Dissertations / Theses on the topic 'Nonlinear water waves'
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Baumstein, Anatoly I. Saffman P. G. Saffman P. G. "Nonlinear water waves with shear /." Diss., Pasadena, Calif. : California Institute of Technology, 1997. http://resolver.caltech.edu/CaltechETD:etd-01042008-093737.
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Bird, Charlotte C. "Nonlinear interactions of water waves, wave groups and beaches." Thesis, University of Bristol, 1999. http://hdl.handle.net/1983/c8fedc4e-9c73-4791-b1d8-b4ff14646025.
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Qu, Wendong Wu Theodore Y. T. "Studies on nonlinear dispersive water waves /." Diss., Pasadena, Calif. : California Institute of Technology, 2000. http://resolver.caltech.edu/CaltechETD:etd-08152006-140314.
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Smith, Susan Frances. "Large transient waves in shallow water." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313296.
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陳健行 and Kin-hang Chan. "Computational studies of forced, nonlinear waves in shallow water." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31224003.
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Ohl, Clifford Owen Groome. "Free surface disturbances and nonlinear runup around offshore structures." Thesis, University of Oxford, 2000. http://ora.ox.ac.uk/objects/uuid:320ff8da-c225-40da-a7dd-d6cf55c97b51.
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Diffraction of regular waves, focused wave groups, and random seas by arrays of vertical bottom mounted circular cylinders is investigated using theoretical, computational, and experimental methods. Free surface elevation η is the defining variable used to test the potential theory developed. In addition, the nonlinearity of focused wave groups is investigated through the Creamer nonlinear transform and analysis of numerical wave tank data. Linear focused wave group theory is reviewed as a method for predicting the probable shape of extreme events from random wave spectra. The Creamer nonlinear transform, a realistic model for steep waves on deep water, is applied in integral form to simulate nonlinear focused wave groups. In addition, the transform is used to facilitate analysis of nonlinear wave-wave interactions within focused wave groups from a uni-directional numerical wave tank developed at Imperial College London. Experiments in an offshore wave basin at HR Wallingford are designed to measure free surface elevation at multiple locations in the vicinity of a multicolumn structure subjected to regular and irregular waves for a range of frequencies and steepness. Results from regular wave data analysis for first order amplitudes are compared to analytical linear diffraction theory, which is shown to be accurate for predicting incident waves of low steepness. However, second and third order responses are also computed, and the effects in the vicinity of a second order near trapping frequency are compared to semi-analytical second order diffraction theory. Analytical linear diffraction theory is extended for application to focused wave groups and random seas. Experimental irregular wave data are analysed for comparison with this theory. Linear diffraction theory for random seas is shown to give an excellent prediction of incident wave spectral diffraction, while linear diffraction theory for focused wave groups works well for linearised extreme events.
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Grataloup, Géraldine Léonie 1979. "Localization of nonlinear water waves over a random bottom." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/16918.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003.Includes bibliographical references (p. 87-90).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
by Géraldine Léonie Grataloup.
S.M.
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Mathew, Joseph. "Nonlinear three-dimensional waves on water of varying depth." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/14065.
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Liang, Junhong. "Linear and nonlinear analysis of shallow mixing layers /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202006%20LIANG.
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Villeneuve, Marc. "Nonlinear, dispersive, shallow-water waves developed by a moving bed." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=55658.
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Xü, Hongbo. "Numerical study of fully nonlinear water waves in three dimensions." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/13067.
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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1992.Title as it appears in the M.I.T. Graduate List, Feb. 1992: Numerical simulations of fully-nonlinear water waves in three dimensions.
Includes bibliographical references (leaves 203-211).
by Hongbo Xü.
Sc.D.
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Yang, Jianke. "Some nonlinear equations arising in the theory of water waves." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/12051.
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Moreira, Roger Matsumoto. "Nonlinear interactions between water waves, free surface flows and singularities." Thesis, University of Bristol, 2001. http://hdl.handle.net/1983/48c03019-9f5d-4aae-83b5-d9ea23c2f6ec.
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Li, Yile 1973. "Linear and nonlinear resonance of water waves near periodic structures." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38266.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (p. 395-401).
In the first part of this thesis, we present a nonlinear theory for the excitation of trapped wave around a circular cylinder mounted at the center of a channel. It is well-known that near an infinite linear array of periodically spaced cylinders trapped waves of certain eigen-frequencies can exist. If there are only a finite number of cylinders in an infinite sea, trapping is imperfect. Simple harmonic incident waves can excite a nearly trapped wave at one of the eigen-frequencies through a linear mechanism. However the maximum amplification ratio increases monotonically with the number of the cylinders, hence the solution is singular in the limit of infinitely many cylinders. A nonlinear theory is developed for the trapped waves excited subharmonically by an incident wave of twice the eigen-frequency. The effects of geometrical parameters on the initial growth of resonance and the final amplification are studied in detail. The nonlinear theory is further extend to random incident waves with a narrow spectrum centered near twice the natural frequency of the trapped wave. The effects of detuning and bandwidth of the spectrum are examined. In the second part of the thesis, we study the Bragg resonance of surface water waves by (i) a line of periodic circular cylinders in a long channel, and (ii) a two-dimensional periodic array of cylinders.
(cont.) For case (i), strong reflection takes place in a channel when the cylinder spacing is one-half that of the incident waves. Solutions for a large but finite number of cylinders in a channel are examined and compared with finite element results. For case (ii) we study an array of cylinders extending in both horizontal directions toward infinity, the Bragg resonance condition is found to be the same as that in the physics of solid state and photonic crystals, and can be determined by Ewald construction. Envelope equations of Klein-Gordon type for resonated waves are derived for multiple resonated waves. For a wide strip of cylinders, analytical solutions of both two-wave and three-wave resonance are discussed in detail. We also extend the theory to include second-order nonlinear effects of the free surface. For a train of periodically modulated incident waves scattered by an one-dimensional line of cylinders, free long waves are found to exist and propagate faster than the set-down long wave bound to the short wave envelopes. At Bragg resonance, the short waves are reflected by the array but the induced free long wave can pass through it. For a train of periodically modulated waves scattered by a finite strip of cylinders, the free long waves can propagate away from the strip or be trapped near the strip depending on the angle of incidence.
by Yile Li.
