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This paper considers the e↵ects of uncertainty on multidisciplinary analysis estimates used in conceptual aircraft design. Specifically, the paper presents an analysis of the stability and control (S&C) characteristics of an illustrative Blended-Wing-Body (BWB) configuration using uncertain aerodynamic estimates. The S&C properties of a BWB are highly nonlinear, and as such pose a challenge for low-fidelity analysis techniques. By propagating bounds on uncertain aerodynamic data them through the analysis, bounds are derived for the resulting S&C limits. These estimates can then be used to guide future research and development e↵orts. Results demonstrate that even moderate uncertainty in estimating aerodynamic lift, drag, and moment coecients translates into large uncertainty in estimating the center of gravity limits, due to the highly nonlinear nature of the S&C model. The paper identifies directions for ongoing work using a multifidelity approach to address this issue., Boeing Company

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012., This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections., Cataloged from student-submitted PDF version of thesis., Includes bibliographical references (p. 415-421)., A new geometry management paradigm for aircraft design utilizes Computer Aided Design (CAD) systems as the source for consistent geometry models across design phases and analysis tools. Yet various challenges inhibit the widespread application of CAD models in aircraft conceptual design because current CAD platforms are not designed for automated shape optimization. In particular, CAD models built with conventional methods can perform poorly in automated design frameworks and their associated CAD systems do not provide shape sensitivities. This thesis aims to remedy these concerns by bridging the computational geometry tools in CAD with aerospace design needs. A methodology for constructing CAD models is presented using concepts of multifidelity/multidisciplinary geometry and design motion. A formalized definition of design intent emerges from this approach that enables CAD models with parameterization flexibility, shape malleability and regeneration robustness for automated design settings. Analytic shape sensitivities are also presented to apply CAD models in gradient-based shape optimization. The parameterization and sensitivities for sketches, extrude, revolve and sweep features are given for mechanical design; shape sensitivities for B-spline curves and surfaces are also presented for airfoil and wing design. Furthermore, analytic methods modeling the sensitivity of intersection edges and nodes in a boundary representation (BRep) are given. Comparisons between analytic and finite-difference gradients show excellent agreement, however an error associated with the finite-difference gradient is found to exist if linearizing the support points of B-spline curves/surfaces and regenerating with a geometry kernel. This important outcome highlights a limitation of the finite-difference method when used on CAD models containing these entities. Finally, various example design problems are shown which highlight the application of the methods presented in the thesis. These, by David Sergio Lazzara., Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004., Includes bibliographical references (p. 85)., This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections., The theoretical and numerical evaluation of synergistic diffusing heat-exchanger design is presented. Motivation for this development is based on current diffuser and heat-exchange technologies in cogeneration plants, which require a large geometric footprint to generate steam using gas-turbine exhaust. A compact design is hypothesized to replace these technologies using synergistic design concepts. An investigation into the feasibility of such design concepts are conducted, providing pressure-recovery, viscous losses and thermal energy extraction sensitivities to cooling and annular blade geometry variations. Results show promising diffusion and heat-transfer capabilities that match or surpass current design performance. Proposed configurations are outlined based on these results that compare favorably to a baseline industrial cogeneration application., by David S. Lazzara., S.M.