This thesis presents new tools and techniques developed to address the challenging problem of high-fidelity aerostructural optimization with respect to large numbers of design variables. A new mesh-movement scheme is developed that is both computationally efficient and sufficiently robust to accommodate large geometric design changes and aerostructural deformations. A fully coupled Newton-Krylov method is presented that accelerates the convergence of aerostructural systems and provides a 20% performance improvement over the traditional nonlinear block Gauss-Seidel approach and can handle more flexible structures. A coupled adjoint method is used that efficiently computes derivatives for a gradient-based optimization algorithm. The implementation uses only machine accurate derivative techniques and is verified to yield fully consistent derivatives by comparing against the complex step method. The fully-coupled large-scale coupled adjoint solution method is shown to have 30% better performance than the segregated approach. The parallel scalability of the coupled adjoint technique is demonstrated on an Euler Computational Fluid Dynamics (CFD) model with more than 80 million state variables coupled to a detailed structural finite-element model of the wing with more than 1 million degrees of freedom. Multi-point high-fidelity aerostructural optimizations of a long-range wide-body, transonic transport aircraft configuration are performed using the developed techniques. The aerostructural analysis employs Euler CFD with a 2 million cell mesh and a structural finite element model with 300000 DOF. Two design optimization problems are solved: one where takeoff gross weight is minimized, and another where fuel burn is minimized. Each optimization uses a multi-point formulation with 5 cruise conditions and 2 maneuver conditions. The optimization problems have 476 design variables are optimal results are obtained within 36 hours of wall time using 435 processors. The TOGW minimization results in a 4.2% reduction in TOGW with a 6.6% fuel burn reduction, while the fuel burn optimization resulted in a 11.2% fuel burn reduction with no change to the takeoff gross weight.

This thesis presents new tools and techniques developed to address the challenging problem of high-fidelity aerostructural optimization with respect to large numbers of design variables. A new mesh-movement scheme is developed that is both computationally efficient and sufficiently robust to accommodate large geometric design changes and aerostructural deformations. A fully coupled Newton-Krylov method is presented that accelerates the convergence of aerostructural systems and provides a 20% performance improvement over the traditional nonlinear block Gauss-Seidel approach and can handle more flexible structures. A coupled adjoint method is used that efficiently computes derivatives for a gradient-based optimization algorithm. The implementation uses only machine accurate derivative techniques and is verified to yield fully consistent derivatives by comparing against the complex step method. The fully-coupled large-scale coupled adjoint solution method is shown to have 30% better performance than the segregated approach. The parallel scalability of the coupled adjoint technique is demonstrated on an Euler Computational Fluid Dynamics (CFD) model with more than 80 million state variables coupled to a detailed structural finite-element model of the wing with more than 1 million degrees of freedom. Multi-point high-fidelity aerostructural optimizations of a long-range wide-body, transonic transport aircraft configuration are performed using the developed techniques. The aerostructural analysis employs Euler CFD with a 2 million cell mesh and a structural finite element model with 300000 DOF. Two design optimization problems are solved: one where takeoff gross weight is minimized, and another where fuel burn is minimized. Each optimization uses a multi-point formulation with 5 cruise conditions and 2 maneuver conditions. The optimization problems have 476 design variables are optimal results are obtained within 36 hours of wall time using 435 processors. The TOGW minimization results in a 4.2% reduction in TOGW with a 6.6% fuel burn reduction, while the fuel burn optimization resulted in a 11.2% fuel burn reduction with no change to the takeoff gross weight.