Ph.D.
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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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Zhao, Zhongxiang. "A study of nonlinear internal waves in the northeastern South China Sea." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 11.38Mb, 181 p, 2005. http://wwwlib.umi.com/dissertations/fullcit/3157312.
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Killen, Sean Martin. "Propagation of nonlinear water waves over variable depth in cylindrical geometry." Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366639.
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Teng, Michelle Hsiao Tsing Wu Theodore Y. T. "Forced emissions of nonlinear water waves in channels of arbitrary shape /." Diss., Pasadena, Calif. : California Institute of Technology, 1990. http://resolver.caltech.edu/CaltechETD:etd-06132005-111317.
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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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Panupintu, Wantana. "The propagation of nonlinear water waves over variable depth with shear flow." Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246653.
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Li, Yile 1973. "Nonlinear shallow water three-dimensional solitary waves generated by high speed vessels." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/91907.
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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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Kim, Won-Gyu 1962. "A Study of Nonlinear Dynamics in an Internal Water Wave Field in a Deep Ocean." Thesis, University of North Texas, 1996. https://digital.library.unt.edu/ark:/67531/metadc278092/.
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The Hamiltonian of a stably stratified incompressible fluid in an internal water wave in a deep ocean is constructed. Studying the ocean internal wave field with its full dynamics is formidable (or unsolvable) so we consider a test-wave Hamiltonian to study the dynamical and statistical properties of the internal water wave field in a deep ocean. Chaos is present in the internal test-wave dynamics using actual coupling coefficients. Moreover, there exists a certain separatrix net that fills the phase space and is covered by a thin stochastic layer for a two-triad pure resonant interaction. The stochastic web implies the existence of diffusion of the Arnold type for the minimum dimension of a non-integrable autonomous system. For non-resonant case, stochastic layer is formed where the separatrix from KAM theory is disrupted. However, the stochasticity does not increase monotonically with increasing energy. Also, the problem of relaxation process is studied via microscopic Hamiltonian model of the test-wave interacting nonlinearly with ambient waves. Using the Mori projection technique, the projected trajectory of the test-wave is transformed to a form which corresponds to a generalized Langevin equation. The mean action of the test-wave grows ballistically for a short time regime, and quenches back to the normal diffusion for a intermediate time regime and regresses linearly to a state of statistical equilibrium. Applying the Nakajima-Zwanzig technique on the test-wave system, we get the generalized master equation on the test-wave system which is non-Markovian in nature. From our numerical study, the distribution of the test-wave has non-Gaussian statistics.
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Hoseini, Sayed Mohammad. "Solitary wave interaction and evolution." Access electronically, 2007. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20080221.110619/index.html.
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Kim, Sungeun 1963. "Nonlinear interaction of water waves with three-dimensional floating bodies in a current." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/10082.
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Sander, Johannes. "Weakly nonlinear unidirectional shallow water waves generated by a moving boundary : a historical essay : experiments and computations /." Zürich, 1990. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=9156.
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Brühl, Markus [Verfasser], and Hocine [Akademischer Betreuer] Oumeraci. "Direct and inverse nonlinear Fourier transform based on the Korteweg-deVries equation (KdV-NLFT) - A spectral analysis of nonlinear surface waves in shallow water / Markus Brühl ; Betreuer: Hocine Oumeraci." Braunschweig : Technische Universität Braunschweig, 2014. http://d-nb.info/1175820547/34.
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Bocchi, Edoardo. "Compressible-incompressible transitions in fluid mechanics : waves-structures interaction and rotating fluids." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0279/document.
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Ce manuscrit porte sur les transitions compressible-incompressible dans les équations aux dérivées partielles de la mécanique des fluides. On s'intéresse à deux problèmes : les structures flottantes et les fluides en rotation. Dans le premier problème, l'introduction d'un objet flottant dans les vagues induit une contrainte sur le fluide et les équations gouvernant le mouvement acquièrent une structure compressible-incompressible. Dans le deuxième problème, le mouvement de fluides géophysiques compressibles est influencé par la rotation de la Terre. L'étude de la limite à rotation rapide montre que le champ vectoriel de vitesse tend vers une configuration horizontale et incompressible.Les structures flottantes constituent un exemple particulier d'interaction fluide-structure, où un solide partiellement immergé flotte à la surface du fluide. Ce problème mathématique modélise le mouvement de convertisseurs d'énergie marine. En particulier, on s'intéresse aux bouées pilonnantes, installées proche de la côte où les modèles asymptotiques en eaux peu profondes sont valables. On étudie les équations de Saint-Venant axisymétriques en dimension deux avec un objet flottant à murs verticaux se déplaçant seulement verticalement. Les hypothèses sur le solide permettent de supprimer le problème à bord libre associé avec la ligne de contact entre l'air, le fluide et le solide. Les équations pour le fluide dans le domaine extérieur au solide sont donc écrites comme un problème au bord quasi-linéaire hyperbolique. Celui-ci est couplé avec une EDO non-linéaire du second ordre qui est dérivée de l'équation de Newton pour le mouvement libre du solide. On montre le caractère bien posé localement en temps du système couplé lorsque que les données initiales satisfont des conditions de compatibilité afin de générer des solutions régulières.Ensuite on considère une configuration particulière: le retour à l'équilibre. Il s'agit de considérer un solide partiellement immergé dans un fluide initialement au repos et de le laisser retourner à sa position d'équilibre. Pour cela, on utilise un modèle hydrodynamique différent, où les équations sont linearisées dans le domaine extérieur, tandis que les effets non-linéaires sont considérés en dessous du solide. Le mouvement du solide est décrit par une équation intégro-différentielle non-linéaire du second ordre qui justifie rigoureusement l'équation de Cummins, utilisée par les ingénieurs pour les mouvements des objets flottants. L'équation