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1
Jamali, Mirmosadegh. "Surface wave interaction with oblique internal waves". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0024/NQ38904.pdf.
Testo completo
2
Leaman, Nye Abigail. "Scattering of internal gravity waves". Thesis, University of Cambridge, 2011. https://www.repository.cam.ac.uk/handle/1810/238679.
Testo completoAbstract (sommario):
Internal gravity waves play a fundamental role in the dynamics of stably stratified regions of the atmosphere and ocean. In addition to the radiation of momentum and energy remote from generation sites, internal waves drive vertical transport of heat and mass through the ocean by wave breaking and the mixing subsequently produced. Identifying regions where internal gravity waves contribute to ocean mixing and quantifying this mixing are therefore important for accurate climate and weather predictions. Field studies report significantly enhanced measurements of turbulence near 'rough' ocean topography compared with those recorded in the ocean interior or near more gradually varying topography (e.g. Toole et al. 1997, J. Geophys. Res. 102). Such observations suggest that interaction of waves with rough topography may act to skew wave energy spectra to high wavenumbers and hence promote wave breaking and fluid mixing. This thesis examines the high wavenumber scatter and spatial partitioning of wave energy at 'rough' topography containing features that are of similar scales to those characterising incident waves. The research presented here includes laboratory experiments using synthetic schlieren and PIV to visualise two-dimensional wavefields produced by small amplitude oscillations of cylinders within linear salt-water stratifications. Interactions of wavefields with planar slopes and smoothly varying sinusoidal topography are compared with those with square-wave, sawtooth and pseudo knife-edge profiles, which have discontinuous slopes. Far-field structures of scattered wavefields are compared with linear analytical models. Scatter to high wavenumbers is found to be controlled predominantly by the relative slopes and characterising length scales of the incident wavefield and topography, as well as the shape and aspect ratio of the topographic profile. Wave energy becomes highly focused and the spectra skewed to higher wavenumbers by 'critical' regions, where the topographic slope is comparable with the slope of the incident wave energy vector, and at sharp corners, where topographic slope is not defined. Contrary to linear geometric ray tracing predictions (Longuet-Higgins 1969, J. Fluid Mech. 37), a significant back-scattered field can be achieved in near-critical conditions as well as a forward scattered wavefield in supercritical conditions, where the slope of the boundary is steeper than that of the incident wave. Results suggest that interaction with rough benthic topography could efficiently convert wave energy to higher wavenumbers and promote fluid mixing in such ocean regions.
3
Fedorov, Alexey V. "Nonlinear effects in surface and internal waves /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1997. http://wwwlib.umi.com/cr/ucsd/fullcit?p9737309.
Testo completo
4
Hurley, David Lee. "Wind waves and internal waves in Base Mine Lake". Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/62524.
Testo completoAbstract (sommario):
Syncrude's Base Mine Lake is the first commercial scale demonstration of end pit lake technology in the Canadian Oil Sands. Following its commissioning in 2012 significant efforts have been made to monitor and understand its evolution. Of particular interest is the impact of surface and internal waves on the resuspension of fluid fine tailings and the effect of hydrocarbons on surface wind wave formation and growth. In this study the first complete description of the wind and internal waves in Base Mine Lake is presented.
Observations of surface wind waves were collected using two subsurface pressure gauges. Data revealed that wind waves in Base Mine Lake have short residence times and rarely generate bottom orbital velocities capable of resuspending fluid fine tailings. Additionally, numerical simulations of the wind waves in Base Mine Lake were performed with the SWAN model. Modeled wave heights were in good agreement with observations, and resuspension of fluid fine tailings was minimal even during the 10 year storm event.
As the surface of Base Mine Lake contains a hydrocarbon film its impact on surface wind waves was investigated in the laboratory and field. It was found that the hydrocarbon film dampens high frequency wind waves and results in a slower growing wind wave field dominated by longer wavelengths. Additionally, the presence of hydrocarbons also increases the critical wind speed needed to initiate wave growth. From these findings it is postulated that the hydrocarbon film on Base Mine Lake acts to decrease the fluxes of momentum, gas, and heat.
The internal waves in Base Mine Lake were simulated using Delft3D Flow. Simulated wave heights as large as 3 m were shown to oscillate for multiple days with little dampening, and despite the small surface area of Base Mine Lake (8 km²) the internal waves were significantly influenced by the Coriolis force. This influence was seen in the form of simulated Kelvin and Poincaré waves which resulted in complex circulation patterns within the lake. The findings presented here provide a first picture into the impacts of waves on the reclamation of Base Mine Lake.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
5
Lerczak, James A. "Internal waves on the southern California shelf /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2000. http://wwwlib.umi.com/cr/ucsd/fullcit?p3035419.
Testo completo
6
Horne, Iribarne Ernesto. "Transport properties of internal gravity waves". Thesis, Lyon, École normale supérieure, 2015. http://www.theses.fr/2015ENSL1027/document.
