Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 21 for “"adjoint methods"”.
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Gradient-Based Optimum Aerodynamic Design Using Adjoint Methods
Continuous adjoint methods and optimal control theory are applied to a pressure-matching inverse design problem of quasi 1-D nozzle flows. Pontryagin’s Minimum Principle is used to derive the adjoint system and the reduced gradient of the cost functional. The properties of adjoint variables at the …
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Shape optimization using feature-based CAD systems and adjoint methods
… model as design variables. This process exploits adjoint methods for the computation of gradients, which predicts how the objective function changes for an infinitesimally small movement of each surface mesh node in the normal direction. The use of adjoint methods results in a computational cost …
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Adjoint Methods and Inverse Modeling for Process Variation Analysis in Silicon Photonics
… particular, this thesis discusses two groups of methods for analysis: adjoint methods for the modeling of variation impact, and inverse modeling for measurement data analysis. In the first half of the thesis, we make necessary extensions to the adjoint methods specifically for the analysis of …
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Simulation of contaminant transport in groundwater systems using Eulerian-Lagrangian localized adjoint methods
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1990.
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Multi-step optimization of internal cooling channels for gas turbine vanes using adjoint methods and machine learning
L'abstract è presente nell'allegato / the abstract is in the attachment
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An a posteriori error control framework for adaptive precision optimization using discontinuous Galerkin finite element method
… significant development over the past decade. Adjoint-based shape design for elliptic systems was first proposed by Pironneau and applied to transonic flow by Jameson . A review of the aerodynamic shape optimization literature and a large list of references is given in. Over the years much …
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On Numerical Error Estimation for the Finite-Volume Method with an Application to Computational Fluid Dynamics
… in numerical solutions. An equivalence between adjoint methods and ETE methods for functional error estimation is presented. This adjoint/ETE equivalence is exploited to efficiently obtain error estimates for multiple output functionals and to extend the higher-order properties of adjoint …
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Design and analysis of transient nonlinear coupled systems
… via both the direct differentiation and adjoint methods. The formulations are particularized to the case of rate-independent elasto-plasticity. Analytic sensitivities for weakly coupled thermo-elasto-plastic systems are computed with the finite element method by implementing the direct …
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Numerical Solution Techniques for Reaction Parameter Sensitivity Coefficients in Multicomponent Subsurface Transport Models
… are also developed to compare the direct and adjoint methods of calculating reaction parameter sensitivity coefficients in batch and transport problems. CPU time comparisons for example transport problems indicate that direct calculation of sensitivity coefficients is much more efficient than …
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Adjoint-accelerated Bayesian inference in thermoacoustics
… far fewer model evaluations than sampling methods. In this framework, parameter inference reduces to a quadratic optimization problem, which we solve using gradient-based optimization, with gradients calculated using adjoint methods. We then estimate the posterior uncertainty using …
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Sensitivity analysis and optimization in low order thermoacoustic models
… thesis a wave-based network model is used. Using adjoint methods the gradients of the eigenvalue with respect to system parameters can be obtained at a low computational cost. This information is used as an input to an optimization routine to find stable thermoacoustic configurations. In this …
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Multi-parameter estimation in glacier models with adjoint and algorithmic differentiation
… very difficult, if not impossible. Computational methods are designed to aid in the development of ice sheet models, ideally identifying the relative importance of each parameter and formulating inverse methods to infer uncertain parameters and thus constrain ice sheet flow. Efficient computation …
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Unsteady adjoint analysis for output sensitivity and mesh adaptation
Adjoint analysis in computational fluid dynamics (CFD) has been applied to design optimization and mesh adaptation, but due to the relative expense of unsteady analysis these applications have predominantly been for steady problems. As the use of adjoint methods continues to becomes more prevalent, …
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Development of a Python-based Data Assimilation Framework (PyDAF). Case Study: Refining Ammonia Emissions Through Observation Data
… WRF-Chem models with iFDMB, 3D-VAR, 4D-VAR, and adjoint methods, using IASI, CrIS, satellite, and Nexrad radar data. For the validation, the Complex Variable Method and pseudo observations are employed. Applying PyDAF, we analyzed an ozone (O3) exceedance in Seoul on June 3, 2019, estimating …
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Development of a Python-based Data Assimilation Framework (PyDAF). Case Study: Refining Ammonia Emissions Through Observation Data
… WRF-Chem models with iFDMB, 3D-VAR, 4D-VAR, and adjoint methods, using IASI, CrIS, satellite, and Nexrad radar data. For the validation, the Complex Variable Method and pseudo observations are employed. Applying PyDAF, we analyzed an ozone (O3) exceedance in Seoul on June 3, 2019, estimating …
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Modelling and analysis of nonlinear thermoacoustic systems using frequency and time domain methods
… networks is investigated, and the use of adjoint methods for understanding the role of the system's parameters on its stability is demonstrated. Then, a nonlinear analysis using various state-of-the-art methods is performed, to highlight the strengths and weaknesses of each method. Two …
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Application of Improved Truncation Error Estimation Techniques to Adjoint Based Error Estimation and Grid Adaptation
… of the numerical solutions obtained via CFD methods and the engineering functionals computed using these solutions. Adjoint error estimation techniques specifically seek to estimate the error in functionals, but are dependent upon accurate truncation error estimates. This work examines the …
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Shape Optimization of Annular Combustors with an Open Source Parallelized Thermoacoustic Helmholtz Solver
… geometries and suggests design changes through adjoint methods combined with geometry parametrization techniques. We implement an inhomogeneous Helmholtz equation solver, helmholtz-x, written in an open-source framework. The mesh is generated with Gmsh and the solver uses DOLFINx and UFL from …
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Selected optimization procedures for CFD-based shape design involving shock waves or computational noise
… cause the objective function to be non-smooth. Methods for robust optimization of the nonsmooth functions are presented. The dissertation is divided into two parts, The first part investigates a simple model problem involving quasi-one-dimensional flow in a duct. The flow field computation is …
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An exact and consistent adjoint method for high-fidelity discretization of the compressible flow equations
Methods and computing hardware advances have enabled accurate predictions of complex compressible turbulence phenomena, such as the generation of jet noise that motivates the present effort. However, limited understanding of underlying physical mechanisms restricts the utility of such predictions …
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