que l'on dérive améliore l'approche linéaire de Cummins en tenant compte des effets non-linéaires. On montre l'existence et l'unicité globale de la solution pour des données petites en utilisant la conservation de l'énergie du système fluide-structure.Dans la deuxième partie du manuscrit, on étudie les fluides en rotation rapide. Ce problème mathématique modélise le mouvement des flots géophysiques à grandes échelles influencés par la rotation de la Terre. Le mouvement est aussi affecté par la gravité, ce qui donne lieu à une stratification de la densité dans les fluides compressibles. La rotation génère de l'anisotropie dans les flots visqueux et la viscosité turbulente verticale tend vers zéro dans la limite à rotation rapide. Notre interêt porte sur ce problème de limite singulière en tenant compte des effets gravitationnels et compressibles. On étudie les équations de Navier-Stokes-Coriolis anisotropes compressibles avec force gravitationnelle dans la bande infinie horizontale avec une condition au bord de non glissement. Celle-ci et la force de Coriolis donnent lieu à l'apparition des couches d'Ekman proche du bord. Dans ce travail on considère des données initiales bien préparées. On montre un résultat de stabilité des solutions faibles globales pour des lois de pression particulières. La dynamique limite est décrite par une équation quasi-géostrophique visqueuse en dimension deux avec un terme d'amortissement qui tient compte des couches limitesThis manuscript deals with compressible-incompressible transitions arising in partial differential equations of fluid mechanics. We investigate two problems: floating structures and rotating fluids. In the first problem, the introduction of a floating object into water waves enforces a constraint on the fluid and the governing equations turn out to have a compressible-incompressible structure. In the second problem, the motion of geophysical compressible fluids is affected by the Earth's rotation and the study of the high rotation limit shows that the velocity vector field tends to be horizontal and with an incompressibility constraint.Floating structures are a particular example of fluid-structure interaction, in which a partially immersed solid is floating at the fluid surface. This mathematical problem models the motion of wave energy converters in sea water. In particular, we focus on heaving buoys, usually implemented in the near-shore zone, where the shallow water asymptotic models describe accurately the motion of waves. We study the two-dimensional nonlinear shallow water equations in the axisymmetric configuration in the presence of a floating object with vertical side-walls moving only vertically. The assumptions on the solid permit to avoid the free boundary problem associated with the moving contact line between the air, the water and the solid. Hence, in the domain exterior to the solid the fluid equations can be written as an hyperbolic quasilinear initial boundary value problem. This couples with a nonlinear second order ODE derived from Newton's law for the free solid motion. Local in time well-posedness of the coupled system is shown provided some compatibility conditions are satisfied by the initial data in order to generate smooth solutions.Afterwards, we address a particular configuration of this fluid-structure interaction: the return to equilibrium. It consists in releasing a partially immersed solid body into a fluid initially at rest and letting it evolve towards its equilibrium position. A different hydrodynamical model is used. In the exterior domain the equations are linearized but the nonlinear effects are taken into account under the solid. The equation for the solid motion becomes a nonlinear second order integro-differential equation which rigorously justifies the Cummins equation, assumed by engineers to govern the motion of floating objects. Moreover, the equation derived improves the linear approach of Cummins by taking into account the nonlinear effects. The global existence and uniqueness of the solution is shown for small data using the conservation of the energy of the fluid-structure system.In the second part of the manuscript, highly rotating fluids are studied. This mathematical problem models the motion of geophysical flows at large scales affected by the Earth's rotation, such as massive oceanic and atmospheric currents. The motion is also influenced by the gravity, which causes a stratification of the density in compressible fluids. The rotation generates anisotropy in viscous flows and the vertical turbulent viscosity tends to zero in the high rotation limit. Our interest lies in this singular limit problem taking into account gravitational and compressible effects. We study the compressible anisotropic Navier-Stokes-Coriolis equations with gravitational force in the horizontal infinite slab with no-slip boundary condition. Both this condition and the Coriolis force cause the apparition of Ekman layers near the boundary. They are taken into account in the analysis by adding corrector terms which decay in the interior of the domain. In this work well-prepared initial data are considered. A stability result of global weak solutions is shown for power-type pressure laws. The limit dynamics is described by a two-dimensional viscous quasi-geostrophic equation with a damping term that accounts for the boundary layers
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Sutherland, James. "The dynamics of nonlinear water wave groups." Thesis, University of Edinburgh, 1992. http://hdl.handle.net/1842/13045.
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A number of accurate measurements of the kinematics under the crests of regular waves and two-component uni-directional wave groups have been made in a laboratory wave flume using Particle Image Velocimetry. The waves were in intermediate to deep water, with relative depths in the range of d/gT2 = 0.05 to 0.085 and were of moderate to high relative steepnesses, in the range H/gT2 = 0.005 to 0.018. (Here d is water depth, T wave period, H wave height and g gravitational acceleration.) The main conclusions are: (1) Regular waves were accurately modelled using an implementation of high order Fourier theory by Rienecker and Fenton, providing Stokes second (zero mass transport) definition of wave celerity was used. (2) Steep, near-breaking two-component waves were modelled accurately using superposition stretching, a derivative linear theory. The input for this is the measured was spectrum, including first and second harmonics. The second harmonic contribution was found to be significant. (3) The kinematics in the crests of different waves of a given height and period can vary considerably. Here, differences of over 20% were noticed at the crest. (4) Wave group lenght affects the internal wave kinematics. (5) Measurements must be made above the level of the wave troughs and should be made above the mean water level also, if experimental results are to have much credence. (6) Particle image velocimetry proved to be an excellent measurement technique to use for measuring velocities as it was capable of measuring close to the free surface of high waves, with a high degree of accuracy.
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Abdolmaleki, Kourosh. "Modelling of wave impact on offshore structures." University of Western Australia. School of Mechanical Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2008.0055.
