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1
Morris-Thomas, Michael. "An investigation into wave run-up on vertical surface piercing cylinders in monochromatic waves." University of Western Australia. School of Oil and Gas Engineering, 2003. http://theses.library.uwa.edu.au/adt-WU2004.0010.
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[Formulae and special characters can only be approximated here. Please see the pdf version of the abstract for an accurate reproduction.] Wave run-up is the vertical uprush of water when an incident wave impinges on a free- surface penetrating body. For large volume offshore structures the wave run-up on the weather side of the supporting columns is particularly important for air-gap design and ultimately the avoidance of pressure impulse loads on the underside of the deck structure. This investigation focuses on the limitations of conventional wave diffraction theory, where the free-surface boundary condition is treated by a Stokes expansion, in predicting the harmonic components of the wave run-up, and the presentation of a simplified procedure for the prediction of wave run-up. The wave run-up is studied on fixed vertical cylinders in plane progressive waves. These progressive waves are of a form suitable for description by Stokes' wave theory whereby the typical energy content of a wave train consists of one fundamental harmonic and corresponding phase locked Fourier components. The choice of monochromatic waves is indicative of ocean environments for large volume structures in the diffraction regime where the assumption of potential flow theory is applicable, or more formally A/a < Ο(1) (A and a being the wave amplitude and cylinder radius respectively). One of the unique aspects of this work is the investigation of column geometry effects - in terms of square cylinders with rounded edges - on the wave run-up. The rounded edges of each cylinder are described by the dimensionless parameter rc/a which denotes the ratio of edge corner radius to half-width of a typical column with longitudinal axis perpendicular to the quiescent free-surface. An experimental campaign was undertaken where the wave run-up on a fixed column in plane progressive waves was measured with wire probes located close to the cylinder. Based on an appropriate dimensional analysis, the wave environment was represented by a parametric variation of the scattering parameter ka and wave steepness kA (where k denotes the wave number). The effect of column geometry was investigated by varying the edge corner radius ratio within the domain 0 <=rc/a <= 1, where the upper and lower bounds correspond to a circular and square shaped cylinder respectively. The water depth is assumed infinite so that the wave run-up caused purely by wave-structure interaction is examined without the additional influence of a non-decaying horizontal fluid velocity and finite depth effects on wave dispersion. The zero-, first-, second- and third-harmonics of the wave run-up are examined to determine the importance of each with regard to local wave diffraction and incident wave non-linearities. The modulus and phase of these harmonics are compared to corresponding theoretical predictions from conventional diffraction theory to second-order in wave steepness. As a result, a basis is formed for the applicability of a Stokes expansion to the free-surface boundary condition of the diffraction problem, and its limitations in terms of local wave scattering and incident wave non-linearities. An analytical approach is pursued and solved in the long wavelength regime for the interaction of a plane progressive wave with a circular cylinder in an ideal fluid. The classical Stokesian assumption of infinitesimal wave amplitude is invoked to treat the free-surface boundary condition along with an unconventional requirement that the cylinder width is assumed much smaller than the incident wavelength. This additional assumption is justified because critical wavelengths for wave run-up on a fixed cylinder are typically much larger in magnitude than the cylinder's width. In the solution, two coupled perturbation schemes, incorporating a classical Stokes expansion and cylinder slenderness expansion, are invoked and the boundary value problem solved to third-order. The formulation of the diffraction problem in this manner allows for third-harmonic diffraction effects and higher-order effects operating at the first-harmonic to be found. In general, the complete wave run-up is not well accounted for by a second-order Stokes expansion of the free-surface boundary condition and wave elevation. This is however, dependent upon the coupling of ka and kA. In particular, whilst the modulus and phase of the second-harmonic are moderately predicted, the mean set-up is not well predicted by a second-order Stokes expansion scheme. This is thought to be caused by higher than second-order non-linear effects since experimental evidence has revealed higher-order diffraction effects operating at the first-harmonic in waves of moderate to large steepness when k < < 1. These higher-order effects, operating at the first-harmonic, can be partially accounted for by the proposed long wavelength formulation. For small ka and large kA, subsequent comparisons with measured results do indeed provide a better agreement than the classical linear diffraction solution of Havelock (1940). To account for the complete wave run-up, a unique approach has been adopted where a correction is applied to a first-harmonic analytical solution. The remaining non-linear portion is accounted for by two methods. The first method is based on regression analysis in terms of ka and kA and provides an additive correction to the first-harmonic solution. The second method involves an amplification correction of the first-harmonic. This utilises Bernoulli's equation applied at the mean free-surface position where the constant of proportionality is empirically determined and is inversely proportional to ka. The experimental and numerical results suggest that the wave run-up increases as rc/a--› 0, however this is most significant for short waves and long waves of large steepness. Of the harmonic components, experimental evidence suggests that the effect of a variation in rc/a on the wave run-up is particularly significant for the first-harmonic only. Furthermore, the corner radius effect on the first-harmonic wave run-up is well predicted by numerical calculations using the boundary element method. Given this, the proposed simplified wave run-up model includes an additional geometry correction which accounts for rc/a to first-order in local wave diffraction. From a practical view point, it is the simplified model that is most useful for platform designers to predict the wave run-up on a surface piercing column. It is computationally inexpensive and the comparison of this model with measured results has proved more promising than previously proposed schemes.
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Kakollu, Satyanarayana. "Numerical simulation of strong turbulence over water waves." Master's thesis, Mississippi State : Mississippi State University, 2003. http://library.msstate.edu/etd/show.asp?etd=etd-12112002-125436.
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Hickerson, David A. "Computational Fluid Dynamic Study of Heaving-to." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23766.
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This study looks at the fluid interactions from the wake of a sail boat performing the heaving-to storm tactic in heavy weather seas with the waves. This interaction causes the wave height in the wake to be reduced. The fluid flow in the top layer of the wave is seen to move with the wake as the hull drifts with the wind. This movement of the top layer of the wave provides a vertical momentum cancelation affect with the portion of the wave that it moves over reducing the wave height.
