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Dissertations / Theses on the topic 'Lagrangian Coherent Structuries'

Author: Grafiati

Published: 4 June 2021

Last updated: 9 February 2022

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1

Suigh, Rafael Oliveira. "Transporte caótico causado por ondas de deriva." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-20122010-204948/.

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Um dos problemas enfrentados pelos cientistas para o confinamento de plasma em Tokamaks, para se obter fusão termonuclear controlada, é o transporte radial de partículas pela borda do plasma. Nessa dissertação, estudamos o transporte através de um modelo que relaciona as flutuações eletrostáticas na borda do plasma às ondas de deriva. Essas ondas criam no plasma regiões de fluxo convectivo, formando ilhas que são, eventualmente, separadas por barreiras. Para apenas uma onda, o sistema é integrável e todas as trajetórias do plano de fase são curvas invariantes que, se não existirem barreiras, e

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2

Harter, Braxton Nicholas. "Lagrangian Coherent Structures in Vortex Ring Formation." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1565828293505214.

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3

Keith, Brendan. "Lagrangian coherent structures in three-dimensional steady flows." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121521.

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The subject of this thesis is the detection of Lagrangian Coherent Structures (LCS) in three-dimensional steady flows. LCS are influential material surfaces that act as skeletons of observed mixing patterns in a dynamical system. We review recent variational results for the construction of LCS in two-dimensional flows, and develop our own numerical implementation of these methods. We first test these implementations on two-dimensional examples, in which we obtain some new results and insights. Next, we apply the two-dimensional variational theory to the two-dimensional Poincaré map of a three-

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4

Fiorentino, Laura A. "Using Lagrangian Coherent Structures to Study Coastal Water Quality." Scholarly Repository, 2011. http://scholarlyrepository.miami.edu/oa_theses/267.

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In order to understand water quality in the coastal ocean and its effects on human health, the necessity arises to locate the sources of contaminants and track their transport throughout the ocean. Dynamical systems methods are applied to the study of transport of enterococci as an indicator of microbial concentration in the vicinity of Hobie Beach, an urban, subtropical beach in Miami, FL that is used for recreation and bathing on a daily basis. Previous studies on water quality have shown that Hobie Beach has high microbial levels despite having no known point source. To investigate the caus

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5

El, Aouni Anass. "Lagrangian coherent structures and physical processes of coastal upwelling." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0146.

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L’étude des processus physiques d’un système d’upwelling est essentielle pour comprendre sa variabilité actuelle et ses changements passés et futurs. Cette thèse présente une étude interdisciplinaire du système d’upwelling côtier à partir de différentes données acquises par satellite, l’accent étant mis principalement sur le système d’upwelling d’Afrique du Nord-Ouest (NWA). Cette étude interdisciplinaire aborde (1) le problème de l’identification et de l’extraction automatiques du phénomène d’upwelling à partir d’observations satellitaires biologiques et physiques. (2) Une étude statistique d

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6

Tallapragada, Phanindra. "Identifying dynamical boundaries and phase space transport using Lagrangian coherent structures." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/28891.

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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 around which maximal exponential expansion of line elements occurs. These codimension-one sets thus act as transport barriers. This geometric framework of transport barriers is used to study various problems in phase space transport, specifically problems of separation in flows that can vary in scale fr

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7

Nolan, Peter Joseph. "Experimental and Theoretical Developments in the Application of Lagrangian Coherent Structures to Geophysical Transport." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/88986.

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The transport of material in geophysical fluid flows is a problem with important implications for fields as diverse as: agriculture, aviation, human health, disaster response, and weather forecasting. Due to the unsteady nature of geophysical flows, predicting how material will be transported in these systems can often be challenging. Tools from dynamical systems theory can help to improve the prediction of material 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

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8

Filippi, Margaux(Martin-Filippi). "Advancing the theory and applications of Lagrangian Coherent Structures methods for oceanic surface flows." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122328.