Testo completoAbstract (sommario):
Les ondes internes sont produites par suite de l’équilibre dynamique entre les forces de flottabilité et la gravité quand une particule de fluide est déplacée verticalement dans un milieu stratifié stable. Les systèmes géophysiques tels que océan et l’atmosphère sont naturellement stratifiés et donc favorables à la propagation des ondes internes. En outre, ces deux environnements stockent une grande quantité de particules tant dans leur intérieur que sur les bords. Par conséquent, les ondes internes et les particules vont inévitablement interagir dans ces systèmes. Au cours de ce travail, des expériences exploratoires sont réalisées pour étudier le transport par érosion des particules, généré par les ondes internes. Afin de déterminer un seuil de transport, les propriétés particulières des réflexions d’ondes internes («réflexion critique ») sont utilisées pour augmenter l’intensité du champ d’ondes à la surface de réflexion. Une méthode a été développée en collaboration avec une équipe de traitement du signal pour améliorer la détermination des composantes de l’onde impliquées dans une réflexion quasi critique. Cela nous a permis de comparer nos résultats expérimentaux avec une théorie de la réflexion critique, montrant un bon accord et permettant d’extrapoler ces résultats à des expériences au-delà de la nôtre et à des conditions océaniques. Nous avons aussi étudié l’interaction des ondes internes avec une colonne de particules en sédimentation. Deux effets principaux ont été observés : la colonne oscille autour d’une position d’équilibre, et elle est déplacée dans son ensemble. La direction du déplacement de la colonne est expliquée par le calcul de l’effet de la dérive Lagrangienne produite pour des ondes. Cet effet pourrait également expliquer la dépendance en fréquence du déplacementInternal waves are produced as a consequence of the dynamic balance between buoyancy and gravity forces when a particle of fluid is vertically displaced in a stably stratified environment. Geophysical systems such as ocean and atmosphere are naturally stratified and therefore suitable for internal waves propagation. Furthermore, these two environments stock a vast amount of particles at their boundaries and in their bulk. Therefore, internal waves and particles will inexorably interact in these systems. In this work, exploratory experiments are performed to study wave generated erosive transport of particles. In order to determine a transport threshold, the peculiar properties of internal waves (“critical reflection”) are employed to increase the intensity of the wave field at the boundaries. A method was developed in collaboration with a signal processing team to improve the determination of the wave components involved in near-critical reflection. This method enabled us to compare our experimental results with a theory of critical reflection, showing good agreement and allowing to extrapolate these results to experiments beyond ours and to oceanic conditions. In addition, we study the interaction of internal waves with a column of particles in sedimentation. Two main effects are observed: the column oscillates around an equilibrium position, and it is displaced as a whole. The direction of the displacement of the column is explained by computing the effect of the Lagrangian drift of the waves. This effect could also explain the frequency dependence of the displacement
7
Nicolaou, D. "Internal waves around a moving body". Thesis, University of Manchester, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383254.
Testo completo
8
Potter, Robert Colin Henry. "Internal waves in the Andaman Sea". Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342768.
Testo completo
9
Dobra, Tom. "Nonlinear interactions of internal gravity waves". Thesis, University of Bristol, 2019. http://hdl.handle.net/1983/4a3f99e2-5e73-4c7c-8d3d-e1141fb23dda.
Testo completoAbstract (sommario):
Internal waves carry more available energy than any other transmission system on Earth: lunar diurnal excitation drives 1 TW of wave power inside the world's oceans. Energy is transmitted over thousands of kilometres and individual waves may be hundreds of metres high. Where they break, they deposit their energy, and, in such regions, they greatly enhance the vertical transport of carbon dioxide, oxygen and heat. Despite their significance, much remains to be understood about internal waves, and this thesis explores some of these questions using a combination of experiments and theory. One way to generate internal waves is by sinusoidally oscillating the boundary of the fluid. A full spectrum of harmonics is generated, whose phases and amplitudes are predicted by perturbation theory. Their origin is identified solely as nonlinear geometric excitation at the boundary; no interactions between the harmonics of the same infinitely wide, monochromatic input are possible within the fluid. However, for narrow wave beams, resonant triadic wave-wave interactions are predicted using a novel numerical implementation of the singular two-dimensional Green's function. To verify the predictions, a new experiment was designed, consisting of an electronically actuated "magic carpet" inserted into the base of a tank. It perturbs the fluid lying above its surface to generate internal waves of almost any shape and size. The carpet is actuated by an array of 100 stepper motors, which are controlled by bespoke software that manages the timing in increments of 30 ns; this ensures precise spatiotemporal control of the waveform. The carpet itself is made of a neoprene-nylon composite, and its bending behaviour is modelled in detail to characterise the waveform imparted on the fluid. The experiments support the theoretical predictions, but also permit strongly nonlinear regimes, such as wave breaking, at amplitudes above the applicable domain of the theory.
10
Thomas, Alexandra Elizabeth. "The interaction of an internal solitary wave with surface gravity waves". Thesis, University of Edinburgh, 2002. http://hdl.handle.net/1842/13106.
Testo completoAbstract (sommario):
Solitary waves are nonlinear, non-oscillatory disturbances of permanent form. Recent advances in synthetic aperture radar imaging and analysis techniques have confirmed in situ observations and measurements that the passage of oceanic internal waves, and in particular internal solitary waves, is associated with modulations in sea surface roughness. It has not only revealed the ubiquity of this phenomenon but also highlighted the global existence of large amplitude, tidally induced, internal solitary waves. It appears, however, that little laboratory-based research has been carried out in this field. This work, therefore, focusses on the study of surface wavetrain modulations resulting from the passage of a single internal solitary wave. Digital Particle Image Velocimetry (DPIV) and Planar Laser Induced Fluorescence (PLIF) were employed to provide two-dimensional instantaneous velocity and density information respectively. Previous studies in this field have been performed with intrusive probe techniques, disturbing the fluid flow during measurement. Preliminary DPIV and PLIF experiments were performed on single internal solitary waves in a two-layer brine - fresh water stratification. To the author’s knowledge, the application of PLIF to the study of these waves had not been done previously. Results from the DPIV measurements concurred with previous research and highlighted the constraints of the DPIV system. The results were also compared to a recently developed and validated fully nonlinear numerical method. From the interaction investigations, both wavelength and amplitude modulations of the surface waves as a function of solitary wave phase were observed. In some cases, the shape of the internal wave was also affected. Velocity profiles were compared to the linear superposition of surface wave linear theory and the fully nonlinear numerical method. In addition, the PLIF analysis showed that, for the wave and stratification parameters investigated, there was no evidence for the compression and expansion of the density interface during the interaction.
