Multidisciplinary design optimisation incorporates several disciplines in one integrated optimisation problem. The benefi t of considering all requirements at once rather than in individual optimisations is that synergies between disciplines can be exploited to fi nd superior designs to what would otherwise be possible. The main obstacle for the use of multidisciplinary design optimisation in an industrial setting is the related computational cost which may become prohibitively large. This work is focused on the development of a multidisciplinary design optimisation framework that extends the existing trust-region based optimisation method known as the mid-range approximation method. The main novel contribution is an approach to solving multidisciplinary design optimisation problems using metamodels built in sub-spaces of the design variable space. Each metamodel is built in the sub-space relevant to the corresponding discipline while the optimisation problem is solved in the full design variable space. Since the metamodels are built in a space of reduced dimensionality, the computational budget for building them can be reduced without compromising their quality. Furthermore, a method for efficiently building kriging metamodels is proposed. This is done by means of a two-step hyper parameter tuning strategy. The fi rst step is a line search where the set of tuning parameters is treated as a single variable. The solution of the fi rst step is used in the second step, a gradient based hyper parameter optimisation where partial derivatives are obtained using the adjoint method. The framework is demonstrated on two examples, a multidisciplinary design optimisation of a thin-walled beam section subject to static and impact requirements, and a multidisciplinary design optimisation of an aircraft wing subject to static and bird strike requirements. In both cases the developed technique demonstrates a reduced computational effort compared to what would typically be achieved by existing methods.

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.

Modern aerospace vehicle design requires the interaction of multiple disciplines, traditionally processed in a sequential order. Multidisciplinary optimization (MDO), a formal methodology for the integration of these disciplines, is evolving toward methods capable of replacing the traditional sequential methodology of aerospace vehicle design by concurrent algorithms, with both an overall gain in product performance and a decrease in design time. A parallel MDO paradigm using variable-complexity modeling and multipoint response surface approximations is presented here for the particular instance of the design of a high speed civil transport (HSCT). This paradigm interleaves the disciplines at one level of complexity, and processes them hierarchically at another level of complexity, achieving parallelism within disciplines, rather than across disciplines. A master-slave paradigm manages a coarse grained parallelism of the analysis and optimization codes required by the disciplines showing reasonable speedups and efficiencies on an Intel Paragon / Master of Science