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Thesis: Sc. D., Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2019<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (pages 207-218).<br>Ocean surface transport is at the core of many environmental disasters, including the spread of marine plastic pollution, the Deepwater Horizon oil spill and the Fukushima nuclear contamination. Understanding and predicting flow transport, however, remains a scientific challenge

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9

Mcclelland, Hunter Grant. "Towards Detecting Atmospheric Coherent Structures using Small Fixed-Wing Unmanned Aircraft." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/90667.

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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 systems (UAS) in detecting these atmospheric coherent structures. The dissertation begins by presenting relevant literature on both LCS and airborne wind estimation. Because model-based wind estimation inherently depends on high quality models, a Flight Dynamic Model (FDM) suitable for a small fixed

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10

Rypina, Irina I. "Lagrangian Coherent Structures and Transport in Two-Dimensional Incompressible Flows with Oceanographic and Atmospheric Applications." Scholarly Repository, 2007. http://scholarlyrepository.miami.edu/oa_dissertations/14.

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The Lagrangian dynamics of two-dimensional incompressible fluid flows is considered, with emphasis on transport processes in atmospheric and oceanic flows. The dynamical-systems-based approach is adopted; the Lagrangian motion in such systems is studied with the aid of Kolmogorov-Arnold-Moser (KAM) theory, and results relating to stable and unstable manifolds and lobe dynamics. Some nontrivial extensions of well-known results are discussed, and some extensions of the theory are developed. In problems for which the flow field consists of a steady background on which a time-dependent perturbatio

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11

Bozorg, Magham Amir Ebrahim. "Atmospheric Lagrangian transport structures and their applications to aerobiology." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/56482.

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Exploring the concepts of long range aerial transport of microorganisms is the main motivation of this study. For this purpose we use theories and concepts of dynamical systems in the context of geophysical fluid systems. We apply powerful notions such as finite-time 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 prediction of FTLE-LCS features and we det

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12

Suigh, Rafael Oliveira. "Estruturas coerentes no transporte caótico induzido por ondas de deriva." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-08112016-102037/.

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Nesta tese foi estudado o transporte de partículas na borda do plasma confinado magneticamente em tokamaks a partir de um modelo para ondas de deriva proveniente de flutuaçõoes eletrostáticas geradas pela não uniformidade do plasma. Para investigar esse problema, consideramos o modelo com duas ondas de deriva, que possui uma complexa dinâmica não linear onde podemos encontrar tanto transporte anômalo quanto transporte difusivo. Para a encontras no plano de fases as Estruturas Lagrangianas Coerentes (ELCs) e os jatos, foram confeccionados mapas de Poincaré, diagramas de expoente de Lyapunov a t

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13

Raben, Samuel Gillooly. "Determination of Three Dimensional Time Varying Flow Structures." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/51818.

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Time varying flow structures are involved in a large percentage of fluid flows although there is still much unknown regarding their behavior. With the development of high spatiotemporal resolution measurement systems it is becoming more feasible to measure these complex flow structures, which in turn will lead to a better understanding of their impact. One method that has been developed for studying these flow structures is finite time Lyapunov exponents (FTLEs). These exponents can reveal regions in the fluid, referred to as Lagragnian coherent structures (LCSs), where fluid elements diver

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14

Schilling, Nathanael [Verfasser], Oliver [Akademischer Betreuer] Junge, Péter [Gutachter] Koltai, Oliver [Gutachter] Junge, and Carsten [Gutachter] Hartmann. "Characterization and efficient computation of Lagrangian coherent structures / Nathanael Schilling ; Gutachter: Péter Koltai, Oliver Junge, Carsten Hartmann ; Betreuer: Oliver Junge." München : Universitätsbibliothek der TU München, 2021. http://d-nb.info/1241740291/34.

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15

Tanaka, Martin L. "Biodynamic Analysis of Human Torso Stability using Finite Time Lyapunov Exponents." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/26580.