11
Sun, Haili. "Ray-tracing internal wave/wave interactions and spectral energy transfer /". Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/10973.
Testo completo
12
Ghaemsaidi, Sasan John. "Interference and resonance of internal gravity waves". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101532.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 91-96).
Internal waves are propagating disturbances within stratified fluids, arising from a balance of gravity, buoyancy, and rotation. As well as being of fundamental scientific interest, they are ubiquitous in a variety of forms in the Earth's oceans, where they are responsible for driving vertical mixing. And it is the rule, rather than the exception, that internal waves propagate through a varying background density stratification. We begin by theoretically studying internal waves that are harmonically forced at a horizontal level above a semi-infinite, non-uniform density stratification. Starting with a two-layer model, we identify the existence of resonance peaks and diminution troughs in the wave transmission spectra, and provide physical insight through the application of ray theory. Thereafter, we proceed to consider smoothly varying stratifications, demonstrating that these resonance and diminution features persist beyond simple models. We conclude by considering the relevance of the results to geophysical settings. As an example, we demonstrate that an ocean stratification is inherently tuned to transmit internal wave energy to the deep ocean at specific combinations of wavelength and frequency. Subsequently, we perform a laboratory experimental study of an internal wave field generated by harmonic, spatially-periodic surface forcing of a strongly-stratified, thin upper layer sitting atop a weakly-stratified, deep lower layer. In linear regimes, the energy flux associated with relatively high frequency internal waves is prevented from entering the lower layer by virtue of evanescent decay. In the experiments, however, we find that the development of parametric subharmonic instability (PSI) in the upper layer transfers energy from the forced primary wave into a pair of subharmonic daughter waves, each capable of penetrating the weakly-stratified lower layer. We find that around 10% of the primary wave energy penetrates into the lower layer via this nonlinear wave-wave interaction for the regime we study. With an emphasis on assessing the role of interference in tuning wave transmission, we perform a series of laboratory experiments in order to measure resonance and diminution in the aforementioned non-uniform stratification. We find that the occurrence of destructive interference in the upper stratification layer naturally yields diminution of the transmitted wave. Conversely, constructive interference results in a notable amplification of the wave field over time scales on the order of the forcing period; the development of nonlinear wave-wave interactions due to wave amplification is observed over longer time scales. Good agreement is obtained between the experimental results and a weakly viscous, long wave model of our system within the linear regime. Given the ubiquity of layering in environmental stratifications, an interesting example being double-diffusive staircase structures in the Arctic water column, we furthermore present the results of a joint theoretical and laboratory experimental study investigating the impact of multiple layering on internal wave propagation. We first present results for a simplified model that demonstrates the nontrivial impact of multiple layering. Incident waves of particular length and time scales can experience constructive interference taking place within the alternating stratified and mixed layers, which in turn appreciably enhances wave transmission. Thereafter, utilizing a weakly viscous, linear model that can handle arbitrary vertical stratifications, we perform a comparison of theory with experiments finding excellent qualitative and quantitative agreement. We conclude by applying this model to a case study of a staircase stratification profile obtained from the Arctic Ocean, finding a rich landscape of transmission behavior.
by Sasan John Ghaemsaidi.
Ph. D.
13
Franklin, James. "Laboratory modelling of breaking internal solitary waves". Thesis, University of Dundee, 2014. https://discovery.dundee.ac.uk/en/studentTheses/bf2741dd-7183-4aa5-817e-f5d533269c95.
Testo completo
14
Hakes, Kyle Jeffrey. "Tidally Generated Internal Waves from Asymmetric Topographies". BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8717.
Testo completoAbstract (sommario):
Internal waves are generated in stratified fluids, like the ocean, where density increases with depth. Tides are one of the major generation mechanisms of internal waves. As the tides move water back and forth over underwater topography, internal waves can be generated. The shape of the topography plays a major part in the properties of the generated internal wave and the type of wave and energy is known for multiple symmetric topographies, such as Gaussian or sinusoidal. In order to further understand the effects topographic shape plays, the effect of asymmetry on internal waves is investigated. First, two experimental methods are compared to evaluate which will capture the relevant information for comparing waves generated from oscillating asymmetric topographies. Two experimental methods are often used in internal wave research, Synthetic Schlieren (SS) and Particle Image Velocimetry (PIV). Both SS and PIV experimental methods are used to analyze a set of experiments in a variety of density profiles and with a variety of topographies. The results from these experiments are then compared both qualitatively and quantitatively to decide which method to use for further research. In the setup, the larger field of view of SS results in superior resolution in wavenumber analysis, when compared to PIV. In addition, SS is 25% faster to setup and significantly cheaper. These are the deciding factors leading to the selection of SS as the preferred experimental method for further tests regarding tidally generated internal waves from asymmetric topographies. Previous experimental and theoretical research on tidally generated internal waves has most often used symmetric topographies. However, due to the complex nature of real ocean topography, the effect of asymmetry can not be overlooked. A few studies have shown that asymmetry can have a significant effect on internal wave generation, but topographic asymmetry has not been studied in a systematic manner up to this point. This work presents a comparison of tidally generated internal waves from nine different asymmetric topographies, consisting of a steeper Gaussian curve on one side, and a wider Gaussian curve on the other. The wider curve has varying amplitude from 1 to 0.6 of the steeper curve's amplitude, and two oscillation frequencies are explored. First, kinetic energy density in tidally generated internal waves is compared qualitatively and quantitatively, in both physical and Fourier space. When compared to similar symmetric topographies, the asymmetric topographies varied distinctly in the amount of internal wave kinetic energy generated. In general, internal wave kinetic energy generated from asymmetric topographies is higher for waves generated at a lower frequency than at a higher frequency. Also, kinetic energy is higher in internal waves on the relatively steeper side of the topography. There is very little kinetic energy in the higher wavenumbers, with most of the internal waves being generated at the lower wavenumbers. The amplitude does not make an appreciable difference in the wavenumber at which the internal waves are generated. Thus, the differences quantified here are due solely to changing slope, showing a significant impact of a relatively slight asymmetry.