STAR-CCM+ CFD software is used to perform the simulations of the steep waves with wavelength of 25 meters, 55 meters, and 67 meters. In the simulation, a propulsive force is used to simulate the wind force on the boat.Master of Science
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Siddorn, Philip David. "Efficient numerical modelling of wave-structure interaction." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:de36bd2f-cd23-4f11-b67f-9d8cd48ecd3c.
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Offshore structures are required to survive in extreme wave environments. Historically, the design of these offshore structures and vessels has relied on wave-tank experiments and linear theory. Today, with advances in computing power, it is becoming feasible to supplement these methods of analysis with fully nonlinear numerical simulation. This thesis is concerned with the development of an efficient method to perform this numerical modelling, in the context of potential flow theory. The interaction of a steep ocean wave with a floating body involves a moving free surface and a wide range of length scales. Attempts to reduce the size of the simulation domain cause problems with wave reflection from the domain edge and with the accurate creation of incident waves. A method of controlling the wave field around a structure is presented. The ability to effectively damp an outgoing wave in a very short distance is demonstrated. Steep incident waves are generated without the requirement for the wave to evolve over a large time or distance before interaction with the body. This enables a general wave-structure interaction problem to be modelled in a small tank, and behave as if it were surrounded by a large expanse of water. The suitability of the boundary element method for performing this modelling is analysed. Potential improvements are presented with respect to accuracy, robustness, and computational complexity. Evidence of third order diffraction is found for an FPSO model.
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Krus, Kristofer. "Wave Model and Watercraft Model for Simulation of Sea State." Thesis, Linköpings universitet, Teoretisk Fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-102959.
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The problem of real-time simulation of ocean surface waves, ship movement and the coupling in between is tackled, and a number of different methods are covered and discussed. Among these methods, the finite volume method has been implemented in an attempt to solve the problem, along with the compressible Euler equations, an octree based staggered grid which allows for easy adaptive mesh refinement, the volume of fluid method and a variant of the Hyper-C advection scheme for compressible flows for advection of the phase fraction field. The process of implementing the methods that were chosen proved to be tricky in many ways, as they involve a large number of advanced topics, and the implementation that was implemented in this thesis work suffered from numerous issues. There were for example problems with keeping the interface intact, as well as a harsh restriction on the time step size due to the CFL condition. Improvements required to make the method sustainable for real-time applications are discussed, and a few suggestions on alternative approaches that are already in use for similar purposes are also given and discussed. Furthermore, a method for compensating for gain/loss of mass when solving the incompressible flow equations with an inaccurately solved pressure Poisson equation is presented and discussed. A momentum conservative method for transporting the velocity field on staggered grids without introducing unnecessary smearing is also presented and implemented. A simple, physically based illumination model for sea surfaces is derived, discussed and compared to the Blinn–Phong shading model, although it is never implemented. Finally, a two-dimensional partial differential equation in the spatial domain for simulating water surface waves for mildly varying bottom topography is derived and discussed, although it is deemed to be too slow for real-time purposes and is therefore never implemented.This publication differs from the printed version of the report in the sense that links are blue in this version and black in the printed version.
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Coutis, Peter F. School of Mathematics UNSW. "Currents, coasts and cays : a study of tidal upwelling and island wakes." Awarded by:University of New South Wales. School of Mathematics, 2000. http://handle.unsw.edu.au/1959.4/18207.
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In this thesis, the phenomenon of flow-topography interaction is considered in the context of two dynamically distinct case studies. In the first study, tidally-driven upwelling is investigated usingfield data collected in Hydrographers Passage (20????S), a narrow, navigable channel in the dense outer reef matrix of the southern Great Barrier Reef, Australia. In the second study, island wake formations at Cato Island (155????32????E, 23????15????S) in the deep, Western Coral Sea are examined using a combination of field data and numerical experiments. The result of the Hydrographers Passage study are of considerable scientific interest since they apply to numerous smaller non-navigable reef-edge passages dotted throughout the southern Great Barrier Reef. Strong, semi-diurnal flood tides flowing through a gap in a distal patch reef system at the shelf break generate strong upwelling, providing a pulsed, semi-diurnal input of nutrients to the reefs offshore of the passage. If stable in the long term, this mechanism could have profound evolutionary implications for large reefal areas in the southern Great Barrier Reef. In the second study, two sets of field observations at Cato Island coincided with conditions of strong (~0.7m s-1), vertically sheared incident currents and weaker (~0.3m s-1), more variable incident flows. The combination of dynamically distinct flow regimes and a tall, steep-sided island penetrating oligotrophic surface waters provides a unique opportunity to investigate the impact of island wakes on hydrographic structure and biological enhancement. Field data indicate that flow disturbances downstream of Cato Island are likely to generate biological enhancement during conditions of eddy shedding and non-shedding wakes. A primitive equation numerical model configured on the basis of field observations faithfully reproduces the key features of both data sets; mechanisms responsible for producing these key features are proposed. Previous numerical studies of island wakes have concentrated primarily on eddy shedding flows. In this thesis, the sub-critical (non-shedding) flow scenario is also considered. It is demonstrated that particle retention in island wakes has a ????hair trigger???? characteristic controlled by incident flow speed. This observation leads to a new proposal to explain the long-standing recruitment problem of biological oceanography.
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Horko, Michael. "CFD optimisation of an oscillating water column wave energy converter." University of Western Australia. School of Mechanical Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0089.
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Although oscillating water column type wave energy devices are nearing the stage of commercial exploitation, there is still much to be learnt about many facets of their hydrodynamic performance. This research uses the commercially available FLUENT computational fluid dynamics flow solver to model a complete OWC system in a two dimensional numerical wave tank. A key feature of the numerical modelling is the focus on the influence of the front wall geometry and in particular the effect of the front wall aperture shape on the hydrodynamic conversion efficiency. In order to validate the numerical modelling, a 1:12.5 scale experimental model has been tested in a wave tank under regular wave conditions. The effects of the front lip shape on the hydrodynamic efficiency are investigated both numerically and experimentally and the results compared. The results obtained show that with careful consideration of key modelling parameters as well as ensuring sufficient data resolution, there is good agreement between the two methods. The results of the testing have also illustrated that simple changes to the front wall aperture shape can provide marked improvements in the efficiency of energy capture for OWC type devices.
