committee Chair(s)

Douglas F. Hunsaker

Committee

Douglas F. Hunsaker

Committee

Thomas H. Fronk

Committee

Stephen A. Whitmore

Abstract

Minimizing drag is a variational problem, and several minimum induced drag solutions have been found using different design constraints. The elliptic lift distribution is commonly used to minimize induced drag, but is only the optimal solution under one set of design constraints. Non-elliptic lift distributions are able to reduce induced drag, when compared to the elliptic lift distribution, by increasing the wingspan while maintaining a consistent wing–structure weight. However, these non-elliptic lift distributions are only optimal if the effects of viscous drag are neglected. In this study, numerical tools are used to estimate the total drag on rectangular wings that are twisted to give both elliptic and non-elliptic lift distributions. It is shown that the optimal lift distribution is described by Bn = 0 for all n ≠ 3 and B3 = -0.0901 or -0.103 depending on twist type. These optimal lift distributions reduce total drag by 1.01 or 1.23% respectively when compared to the elliptic lift distribution. These values are compared to lift distributions that minimize only induced drag, to understand the effects of using a non-elliptic lift distribution on the efficiency of an aircraft and the viability of using non-elliptic lift distributions on aircraft, specifically morphing-wing aircraft.

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