15
Smith, Sean Paul. "Laboratory Experiments on Colliding Nonresonant Internal Wave Beams". BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3300.
Testo completoAbstract (sommario):
Internal waves are prominent fluid phenomena in both the atmosphere and ocean. Because internal waves have the ability to transfer a large amount of energy, they contribute to the global distribution of energy. This causes internal waves to influence global climate patterns and critical ocean mixing. Therefore, studying internal waves provides additional insight in how to model geophysical phenomena that directly impact our lives. There is a myriad of fluid phenomena with which internal waves can interact, including other internal waves. Equipment and processes are developed to perform laboratory experiments analyzing the interaction of two colliding nonresonant internal waves. Nonresonant interactions have not been a major focus in previous research. The goal of this study is to visualize the flow field, compare qualitative results to Tabaei et al., and determine the energy partition to the second-harmonic for eight unique interaction configurations. When two non-resonant internal waves collide, harmonics are formed at the sum and difference of multiples of the colliding waves' frequencies. In order to create the wave-wave interaction, two identical wave generators were designed and manufactured. The interaction flow field is visualized using synthetic schlieren and the energy entering and leaving the interaction region is analyzed. It is found that the energy partitioned to the harmonics is much more dependent on the general direction the colliding waves approach each other than on the angle. Depending on the configurations, between 0.5 and 7 percent of the energy within the colliding waves is partitioned to the second-harmonics. Interactions in which the colliding waves have opposite signed vertical wavenumber partition much more energy to the harmonics. Most of the energy entering the interaction is dissipated by viscous forces or leaves the interaction within the colliding waves. For all eight configurations studied, 5 to 8 percent of the energy entering the interaction has an unknown fate.
16
Kim, Sungphil. "Internal Tides and Internal Solitary Waves in the Northern South China Sea". NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-05152009-141246/.
Testo completoAbstract (sommario):
Large-amplitude internal solitary waves (ISWs) are frequently observed in the northern South China Sea (SCS). In a project sponsored by the US Office of Naval Research, four moorings were deployed between the Luzon Strait and the Chinese continental shelf by Steve Ramp of the Naval Postgraduate School and David Tang of National Taiwan University from late April 2005 to May 2006. Several CTD sections were taken during April and July in 2005. Satellite pictures were also collected during that period. In this study, these data were used to examine the characteristics, generation, and propagation of ISWs. In the satellite images, monthly change in stratification may cause northward shift of the propagation path, and ISWs are more frequently observed in July than in April and May. Speed estimation shows that ISWs propagate faster in the deep basin than over the continental margin and near the ridge. The generation of internal tides correlates with the eastward tidal flow over the ridge, while ISWs are produced by northwestward tidal currents over the ridges in the Luzon Strait.
17
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.
Testo completo
18
Aigner, Andreas 1972. "Numerical simulations of internal and inertial solitary waves". Monash University, Dept. of Mathematics and Statistics, 2001. http://arrow.monash.edu.au/hdl/1959.1/8880.
Testo completo
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Sherwin, T. J. "Internal waves and mixing processes in shelf seas". Thesis, Bangor University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308320.
Testo completo
20
Griffiths, R. M. "The interaction between vorticity and internal gravity waves". Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599729.
Testo completoAbstract (sommario):
Our dissertation investigates the interaction between a localised region of vorticity and internal gravity waves, using only analytical methods. We aim to understand further the mechanism by which internal gravity waves radiate vorticity and to address the validity of applying an analogy of Lighthill's sound generation theory to the generation of internal gravity waves. We consider an initial value problem for a two-dimensional incompressible density-stratified fluid. The buoyancy frequency is taken to be constant and the Boussinesq approximation is imposed. To make the analysis as general as possible, and more importantly to assess the importance of nonlinear mechanisms in the generation of internal gravity waves, we include nonlinear terms in the equations of motion. To make further analytical progress we consider the case of a large internal Froude number Fr, which is more often realised in physical scenarios. We attempt solutions to the equations of motion via asymptotic expansions in the small parameter ε = 1/Fr2. We consider the main results of the dissertation to be twofold. First we see the appearance of distinct regions in space-time where different dominant balances occur in the equations of motion. In particular we have an inner region, a far field and a wave region, and we have been able to perform an asymptotic matching of the different solutions in these regions successfully. The magnitude of these regions is characterised by the small parameter ε. It is hoped that the existence of such regions could be confirmed experimentally. Such space-time regions do not occur in the linear analysis of this problem, but are only evident when nonlinear terms are retained in the equations of motion. The second part of our analysis that we consider to be important arises through the study of the dynamics of vorticity transfer in our problem. The introduction of stratification destroys conservation of vorticity; the non-conservation of vorticity is observed in the inner region and the far field.
