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 25 for “"Lagrangian coherent structures"”.
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Identifying dynamical boundaries and phase space transport using Lagrangian coherent structures
In many problems in dynamical systems one is interested in the identification of sets which have qualitatively different fates. The finite-time Lyapunov exponent (FTLE) method is a general and equation-free method that identifies codimension-one sets which have a locally high rate of stretching …
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Lagrangian coherent structures and trajectory similarity: two important tools for scientific visualization
… studies the computation and visualization of Lagrangian coherent structures (LCS), an emerging technique for analyzing time-varying velocity fields (e.g. blood vessels and airflows), and the measure of similarity for trajectories (e.g. hurricane paths). LCS surfaces and trajectory-based …
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Advancing the theory and applications of Lagrangian Coherent Structures methods for oceanic surface flows
… dynamics. Building on the recent emergence of Lagrangian methods, this thesis investigates the present-day abilities to describe and understand the organization of flow transport at the ocean surface, including the abilities to detect the underlying key structures, the regions of stirring and …
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Advancing the theory and applications of Lagrangian Coherent Structures methods for oceanic surface flows
… dynamics. Building on the recent emergence of Lagrangian methods, this thesis investigates the present-day abilities to describe and understand the organization of flow transport at the ocean surface, including the abilities to detect the underlying key structures, the regions of stirring and …
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Experimental and Theoretical Developments in the Application of Lagrangian Coherent Structures to Geophysical Transport
… transport by revealing important transport structures. These transport structures reveal areas of the flow where fluid parcels, and thus material transported by those parcels, are likely to converge or diverge. Typically, these transport structures have been uncovered by the use of …
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Observing and quantifying kinematic properties and lagrangian coherent structures of ocean flows using drifter experiments
… in mesoscale and submesoscale flows. Second, Lagrangian coherent structures (LCS) are features which categorize ocean flows into regimes of distinct behavior. These structures are also difficult to quantify in the real ocean, since sets of gridded trajectories from real ocean data (rather than …
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Observing and Quantifying Kinematic Properties and Lagrangian Coherent Structures of Ocean Flows using Drifter Experiments
… in mesoscale and submesoscale flows. Second, Lagrangian coherent structures (LCS) are features which categorize ocean flows into regimes of distinct behavior. These structures are also difficult to quantify in the real ocean, since sets of gridded trajectories from real ocean data (rather than …
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Laboratory investigations of a chaotic flow using braid theory
… industrial and natural flows. The detection of Lagrangian structures that stay coherent over time helps gain insight into the evolution of a system's dynamics and the fate of transport. Whereas most techniques to detect coherent structures rely on a dense velocity field, techniques based on …
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Particle filtering with Lagrangian data in a point vortex model
… In fluid dynamics, a popular problem called Lagrangian data assimilation (LaDA) uses Lagrangian measurements in the form of tracer positions to learn about the changing flow field. Particle filtering can be applied to LaDA to track the flow field over a period of time. As opposed to …
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Atmospheric Lagrangian transport structures and their applications to aerobiology
… Lyapunov exponent (FTLE) and the associated Lagrangian coherent structures (LCS) and we attempt to provide mathematical explanations and frameworks for some applied questions which are based on realistic concerns of atmospheric transport phenomena. Accordingly, we quantify the accuracy of …
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Towards Detecting Atmospheric Coherent Structures using Small Fixed-Wing Unmanned Aircraft
The theory of Lagrangian Coherent Structures (LCS) enables prediction of material transport by turbulent winds, such as those observed in the Earth's Atmospheric Boundary Layer. In this dissertation, both theory and experimental methods are developed for utilizing small fixed-wing unmanned aircraft …
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Detecting and analyzing coherent structures in two-dimensional dynamical systems
The identification of coherent structures enhances the understanding of transport by complex flows such as those found at the ocean surface. The rapidly developing approach of Lagrangian Coherent Structures (LCSs) is based on the identification of codimension-1 structures that are locally the …
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Biodynamic Analysis of Human Torso Stability using Finite Time Lyapunov Exponents
… from time series data. Using these methods, Lagrangian coherent structures (LCS) are found for an inverted pendulum, the Acrobot, and planar wobble chair models. The LCS are ridges in the FTLE field that separate two inherently different types of motion when applied to rigid-body dynamic …
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Chaotic advection, mixing, and property exchange in three-dimensional ocean eddies and gyres
This work investigates how a Lagrangian perspective applies to models of two oceanographic flows: an overturning submesoscale eddy and the Western Alboran Gyre. In the first case, I focus on the importance of diffusion as compared to chaotic advection for tracers in this system. Three methods are …
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Riemannian geometry of matrix manifolds for Lagrangian uncertainty quantification of stochastic fluid flows
… dominant classes of techniques for extracting Lagrangian Coherent Structures are reviewed and compared and some improvements are suggested for their pragmatic applications on realistic high-dimensional deterministic ocean velocity fields. In the stochastic case, estimating the uncertain …
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Chaotic advection, mixing, and property exchange in three-dimensional ocean eddies and gyres
This work investigates how a Lagrangian perspective applies to models of two oceanographic flows: an overturning submesoscale eddy and the Western Alboran Gyre. In the first case, I focus on the importance of diffusion as compared to chaotic advection for tracers in this system. Three methods are …
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Nonlinear Models and Geometric Structure of Fluid Forcing on Moving Bodies
… its application to approximate a variety of structures including slow manifolds and Lagrangian coherent structures. This dissertation applies nonlinear theoretical and numerical techniques to analyze models of fluid forcing and their geometric structure. The tools developed in this …
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Vortex detection and tracking in massively separated and turbulent flows
… function and 𝑄 criterion are used along with the Lagrangian coherent structures (LCS) analyses including the finite-time Lyapunov exponent (FTLE), the geodesic LCS, and the Lagrangian-Averaged Vorticity Deviation (LAVD). Each of \h{these} Lagrangian methods \h{is} applied at the centers and …
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High order stochastic transport and Lagrangian data assimilation
… matter, etc.). Understanding such uncertain Lagrangian transport is imperative for reducing environmental damage due to natural hazards and for allowing rigorous risk analysis and effective search and rescue. While secondary variables and trajectories have classically been used for the …
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