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[Truncated abstract] The hydrodynamics of wave impact on offshore structures is not well understood. Wave impacts often involve large deformations of water free-surface. Therefore, a wave impact problem is usually combined with a free-surface problem. The complexity is expanded when the body exposed to a wave impact is allowed to move. The nonlinear interactions between a moving body and fluid is a complicated process that has been a dilemma in the engineering design of offshore and coastal structures for a long time. This thesis used experimental and numerical means to develop further understanding of the wave impact problems as well as to create a numerical tool suitable for simulation of such problems. The study included the consideration of moving boundaries in order to include the coupled interactions of the body and fluid. The thesis is organized into two experimental and numerical parts. There is a lack of benchmarking experimental data for studying fluid-structure interactions with moving boundaries. In the experimental part of this research, novel experiments were, therefore, designed and performed that were useful for validation of the numerical developments. By considering a dynamical system with only one degree of freedom, the complexity of the experiments performed was minimal. The setup included a plate that was attached to the bottom of a flume via a hinge and tethered by two springs from the top one at each side. The experiments modelled fluid-structure interactions in three subsets. The first subset studied a highly nonlinear decay test, which resembled a harsh wave impact (or slam) incident. The second subset included waves overtopping on the vertically restrained plate. In the third subset, the plate was free to oscillate and was excited by the same waves. The wave overtopping the plate resembled the physics of the green water on fixed and moving structures. An analytical solution based on linear potential theory was provided for comparison with experimental results. ... In simulation of the nonlinear decay test, the SPH results captured the frequency variation in plate oscillations, which indicated that the radiation forces (added mass and damping forces) were calculated satisfactorily. In simulation of the nonlinear waves, the waves progressed in the flume similar to the physical experiments and the total energy of the system was conserved with an error of 0.025% of the total initial energy. The wave-plate interactions were successfully modelled by SPH. The simulations included wave run-up and shipping of water for fixed and oscillating plate cases. The effects of the plate oscillations on the flow regime are also discussed in detail. The combination of experimental and numerical investigation provided further understanding of wave impact problems. The novel design of the experiments extended the study to moving boundaries in small scale. The use of SPH eliminated the difficulties of dealing with free-surface problems so that the focus of study could be placed on the impact forces on fixed and moving bodies.
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Abreu, Manuel A. "Nonlinear transformation of directional wave spectra in shallow water." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/28400.
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De, Azevedo Jose Paulo Soares. "Application of the boundary element method to two-dimensional nonlinear gravity wave problems." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292283.
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Schuh, K., P. Rosenow, M. Kolesik, E. M. Wright, S. W. Koch, and J. V. Moloney. "Nonlinear rovibrational polarization response of water vapor to ultrashort long-wave infrared pulses." AMER PHYSICAL SOC, 2017. http://hdl.handle.net/10150/625977.
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We study the rovibrational polarization response of water vapor using a fully correlated optical Bloch equation approach employing data from the HITRAN database. For a 10-mu m long-wave infrared pulse the resulting linear response is negative, with a negative nonlinear response at intermediate intensities and a positive value at higher intensities. For a model atmosphere comprised of the electronic response of argon combined with the rovibrational response of water vapor this leads to a weakened positive nonlinear response at intermediate intensities. Propagation simulations using a simplified noncorrelated approach show the resultant reduction in the peak filament intensity sustained during filamentation due to the presence of the water vapor.
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Godey, Cyril. "Bifurcations locales et instabilités dans des modèles issus de l'optique et de la mécanique des fluides." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCD008/document.
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Cette thèse présente quelques contributions à l'étude qualitative de solutions d'équations aux dérivées partielles non linéaires dans des modèles issus de l'optique et de la mécanique des fluides. Nous nous intéressons plus précisément à l'existence de solutions et à leur stabilité temporelle. Le Chapitre 1 est consacré à l'équation de Lugiato-Lefever, qui est une variante de l'équation de Schrödinger non linéaire et qui a été dérivée dans plusieurs contextes en optique. En utilisant des outils de la théorie des bifurcations et des formes normales, nous procédons à une étude systématique des solutions stationnaires de cette équation, et prouvons l'existence de solutions périodiques et localisées. Dans le Chapitre 2, nous présentons un critère simple d'instabilité linéaire pour des ondes non linéaires. Nous appliquons ce résultat aux équations de Lugiato-Lefever, de Kadomtsev-Petviashvili-I et de Davey-Stewartson. Ces deux dernières équations sont des équations modèles dérivées en mécanique des fluides. Dans le Chapitre 3, nous montrons un critère d'instabilité linéaire pour des solutions périodiques de petite amplitude, par rapport à certaines perturbations quasipériodiques. Ce résultat est ensuite appliqué à l'équation de Lugiato-LefeverIn this thesis we present several contributions to qualitative study of solutions of nonlinear partial differential equations in optics and fluid mechanics models. More precisely, we focus on the existence of solutions and their stability properties. In Chapter 1, we study the Lugiato-lefever equation, which is a variant of the nonlinear Schrödinger equation arising in sereval contexts in nonlinear optics. Using tools from bifurcation and normal forms theory, we perfom a systematic analysis of stationary solutions of this equation and prove the existence of periodic and localized solutions. In Chapter 2, we present a simple criterion for linear instability of nonlinear waves. We then apply this result to the Lugiato-Lefever equation, to the Kadomtsev-Petviashvili-I equation and the Davey-Stewartson equations. These last two equations are model equations arising in fluid mechanics. In Chapter 3, we prove a criterion for linear instability of periodic solutions with small amplitude, with respect to certain quasiperiodic perturbations. This result is then applied to the Lugiato-Lefever equation
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Zhou, Zhengquan. "A theory and analysis of planing catamarans in calm and rough water." ScholarWorks@UNO, 2003. http://louisdl.louislibraries.org/u?/NOD,45.
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Thesis (Ph.D)--University of New Orleans, 2003.Title from electronic submission form. "A dissertation ... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Engineering and Applied Science"--Dissertation t.p. Vita. Includes bibliographical references.