21
Perry, Jonathan Redvers. "The radar remote sensing of oceanic internal waves". Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47220.
Testo completo
22
Richardson, Alan Ph D. Massachusetts Institute of Technology. "Seismic imaging using internal multiples and overturned waves". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98671.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 199-205).
Incorporating overturned waves and multiples in seismic imaging is one of the most plausible means by which imaging results might be improved, particularly in regions of complex subsurface structure such as salt bodies. Existing migration methods, such as Reverse Time Migration, are usually designed to image solely with primaries, and so do not make full use of energy propagating along other wave paths. In this thesis I describe several modifications to existing seismic migration algorithms to enable more effective exploitation of the information contained in these arrivals to improve images of subsurface structure. This is achieved by extending a previously proposed modification of one-way migration so that imaging with overturned waves is possible, in addition to multiples and regular primaries. The benefit of using this extension is displayed with a simple box model and the BP model. In the latter, the proposed method is able to image the underside of a salt overhang when even RTM fails, although substantial artifacts are also present. Progressing to the two-way wave equation, I explain three new ways in which a wavefield may be separated by wave propagation direction, and use these in proposed modifications to the RTM algorithm. With these modifications, overturned waves and multiples can be used more effectively, as they no longer risk subtracting from the image contributions of primaries, their amplitude is boosted to produce greater relative amplitude accuracy, and artifacts usually associated with the use of these arrivals are attenuated. The modifications also provide two means of expressing image uncertainty. Among the results I show are a demonstration of the superior image obtained using the proposed method compared to the source-normalized imaging condition, and an improved image of a salt body in the SEAM model. Finally, I describe another modification to RTM that further reduces artifacts associated with the inclusion of multiples, exhibiting its effectiveness with simple layer models, and on a portion of the SEAM model.
by Alan Richardson.
Ph. D.
23
Pringle, James M. "Cooling and internal waves on the Continental Shelf". Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/58861.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1998.Includes bibliographical references.
by James Maxwell Pringle.
Ph.D.
24
Gómez, Giraldo Evelio Andrés. "Observations of energy transfer mechanisms associated with internal waves /". Connect to this title, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0045.
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Winters, Kraig B. "Intensification and instability of internal gravity waves at caustics and critical levels /". Thesis, Connect to this title online; UW restricted, 1989. http://hdl.handle.net/1773/6792.
Testo completo
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Raja, Keshav Jayakrishnan. "Internal waves and mean flow in the presence of topography". Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAU006/document.
Testo completoAbstract (sommario):
Les ondes internes jouent un rôle important dans de nombreux processus dans les océans.L’interaction entre les vagues internes et la topographie océanique a longtemps été un champ de recherche actif. Pourtant, il reste beaucoup de questions sur le sujet. Dans cette thèse, deux processus principaux sont examinés, à savoir la réflexion de faisceaux d’ondes internes sur une pente, et la génération d’ondes sous le vent sur un obstacle tridimensionnel, en utilisant des expériences de laboratoire et des simulations numériques.La réflexion non linéaire d’un faisceau d’onde interne sur une pente uniforme est étudiée à l’aide de la théorie des invisques bidimensionnels et de simulations numériques. Les interactions triadiques résonnantes entre les faisceaux d’ondes incidentes, réfléchies et de deuxième harmonique sont étudiées en développant la théorie existante et en les vérifiant avec des résultats pour des simulations numériques.Dans le cas de la réflexion de faisceaux d’ondes internes tridimensionnels, un fort flux horizontal moyen est induit par le faisceau d’onde, qui perturbe le champ d’onde et affaiblit les secondes harmoniques. La génération de ce flux moyen induit par les vagues est examinée à l’aide des résultats d’expériences et de simulations numériques tridimensionnelles. De plus,les effets de la rotation de fond sur le débit moyen induit par les vagues sont également étudiés à l’aide de simulations numériques.Le courant circumpolaire antarctique est considéré comme l’une des principales sources de mélange dans les océans. La modélisation en laboratoire du courant circumpolaire antarctique a été réalisée sur la plate-forme de Coriolis à LEGI pour étudier la traînée induite par la topographie sur le courant. L’expérience et ses résultats sont également présentésInternal waves play an important role in many processes in oceans. The interaction be-tween internal waves and ocean topography has been an active field of research for long. Yetthere are many questions remaining on the topic. In this thesis, two main processes are ex-amined namely, the reflection of internal wave beams on a slope, and generation of lee wavesover a three-dimensional obstacle, using laboratory experiments and numerical simulations.The nonlinear reflection of an internal wave beam on a uniform slope is studied using two-dimensional inviscid theory and numerical simulations. The resonant triadic interactionsamong the incident, reflected and second harmonic wave beams are investigated developingon existing theory and verifying them with results for numerical simulations.In the case of reflection of three-dimensional internal wave beams, a strong mean horizon-tal flow is found to be induced by the wave beam, which perturbs the wave field and weakensthe second harmonics. The generation of this wave-induced mean flow is examined usingresults from experiments and three-dimensional numerical simulations. Furthermore, theeffects of background rotation on the wave induced mean flow are also studied using numer-ical simulations.The Antarctic Circumpolar Current is considered as one of the main sources of mixing inoceans. Laboratory modelling of the Antarctic Circumpolar Current was done in the Coriolisplatform at LEGI to study the topography induced drag on the current. The experiment andits results are also presented
27
Helfrich, L. Cody. "Estimating oceanic internal wave energy from seismic reflector slope spectra". Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1594476671&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
Testo completo
28
Gomez, Giraldo Evelio Andres. "Observations of energy transfer mechanisms associated with internal waves". University of Western Australia. Centre for Water Research, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0045.