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Fu, Yun. "Linear stability of an interface between two incompressible fluids." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1142955745.
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Khan, Muhammad Ahsan. "CFD Applications for Wave Energy Conversion Devices (MoonWEC) and Turbulent Fountains for Environmental Fluid Mechanics." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
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This thesis is based on two studies that are related to floating wave energy conversion (WEC) devices and turbulent fountains. The ability of the open-source CFD software OpenFOAM® has been studied to simulate these phenomena. The CFD model has been compared with the physical experimental results.
The first study presents a model of a WEC device, called MoonWEC, which is patented by the University of Bologna. The CFD model of the MoonWEC under the action of waves has been simulated using OpenFOAM and the results are promising. The reliability of the CFD model is confirmed by the laboratory experiments, conducted at the University of Bologna, for which a small-scale prototype of the MoonWEC was made from wood and brass.
The second part of the thesis is related to the turbulent fountains which are formed when a heavier source fluid is injected upward into a lighter ambient fluid, or else a lighter source fluid is injected downward into a heavier ambient fluid. For this study, the first case is considered for laboratory experiments and the corresponding CFD model. The vertical releases of the source fluids into a quiescent, uniform ambient fluid, from a circular source, were studied with different densities in the laboratory experiments, conducted at the University of Parma. The CFD model has been set up for these experiments. Favourable results have been observed from the OpenFOAM simulations for the turbulent fountains as well, indicating that it can be a reliable tool for the simulation of such phenomena.
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Wood, Dylan M. "Finite Element Modeling for Assessing Flood Barrier Risks and Failures due to Storm Surges and Waves." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595572799377091.
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Sakib, Salman. "Design Optimization and Field Performance Evaluation of the Wave Suppression and Sediment Collection (WSSC) System| Computational Fluid Dynamics (CFD) Modeling, Surface Elevation Table (SET) Survey, and Marker Clay Study." Thesis, University of Louisiana at Lafayette, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10618338.
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Coastal erosion is an issue of concern for Louisiana, in the United States, and for all other coastal communities in the world. Among many coastal protection and restoration technologies, shoreline protection structures focus on wave reductions to prevent waves from hitting the coastal landforms directly. A novel technology called the Wave Suppression and Sediment Collection (WSSC) system focuses on solving the limitations of conventional shoreline protection structures regarding mobility, constructability, and sustainability. The primary goals of this study are to optimize the WSSC units for wave reduction and sediment transport and to verify the performance of this technology in an actual field environment. Computational Fluid Dynamics (CFD) simulations were carried out to optimize the designs of the units in terms of pipe diameters and face slope. Results have indicated that increasing pipe diameters decreases wave reduction and increases sediment transport ability of the units. Further, it was found that increasing the face slope decreases the wave reduction ability; however, no effect was found on the sediment transport efficiency. Parametric optimization suggested that a porosity (open-to-total area ratio) of 30% should yield satisfactory wave reduction and balanced sediment transport by the units. For better output from the units, the designs should be modified according to site-specific requirements. Field site investigations involved Surface Elevation Table (SET) surveying and marker clay experiments. SET surveys showed significant sediment accumulation over eleven months behind the units. Also, no significant change was observed at the control site over three months, which proves the effectiveness of the technology in stopping erosion and facilitating land building. Marker clay experiments validated the SET measurements and proved that there was a significant amount of sediment deposition over the white Feldspar clay layer over six months. This strengthens the conclusion that the WSSC units can be used successfully in a Louisiana marsh environment to battle coastal erosion and land loss.
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Koudella, Christophe. "Ondes internes de gravité en fluide stratifié: instabilités, turbulence et vorticité potentielle." Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 1999. http://tel.archives-ouvertes.fr/tel-00005960.
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Une étude numérique de la dynamique d'ondes internes de gravité en fluide stablement stratifié est menée. On décrit un algorithme pseudo-spectralparallèle permettant d'intégrer les équations de Navier-Stokes sur une machine paralèele. En deux dimensions d'espace, on analyse la dynamique d'un
champ d'ondes internes propagatives, d'amplitude modérée et initialement plan et monochromatique. Le champ d'ondes est instable et déferle. Le déferlement produit une turbulence de petites échelles spatiales influencées par la stratification. L'étude
est étendue au cas tridimensionnel, plus réaliste. En trois dimensions, on étudie le même champ d'ondes internes, que l'on perturbe par un bruit infinitésimal ondulatoire tridimensionnel, mais on considère des ondes statiquement stables et
instables (grandes amplitudes). On montre que le déferlement d'une onde interne est un processus intrinsèquement tridimensionnel, y compris pour les ondes de faible amplitude. La tridimensionalisation du champ d'ondes s'opère dans les zones de l'espace où le champ de densité devient statiquement instable. L'effondrement gravitationnel d'une zone est de structure transverse au plan de propagation de l'onde. Les effets de la turbulence des petites échelles sur la production de la composante non propagatrice de l'écoulement, le mode de vorticité potentielle et la production d'un écoulement moyen, permet de conclure que seule une petite proportion de l'énergie mécanique initiale est convertie sous ses deux formes, la majeure partie étant dissipée par la dissipation visqueuse et conduction thermique. On reconsidère le mode de vorticiée potentielle par une approche Hamiltonienne non-canonique du fluide parfait stratifié. La dérivation d'un système de dynamique modifiée permet d'étudier la relaxation d'un écoulement stratifié, conservant sa vorticité potentielle et sa densité, vers un état stationnaire d'énergie minimale, correspondant au mode de vorticité potentielle.
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Velez, Carlos Alberto Busto. "CFD analysis of a uni-directional impulse turbine for wave energy conversion." Master's thesis, University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4714.