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Wang, Yunli. "Etude expérimentale et numérique des oscillations hydrodynamiques en milieux poreux partiellement saturés." Thesis, Toulouse, INPT, 2010. http://www.theses.fr/2010INPT0127/document.
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Cette thèse vise à étudier expérimentalement, analytiquement et numériquement, les conséquences de variations et d'oscillations hydrodynamiques à forte variabilité temporelle en milieux poreux partiellement saturés. Les problèmes que nous étudions comportent des surfaces libres tant à l'extérieur qu'à l'intérieur des milieux poreux, celles-ci étant définies comme des isosurfaces de pression d'eau égale à la pression atmosphérique (Pwater = Patm). Les différentes études expérimentales réalisées en laboratoire sont, respectivement : une expérience d'imbibition dans une boite à sable avec effets capillaires importants; la transmission d'oscillations de la surface libre à travers un massif sableux intercalaire dans un petit canal à houle (IMFT, Toulouse); l'étude de la dynamique et de la propagation des oscillations des niveaux d'eau dans un grand canal à houle (HYDRALAB, Barcelone), partiellement recouvert d'un fond sableux incliné, avec mesures de niveaux d'eau en pleine eau et sous le sable, et mesures du fond sableux (érosion/dépôts). Pour les études théoriques, nous avons développés des solutions analytiques linéarisées. Un exemple de problème traité analytiquement est: l'équation linéarisée de Dupuit-Boussinesq (D-B) transitoire à surface libre, en hypothèse d'écoulements plans et vidange/remplissage instantané : oscillations forcées, transmission et dissipation d'ondes à travers une boite à sable rectangulaire. Nous avons aussi développé une solution de l'équation faiblement non linéaire de Dupuit- Boussinesq (D-B) pour étudier le problème d'imbibition avec variation abrupte du niveau d'eau amont (suivi temporel du front de saturation). Nous avons pu étudier les différents types de problèmes transitoires liés aux expériences citées plus haut par simulation numérique. En particulier, nous avons simulé des écoulements partiellement saturés et insaturés, en coupe verticale, à l'aide d'un code de calcul (BIGFLOW 3D) qui résoud l'équation de Richards généralisée en régime transitoire. Nous avons ainsi étudié numériquement en régime non saturé, l'expérience d'imbibition dans un sable initialement sec à frontières verticales (IMFT sandbox), puis l'expérience de propagation d'ondes dans le grand canal à houle de Barcelone (laboratoire HYDRALAB) comportant une plage de sable inclinée, avec un couplage complètement intégré entre les zones micro-poreuse (sable) et “macro-poreuse” (pleine eau). Pour analyser les résultats de cette dernière expérience et les comparer aux simulations, nous avons utilisé plusieurs méthodes de traitement et d'analyse des signaux : analyse de Fourier (spectres de fréquences) ; ondelettes discrètes multi-résolution (Daubechies) ; analyses corrélatoires simple et croisée. Ces méthodes sont combinées avec des méthodes de préfiltrage pour estimer dérives et résidus (moyennes mobiles ; ondelettes multi-résolution). Cette analyse des signaux a permis de comprendre et quantifier la propagation à travers une plage de sable. Au total, les différentes approches de modélisation mis en oeuvre, associé à des procédures de calage en situation de couplage transitoire non linéaire ont permis de reproduire globalement les phénomènes de propagation de teneur en eau et de niveau d'eau dans les différentes configurations étudiéesThis thesis aims at investigating experimentally, analytically and numerically, the consequences of hydrodynamic variations and oscillations with high temporal variability in partially saturated porous media. The problems investigated in this work involve “free surfaces” both outside and inside the porous media, the free surface being defined as the “atmospheric” water pressure isosurface (Pwater = Patm). The laboratory experiments studied in this work are, respectively: Lateral imbibition in a dry sand box with significant capillary effects; Transmission of oscillations of the free surface through a vertical sand box placed in a small wave canal (IMFT, Toulouse); Dynamics of free surface oscillations and wave propagation in a large wave canal (HYDRALAB, Barcelona), partially covered with sand, with measurements of both open water and groundwater levels, and of sand topography (erosion / deposition). For theoretical studies, we have developed linearized analytical solutions. Here is a sample problem that was treated analytically in this work: The linearized equation of Dupuit-Boussinesq (DB) for transient free surface flow, assuming horizontal flow and instantaneous wetting/drainage of the unsaturated zone: forced oscillations, wave transmission and dissipation through a rectangular sandbox. We also developed a weakly nonlinear solution of the Dupuit-Boussinesq equation to study the sudden imbibition (temporal monitoring of the wetting front). We have studied the different types of transient flow problems related to the experiments cited above by numerical simulation. In particular, we have simulated unsaturated or partially saturated transient flows in vertical cross-section, using a computer code (BIGFLOW 3D) which solves a generalized version of Richards’ equation. Thus, using the Richards / BIGFLOW 3D model, we have studied numerically the experiment of unsaturated imbibition in a dry sand (IMFT sandbox), and then, with the same model, we have also studied the partially saturated wave propagation experiment in the large Barcelona wave canal (HYDRALAB laboratory), focusing on the sloping sandy beach, with coupling between the micro-porous zone (sand) and the “macro-porous” zone (open water). To interpret the results of the latter experiment and compare them to simulations, we use several methods of signal analyzis and signal processing, such as: Fourier analysis, discrete multi-resolution wavelets (Daubechies), auto and cross-correlation functions. These methods are combined with pre-filtering methods to estimate trends and residuals (moving averages; discrete wavelet analyses). This signal analyzis has allowed us to interpret and quantify water propagation phenomena through a sandy beach. To sum up, different modeling approaches, combined with model calibration procedures, were applied to transient nonlinear coupled flow problems. These approaches have allowed us to reproduce globally the water content distributions and water level propagation in the different configurations studied in this work
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Baumstein, Anatoly I. "Nonlinear water waves with shear." Thesis, 1997. https://thesis.library.caltech.edu/29/1/Baumstein_ai_1997.pdf.