A exploração de bacias petrolíferas do pré-sal, principalmente campos gigantes como o campo de Libra, na bacia de Santos, traz consigo demandas por sistemas capazes de operar com poços de alta capacidade de produção e em grandes profundidades. Nesse cenário, linhas de produção ou injeção (risers) rígidas em catenária livre apresentam a forma mais simples de solução para essas demandas. A utilização de risers rígidos em catenária livre, como já sabido, permite uma maior produtividade por linha devido a possibilidade de utilização de dutos de maiores diâmetros, ao mesmo tempo em que resistem a maiores pressões, possibilitando a exploração de forma mais eficiente de poços em grandes profundidades. No entanto, este tipo de solução, devido a sua natureza de maior rigidez quando comparado com dutos flexíveis, é submetida a esforços dinâmicos elevados impostos no topo do riser pela grande movimentação da embarcação, principalmente em operações em águas profundas, inviabilizando sua aplicação em unidades do tipo FPSOs convencionais, construídos a partir da conversão de um navio petroleiro. Este problema dinâmico é agravado pelas condições ambientais da região, que são mais severas do que as observadas na Bacia de Campos, tornando difícil a aplicação das tecnologias existentes. A alta produtividade dos poços do pré-sal da Bacia de Santos também estimula a utilização de plantas de processo de alta capacidade de processamento de óleo, maiores do que as utilizadas até hoje no offshore brasileiro. Estimativas iniciais mostram que estas plantas gigantes demandam uma área de convés muito maior do que as plataformas convencionais, e, mais do que isso, de uma maior largura (boca) da embarcação. Para atender requisitos tão conflitantes, foi desenvolvido o conceito ULFPSO (Unidade Flutuante de Produção, Armazenamento e Alívio Ultra-Larga), que se caracteriza por sua proa e popa circulares e pela presença do moonpool, de forma a viabilizar a conexão dos risers mais próximos ao centro de gravidade da plataforma, reduzindo assim o esforço dinâmico. Adicionalmente a forma do casco é otimizada para redução do nível de movimentos verticais, reduzindo os esforços dinâmicos nos risers. Nesta dissertação de mestrado serão apresentados os estudos relativos à comprovação de viabilidade do conceito, dividido em três etapas: A primeira com foco no entendimento do problema e dimensionamento preliminar da unidade; A segunda focada na avaliação experimental do conceito; E finalmente, a terceira, com objetivo de avaliar o modelo de síntese para otimização do projeto do casco, com base nos resultados obtidos nas fases anteriores. / The offshore exploitation of oil fields in the pre-salt, especially giant fields such as Libra, in the Santos basin, brings with it demands for systems capable of operating with high capacity production wells and at ultra-deep waters. In this scenario production or injection steel catenary risers present the simplest solution for these demands. As known in industry, the use of steel catenary risers in free-hanging configuration allows greater productivity per line due to the possibility of using pipes of larger diameters, at the same time withstand higher pressures, allowing for more efficient wells operation at great depths. However, due to its nature more rigid compared to flexible pipe, this kind of solution is subjected to high dynamic forces imposed on the top of the riser by the large movement of the vessel, especially in deepwater operations, impeding their application in FPSO conventional units, constructed from the conversion of an oil tanker. This dynamic problem is compounded by environmental conditions of the region, which are harsher than those observed in the Campos Basin, making it difficult to apply other extant technologies. The high productivity of the pre-salt of Santos Basin wells stimulate the use of plants to high-capacity oil processing process, larger than those used today in the Brazilian offshore. Initial estimates show that these plants require a much larger deck area than conventional platforms and, more than that, a greatest width (breadth) of the vessel. To satisfy such conflicting requirements, the ULFPSO (Ultra Large Floating Production, Storage and Offloading) concept was developed, which is characterized by its circular bow and stern and the presence of the moonpool, to enable the connection of the risers closest to the platform\'s center of gravity, thereby reducing the dynamic tension. Additionally, the hull shape is optimized to reduce vertical movements, reducing dynamic stresses on the riser. In this master\'s thesis will be presented studies on the proof of concept viability, divided into three stages: The first focused on understanding the problem and preliminary sizing of the unit; The second focused on the experimental evaluation of the concept; And finally, the third, to evaluate the synthesis model for optimizing hull design, based on the results obtained in the previous phases.

No description available.

abstract: This dissertation considers an integrated approach to system design and controller design based on analyzing limits of system performance. Historically, plant design methodologies have not incorporated control relevant considerations. Such an approach could result in a system that might not meet its specifications (or one that requires a complex control architecture to do so). System and controller designers often go through several iterations in order to converge to an acceptable plant and controller design. The focus of this dissertation is on the design and control an air-breathing hypersonic vehicle using such an integrated system-control design framework. The goal is to reduce the number of system-control design iterations (by explicitly incorporate control considerations in the system design process), as well as to influence the guidance/trajectory specifications for the system. Due to the high computational costs associated with obtaining a dynamic model for each plant configuration considered, approximations to the system dynamics are used in the control design process. By formulating the control design problem using bilinear and polynomial matrix inequalities, several common control and system design constraints can be simultaneously incorporated into a vehicle design optimization. Several design problems are examined to illustrate the effectiveness of this approach (and to compare the computational burden of this methodology against more traditional approaches). / Dissertation/Thesis / Ph.D. Electrical Engineering 2014