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Ocean energy research has grown in popularity in the past decade and has produced various designs for wave energy extraction. This thesis focuses on the performance analysis of a uni-directional impulse turbine for wave energy conversion. Uni-directional impulse turbines can produce uni-directional rotation in bi-directional flow, which makes it ideal for wave energy extraction as the motion of ocean waves are inherently bi-directional. This impulse turbine is currently in use in four of the world's Oscillating Wave Columns (OWC). Current research to date has documented the performance of the turbine but little research has been completed to understand the flow physics in the turbine channel. An analytical model and computational fluid dynamic simulations are used with reference to experimental results found in the literature to develop accurate models of the turbine performance. To carry out the numerical computations various turbulence models are employed and compared. The comparisons indicate that a low Reynolds number Yang-shih K-Epsilon turbulence model is the most computationally efficient while providing accurate results. Additionally, analyses of the losses in the turbine are isolated and documented. Results indicate that large separation regions occur on the turbine blades which drastically affect the torque created by the turbine, the location of flow separation is documented and compared among various flow regimes. The model and simulations show good agreement with the experimental results and the two proposed solutions enhance the performance of the turbine showing an approximate 10% increase in efficiency based on simulation results.ID: 030646261; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.A.E.)--University of Central Florida, 2011.; Includes bibliographical references (p. 81-82).
M.S.A.E.
Masters
Mechanical and Aerospace Engineering
Engineering and Computer Science
Aerospace Engineering; Thermofluid Aerodynamics Systems Track
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Beem, Heather Rachel. "Passive wake detection using seal whisker-inspired sensing." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/97768.
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Thesis (Ph. D.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2015This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 183-193).
This thesis is motivated by a series of biological experiments that display the harbor seal's extraordinary ability to track the wake of an object several seconds after it has swum by. They do so despite having auditory and visual cues blocked, pointing to use of their whiskers as sensors of minute water movements. In this work, I elucidate the basic uid mechanisms that seals may employ to accomplish this detection. Key are the unique ow-induced vibration properties resulting from the geometry of the harbor seal whisker, which is undulatory and elliptical in cross-section. First, the vortex-induced vibration (VIV) characteristics of the whisker geometry are tested. Direct force measurements and ow visualizations on a rigid whisker model undergoing a range of 1-D imposed oscillations show that the geometry passively reduces VIV (factor of > 10), despite contributions from eective added mass and damping. Next, a biomimetic whisker sensor is designed and fabricated. The rigid whisker model is mounted on a four-armed flexure, allowing it to freely vibrate in both in-line and crossflow directions. Strain gauges on the flexure measure deflections at the base. Finally, this device is tested in a simplified version of the sh wake { seal whisker interaction scenario. The whisker is towed behind an upstream cylinder with larger diameter. Whereas in open water the whisker exhibits very low vibration when its long axis is aligned with the incoming ow, once it enters the wake it oscillates with large amplitude and its frequency coincides with the Strouhal frequency of the upstream cylinder. This makes the detection of an upstream wake as well as an estimation of the size of the wake-generating body possible. A slaloming motion among the wake vortices causes the whisker to oscillate in this manner. The same mechanism has been previously observed in energy-extracting foils and trout actively swimming behind bluff cylinders in a stream.
by Heather Rachel Beem.
Ph.D.
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Haley, Joseph. "Fluid forcing in the crests of large ocean waves." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/60082.
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A sequence of new experimental investigations is presented that addresses the modelling of the wave loads within the crests of limiting and breaking waves. This study identifies important sources of uncertainty within wave loading models that are applied to the steepest wave conditions. By examining the origins of this uncertainty, existing loading models are assessed and improvements proposed. In particular, the local wave impact loads arising on individual horizontal and vertical members in the crest region are evaluated. In terms of wave modelling, the key factors are the wave shape and the associated water particle kinematics. In addressing these points, the present results have shown that only nonlinear modelling methods are capable of accurately describing a limiting wave profile. Indeed, the departures from established analytical solutions, commonly used in design, highlight the importance of high-order effects in steep waves approaching their breaking limit. In predicting the wave impact forces on a body, the gradient or slope of the water surface is of fundamental importance. Detailed experimental analysis of the magnitude and direction of the impact force on a horizontal cylinder has highlighted an important source of uncertainty. This relates to the nonparallel nature of the normal to the water surface and the direction of the resultant water particle kinematics. The present work has shown that in the crests of large, steep waves, this angular difference creates an important variability in the force predictions. However, having taken account of this effect, the magnitude of the impact force can be reliably predicted using a slamming coefficient of Cs = 5.19. This is shown to be appropriate to a wide range of oblique wave-structure impacts. When considering the wave forces on a vertical column the present study has shown that it is crucial to consider both the type of wave breaking and also the additional complexity of free surface deformation during the loading event. Overall, measurements of wave run-up are shown to be less dependent on the occurrence of wave impact forces than previously hypothesised. However, the extent of the column area subject to large impact loads is shown to be critically dependent upon the type of wave breaking.
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Faulkner, Jay Allen. "Beauty waves: an artistic representation of ocean waves using Bezier curves." Texas A&M University, 2006. http://hdl.handle.net/1969.1/4682.
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In this thesis, we present a method for computing an artistic representation of
ocean waves using Bezier curves. Wave forms are loosely based on procedural wave
models and are designed to emulate those found in both art and nature. The wave
forms are generated using a slice method which is user defined by structured input,
thus providing the artist with full control over crest shape and placement. Wave
propagation is obtained by interpolating between defined crest shapes and positions.
We also present a method for computing a stylized representation of breaking crests
in shallow water.
Artists may use our model to create many interesting wave forms, including basic
sinusoidal waves and waves with breaking crests that have a rotation that is cyclical
in time. The major drawbacks to our solution are that data entry can be tedious and
it can be difficult to produce waves that animate with a natural appearance.
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Yu, Xuri. "Dynamics of seasonal and interannual variability in the equatorial Pacific." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/11065.
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Kalisch, Henrik W. "Models for internal waves in two-fluid systems." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3023554.
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Arkell, Richard Henry. "Wake dynamics of cylinders encountering free surface waves." Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/8668.
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Masse, Robert K. "Fluid dynamics of the shock wave reactor /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/9961.
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Pezzi, Luciano Ponzi. "Equatorial Pacific dynamics : lateral mixing and tropical instability waves." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274585.
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Earnshaw, Paul David. "A study in fluid dynamics of rotating spherical systems." Thesis, University of Exeter, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288710.
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Cheng, Yiu-woon. "Boundary effect on ship-generated waves /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19669215.