Full textAbstract:
Various aspects of nonlinear inviscid gravity waves in the presence of shear in the air and water are investigated. The shear, which appears due to the presence of wind in the air and current in the water, is modeled by a piecewise linear velocity profile.
The interaction of short and long gravity waves is studied numerically, using spectral methods, and analytically, using perturbation methods. Special attention is paid to the verification of observations and experimental results. It is confirmed that finite amplitude waves propagating in the same direction as the wind or current are more stable with respect to superharmonic infinitesimal perturbations than the waves moving against the wind or current.
Infinitesimal perturbations in the form of side bands are also investigated both numerically and analytically. The nonlinear cubic Schrodinger equation for the wave envelope of a slowly varying wave train is derived. It is shown that depending on the direction of propagation (along or against the shear) of the finite amplitude waves, the effect of the shear on the stability is substantially different. In most cases, however, the shear strength increase first enhances the instability, but later suppresses it.
Three-wave interactions of gravity waves with shear in the water are considered. The interaction equations are derived with the help of two different perturbation approaches. The question of stability is addressed for both resonant and near-resonant interactions. The regions of explosive and "pump-wave" instability are identified for various types of three-wave interactions.
A new type of steady two-dimensional gravity waves with water shear is computed numerically. These waves appear at relatively low amplitudes and lack symmetry with respect to any crest or trough. A boundary integral formulation is used to obtain a one-parameter family of non-symmetric solutions through a symmetry-breaking bifurcation.
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Qu, Wendong. "Studies on Nonlinear Dispersive Water Waves." Thesis, 2000. https://thesis.library.caltech.edu/3134/1/Qu_w_2000.pdf.
Full textAbstract:
This study investigates the phenomena of evolution of two-dimensional, fully nonlinear, fully dispersive, incompressible and irrotational waves in water of uniform depth in single and in double layers. The study is based on an exact fully nonlinear and fully dispersive (FNFD) wave model developed by Wu (1997, 1999a). This FNFD wave model is first based on two exact equations involving three variables all pertaining to their values at the water surface. Closure of the system of model equations is accomplished either in differential form, by attaining a series expansion of the velocity potential, or in integral form by adopting a boundary integral equation for the velocity field.
A reductive perturbation method for deriving asymptotic theory for higher-order solitary waves is developed using the differential closure equation of the FNFD wave theory. Using this method, we have found the leading 15th-order solitary wave solutions. The solution is found to be an asymptotic solution which starts to diverge from the 12th-order so that the 11th-order solution appears to provide the best approximation to the fully nonlinear solitary waves, with a great accuracy for waves of small to moderately large amplitudes.
Two numerical methods for calculating unsteady fully nonlinear waves, namely, the FNFD method and the Point-vortex method, are developed and applied to compute evolutions of fully nonlinear solitary waves. The FNFD method, which is based on the integral closure equation of Wu's theory, can provide good performance on computation of solitary waves of very large amplitude. The Point-vortex method using the Lagrange markers is very efficient for computation of waves of small to moderate amplitudes, but has intrinsic difficulties in computing waves of large amplitudes. These two numerical methods are applied to carry out a comparative study of interactions between solitary waves.
Capillary-gravity solitary waves are investigated both theoretically and numerically. The theoretical study based on the reductive perturbation method provides asymptotic theories for higher-order capillary-gravity solitary waves. A stable numerical method (FNFD) for computing exact solutions for unsteady capillary-gravity solitary waves is developed based on the FNFD wave theory. The results of the higher-order asymptotic theories compare extremely well with those given by the FNFD method for waves of small to moderate amplitudes.
A numerical method for computing unsteady fully nonlinear interfacial waves in two-layer fluid systems is developed based on the FNFD model. The subcritical and supercritical cases can be clearly distinguished by this method, especially for waves of amplitudes approaching the maximum attainable for the fully nonlinear theory.
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Liu, Chin-Yung, and 劉晉湧. "Analysis for the evolution of wave front in deep-water nonlinear waves." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/67926079437895787469.
Full textAbstract:
碩士國立成功大學
水利及海洋工程學系碩博士班
95
We observe the front wave change from the quiet water state to steady wave motion state, when the wave train which are created by wave maker are delivered to the lower reaches of water flume. There is the non-linear and unstable wave between quiet water state and steady state. We call it wave front of wave train. The phenomenon of wave front shows the wave modulation, and finally becomes The phenomenon of wave group looking like real sea level. Due to understanding the characteristic of wave front, we can continue to discuss the wave group at field ocean or the characteristic of stormy waves which is created from quiet water state. We will use the experimental data of non-linear wave front to illustrate the evolution of it on the research. The experiments were carried out in a super wave flume whose length is 300m, and width is 5m, and height is 5.2m at Tainan Hydraulics Laboratory in National Cheng-Kung University. We analyse the development of non-linear wave front that are derived from two typical non-linear wave train. The two typical non-linear wave train are regular wave and Bichromatic waves. Because the analysis of used Fourier analysis only can show the change in whole frequency, we decide to use wavelet analysis that have analytical ability of frequency and time domain, and also have good ability to analyse Bichromatic waves. We discuss the development of wave front that are derived from deep-water non-linear wave train by using it. From the result of the wavelet analysis, both regular wave and Bichromatic wave clearly show the change of peak frequency at any time. In wavelet spectrum, the peak frequency of high amplitude is taller than steady section. We also discuss the change of wave steepness and phase velocity. Contrasted to wavelet spectrum, we find that the power of slow phase velocity become more concentrated. After wave front separate from leading wave, the frequency of phase velocity and the wave's steepness of the biggest wave also turn into stable value.
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Wei, Ge. "Simulation of water waves by Boussinesq models." 1997. http://catalog.hathitrust.org/api/volumes/oclc/40868412.html.
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Choi, Jongho. "Long nonlinear water waves over a periodic bottom topography." 2000. http://www.library.wisc.edu/databases/connect/dissertations.html.
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Teng, Michelle Hsiao Tsing. "Forced emissions of nonlinear water waves in channels of arbitrary shape." Thesis, 1990. https://thesis.library.caltech.edu/2569/1/Teng_mht_1990.pdf.