A exploração de bacias petrolíferas do pré-sal, principalmente campos gigantes como o campo de Libra, na bacia de Santos, traz consigo demandas por sistemas capazes de operar com poços de alta capacidade de produção e em grandes profundidades. Nesse cenário, linhas de produção ou injeção (risers) rígidas em catenária livre apresentam a forma mais simples de solução para essas demandas. A utilização de risers rígidos em catenária livre, como já sabido, permite uma maior produtividade por linha devido a possibilidade de utilização de dutos de maiores diâmetros, ao mesmo tempo em que resistem a maiores pressões, possibilitando a exploração de forma mais eficiente de poços em grandes profundidades. No entanto, este tipo de solução, devido a sua natureza de maior rigidez quando comparado com dutos flexíveis, é submetida a esforços dinâmicos elevados impostos no topo do riser pela grande movimentação da embarcação, principalmente em operações em águas profundas, inviabilizando sua aplicação em unidades do tipo FPSOs convencionais, construídos a partir da conversão de um navio petroleiro. Este problema dinâmico é agravado pelas condições ambientais da região, que são mais severas do que as observadas na Bacia de Campos, tornando difícil a aplicação das tecnologias existentes. A alta produtividade dos poços do pré-sal da Bacia de Santos também estimula a utilização de plantas de processo de alta capacidade de processamento de óleo, maiores do que as utilizadas até hoje no offshore brasileiro. Estimativas iniciais mostram que estas plantas gigantes demandam uma área de convés muito maior do que as plataformas convencionais, e, mais do que isso, de uma maior largura (boca) da embarcação. Para atender requisitos tão conflitantes, foi desenvolvido o conceito ULFPSO (Unidade Flutuante de Produção, Armazenamento e Alívio Ultra-Larga), que se caracteriza por sua proa e popa circulares e pela presença do moonpool, de forma a viabilizar a conexão dos risers mais próximos ao centro de gravidade da plataforma, reduzindo assim o esforço dinâmico. Adicionalmente a forma do casco é otimizada para redução do nível de movimentos verticais, reduzindo os esforços dinâmicos nos risers. Nesta dissertação de mestrado serão apresentados os estudos relativos à comprovação de viabilidade do conceito, dividido em três etapas: A primeira com foco no entendimento do problema e dimensionamento preliminar da unidade; A segunda focada na avaliação experimental do conceito; E finalmente, a terceira, com objetivo de avaliar o modelo de síntese para otimização do projeto do casco, com base nos resultados obtidos nas fases anteriores. / The offshore exploitation of oil fields in the pre-salt, especially giant fields such as Libra, in the Santos basin, brings with it demands for systems capable of operating with high capacity production wells and at ultra-deep waters. In this scenario production or injection steel catenary risers present the simplest solution for these demands. As known in industry, the use of steel catenary risers in free-hanging configuration allows greater productivity per line due to the possibility of using pipes of larger diameters, at the same time withstand higher pressures, allowing for more efficient wells operation at great depths. However, due to its nature more rigid compared to flexible pipe, this kind of solution is subjected to high dynamic forces imposed on the top of the riser by the large movement of the vessel, especially in deepwater operations, impeding their application in FPSO conventional units, constructed from the conversion of an oil tanker. This dynamic problem is compounded by environmental conditions of the region, which are harsher than those observed in the Campos Basin, making it difficult to apply other extant technologies. The high productivity of the pre-salt of Santos Basin wells stimulate the use of plants to high-capacity oil processing process, larger than those used today in the Brazilian offshore. Initial estimates show that these plants require a much larger deck area than conventional platforms and, more than that, a greatest width (breadth) of the vessel. To satisfy such conflicting requirements, the ULFPSO (Ultra Large Floating Production, Storage and Offloading) concept was developed, which is characterized by its circular bow and stern and the presence of the moonpool, to enable the connection of the risers closest to the platform\'s center of gravity, thereby reducing the dynamic tension. Additionally, the hull shape is optimized to reduce vertical movements, reducing dynamic stresses on the riser. In this master\'s thesis will be presented studies on the proof of concept viability, divided into three stages: The first focused on understanding the problem and preliminary sizing of the unit; The second focused on the experimental evaluation of the concept; And finally, the third, to evaluate the synthesis model for optimizing hull design, based on the results obtained in the previous phases.