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Zhang, Jin E. Wu Theodore Y. T. Wu Theodore Y. T. "I. Run-up of ocean waves on beaches. : II. Nonlinear waves in a fluid-filled elastic tube /." Diss., Pasadena, Calif. : California Institute of Technology, 1996. http://resolver.caltech.edu/CaltechETD:etd-01072008-105605.
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鄭耀煥 and Yiu-woon Cheng. "Boundary effect on ship-generated waves." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31215063.
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Fleming, Conor F. "Tidal turbine performance in the offshore environment." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:f51fd313-1589-4e9c-98cc-ae6e64c1184b.
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A three dimensional computational model of a full scale axial flow tidal turbine has been used to investigate the effects of a range of realistic environmental conditions on turbine performance. The model, which is based on the Reynolds averaged Navier-Stokes equations, has been developed using the commercial flow solver ANSYS Fluent. A 1:30 scale tidal turbine is simulated in an open channel for comparison to existing experimental data. The rotor blades are directly resolved using a body-fitted, unstructured computational grid. Rotor motion is enabled through a sliding mesh interface between the rotor and the channel boundaries. Reasonably good agreement in thrust and power is observed. The computed performance curves are offset from the measured performance curves by a small increment in rotor speed. Subsequently, a full scale axial flow turbine is modelled in a variety of conditions representative of tidal channel flows. A parametric study is carried out to investigate the effects of flow shear, confinement and alignment on turbine performance, structural loading, and wake recovery. Mean power and thrust are found to be higher in sheared flow, relative to uniform flow of equivalent volumetric flow rate. Large fluctuations in blade thrust and torque occur in sheared flow as the blade passes through the high velocity freestream flow in the upper portion of the profile and the lower velocity flow near the channel bed. A stronger shear layer is formed around the upper portion of the wake in sheared flow, leading to enhanced wake mixing. Mean power and thrust are reduced when the turbine is simulated at a lower position in a sheared velocity profile. However, fluctuations in blade loading are increased due to the higher velocity gradient. The opposite effects are observed when the turbine operates at greater heights in sheared flow. Flow misalignment has a negative impact on mean rotor thrust and power, as well as on unsteady blade loading. Although the range of unsteady loading is not increased significantly, additional perturbations are introduced due to interactions between the blade and the nacelle. A deforming surface is introduced using the volume-of-fluid method. Linear wave theory is combined with the existing free surface model to develop an unsteady inflow boundary condition prescribing combined sheared flow and free surface waves. The relative effects of the sheared profile and wave-induced velocities on turbine loading are identified through frequency analysis. Rotor and blade load fluctuations are found to increase with wave height and wave length. In a separate study, the performance of bi-directional ducted tidal turbines is investigated through a parametric study of a range of duct profiles. A two dimensional axi-symmetric computational model is developed to compare the ducted geometries with an unducted device under consistent blockage conditions. The best-performing ducted device achieves a peak power coefficient of approximately 45% of that of the unducted device. Comparisons of streamtube area, velocity and pressure for the flow through the ducted device shows that the duct limits the pressure drop across the rotor and the mass flow through the rotor, resulting in lower device power.
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Geiman, Joe D. "Vorticity dynamics in the presence of shallow water waves." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 138 p, 2008. http://proquest.umi.com/pqdweb?did=1650510201&sid=7&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Boss, Emmanuel. "Dynamics of potential vorticity fronts /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/11031.
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Zhang, Xueyan. "Mechanics of viscoelastic mud under water waves." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B36710003.
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Zhang, Xueyan, and 張雪岩. "Mechanics of viscoelastic mud under water waves." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B36710003.
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The Best M.Phil Thesis in the Faculties of Dentistry, Engineering, Medicine and Science (University of Hong Kong), Li Ka Shing Prize,2005-2006published_or_final_version
abstract
Mechanical Engineering
Master
Master of Philosophy
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Bailey, J. S. L. "Experimentally verified fluid loading models for slender horizontal cylinders in waves." Thesis, University of Sussex, 2000. http://sro.sussex.ac.uk/id/eprint/737/.
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This thesis reports on research work aimed at improving methods for predicting the fluid loading on fixed- and compliant offshore structures in waves. In focusing on slender member fluid-interaction models, the limitations and uncertainties associated with the widely-used Morison equation are examined. An improved empirical model has been developed and tested extensively alongside the Morison equation, using real experimental data. This improved model gives a better representation of the frequency dependency of the fluid-loading coefficients: this is particularly important in compliant motion conditions where the so-called relative velocity concept still needs to be verified under carefully controlled experimental conditions. The model is based entirely on the use of linear wave kinematics, thus simplifying calibration in irregular conditions and avoiding the need for a consistent non-linear wave theory (which is still lacking). By appropriate adaptation the improved model can also be extended to include amplitude dependency in the loading coefficients. The Improved Model has been developed through an analysis of experimental data. For this purpose the experimental work was focused on a horizontal cylinder, at model scale, located in a wave tank at the University of Sussex. The fluid loading experienced by a fixed cylinder, in both regular and irregular waves conditions, was measured and examined in detail. In addition, a comprehensive study of the loading on compliant cylinders, in both regular and irregular waves, was undertaken. Extensive use was made of appropriate parameter estimation techniques with initial attention (using simulated data) given to their accuracy for use with noisy experimental measurements. The effects of subtle (but undesirable) tank characteristics were also carefully taken into account. The study shows that, for fixed horizontal cylinders, benefits can be clearly identified in using the improved model, with frequency dependent coefficients, over the frequency dependent Morison equation. Moreover, the study shows that the relative velocity concept is more appropriate for use with the improved model than with the Morison model.
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Suh, Il Ho. "Statistics of amplitude and fluid velocity of large and rare waves in the ocean." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/10945/3001.