Full textAbstract:
This thesis is a joint theoretical, numerical and experimental study concentrated on investigating the phenomenon of weakly nonlinear, weakly dispersive long water waves being generated and propagating in a channel of arbitrary cross section. The water depth and channel width are assumed comparable in size and they may vary both in time and space. Two types of theoretical models, i.e., the generalized channel Boussinesq (gcB) two-equation model and the forced channel Korteweg-de Vries (cKdV) model, are derived by using perturbation expansions for quasi-one-dimensional long waves in shallow water. In the special case for channels of variable shape and dimension but fixed in time, the motion of free traveling solitons may be calculated by our models to predict their propagation with modulated amplitude, velocity and phase. In the precence of external forcings, such as a surface pressure distribution or a submerged obstacle moving with a near critical speed, solitary waves can be produced periodically to advance upstream. Analytical solutions for three specific cross-sectional shapes, namely, the rectangular, triangular and semi-circular sections, are obtained in closed form and with the main features of the solutions examined. The specific geometry of the cross section is found to affect only the magnitude of the dispersive terms in the equations. For a submerged moving object taken as an external forcing, its effective strength of forcing is directly related to the blockage-ratio of the cross-sectional area. Our long-wave models have their useful applications to the areas of river dynamics, near-coastal engineering, and other related fields.
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MARINO, ENZO. "An integrated nonlinear wind-waves model for offshorewind turbines." Doctoral thesis, 2010. http://hdl.handle.net/2158/600464.
Full textAbstract:
This thesis presents a numerical model capable of simulating offshore wind turbines exposed to extreme loading conditions. External condition-based extreme responses are reproduced by coupling a fully nonlinear wave kinematic solver with a hydro-aero-elastic simulator. First, a two-dimensional fully nonlinear wave simulator is developed.
The transient nonlinear free surface problem is formulated assuming the potential theory and a higher-order boundary element method (HOBEM) is implemented to discretize Laplace's equation. For temporal evolution a second-order Taylor series expansion is used. The code, after validation with experimental data, is successfully adopted to simulate overturning plunging
breakers which give rise to dangerous impact loads when they break against wind turbine substructures. The impact force is quanti ed by means of an analytical model and the total hydrodynamic action is nally obtained by adding the impulsive term to the drag and inertial ones.
In the second main core of the thesis, emphasis is placed on the random nature of the waves. Indeed, a global simulation framework embedding the numerical wave simulator into a more general stochastic environment is developed. Namely, rst a linear irregular sea is generated by the spectral approach, then, only on critical space-time sub-domains, the fully nonlinear solver is invoked for a more re ned simulation. The space-time sub-domains are de ned as a wind turbine near eld (space) times a time interval when wave impacts are expected (time). Such a domain decomposition approach permits systematically accounting for dangerous effects on the structural response,
which would be totally missed by adopting linear or weakly nonlinear wave theories alone, without penalizing the computational effort normally required.
At the end of the work the attention is moved to the consequences that the proposed model would have in the quantification of the structural risk.
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Hardjanto, Fauzi Adi. "A computational procedure for three-dimensional simulation of nonlinear gravity wave propagation and response of floating structures." 2002. http://wwwlib.umi.com/cr/utexas/fullcit?p3099461.
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Tung, Chih Ming, and 董志明. "Numerical Simulation on the Transformation of Nonlinear Water Waves over Varying Bottoms." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/17412710652063535601.
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Huang, Jing-Guang, and 黃景光. "Numerical Studies on the Transformation and Mean Water Level Variation of Nonlinear Waves." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/hs453w.
Full textAbstract:
碩士國立成功大學
水利及海洋工程學系碩博士班
90
The Fourier approximation method which depends on the conversation of energy flux and momentum flux with considering of energy loss due to bottom friction and wave breaking regardless of reflection in the shallows is applied to solving the problem of wave transformation on general slope including waves shoaling, breaking and attenuation after breaking as well as wave set-up and set-down during the wave advancing towards the coast. In comparison with the present results as well as experimental data accomplished by the previous method, very good coincidence is obtained. This comparison confirms that present method that solved the waves transformation of the nonlinear waves is applicable. The numerical results that wavelength, wave height, wave energy, energy transmitted velocity, radiation stress and mean water level variation are related to the steepness of deep sea of incident wave and slopes of bottoms, however the influence of slopes on the wavelength, wave height and energy transmitted velocity can be neglected are found. The greater wave steepness of deep sea and slopes are, the faster wave height increases and easier wave breaks. After wave breaks, wave height and set-up are in relation with the wave steepness of deep sea and slopes, that is, the greater wave steepness of deep sea and milder slopes result in the smaller wave height at same water depth and rapider rate of set-up .The computational results of characteristics of breaking waves and attenuation after breaking are compared with experiment data and various available empirical formulas and agreement is found to be good. Finally, the coefficient of shoaling, mean water level variation and attenuation of wave height after breaking will be draw a diagram for designing of engineering.
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Sagers, Jason Derek. "Predicting acoustic intensity fluctuations induced by nonlinear internal waves in a shallow water waveguide." Thesis, 2012. http://hdl.handle.net/2152/ETD-UT-2012-08-6025.