Testo completoAbstract (sommario):
[Truncated abstract] Internal waves redistribute energy and momentum in stratified lakes and constitute the path through which the energy that is introduced at the lake scale is cascaded down to the turbulent scales where mixing and dissipation take place. This research, based on intensive field data complemented with numerical simulations, covers several aspects of the energy flux path ranging from basin-scale waves with periods of several hours to high frequency waves with periods of few minutes. It was found that, at the basin-scale level, the horizontal shape of the lake at the level of the metalimnion controls the period and modal structure of the basin-scale natural modes, conforming to the dispersion relationship of internal waves in circular basins. The sloping bottom, in turn, produces local intensification of the wave motion due to focusing of internal wave rays over near-critical slopes, providing hot spots for the degeneration of the basin-scale waves due to shear instabilities, nonlinear processes and dissipation. Different types of high-frequency phenomena were observed in a stratified lake under different forcing conditions. The identification of the generation mechanisms revealed how these waves extract energy from the mean flow and the basin-scale waves. The changes to the stratification show that such waves contribute to mixing in different ways . . . Detailed field observations were used to develop a comprehensive description of an undocumented energy flux mechanism in which shear-instabilities with significant amplitudes away from the generation level are produced in the surface layer due to the shear generated by the wind. The vertical structure of these instabilities is such that the growing wave-related fluctuations strain the density field in the metalimnion triggering secondary instabilities. These instabilities also transport energy vertically to the thermocline where they transfer energy back to the mean flow through interaction with the background shear.
29
Mahta, Adarsh P. "Excitation of internal waves in a three-layer fluid". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0015/MQ47068.pdf.
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Blumenthal, Martin Benno. "Interpretation of equatorial current meter data as internal waves". Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/51460.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, and Woods Hole Oceanographic Institution, 1987.Bibliography: v. 2, leaves 376-381.
by Martin Benno Blumenthal.
Ph.D.
31
MARKOVIĆ, SARA. "Internal waves and turbulent mixing in closed stratified basins". Doctoral thesis, Università degli Studi di Trieste, 2021. http://hdl.handle.net/11368/2996098.
Testo completoAbstract (sommario):
We present results of numerical simulations of a stratified reservoir with a three-layer stratification, subject to an oscillating surface shear stress. The simulations are carried out at a laboratory scale, using Large Eddy Simulation. We solve the three-dimensional Navier-Stokes equations under the Boussinesq approximation using a second-order accurate finite volume solver. The model was validated by reproducing experimental results for the reservoir response to surface shear stress and resonant frequencies of internal waves.
In the first part of our research, we investigate the effect of sloped end-walls on mixing and internal wave adjustment to forcing within the basin, for three different periods of forcing. We find interesting combinations of wave modes and mixing under variation of the forcing frequencies and of the inclination of the end-walls. When the frequency of the forcing is close to the fundamental mode wave frequency, a resonant internal seiche occurs and the response is characterized by the first vertical mode. For forcing periods twice and three times the fundamental period the dominant response is in terms of the second vertical mode. Adjustment to forcing via second vertical mode is accompanied by the cancellation of the fundamental wave and energy transfer towards the high-frequency waves. The study shows that the slope of the end-walls dramatically affects the location of mixing, which has feedback on the wave field promoting higher vertical modes.
The second part of our research is devoted to the investigation of the influence of Earth's rotation on the wave field. In this case, the ratio of forcing to inertial period plays the important role in discerning whether Kelvin or Poincare type waves will be excited which has direct consequences on the wave modal structure and the turbulent quantities. Superinertial forcing frequency excites Poincare waves that are observed to increase the amount of turbulent dissipation rate in the system. In the two cases, where the forcing period was half and twice the fundamental one, we observed that superinertial forcing frequency pushed the dominant internal wave response from first to second vertical mode. The study shows that the increase of the importance of the rotation rate over forcing increases the turbulent dissipation rate in the interior while decreasing it in the near-surface and near-boundary regions.
32
FRATERNALE, FEDERICO. "Internal waves in fluid flows. Possible coexistence with turbulence". Doctoral thesis, Politecnico di Torino, 2017. http://hdl.handle.net/11583/2687873.
Testo completoAbstract (sommario):
Waves in fluid flows represents the underlying theme of this research work. Wave interactions in fluid flows are part of multidisciplinary physics. It is known that many ideas and phenomena recur in such apparently diverse fields, as solar physics, meteorology, oceanography, aeronautical and hydraulic engineering, optics, and population dynamics. In extreme synthesis, waves in fluids include, on the one hand, surface and internal waves, their evolution, interaction and associated wave-driven mean flows; on the other hand, phenomena related to nonlinear hydrodynamic stability and, in particular, those leading to the onset of turbulence. Close similarities and key differences exist between these two classes of phenomena. In the hope to get hints on aspects of a potential overall vision, this study considers two different systems located at the opposite limits of the range of existing physical fluid flow situations: first, sheared parallel continuum flows - perfect incompressibility and charge neutrality - second, the solar wind - extreme rarefaction and electrical conductivity. Therefore, the activity carried out during the doctoral period consists of two parts. The first is focused on the propagation properties of small internal waves in parallel flows. This work was partly carried out in the framework of a MISTI-Seeds MITOR project proposed by Prof. D. Tordella (PoliTo) and Prof. G. Staffilani (MIT) on the long term interaction in fluid flows. The second part regards the analysis of solar-wind fluctuations from in situ measurements by the Voyagers spacecrafts at the edge of the heliosphere. This work was supported by a second MISTI-Seeds MITOR project, proposed by D. Tordella (PoliTo), J. D. Richardson (MIT, Kavli Institute), with the collaboration of M. Opher (BU).