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CIVINSThe understanding of large and rare waves in the ocean is becoming more important as these rare events are turning into more common observances. In order to design a marine structure or vehicle to withstand such a potentially devastating phenomenon, the designer must have knowledge of extreme waves with return periods of 50 and 100 years. Based on satellite radar altimeter data, researchers have successfully predicted extreme significant wave heights with the return periods of 50 and 100 years. This thesis extends their research further by estimating the most probable extreme wave heights and other wave statistics based on spectral analysis. The same technique used for extreme significant wave height prediction is applied to extrapolation of corresponding mean wave periods, and they are used to construct two parameter spectra representing storm sea conditions. The prediction of the most probable extreme wave heights as well as other statistical data is based on linear theory and short term order statistics. There exists sufficient knowledge of second order effects on wave generation, and it could be applied to a logical progression of the simulation approach in this thesis. However, because this greatly increases computation time, and the kinematics of deep sea spilling breakers are not yet fully understood for which substantial new research is required, the nonlinear effects are not included in this thesis. Spectral analysis can provide valuable statistical information in addition to extreme wave height data, and preliminary results show good agreement with other prediction methods including wave simulation based on the Pierson-Moskowitz spectrum.
Contract number: N662271-97-G-0025
CIVINS
US Navy (USN) author
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Marasli, Barsam. "Spatially traveling waves in a two-dimensional turbulent wake." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184811.
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Hot-wire measurements taken in the turbulent wake of a flat plate are presented. Symmetrical and antisymmetrical perturbations at various amplitudes and frequencies were introduced into the wake by small flap oscillations. As predicted by linear stability theory, the sinuous (antisymmetric) mode was observed to be more significant than the varicose (symmetric) mode. When the amplitude of the perturbation was low, the spatial development of the introduced coherent perturbation was predicted well by linear stability theory. At high forcing levels, the wake spreading showed dramatic deviations from the well known square-root behavior of the unforced case. Measured coherent Reynolds stresses changed sign in the neighborhood of the neutral point of the perturbation, as predicted by the linear theory. However, the linear theory failed to predict the disturbance amplitude and transverse shapes close to the neutral point. Some nonlinear aspects of the evolution of instabilities in the wake are discussed. Theoretical predictions of the mean flow distortion and the generation of the first harmonic are compared to experimental measurements. Given the unforced flow and the amplitude of the fundamental wave, the mean flow distortion and the amplitude of the first harmonic are predicted remarkably well.
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Lai, Wing-chiu Derek. "The propagation of nonlinear waves in layered and stratified fluids /." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk:8888/cgi-bin/hkuto%5Ftoc%5Fpdf?B23234398.
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Hakim, Ammar H. "High resolution wave propagation schemes for two-fluid plasma simulations /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/7024.
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Katzman, Rafael. "Structure and dynamics of the Pacific upper mantle /." Woods Hole, Mass. : Massachusetts Institute of Technology, Woods Hole Oceanographic Institution, Joint Program in Oceanography/Applied Ocean Science Engineering, 1998. http://hdl.handle.net/1912/1834.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1998."February 1998." "Doctoral dissertation." Includes bibliographical references (p. 189-198).
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Lefauve, Adrien Sébastien Paul. "Waves and turbulence in sustained stratified shear flows." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/277352.
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The speed and efficiency of stratified turbulent mixing in homogenising temperatures, chemical composition and flow speeds makes it one of farthest reaching fluid mechanical phenomenon for life on earth. It is an aesthetically beautiful phenomenon, rich in complex physical behaviours and extremely challenging to model mathematically. Laboratory experiments have a valuable role to play to guide theoretical and numerical work towards a better understanding of this phenomenon by providing insight into real flows under controlled conditions. This dissertation addresses some aspects of the laboratory buoyancy-driven exchange flows through an inclined duct connecting two reservoirs containing fluids of different densities. We employ a novel experimental technique to perform near-instantaneous, volumetric measurements of the three-component velocity field and density field simultaneously, providing an unprecedented quantitative picture of these sustained stratified shear flows. We start by characterising the variety of observed behaviours, or flow regimes, as we vary the density difference between the two reservoirs, the angle of inclination of the duct with respect to the horizontal, the way the density difference is achieved (solutions of salt/fresh water or cold/warm water) and the geometry of the duct. These empirical observations allow us to formulate a number of specific research questions, guiding the work of the next chapters. We then focus on the regime in which Holmboe waves are observed, and demonstrate that these well-known interfacial travelling disturbances have a distinct structure when confined by solid boundaries. We characterise this structure and identify the physical mechanisms at its origin by means of linear stability theory. Since Holmboe waves are found in the intermediate, transitional regime between laminar and turbulent flows, we conjecture that their structure may be relevant to more turbulent flows, where resembling structures are indeed observed. Next, we tackle the quantitative analysis of universal transition curves separating the observed flow regimes (laminar, waves, intermittently turbulent or fully turbulent) as well and the net mass flow rate exchanged by the reservoirs. We show that these long-lasting questions in the study of exchange flows can be addressed in the framework of frictional hydraulic theory, and we derive detailed scaling laws involving only a few nondimensional parameters. Finally, we overcome some of the limitations of hydraulic theory by performing a more detailed, time-resolved, three-dimensional analysis of the energetics of the wave, intermittent and turbulent regimes. We identify and quantify the sources and sinks of energy in each regime, and identify some of the structures responsible for viscous energy dissipation and mixing. We also suggest possible future directions for the present work given recent progress in the literature.
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Gay, Etienne. "Coherent interferometric imaging in fluid dynamics." Thesis, Université de Paris (2019-....), 2019. http://www.theses.fr/2019UNIP7029.
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La présente recherche vise à développer des algorithmes d’imagerie par interférométrie cohérente (CINT) pour localiser des sources et des réflecteurs dans des applications impliquant des écoulements. L’imagerie CINT s’est avérée efficace et statistiquement stable dans des milieux inhomogènes au repos, où les techniques classiques d’imagerie, telles que la migration de Kirchhoff (KM), peuvent éventuellement échouer en raison de leur manque de robustesse statistique. Nous visons à étendre ces méthodes aux milieux en mouvement inhomogènes, car elles concernent l’aéroacoustique, l’acoustique atmosphérique et sous-marine, la propagation des infrasons, voire l’astrophysique. Dans ce rapport de thèse, nous abordons à la fois le problème direct de la modélisation de la propagation des ondes acoustiques dans un écoulement ambiant hétérogène et aléatoire, et le problème inverse de la recherche de la position de sources ou de réflecteurs par l'algorithme CINT mis en œuvre avec les traces des ondes acoustiques qui ont traversé l’écoulementThe present research is aimed at developing coherent interferometric (CINT) imaging algorithms to localize sources and reflectors in applications involving fluid flows. CINT imaging has been shown to be efficient and statistically stable in quiescent cluttered media where classical imaging techniques, such as Kirchhoff’s migration (KM), may possibly fail due to their lack of statistical robustness. We aim at extending these methods to inhomogeneous moving media, for it has relevance to aero-acoustics, atmospheric and underwater acoustics, infrasound propagation, or even astrophysics. In this thesis report we address both the direct problem of modeling the propagation of acoustic waves in a randomly heterogeneous ambient flow, and the inverse problem of finding the position of sources or reflectors by the CINT algorithm implemented with the traces of the acoustic waves that have travelled through the flow
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Pirilla, Patrick Brian. "On the Trajectories of Particles in Solitary Waves." Youngstown State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1311100628.