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Many problems in shallow water acoustics require accurate predictions of the acoustic field in space and time. The accuracy of the predicted acoustic field depends heavily on the accuracy of the inputs to the propagation model. Oceanographic internal waves are known to introduce considerable temporo-spatial variability to the water column, subsequently affecting the propagation of acoustic waves. As a result, when internal waves are present, errors in model inputs can significantly degrade the accuracy of the predicted acoustic field. Accurate temporo-spatial predictions of the acoustic field in the presence of internal waves therefore depend largely on one's ability to accurately prescribe the water column properties for the acoustic model. This work introduces a data-driven oceanographic model, named the evolutionary propagated thermistor string (EPTS) model, that captures the temporo-spatial evolution of the internal wave field along a fixed track, thereby permitting prediction of temporal fluctuations in the acoustic field. Simultaneously-measured oceanographic and acoustic data from the Office of Naval Research Shallow Water 2006 experiment are utilized in this work. Thermistor measurements, recorded on four oceanographic moorings spaced along the continental shelf, provide the data from which the EPTS model constructs the internal wave field over a 30 km track. The acoustic data were acquired from propagation measurements over a co-located path between a moored source and a vertical line array. Acoustic quantities computed in the model space, such as received level, depth-integrated intensity, and scintillation index are directly compared to measured acoustic quantities to evaluate the fidelity of the oceanographic model. In addition, a strong correlation is observed between the amplitude of the internal wave field and acoustic intensity statistics at a distant receiving array. It is found that the EPTS model possessed sufficient fidelity to permit the prediction of acoustic intensity distributions in the presence of nonlinear internal waves.text
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Ussembayev, Nail. "Nonlinear Wave Motion in Viscoelasticity and Free Surface Flows." Diss., 2020. http://hdl.handle.net/10754/664399.
Full textAbstract:
This dissertation revolves around various mathematical aspects of nonlinear wave motion
in viscoelasticity and free surface flows.
The introduction is devoted to the physical derivation of the stress-strain constitutive
relations from the first principles of Newtonian mechanics and is accessible to a broad
audience. This derivation is not necessary for the analysis carried out in the rest of the
thesis, however, is very useful to connect the different-looking partial differential equations
(PDEs) investigated in each subsequent chapter.
In the second chapter we investigate a multi-dimensional scalar wave equation with
memory for the motion of a viscoelastic material described by the most general linear
constitutive law between the stress, strain and their rates of change. The model equation is
rewritten as a system of first-order linear PDEs with relaxation and the well-posedness of
the Cauchy problem is established.
In the third chapter we consider the Euler equations describing the evolution of a perfect,
incompressible, irrotational fluid with a free surface. We focus on the Hamiltonian
description of surface waves and obtain a recursion relation which allows to expand the
Hamiltonian in powers of wave steepness valid to arbitrary order and in any dimension. In
the case of pure gravity waves in a two-dimensional flow there exists a symplectic coordinate
transformation that eliminates all cubic terms and puts the Hamiltonian in a Birkhoff
normal form up to order four due to the unexpected cancellation of the coefficients of all
fourth order non-generic resonant terms. We explain how to obtain higher-order vanishing
coefficients.
Finally, using the properties of the expansion kernels we derive a set of nonlinear evolution
equations for unidirectional gravity waves propagating on the surface of an ideal fluid
of infinite depth and show that they admit an exact traveling wave solution expressed in
terms of Lambert’s W-function. The only other known deep fluid surface waves are the
Gerstner and Stokes waves, with the former being exact but rotational whereas the latter
being approximate and irrotational. Our results yield a wave that is both exact and irrotational,
however, unlike Gerstner and Stokes waves, it is complex-valued.
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Nimmala, Seshu B. "An efficient high-performance computing based three-dimensional numerical wave basin model for the design of fluid-structure interaction experiments." Thesis, 2010. http://hdl.handle.net/1957/18829.
Full textAbstract:
Fluid-structure interaction (FSI) is an interesting and challenging interdisciplinary area comprised of fields such as engineering- fluids/structures/solids, computational science, and mathematics. FSI has several practical engineering applications such as the design of coastal infrastructure (such as bridges, levees) subjected to harsh environments from natural forces such as tsunamis, storm surges, etc. Development of accurate input conditions to more detailed and complex models involving flexible structures in a fluid domain is an important requirement for the solution of such problems. FSI researchers often employ methods that use results from physical wave basin experiments to assess the wave forces on structures. These experiments, while closer to the physical phenomena, often tend to be time-consuming and expensive. Experiments are also not easily accessible for conducting parametric studies. Alternatively, numerical models
when developed with similar capabilities will complement the experiments very well because of the lower costs and the ability to study phenomena that are not feasible in the laboratory.
This dissertation is aimed at contributing to the solution of a significant component of the FSI problem with respect to engineering applications, covering accurate input to detailed models and a numerical wave basin to complement large-scale laboratory experiments. To this end, this work contains a description of a three-dimensional numerical wave tank (3D-NWT), its enhancements including the piston wavemaker for generation of waves such as solitary, periodic, and focused waves, and validation using large-scale experiments in the 3D wave basin at Oregon State University.
Performing simulations involving fluid dynamics is computational-intensive and the complexity is magnified by the presence of the flexible structure(s) in the fluid domain. The models are also required to take care of large-scale domains such as a wave basin in order to be applicable to practical problems. Therefore, undertaking these efforts requires access to high-performance computing (HPC) platforms and development of parallel codes. With these objectives in mind, parallelization of the 3D-NWT is carried out and discussed in this dissertation.Graduation date: 2011
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Chien, Shao-Chin, and 簡紹欽. "Numerical modeling of nonlinear waves in regional coastal waters." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/82865861665453872595.
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碩士國立臺灣大學
土木工程學系
86
Numerical modeling of nonlinear waves in regional coastal waters Shao-Chin Chien Abstract This research is to study the wave deformation under nonlinear effects, and to develop a numerical model of nonlinear waves to describe the wave propagation from deep seas to shallow waters. Based on the results of Wu (1996), a two-dimensional numerical model of nonlinear waves is developed by using finite element method. It can compute the wave field in an irregular region with varying depths. Due to the fact of using perturbation methods, present model provides both linear and nonlinear solutions. To extend applicability of this model, a general sparse method to minimize the computer storage requirement is integrated. It is found that with same computer resource, this model can use more meshes to calculate more precise solutions. Comparisons of present numerical results with experimental data are performed ( Beji & Battjes, 1994; Kittitanasuan, Goda & Shiobara, 1993 ). In weakly nonlinear effects, this model can describe the spatial wave profile and time series wave profile accurately. Computing the wave field around a circular island with paraboloid-varied depths, nonlinear motions of waves with reflection, diffraction and refraction are studied.