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This thesis work presents detailed results of the application of energy- and exergy-based methods to the integrated synthesis/design of an Air-to-Air Fighter (AAF) aircraft with and without wing-morphing capability. In particular, a morphing-wing AAF is compared to a traditional fixed-wing AAF by applying large-scale optimization using exergy- and energy-based objective functions to the synthesis/design and operation of the AAF which consists of an Airframe Subsystem (AFS-A) and Propulsion Subsystem (PS). A number of key synthesis/design and operational decision variables are identified which govern the performance of the AFS-A and PS during flight, and detailed models of the components of each of the subsystems are developed. Rates of exergy destruction and exergy loss resulting from irreversible loss mechanisms are determined in each of the AAF vehicle subsystems and their respective components. Multiple optimizations are performed on both types of AAF for a typical fighter aircraft mission consisting of 22 segments. Four different objective functions are used in order to compare exergy-based performance measures to the more traditional energy-based ones. The results show that the morphing-wing AAF syntheses/designs outperform those for the fixed-wing aircraft in terms of exergy destroyed/lost and fuel consumed. These results also show that the exergy-based objectives not only produce the "best" of the optimal syntheses/designs for both types of AAF in terms of exergy destroyed/lost and fuel consumed but as well provide details of where in each subsystem/component and how much specifically each source of irreversibility contributes to the optimal syntheses/designs found. This is not directly possible with an energy-based approach. Finally, after completion of the synthesis/design optimizations, a parametric study is performed to explore the effect on morphing-wing effectiveness of changing the weight and energy penalties used to model the actuations required for morphing. The results show that the morphing-wing AAF exhibits significant benefits over the fixed-wing aircraft even for unrealistic weight and energy penalties. / Master of Science

This thesis describes some of the processes and results obtained during the design and prototyping of a single seat experimental aircraft. The major aim was to maximise the Triaviation score of the aircraft. This score is a combination of the top speed, the stall speed and the rate of climb. The aircraft has been designed constructed, inspected and flown. The process of designing and prototyping is outlined in this thesis. Details are provided regarding preliminary design, numerical optimisation and the process of building the prototype. The aircraft registered VH-ZYY is a shoulder wing monoplane using a Continental IO-240 aircraft engine. The aircraft has a high power to weight ratio and light wing loading to assist it to climb well and fly slowly. Full span flaperons are used to increase the maximum coefficient of lift at the stall. The primary structure is aluminium with a carbon fibre and nomex cored cowl. All steel components have been formed with 4130 chrome molybdenum aircraft grade tubing. All hardware uses AN specification parts. VH-ZYY is registered in Australia as an Experimental aircraft.

This dissertation investigates the advantages of using curvilinear spars and ribs, termed SpaRibs, to design supersonic aircraft wing-box in comparison to the use of classic design concepts that employ straight spars and ribs. The intent is to achieve a more efficient load-bearing mechanism and to passively control aeorelastic behavior of the structure under the flight loads. The use of SpaRibs broadens the design space and allows for the natural frequencies and natural mode shape tailoring. The SpaRibs concept is implemented in a new MATLAB-based optimization framework referred to as EBF3SSWingOpt. This framework interfaces different analysis software to perform the tasks required. VisualDOC is used as optimizer; the generation of the SpaRibs geometry and of the structure Finite Element Model (FEM) is performed by MD.PATRAN; MD.NASTRAN is utilized to compute the weight of the structure, the linear static stress analysis and the linear buckling analysis required for the calculation of the response functions. EBF3SSWingOpt optimization scheme performs both the sizing and the shaping of the internal structural elements. Two methods are compared while optimizing the wing-box; a One-Step method in which sizing and topology optimization are carried out simultaneously and a Two-Step method, in which the sizing and topology optimization are carried out separately but in an iterative way. The optimization problem statements for the One-Step and the Two-Step methodologies are presented. Three methods to define the shape of the SpaRibs parametrically are described: (1) the Bounding Box and Base Curves method defines the shape of the SpaRibs based on the shape of two curves called Base Curves which are positioned into the Bounding Box, a rectangular region defined on the plane z=0 and containing the projection of the wing plan-form onto the same plane; (2) the Linked Shape method defines the shape of a set of SpaRibs in a one by one square domain of the natural space. The set of curves is subsequently transformed in the physical space for creating the wing structure geometry layout. The shape of each curve of each set is unique however, mathematical relations link their curvature in an effort to reduce the number of design variables; and (3) the Independent Shape parameterization is similar to the Linked Shape parameterization however, the shape of each curve is unique. The framework and parameterization methods described are applied to optimize different types of wing structures. Following results are presented and discussed: (1) a rectangular wing-box subjected to a chord-wise linearly varying load, optimized using SpaRibs parameterized with Bounding-Box and Base Curves method; (2) a rectangular wing-box subjected to a chord-wise linearly varying load, optimized using SpaRibs parameterized with Linked Shape method; (3) a generic fighter wing subjected to uniform distributed pressure load, optimized using SpaRibs parameterized with Bounding-Box and Base Curves method; (4) a general business jet wing subjected to pull-up maneuver loads computed using ZESt (ZONA Technology Inc. Steady Euler equations solver), optimized using SpaRibs parameterized with Independent Shape method; (5) a preliminary application of the Linked Shape parameterization to place SpaRibs into a high speed commercial transport aircraft wing-box characterized by high geometry layout complexity; and (6) an optimization of panels subjected to axial and shear loads using curvilinear stiffeners and grids of curvilinear stiffeners. The results for the optimization of the rectangular wing-box show 36.8% weight reduction from the baseline, when the Bounding Box and Base Curves parameterization is applied and the Two-Step framework is implemented. For the same structure the weight reduction amounts to 46.7% when the Linked Shape parameterization and the Two-Step framework are used. Similar results are obtained for the generic fighter wing-box structure. In this case, the weight saving is about 20%. Bounding Box and Base Curves parameterization and Two-Step framework are used. Finally, the weight reduction for the general business jet wing-box structure amounts to 17% of the baseline weight. In this case, the computation is carried out using the Independent Shape parameterization and the Two-Step framework. In general, the Two-Step optimization framework finds better optimal structure configurations as compared to the One-Step optimization framework. However, the computational time required to find to optimum with the Two-Step optimization is larger when a small number of particles are used in the particle swarm optimization method. For larger number of particles, the computational time for the two methods is comparable. Finally for very large number of particles the Two-Step optimization requires less computational time. It is also important to notice how the Two-Step framework consistently leads to a better optimum than the One-Step framework, for the same number of particles. / Ph. D.