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Low back pain is a common medical problem around the world afflicting 80% of the population some time in their life. Low back injury can result from a loss of torso stability causing excessive strain in soft tissue. This investigation seeks to apply existing methods to new applications and to develop new methods to assess torso stability. First, the time series averaged finite time Lyapunov exponent is calculated from data obtained during seated stability experiments. The Lyapunov exponent is found to increase with increasing task difficulty. Second, a new metric for evaluating torso stabi

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16

Chang, Yen-Tso, and 張彥佐. "Lagrangian Coherent Structure Analysis of Dynamical Systems." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/24aawm.

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博士<br>國立臺北科技大學<br>機電科技研究所<br>104<br>In the case of steady state flow systems, the exploration of the flow field structure is relatively simple and easy because streamlines coincide with trajectories. Thereforek, the velocity fields or dimensionless quantities derived from the systems can clearly demonstrate flow-field geometry. To unsteady-flow systems, this is not so simple. A more direct solution natural choice is to choose to trace particle trajectories (i.e., the Lagrangian viewpoint). While direct interpretation of the chaotic behavior of trajectories of unsteady systems is difficult, mor

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17

Lu, Jin-Tung, and 呂金童. "Investigation of cavitating flow by lagrangian coherent structure." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/89581304463772204259.

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碩士<br>國立中山大學<br>機械與機電工程學系研究所<br>101<br>Turbulent cavitating flows are ubiquitous in our daily life and technologies, which will induce the noises, material removal, and efficiency reduction of the flow machinery. As the result, it is important to investigate the flow structures of the cavitating flow to predict its dynamical behaviors effectively. In the present study, we utilize the volume of fraction techniques to time-dependent turbulent cavitating flows. Lagrangian Coherent Structures (LCS) have been developed to highlight the flow structures recently. It is a trajectory-basedapproach from

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18

El, aouni Anass. "Lagrangian coherent structures and physical processes of coastal upwelling." Thesis, 2019. http://www.theses.fr/2019BORD0146.

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L’étude des processus physiques d’un système d’upwelling est essentielle pour comprendre sa variabilité actuelle et ses changements passés et futurs. Cette thèse présente une étude interdisciplinaire du système d’upwelling côtier à partir de différentes données acquises par satellite, l’accent étant mis principalement sur le système d’upwelling d’Afrique du Nord-Ouest (NWA). Cette étude interdisciplinaire aborde (1) le problème de l’identification et de l’extraction automatiques du phénomène d’upwelling à partir d’observations satellitaires biologiques et physiques. (2) Une étude statistique d

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19

Chang, Ching, and 張敬. "Stretching and folding of Lagrangian coherent structure in cavity flows." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/72979371872477767914.

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碩士<br>臺灣大學<br>機械工程學研究所<br>98<br>For a general unsteady flow, there are some unique geometry patterns that developed by the flow field as time evolution. These special structures are called “coherent structures”. In the fluid mechanics, the properties like velocity, pressure, vorticity etc., are described from the Eulerian viewpoint. The lack of an unambiguous value to define which flow region is coherent makes it difficult to locate the coherent structure using the Eulerian properties. The dynamical systems theory can provide some useful concepts to approximate the coherent structure in flows:

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20

Zhang, Zhonglin. "Identification of Lagrangian coherent structures around swimming jellyfish from experimental time-series data." Thesis, 2008. http://thesis.library.caltech.edu/6226/1/Thesis_part1.pdf.

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The unique body kinematics of jellyfish embodies the most intriguing form of biological propulsion, which makes jellyfish a promising resource for developing new locomotion systems. Instead of the conventional Eulerian method, we take an unprecedented Lagrangian approach by tracking individual fluid particles around a swimming jellyfish over a finite time interval. Specifically, we utilize the Lagrangian coherent structures (LCS) in the flow field to investigate the flow characteristics around a jellyfish. LCS are separatrices or invariant manifolds, which separate the flow field into distinct

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21

Zhang, Zhonglin Johnny. "Identification of Lagrangian Coherent Structures Around Swimming Jellyfish from Experimental Time-Series Data." Thesis, 2008. https://thesis.library.caltech.edu/10642/1/ZhonglinJZhangThesis_seniorthesis.pdf.

