Parametric surface geometry definition for multidisciplinary design optimization of aircraft

Neal A Allgood, Purdue University

Abstract

Aircraft design has long been a complicated design process that requires intuition, historical data, and judgment calls in addition to rigorous analysis. As aircraft grow increasingly more sophisticated and expensive, the need for multidisciplinary design optimization to produce an innovative aircraft grows increasingly more important. However, with typical design techniques, the concept level choices made during the early phases of design are very difficult to change later in the design process. Additionally, these choices are made at a time when the least is known about the candidate design. Therefore, it is imperative to increase the level of knowledge in any aircraft design during the conceptual and preliminary designs. To accomplish this, a Multidisciplinary Design Optimization (MDO) framework is used to systematically analyze and improve potential aircraft designs. The thesis augments the MDO tool developed by Dr. Liaquat Iqbal and Professor John P. Sullivan at Purdue University by applying a surface geometry optimization tool that utilizes a parametric airfoil generation technique developed by Brenda Kulfan and others. This method, known as the class function/shape function transformation (CST), employs Bernstein Polynomials with class and shaping functions to yield a rounded nose and tapered trailing edge type airfoil. This approach was chosen for its ability to model an endless variety of airfoil as well as fuselage shapes with a single geometric formulation. Additionally, the ability to choose the appropriate degree of polynomial based on the definition needs can reduce the design variables, which benefits the optimization. The surface geometry optimization tool was confirmed through the development of a mission specific airfoil and comparing it to one found through traditional airfoil selection techniques. Likewise, the profile drag module was validated using analytical estimations for planform optimization. Ultimately, a UAV was designed using the whole MDO tool, demonstrating the usefulness and capacity of this development tool. The results of this work demonstrate the capability and advantages of utilizing a surface geometry definition tool as part of a larger MDO framework during the early stages of aircraft design.

Degree

M.S.A.A.

Advisors

Sullivan, Purdue University.

Subject Area

Aerospace engineering

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