Papers by Joaquim R R A Martins
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Wind turbine upscaling is motivated by the fact that larger machines can achieve lower levelized ... more Wind turbine upscaling is motivated by the fact that larger machines can achieve lower levelized cost of energy. However, there are several fundamental issues with the design of such turbines, and there is little public data available for large wind turbine studies. To address this need, we develop a 20 MW common research wind turbine design that is available to public. Multidisciplinary design optimization is used to define the aeroservoelastic design of the rotor and tower subject to the following constraints: blade-tower clearance, stresses, modal frequencies, tip-speed and fatigue damage at several sections of the tower and blade. For blade the design variables include blade length, twist and chord distribution, structural thicknesses distribution and rotor speed at the rated. The tower design variables are the height, and the diameter distribution in the vertical direction. For the other components, mass models are employed to capture their dynamic interactions. The associated cost of these components is obtained by using cost models. The design objective is to minimize the levelized cost of energy. The results of this research show the feasibility of a 20 MW wind turbine, and provide a model with the corresponding data for wind energy researchers to use in the investigation of different aspects of wind turbine design and upscaling.
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Wind energy has experienced a continuous cost reduction in the last decades. A popular cost reduc... more Wind energy has experienced a continuous cost reduction in the last decades. A popular cost reduction technique is to increase the rated power of the wind turbine by making it larger. However, it is not clear whether further upscaling of the existing wind turbines beyond the 5 to 7 MW range is technically feasible and economically attractive. To address this question, this study uses 5, 10, and 20 MW wind turbines that are developed using multidisciplinary design optimization as upscaling data points. These wind turbines are upwind, 3-bladed, pitch-regulated, variable-speed machines with a tubular tower. Based on the design data and properties of these wind turbines, scaling trends such as loading, mass, and cost are developed. These trends are used to study the technical and economical aspects of upscaling and its impact on the design and cost. The results of this research show the technical feasibility of the existing wind turbines up to 20 MW, but the design of such an upscaled machine is cost prohibitive. Mass increase of the rotor is identified as a main design challenge to overcome. The results of this research support the development of alternative lightweight materials and design concepts such as a two-bladed downwind design for upscaling to remain a cost effective solution for future wind turbines.
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The complex-step derivative approximation and its application to numerical algorithms are present... more The complex-step derivative approximation and its application to numerical algorithms are presented. Improvements to the basic method are suggested that further increase its accuracy and robustness and unveil the connection to algorithmic differentiation theory. A general procedure for the implementation of the complex-step method is described in detail and a script is developed that automates its implementation. Automatic implementations of the complex-step method for Fortran and C/C++ are presented and compared to existing algorithmic differentiation tools. The complex-step method is tested in two large multidisciplinary solvers and the resulting sensitivities are compared to results given by finite differences. The resulting sensitivities are shown to be as accurate as the analyses. Accuracy, robustness, ease of implementation and maintainability make these complex-step derivative approximation tools very attractive options for sensitivity analysis.
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Aiaa Journal, Dec 1, 2011
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ABSTRACT
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53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference<BR>20th AIAA/ASME/AHS Adaptive Structures Conference<BR>14th AIAA, 2012
In this paper we present several significant improvements to both coupled solution methods and se... more In this paper we present several significant improvements to both coupled solution methods and sensitivity analysis techniques for high-fidelity aerostructural systems. We consider the analysis of full aircraft configurations using Euler CFD models with more than 80 million state variables and structural finite-element models with more than 1 million degrees of freedom. A coupled Newton–Krylov solution method for the aerostructural system is presented that accelerates the convergence rate for highly flexible structures. A coupled ...
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12th AIAA Aviation Technology, Integration, and Operations (ATIO) Conference and 14th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference, 2012
In this paper we examine the design of metallic and composite aircraft wings in order to assess h... more In this paper we examine the design of metallic and composite aircraft wings in order to assess how the use of composites modifies the trade-off between structural weight and drag. In order to perform this assessment, we use a gradient-based aerostructural design optimization framework that combines a high-fidelity finite-element structural model that includes panel-level design variables with a medium fidelity aerodynamic panel method with profile and compressibility drag corrections. In order to examine the effect of the choice of ...