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Xu, Xu. "Nonlinear dynamics of parametric pendulum for wave energy extraction." Thesis, University of Aberdeen, 2005. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=189414.
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A new concept, extracting energy from sea waves by parametric pendulor, has been explored in this project. It is based on the conversion of vertical oscillations to rotational motion by means of a parametrically-excited pendulor, i.e. a pendulum operating in rotational mode. The main advantage of this concept lies in a direct conversion from vertical oscillations to rotations of the pendulum pivot. This thesis, firstly, reviewed a number of well established linear and nonlinear theories of sea waves and Airy’s sea wave model has been used in the modelling of the sea waves and a parametric pendulum excited by sea waves. The third or fifth order Stokes’s models can be potentially implemented in the future studies. The equation of motion obtained for a parametric pendulum excited by sea waves has the same form as for a simple parametrically-excited pendulum. Then, to deepen the fundamental understanding, an extensive theoretical analysis has been conducted on a parametrically-excited pendulum by using both numerical and analytical methods. The numerical investigations focused on the bifurcation scenarios and resonance structures, particularly, for the rotational motions. Analytical analysis of the system has been performed by applying the perturbation techniques. The approximate solutions, resonance boundary and existing boundary of rotations have been obtained with a good correspondence to numerical results. The experimental study has been carried out by exploring oscillations, rotations and chaotic motions of the pendulum.
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Dolven, Eric T. "Seaquake waves - standing wave dynamics with Faraday excitation and radiative loss /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/6785.
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Harris, David Benjamin. "OpenFOAM Implementation of Microbubble Models for Ocean Applications." Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/104418.
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An investigation was carried out on the current state of the art in bubble modelling for computational fluid dynamics, and comparisons made between the different methods for both polydisperse and monodisperse multiphase flows. A multigroup method for polydisperse bubbly flows with the bubbles binned in terms of mass was selected from the various alternatives, which included other multigroup models and moment methods. The latter of these involve the integration of moments of the bubble number density function and transport of these quantities. The equations from this multigroup solver were then changed to more accurately and efficiently model cases involving extremely small bubbles over significant amounts of time, as the original model which was subsequently adapted had, as its primary purpose, simulation of larger bubbles over shorter periods of time. This was done by decoupling the gas and liquid momentum equations and adding an empirical rise velocity term for the bubbles. This new model was then partially implemented into OpenFOAM. The functioning of this new solver was confirmed by comparisons between the results and basic analytical solutions to the problems, as well as by means of comparison with another similar multiphase CFD solver (pbeTransportFoam). Following this confirmation of its functionality, the bubble model was implemented into another solver specifically designed for modelling wakes. Finally, the newly created solver was used to run some cases of interest involving a submerged wake.Master of Science
Bubbles in the ocean are significant for a number of reasons, ranging from mixing of the upper layer of the ocean to scavenging of biological matter, by which means they can also impact the state of the ocean's surface where they are present. They serve as an important mechanism by which air is dissolved in the ocean, and their breaking at the surface can cause particles or droplets to be ejected into the atmosphere. They can be created by a variety of sources, ranging from the movement of ship propellers and hulls to natural processes, both abiotic and from microorganisms or other living things. They can have exceedingly variable sizes, meaning bubbles behave very differently from one another in the same area. For these reasons, their study is both interesting and sometimes challenging. In this research, methods were developed to simulate the movement over a significant amount of time of a wide size variety of very small bubbles within the ocean. First, study was undertaken of preexisting methods of bubble simulation and the different cases they were intended to represent. One of these existing methods was selected for use and then changed to more accurately represent smaller bubbles, as well as including simplifications to allow the simulations to run faster. Lastly, these methods were implemented into OpenFOAM, an open-source set of solvers for computational fluid dynamics (CFD). These new methods for simulation were finally applied to some cases involving submerged bubbles in the ocean and the movement of bubbles in these cases studied.
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Lai, Wing-chiu Derek, and 黎永釗. "The propagation of nonlinear waves in layered and stratified fluids." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B29750441.
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Zhong, Yisen. "Submesoscale dynamics and transport properties in the Gulf of Mexico." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50385.
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Submesoscale processes, characterized by O(1km) horizontal scale and O(1) Rossby number, are ubiquitous in the world ocean and play an important role in the vertical flux of mass, buoyancy and tracers in the upper ocean. However, they have not been intensively studied due to the requirement of uniquely high spatial and temporal resolution in the observation and computer modeling. In this thesis, using a suite of high-resolution numerical experiments in the northwestern Gulf of Mexico, where rich submesoscale structures are accompanied by the strong mesoscale Loop Current eddies, the impact of resolving submesoscales on the tracer distribution and 3-D transport was extensively examined. It was concluded that, submesoscale dynamics aggregated the surface tracers and formed characteristic patterns at scales of kilometers near the ocean surface by enhanced convergence/divergence zones associated with strong ageostrophic processes. This distinctive phenomenon was evident in recent ocean color satellite images which showed similar extensive lines and spirals of floating Sargassum in the western Gulf of Mexico. In addition, better-resolved submesoscale activities increased the horizontal resolution dramatically and elevated local vertical velocity both within and below the mixed layer while leaving the horizontal component almost unaltered. The vertical dispersion increased by several fold with the largest difference close to the surface. Considering the pervasive presence of submesoscale structures at the surface ocean, these models predict that submesoscale processes may serve as an important nutrient supply mechanism in the upper ocean and potentially make a significant contribution on balancing the global biogeochemical tracer budget.