The research examines how the Bi-Level Integrated System Synthesis decomposition technique can be adapted to perform as the conceptual aeroelastic design tool. The study describes a comprehensive solution of the aeroelastic coupled problem cast in this decomposition format and implementation in an integrated framework. The method is supported by application details of a proof-of-concept high speed vehicle. Physics-based codes such as finite element and an aerodynamic panel method are used to model the high-definition geometric characteristics of the vehicle. A synthesis and sizing code was added to referee the conflicts that arise between the two disciplines. This research's novelty lies in four points. First is the use of physics-based tools at the conceptual design phase to calculate the aeroelastic properties. Second is the projection of flutter and divergence velocity constraint lines in a power loading versus wing loading graph. The mapping of such constraints in a designer's familiar format is a valuable tool for fast examination of the design space. Third is the improvement of the aeroelastic assessment given the time allotted. Until recently, because of extensive computational and time requirements, aeroelasticity was only assessed at the preliminary design phase. This research illustrates a scheme whereby, for the first time, aeroelasticity can be assessed at the early design formulation stages. Forth, this assessment allowed to verify the impact of changing velocity, altitude, and angle of attack and identify robust design space with these three mission properties. The method's application to the quiet supersonic business jet gave a delta shaped wing for the supersonic speed regime. A subsonic case resulted in a high aspect ratio wing. The scaling approach allowed iso-flutter and iso-divergence lines to be plotted. The main effects of velocity, altitude, and angle of attack on these iso-lines were also discussed, as was the identification of robust design space. The response surface surrogate models allowed convergence of the system optimization but questions were posed as to the accuracy of these quadratic models. Other future improvements include the addition of more disciplines and more detailed models.