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KIANI, HARCHEGANI Farkhondeh. "The role of internal waves in ancient carbonate systems". Doctoral thesis, Università degli studi di Ferrara, 2019. http://hdl.handle.net/11392/2478779.
Testo completoAbstract (sommario):
Le onde interne sono delle perturbazioni che si propagano lungo la picnoclina, la superficie che delimita due masse d’acqua a differente densità. Sebbene siano ben note dagli oceanografi e dai biologi marini, il loro impatto sul record sedimentario è ancora poco conosciuto e documentato, e in alcuni casi completamente ignorato da Sedimentologi e Stratigrafi.
Nei sistemi carbonatici le onde interne, oltre a creare gli stessi effetti idrodinamici dei sistemi silicoclastici, possono influenzare la produzione carbonatica in prossimità della picnoclina attraverso il pompaggio di acque più o meno ricche di nutrienti, creando un contesto ideale in cui le comunità bentoniche di metazoi possano proliferare. Infatti, la base della picnoclina è comunemente associata con la zona di massima concentrazione della clorofilla e che in alcuni contesti coincide con la parte bassa della zona fotica.
Un altro fattore di controllo importante nei sistemi carbonatici è la penetrazione della luce che condiziona il tipo, la quantità e il luogo di produzione carbonatica.
Recentemente, le onde interne sono state considerate come potenziale processo che potrebbe spiegare la presenza e sviluppo di numerose carbonate factories meso/oligophotiche e le loro peculiari associazioni di facies.
Durante il Giurassico Superiore e l’Oligocene superiore, diversi sistemi carbonatici si sono sviluppati lungo i margini della Tetide o dell’area Mediterranea. In questo progetto di dottorato, sono stati considerati tre casi studio ricadenti in questo intervallo temporale allo scopo di caratterizzare le facies di margine biocostruito e il possibile ruolo delle onde interne nello sviluppo e ubicazione di questi sistemi carbonatici.
Le facies ricche di stromatoporoidi del Giurassico Superiore dei Calcari di Monte Sacro (MSL) affiorano lungo il margine della Piattaforma Carbonatica Apula (ACP) nel Promontorio del Gargano. La MSL è caratterizzata da tre facies LF1-stromatoporoidi-rich, facies LF2-stromatoporoidi-coralli e facies LF3-stromatoporoidi-microbialiti. LF1 è la litofacies principale sviluppata nei MSL e caratterizzata dalla crescita di stromatoporoidi in condizioni mesofotiche a bassa energia (LF1-S1) associate a facies di alta energia intraclastiche-bioclastiche (LF1-S2). L'origine delle facies ad alta energia in MSL può essere collegata all'azione delle onde interne. In primo luogo, le onde interne possono fornire i nutrienti necessari per la crescita dei buildup a stromatoporoidi. Questi accumuli possono essere influenzati periodicamente da turbolenza, producendo una grande quantità di facies detritiche di alta energia (LF1-S2).
Per i sistemi dell’Oligocene superiore sono stati scelti due sistemi carbonatici caratterizzati da facies con abbondanti coralli, ubicati rispettivamente nel Promontorio del Gargano e nell’Iran Centrale (Monti Zagros). La facies ricca di coralli dell'Oligocene superiore (Cattiano) è ben sviluppata nei Calcari di Grotta di San Michele (GSML) nel Gargano, e nella Formazione di Asmari, Monti Zagros, Iran.
I coralli della GSML sono circondati da una matrice dominata da sedimenti fini fangosi, e che indica un ambiente a bassa energia. Sebbene questi coralli mesofotici possano essere mescolati con componenti eufotici le onde interne possono essere un fattore per fornire acqua ricca di nutrienti per le colonie di coralli che si sviluppino in queste condizioni a bassa energia.Internal waves are perturbations propagating along the pycnocline, a boundary layer between two different density water masses. Although they are well known by oceanographers, their impact on the sedimentary record still poorly documented. In carbonate settings, internal waves can influence the carbonate production at the depth of pycnocliene by pumping the nutrient-rich waters to the carbonate buildups and create an ideal setting where the metazoan communities can thrive. Recently, the role of internal waves, as a source of water turbulence, has been considered as a useful tool in the interpretation of mesophotic carbonate communities. During the Late Jurassic and Late Oligocene, extensive carbonate reefs have been developed along the Tethys. In this PhD project, two case studies from the Upper Jurassic stromatoporoid-rich facies and Late Oligocene (Chattian) coral-rich facies have been studied in order to study the role of internal waves in development of these carbonate communities. The Upper Jurassic stromatoporoid-rich facies of Monte Sacro Limestones (MSL) crop out along the platform margin of Apulia Carbonate Platform (ACP) in Gargano area. The stromatoporoid buildups in MSL are characterized by high percentage of high-energy debris-rich facies associated with low-energy facies. The origin of these high-energy facies are still matter of debates. The MSL is characterized by three lithofacies LF1- stromatoporoid-rich facies, LF2- stromatoporoid-coral facies, and LF3- stromatoporoid-microbial facies. LF1 is the main lithofacies developed in MSL and characterized by stromatoporoids growth in low-energy mesophotic condition (LF1-S1) associated with high-energy intraclastic-bioclastic rich facies (LF1-S2). The stromatoporoid-rich buildups (LF1) in ACP can be categorized as phototrophic-heterotrophic reefs generated in a pure carbonate environment. The light penetration was confined, resulted in the high development of light-independent micro-encrusters (Tubiphytes morronensis), in a mesophotic condition, where the environment was not ideal for light-dependent microencrusters (Lithocodium- Bacinella) to grow. The origin of high-energy facies developed associated with mesophotic stromatoporoid buildups in MSL can be linked to the effect of internal waves. Firstly, internal waves can provide nutrient-rich water needed by stromatoporoid buildups to grow. Latterly, the buildups can be affected by high-energy turbulence, producing a large amount of high-energy debris rich facies (LF1-S2) in MSL. Moving on to a different age, the Late Oligocene (Chattian) coral-rich facies are well developed in Grotta San Michele Limestone (GSML) Gargano, Italy, as well as Asmari Formation, Zagros, Iran. The corals in GSML are surrounded by a mud-dominated matrix, indicating development in low-energy environments. The corals, are associated with meso-oligophotic components such as non-articulate red algae, rhodolith and Polystrata alba. However, the euphotic components such as articulated red-algae, and rare miliolids are associated with corals. Although these mesophotic corals can be mixed with euphotic components shed down from the shallower depth, the internal waves can be a factor to provide nutrient-rich water for coral colonies to develop in this low-energy settings.