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Shipton, Jemma. "Balance, gravity waves and jets in turbulent shallow water flows." Thesis, University of St Andrews, 2009. http://hdl.handle.net/10023/708.
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This thesis contains a thorough investigation of the properties of freely decaying turbulence in a rotating shallow water layer on a sphere. A large number of simulations, covering an extensive range of Froude and Rossby numbers, have been carried out using a novel numerical algorithm that exploits the underly- ing properties of the flow. In general these flows develop coherent structures; vortices interact, merge and migrate polewards or equatorwards depending or their sign, leaving behind regions of homogenized potential vorticity separated by sharp zonal jets. In the first half of the thesis we investigate new ways of looking at these structures. In the second half of the thesis we examine the properties of the potential vorticity (PV) induced, balanced component and the residual, unbalanced component of the flows. Cyclone-anticyclone asymmetry has long been observed in atmospheric and oceanic data, laboratory experiments and numerical simulations. This asymmetry is usually seen to favour anticyclonic vorticity with the asymmetry becoming more pronounced at higher Froude numbers (e.g. Polvani et al. [1994a]). We find a similar result but note that the cyclones, although fewer, are significantly more intense and coherent. We present several ways of quantifying this across the parameter space. Potential vorticity homogenization is an important geophysical mechanism responsible for sharpening jets through the expulsion of PV gradients to the edge of flow structures or domains. Sharp gradients of PV are obvious in contour plots of this field as areas where the contours are bunched together. This suggests that we can estimate the number of zonal jets by performing a cluster analysis on the mean latitude of PV contours (this diagnostic is also examined by Dritschel and McIntyre [2007]). This provides an estimate rather than an exact count of the number of jets because the jets meander signficantly. We investigate the accuracy of the estimates provided by different clustering techniques. We find that the properties of the jets defy such simple classification and instead demand a more local examination. We achieve this by examining the palinstrophy field. This field, calculated by taking the gradient of the PV, highlights the regions where PV contours come closer together, exactly what we would expect in regions of strong jets. Plots of the palinstrophy field reveal the complex structure of these features. The potential vorticity field is even more central to the flow evolution than the strong link with jets suggests. From a knowledge of the spatial distribution of PV, it is possible to diagnose the balanced components of all other fields. These components will not contain inertia-gravity waves but will contain the dominant, large scale features of the flow. This inversion, or decomposition into balanced (vortical) and unbalanced (wave) components, is not unique and can be defined to varying orders of accuracy. We examine the results of four dfferent definitions of this decomposition, two based on truncations of the full equations and two based on an iterative procedure applied to the full equations. We find the iterative procedure to be more accurate in that it attributes more of the flow to the PV controlled, balanced motion. However, the truncated equations perform surprisingly well and do not appear to suffer in accuracy at the equator, despite the fact that the scaling on which they are based has been thought to break down there. We round off this study by considering the impact of the unbalanced motion on the flow. This is accomplished by splitting the integration time of the model into intervals τ < t < τ+dτ and comparing, at the end of each interval, the balanced components of the flow obtained by a) integrating the model from t = 0 and b) integrating the full equations, initialised at t = τ with the balanced components from a) at t = τ. We find that any impact of the unbalanced component of the flow is less than the numerical noise of the model.
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Meuleners, Michael Joseph. "A numerical study of the mesoscale eddy dynamics of the Leeuwin Current system /." Connect to this title, 2005. http://theses.library.uwa.edu.au/adt-WU2007.0134.
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Komarova, Natalia 1971. "Essays on nonlinear waves: Patterns under water; pulse propagation through random media." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/282787.
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This is a collection of essays on weakly and strongly nonlinear systems and possible ways of solving/interpreting them. Firstly, we study sand patterns which are often observed on sea (river) beds. One of the most common features looks like straight rolls perpendicular to the water motion. In many cases, the straight rolls are superimposed on a much longer wave so that two vastly different length scales coexist. In general, there are at least two mechanisms responsible for the growth of periodic sand waves. One is linear instability, and the other is nonlinear coupling between long waves and short waves. One novel feature of this work is to suggest that the latter can be much more important than the former one for the generation of long waves. A weakly nonlinear analysis of the corresponding physical system suggests that the nonlinear coupling leads to the growth of the longer features if the amplitude of the shorter waves has a non-zero curvature. For the case of a straight channel and a tidal shallow sea, we derive nonlinear amplitude equations governing the dynamics of the main features. Estimates based on these equations are consistent with measurements. Secondly, we consider strongly nonlinear systems with randomness. The phenomenon of self-induced transparency (SIT) is reinterpreted in the context of competition between randomness, nonlinearity and dispersion. The problem is then shown to be isomorphic to a problem of the nonlinear Schroedinger (NLS) type with a random (in space) potential. It is proven that the SIT result continues to hold when the uniform medium of inhomogeneously broadened two-level atoms is replaced by a series of intervals in each of which the frequency mismatch is randomly chosen from some distribution. The exact solution of this problem suggests that nonlinearity can improve the transparency of the medium. Also, the small amplitude, almost monochromatic limit of SIT is taken and results in an envelope equation which is an exactly integrable combination of NLS and a modified SIT equation. Some generalizations are made to describe a broad class of integrable systems which combine randomness, nonlinearity and dispersion.
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Quirk, J. J. "An adaptive grid algorithm for computational shock hydrodynamics." Thesis, Boston Spa, U.K. : British Library Document Supply Centre, 1991. http://ethos.bl.uk/OrderDetails.do?did=1&uin=uk.bl.ethos.280913.
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Kuehl, Joseph J. "Finite time invariant manifold detection from experimental phase space trajectories /." View online ; access limited to URI, 2009. http://digitalcommons.uri.edu/dissertations/AAI3378087.
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Chumbinho, Rogřio Paulo Antunes. "Kinematics and dynamics of a cyclonic eddy off Pt. Arena, California /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA298587.
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Dissertation (Ph. D. in Physical Oceanography) Naval Postgraduate School, December 1994."December 1994." Dissertation supervisor(s): R.L. Haney. Includes bibliographical references (p. 75-79). Also available online.