Advances in computational power have produced great strides in the later design and production portions of an aircraft s life cycle, and these advances have included the internal layout component of the design and manufacturing process. However, conceptual and preliminary design tools for internal layout remain primarily based on historical regressions and estimations a situation that becomes untenable when considering revolutionary designs or component technologies. Bringing internal layout information forward in the design process can encourage the same level of benefits enjoyed by other disciplines as advances in aerodynamics, structures and other fields propagate forward in the design of complex systems. Accurate prediction of the volume required to contain all of an aircraft s internal components results in a more accurate prediction of aircraft specifications, mission effectiveness, and costs, helping determine if an aircraft is the best choice for continued development. This is not a computationally simple problem, however, and great care must be taken to ensure the efficiency of any proposed solution. Any solution must also address the uncertainty inherent in describing internal components early in the design process. Implementing a methodology that applies notions of an intelligent search for a solution, as well as deals robustly with component sizing, produces a high chance of success. Development of a robust, rapid method for assessing the volumetric characteristics of an aircraft in the context of the conceptual and preliminary design processes can offer many of the benefits of a complete internal layout without the immense assignment of resources typical in the detail phase of the design process. A simplified methodology for volumetrically sizing an aircraft is presented here as well as an assessment of the state-of-the-art techniques for volumetric considerations used in current aircraft design literature. A prototype tool using a combination of original code and publicly available libraries is developed and explored. A sample aircraft design is undertaken with the prototype tool to demonstrate the effectiveness of the methodology.

When aggressive aircraft performance goals are set, he integration of new, advanced technologies into next generation aircraft concepts is required to bridge the gap between current capabilities and required capabilities. A large number of technologies exists that can be pursued, and only a subset may practically be selected to reach the chosen objectives. Additionally, the appropriate numerical and physical experimentation must be identified to further develop the selected technologies. These decisions must be made under a large amount of uncertainty because developing technologies introduce phenomena that have not been previously characterized. Traditionally, technology selection decisions are made based on deterministic performance assessments that do not capture the uncertainty of the technology impacts. Model-driven environments and new, advanced uncertainty quantification techniques provide the ability to characterize technology impact uncertainties and pinpoint how they are driving the system performance, which will aid technology selection decisions. Moreover, the probabilistic assessments can be used to plan experimentation that facilitates uncertainty reduction by targeting uncertainty sources with large performance impacts. The thesis formulates and implements a process that allows for risk-informed decision making throughout technology development. It focuses on quantifying technology readiness risk and performance risk by synthesizing quantitative, probabilistic performance information with qualitative readiness assessments. The Quantitative Uncertainty Modeling, Management, and Mitigation (QuantUM3) methodology was tested through the use of an environmentally-motivated aircraft design case study based upon NASAs Environmentally Responsible Aviation (ERA) technology development program. A physics-based aircraft design environment was created that has the ability to provide quantitative system-level performance assessments and was employed to model the technology impacts as probability distributions to facilitate the development of an overall process required to enable risk-informed technology and experimentation decisions. The outcome of the experimental e orts was a detailed outline of the entire methodology and a confirmation that the methodology enables risk-informed technology development decisions with respect to both readiness risk and performance risk. Furthermore, a new process for communicating technology readiness through morphological analysis was created as well as an experiment design process that utilizes the readiness information and quantitative uncertainty analysis to simultaneously increase readiness and decrease technology performance uncertainty.

Automatic Implementation of Multidisciplinary Design Optimization Architectures Using piMDO Christopher Marriage Masters of Applied Science Graduate Department of Aerospace Engineering University of Toronto 2008 Multidisciplinary Design Optimization (MDO) provides optimal solutions to complex, coupled, multidisciplinary problems. MDO seeks to manage the interactions between disciplinary simulations to produce an optimum, and feasible, design with a minimum of computational effort. Many MDO architectures and approaches have been developed, but usually in isolated situations with little chance for comparison. piMDO was developed to provide a unified framework for the solution of coupled op- timization problems and refinement of MDO approaches. The initial implementation of piMDO showed the benefits of a modular, object oriented, approach and laid the groundwork for future development of MDO architectures. This research furthered the development of piMDO by expanding the suite of available problems, incorporat- ing additional MDO architectures, and extending the object oriented approach to all of the required components for MDO. The end result is a modular, flexible software framework which is user friendly and intuitive to the practitioner. It allows complex problems to be quickly implemented and optimized with a variety of powerful numerical tools and MDO architectures. Importantly, it allows any of its components to be reorganized and sets the stage for future researchers to continue the development of MDO methods.