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AIAA Atmospheric Flight Mechanics Conference, 2009
In this paper, a new control framework is proposed to address the gust load alleviation for very ... more In this paper, a new control framework is proposed to address the gust load alleviation for very flexible aircraft. The novelty of this framework is two folded: on one hand, the deformable dynamics is considered at all stages of design to address the structural interaction challenge; on the other hand, the designed control function does not distinguish between flight dynamics and aeroelasticity to make it possible to improve the control of very flexible aircraft. To demonstrate the capability and effectiveness of the proposed structure, the nonlinear equations of motion for a very ...
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53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference<BR>20th AIAA/ASME/AHS Adaptive Structures Conference<BR>14th AIAA, 2012
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SAE Technical Paper Series, 2009
Abstract: This paper presents an integrated design framework for the concurrent design and analys... more Abstract: This paper presents an integrated design framework for the concurrent design and analysis of aircraft airframes, engines and mission profiles. The objective of this framework is to perform the conceptual design of an aircraft using multidisciplinary design optimization (MDO) methodologies in order to develop optimal environmentally-friendly aircraft. The MDO problems investigated within this framework are aimed at finding optimal aircraft configurations taking into consideration the requirements and constraints of traditional ...
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Structural and Multidisciplinary Optimization, 2012
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Journal of Mechanical Design, 2011
ABSTRACT
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Journal of Guidance, Control, and Dynamics, 2012
R��sum��/Abstract In this paper, a gust load alleviation system based on model-predictive control... more R��sum��/Abstract In this paper, a gust load alleviation system based on model-predictive control is developed for a very flexible aircraft. Two main contributions presented in this work are as follows. First, a unified dynamics framework is developed to represent the full six-degrees-of-freedom rigid body along with the structural dynamics. This allows for an integrated control design to account for maneuverability (flying qualities) and aeroelasticity simultaneously, leading to a new and improved configuration for a very flexible aircraft. ...
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AIAA Journal
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12th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference, 2008
A novel approach to the aerostructural optimization of wing-box structures called asymmetric subs... more A novel approach to the aerostructural optimization of wing-box structures called asymmetric subspace optimization, is presented and compared to the traditional multidisciplinary feasible (MDF) approach. In the asymmetric subspace optimization approach, the analyst chooses local and global sets of design variables and constraints. The local constraints and variables form a local optimization problem that is solved at each global iteration. This requirement changes the sensitivities of the global objective and constraints and requires a post-optimality ...
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52nd Aerospace Sciences Meeting, 2014
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Finite Elements in Analysis and Design, 2014
ABSTRACT Structural optimization using gradient-based methods is a powerful design technique that... more ABSTRACT Structural optimization using gradient-based methods is a powerful design technique that is well suited for the design of high-performance structures. However, the ever-increasing complexity of finite-element models and design formulations results in a bottleneck in the computation of the gradients required for the design optimization. Furthermore, in light of current high-performance computing trends, any methods intended to address this bottleneck must efficiently utilize parallel computing resources. Therefore, there is a need for solution and gradient evaluation methods that scale well with the number of design variables, constraints, and processors. We address this need by developing an integrated parallel finite-element analysis tool for gradient-based design optimization that is designed to use specialized parallel solution methods to solve large-scale high-fidelity structural optimization problems with thousands of design variables, millions of state variables, and hundreds of load cases. We describe the most relevant details of the parallel algorithms used within the tool. We present consistent constraint formulations and aggregation techniques for both material failure and buckling constraints. To demonstrate both the solution and functional accuracy, we compare our results to an exact solution of a pressure-loaded cylinder made with either isotropic or orthotropic material. To demonstrate the parallel solution and gradient evaluation performance, we perform a structural analysis and gradient evaluation for a large transport aircraft wing with over 5.44 million unknowns. The results show near-ideal scalability of the structural solution and gradient computation with the number of design variables, constraints, and processors, which makes this framework well suited for large-scale high-fidelity structural design optimization.
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Papers by Joaquim R R A Martins