The aviation industry is growing at a steady rate but presently, the industry is highly dependent on fossil fuel. As the world is running out of fossil fuels and the wide-spread acceptance of climate change due to carbon emissions, both the governments and industry are spending a significant amount of resources on research to reduce the weight and hence the fuel consumption of commercial aircraft. A commercial fixed-wing aircraft wing consists of spars which are beams running in span-wise direction, carrying the flight loads and ribs which are panels with holes attached to the spars to preserve the outer airfoil shape of the wing. Kapania et al. at Virginia Tech proposed the concept of reducing the weight of aircraft wing using unconventional design of the internal structure consisting of curvilinear spars and ribs (known as SpaRibs) for enhanced performance. A research code, EBF3GLWingOpt, was developed by the Kapania Group. at Virginia Tech to find the best configuration of SpaRibs in terms of weight saving for given flight conditions. However, this software had a number of limitations and it can only create and analyze limited number of SpaRibs configurations. In this work, the limitations of the EBF3GLWingOpt code has been identified and new algorithms have been developed to make is robust and analyze larger number of SpaRibs configurations. The code also has the capability to create cut-outs in the SpaRibs for passage of fuel pipes and wirings. This new version of the code can be used to find best SpaRibs configuration for multiple objectives such as reduction of weight and increase flutter velocity. The code is developed in Python language and it has parallel computational capabilities. The wing is modeled using commercial FEA software, MSC.PATRAN and analyzed using MSC.NASTRAN which are from within EBF3GLWingOpt. Using this code a significant weight reduction for a transport aircraft wing has been achieved. / PHD / The aviation industry is growing at a steady rate but presently, the industry is highly dependent on fossil fuel. As the world is running out of fossil fuels and the wide-spread acceptance of climate change due to carbon emissions, both the governments and industry are spending a significant amount of resources on research to reduce the weight and hence the fuel consumption of commercial aircraft. A commercial fixed-wing aircraft wing consists of spars which are beams running in span-wise direction, carrying the flight loads and ribs which are panels with holes attached to the spars to preserve the outer airfoil shape of the wing. Kapania et al. at Virginia Tech proposed the concept of reducing the weight of aircraft wing using unconventional design of the internal structure consisting of curvilinear spars and ribs (known as SpaRibs) for enhanced performance. A research code, EBF3GLWingOpt, was developed by the Kapania Group. at Virginia Tech to find the best configuration of SpaRibs in terms of weight saving for given flight conditions. However, this software had a number of limitations and it can only create and analyze limited number of SpaRibs configurations. In this work, the limitations of the EBF3GLWingOpt code has been identified and new algorithms have been developed to make is robust and analyze larger number of SpaRibs configurations. The code also has the capability to create cut-outs in the SpaRibs for passage of fuel pipes and wirings. This new version of the code can be used to find best SpaRibs configuration for multiple objectives such as reduction of weight and increase flutter velocity. The code is developed in Python language and it has parallel computational capabilities. The wing is modeled using commercial FEA software, MSC.PATRAN and analyzed using MSC.NASTRAN which are from within EBF3GLWingOpt. Using this code a significant weight reduction for a transport aircraft wing has been achieved.

There are many challenges facing the aerospace industry that can be addressed with new concepts, technologies, and materials. However, current design methods make it difficult to include these new ideas early in the design of aircraft. This is especially true in the structures discipline, which often uses weight-based methods based upon statistical regressions of historical data. A way to address this is to use physics-based structural analysis and design to create more detailed structural data. Thus, the overall research objective of this dissertation is to develop a physics-based structural analysis method to incorporate new concepts, technologies, and materials into the conceptual design phase. The design space of physics-based structural design problem is characterized as highly multimodal with numerous discontinuities; thus, a large number of alternatives must be explored. Current physics-based structural design methods tend to use high fidelity modeling and analysis tools that are computationally expensive. This dissertation proposes a modeling & simulation environment based on classical structural analysis methods. Using classical structural analysis will enable increased exploration of the design space by reducing the overall run time necessary to evaluate one alternative. The use of physics-based structural optimization using classical structural analysis is tested through experimentation. First the underlying hypotheses are tested in a canonical example by comparing different optimization algorithms ability to locate a global optimum identified through design space exploration. Then the proposed method is compared to a method based on higher fidelity finite element analysis as well as a method based on weight-based empirical data to validate the overall research objective.