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 101 for “"Time Stepping"”.
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Time Stepping Methods for Multiphysics Problems
… future states of the system and its evolution in time. This thesis investigates current methods in numerical time-stepping schemes, identifying a number of important features needed to speed up and increase the accuracy of the solutions. The focus is on developing new methods suitable for …
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Automatic Construction of Scalable Time-Stepping Methods for Stiff PDES
… have been demonstrated to be highly scalable time-stepping methods for stiff nonlinear PDEs. However, ensuring this scalability requires analytic computation of frequency-dependent quadrature nodes from the coefficients of the spatial differential operator. This thesis describes how this …
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STRUCTURE-OPTIMIZED AND ORDER-PRESERVING METHODS FOR ADVECTION AND TIME STEPPING
… by the need for numerical methods with long-time accurate solutions in complex advection-dominated problems, we first address whether there are numerical schemes for constant-coefficient advection problems that can yield convergent solutions for an infinite time horizon. After establishing a …
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Electrohydrodynamic Simulations of Capsule Deformation Using a Dual Time-Stepping Lattice Boltzmann Scheme
… fluid equations are solved using a novel dual time-stepping (DTS) lattice Boltzmann method (LBM), which decouples the fluid and capsule discretizations. The computational efficiency of the DTS scheme is studied for capsules in shear flow where it is found that the newly proposed scheme …
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Efficient Time Stepping Methods and Sensitivity Analysis for Large Scale Systems of Differential Equations
… dissertation are the creation of new families of time integration methods for multiscale and multiphysics simulations, and the development of industrial-strengh tools for sensitivity analysis. This work develops novel implicit-explicit (IMEX) general linear time integration methods for …
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The state of the art time-domain wavefield imaging using a discontinuous Galerkin forward-backward time-stepping method
… wavefield imaging technique of Forward/Backward Time-Stepping (FBTS) in the Time Domain (TD) is developed, employing the Discontinuous Galerkin Method (DGM) as the spatial-discretization technique. The FBTS method is based on calculating gradients of a TD cost functional with respect to the …
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On matrix-free pseudo-arclength continuation methods applied to a nonlocal partial differential equation in 1+1D with pseudo-spectral time-stepping
In this thesis we examine a recent animal aggregation model which describes the evolution of two populations of animals moving on a 1-dimensional spatial domain differing only by the direction they travel. The equations describing the evolution of the populations is a hyperbolic, nonlocal partial …
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Stabilized Explicit Time Integration for Parallel Air Quality Models
… concentrations over a certain period of time. The predictions can be used in setting limits for the emission levels of industrial facilities. The input data for the air quality models are very large and encompass various environmental conditions like wind speed, turbulence, temperature …
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Stability Analysis of Krylov Subspace Spectral Methods for the 1-D Wave Equation in Inhomogeneous Media
… (KSS) methods are high-order accurate, explicit time-stepping methods for partial differential equations (PDEs) that also possess the stability characteristic of implicit methods. Unlike other time-stepping approaches, KSS methods compute each Fourier coefficient of the solution from an …
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Diagonalization of 1-D Schrodinger Operators with Piecewise Constant Potentials
… operator in this equation also makes current time-stepping methods not practical. The method used here will apply an eigenfunction expansion technique used in previous research that eliminates the current time-stepping problems.</p>
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Hybrid explicit-implicit FDTD-FEM time-domain solver for electromagnetic problems
The Finite-Difference Time-Domain (FDTD) method and Finite-Element (FEM) method are numerical techniques used for solving Maxwell's electromagnetic equations. FDTD-FEM hybrid methods opt for combining the advantages of both FDTD and FEM. In this dissertation, signal processing techniques were used …
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Rapid Implicit Diagonalization of Variable-Coefficient Differential Operators Using the Uncertainty Principle
… to create a new numerical method for a class of time-dependent PDEs (second-order, one space dimension, Dirichlet boundary conditions) that can be used to obtain more accurate and reliable solutions than traditional methods. Previously, it was shown that conventional time-stepping methods could …
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Finite element analysis and design optimisation of shaded pole induction motors
… the research, a more accurate two-dimensional time-stepping eddy-current FE model was developed. The multi-slice technique, justified as the more efficient way to consider the effect of a skewed rotor, has been adopted in the model. For the first time,the end-ring resistance was investigated …
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A Hybrid Spectral-Element / Finite-Element Time-Domain Method for Multiscale Electromagnetic Simulations
… study we propose a fast hybrid spectral-element time-domain (SETD) / finite-element time-domain (FETD) method for transient analysis of multiscale electromagnetic problems, where electrically fine structures with details much smaller than a typical wavelength and electrically coarse structures …
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A New Node-to-Node Approach to Contact/impact Problems for Two Dimensional Elastic Solids Subject to Finite Deformation
… implicit mid-point rule is used as the primary time stepping algorithm to find the solution incrementally. In order to conserve the system energy, the persistency condition is incorporated as the contact constraint. The augmented Lagrangian method is primarily used to apply contact constraints. …
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Parallel algorithms for direct blood flow simulations
… contrast. The algorithms incorporate a stable time-stepping scheme, high-order spatiotemporal discretizations, spectral preconditioners, and a reparametrization scheme capable of resolving extreme mesh distortions in dynamic simulations. The associated linear systems are solved in optimal time …
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Boundary integral/spectral element solution of the Navier-Stokes equations
… rendered a linear spatial problem at sequential time increments. For low to moderate Reynolds number flows, time stepping tests of the complete method provided stable Navier-Stokes simulations for simple model flows in an arbitrary geometry. The patching of the elemental solution fields into a …
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Numerical study of nonlinear free-surface flows
… mixed Eulerian-Lagrangian approach and involving time stepping is used to simulate the flow. At each time step, the boundary value problem is solved using the Complex Boundary Element Method. The numerical performance of the method is studied by considering cases where the exact solution is known. …
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Multi-Time-Step Domain Decomposition and Coupling Methods for Non-Linear Structural Dynamics
The present multi-time-step coupling method is based on a dual Schur domain decomposition method that uses Lagrange multipliers to enforce the continuity of the solution across the interfaces between the subdomains. The subdomains can be integrated with different time steps and/or time stepping …
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The analysis and detection of faults in three phase induction machines using finite element techniques.
… mesh finite element package, and later using a time-stepping software package which was designed specifically for modelling rotating electrical machines. The first model, using the fixed mesh package, required the development of an external software program to control the simulation so that …
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