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The unique body kinematics of jellyfish embodies the most intriguing form of biological propulsion, which makes jellyfish a promising resource for developing new locomotion systems. Instead of the conventional Eulerian method, we take an unprecedented Lagrangian approach by tracking individual fluid particles around a swimming jellyfish over a finite time interval. Specifically, we utilize the Lagrangian coherent structures (LCS) in the flow field to investigate the flow characteristics around a jellyfish. LCS are separatrices or invariant manifolds, which separate the flow field into distinct

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22

Wen, Cheng-Yu, and 溫政昱. "Comparison of two definitions of Lagrangian coherent structures in fluid flows and their numerical implementations." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/24803505588511659262.

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碩士<br>臺灣大學<br>機械工程學研究所<br>98<br>The mixing of passive tracers in two-dimensional fluid flows is intimately linked to the presence of coherent structures. Without being specific about their definition for now, we shall picture these structures, and refer to them as Lagrangian coherent structures. We introduce two definitions of Lagrangian coherent structures in two-dimensional turbulence. The first definition is Hyperbolic Time Approach(HTA), the second is Finite-Time Lyapunov Exponents(FTLE). The Lagrangian coherent structures are defined as material lines that are stable or unstable for l

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23

Huang, Yin, and 黃尹. "Investigation of the Dynamics of Steady Granular Flow in a Rotating Drum by Lagrangian Coherent Structure Evolution." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/40378483872784057734.

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碩士<br>國立臺灣大學<br>機械工程學研究所<br>102<br>This thesis studies the Lagrangian coherent structures (LCS) for a dry or a fully immersed steady granular flow in a rotating drum by systematic experiments to complement the information based on Eulerian description. In this thesis, LCS is located by the Finite-Time Lyapunov Exponent (FTLE) field. We drove the drum at various constant speeds (w = 0.135~0.4654rad/s) so that the Froude numbers are 6.28*10^-4~7.5*10^-3 giving flows in the rolling regime. The granulate motion was monitored by high speed digital camera and we developed a method of index similari

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24

"The Domain Dependence of Chemotaxis in a Two-Dimensional Turbulent Flow." Master's thesis, 2015. http://hdl.handle.net/2286/R.I.34877.

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abstract: Presented is a study on the chemotaxis reaction process and its relation with flow topology. The effect of coherent structures in turbulent flows is characterized by studying nutrient uptake and the advantage that is received from motile bacteria over other non-motile bacteria. Variability is found to be dependent on the initial location of scalar impurity and can be tied to Lagrangian coherent structures through recent advances in the identification of finite-time transport barriers. Advantage is relatively small for initial nutrient found within high stretching regions of the flow,

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25

Joly, Florian. "Numerical Insights for AAA Growth Understanding and Predicting: Morphological and Hemodynamic Risk Assessment Features and Transient Coherent Structures Uncovering." Thèse, 2019. http://hdl.handle.net/1866/22597.

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26

"Effective-diffusion for general nonautonomous systems." Doctoral diss., 2018. http://hdl.handle.net/2286/R.I.49071.

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abstract: The tools developed for the use of investigating dynamical systems have provided critical understanding to a wide range of physical phenomena. Here these tools are used to gain further insight into scalar transport, and how it is affected by mixing. The aim of this research is to investigate the efficiency of several different partitioning methods which demarcate flow fields into dynamically distinct regions, and the correlation of finite-time statistics from the advection-diffusion equation to these regions. For autonomous systems, invariant manifold theory can be used to separate

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27

Finn, Justin Richard. "A numerical study of inertial flow features in moderate Reynolds number flow through packed beds of spheres." Thesis, 2013. http://hdl.handle.net/1957/37715.

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In this work, flow through synthetic arrangements of contacting spheres is studied as a model problem for porous media and packed bed type flows. Direct numerical simulations are performed for moderate pore Reynolds numbers in the range, 10 ≤ Re ≤ 600, where non-linear porescale flow features are known to contribute significantly to macroscale properties of engineering interest. To first choose and validate appropriate computational models for this problem, the relative performance of two numerical approaches involving body conforming and non-conforming grids for simulating porescale flows is

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