34
Winkel, David Patrick. "Influences of mean shear in Florida current on turbulent production by internal waves /". Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/11024.
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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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Boegman, Leon. "The degeneration of internal waves in lakes with sloping topography". University of Western Australia. Centre for Water Research, 2004. http://theses.library.uwa.edu.au/adt-WU2005.0043.
Testo completoAbstract (sommario):
[Truncated abstract] Observations are presented from Lake Biwa (Japan) and Lake Kinneret (Israel) showing the ubiquitous and often periodic nature of high-frequency internal waves in large stratified lakes. In both lakes, high-frequency wave events were observed within two distinct categories: (1) Vertical mode one solitary waves with wavelength ˜100-500 m and frequency near 103 Hz and (2) sinusoidal vertical mode one waves with wavelength ˜5-30 m and frequency just below the local maximum buoyancy frequency near 102 Hz. The sinusoidal waves were associated with shear instability and were shown to dissipate their energy sporadically within the lake interior. Conversely, the solitary waves were found to be capable of propagating to the lake perimeter where they may break upon sloping topography, each releasing ˜1% of the total basin-scale internal wave energy to the benthic boundary layer.
37
Rees, J. M. "Studies of internal gravity waves in the stably stratified troposphere". Thesis, University of Leeds, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383343.
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38
Johnston, Thomas Michael Shaun. "Internal tide scattering at midocean topography". Thesis, University of Hawaii at Manoa, 2003. http://proquest.umi.com/pqdweb?index=0&did=765959661&SrchMode=2&sid=6&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1209407173&clientId=23440.
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Hall, Robert Alan. "Internal waves and slope mixing in the Faroe-Shetland Channel". Thesis, University of Liverpool, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.507197.
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40
Schmidt, Nathan Philip. "Generation, propagation and dissipation of second mode internal solitary waves". Thesis, University of Canterbury. Civil Engineering, 1998. http://hdl.handle.net/10092/7811.
Testo completoAbstract (sommario):
The behaviour of large amplitude second mode internal solitary waves has been investigated. Waves were generated in the laboratory by a variety of methods and were observed using dye and particle visualisation techniques. Observations of wave generation, propagation and dissipation were used to develop new theories about the behaviour of such waves.
Waves were generated by exchange flow, forced inflow and gravity collapse. The generation sequence was found to be similar for all three methods, with the gravity collapse technique allowing the most rapid and repeatable generation of second mode waves.
External propagation characteristics (wave celerity and geometry) were investigated using waves of dimensionless amplitude up to a/h = 11.6. It was found that wave geometry was described well by existing theory over the entire range of amplitudes, but the existing wave celerity relationships were only accurate up to a/h ≌ 3. A new analytical approach produced a relationship which is applicable to all large amplitude waves.
Internal propagation characteristics (internal circulation, entrainment and mass transport) were investigated using both particle visualisation and laser induced fluorescence techniques. It was found that internal circulation differs from the pattern suggested by existing numerical models. The interior of the wave is made up of an assemblage of vortices, symmetrical about the wave centreline, with a net flow rearwards along the centreline. These vortices are seen to play an important role in the entrainment of fluid into the wave. Entrainment appears to be caused by a non-symmetric Holmboe instability at the wave boundary. The entrainment into and expulsion of fluid from the wave results in the flushing of fluid from the wave. Measurements indicate that the rate of flushing is linearly proportional to distance and Richardson number during the primary flushing phase (from 100% to 10% tracer concentration). During the secondary flushing phase (from 10% to 1% tracer concentration) the flushing rate is lower but also linearly proportional to distance and Richardson number.
Wave dissipation experiments indicate that wave amplitude decay rate is constant for any wave but varies with densimetric factor. Waves with larger densimetric factors decay at a slower rate. An expression for wave energy was formulated and the wave energy decay rate was examined. It was found that the radiation of first mode waves does not provide a significant contribution to wave decay. Wall shear was quantified and found to vary with flume width. In this study it was responsible for approximately 9% of the dissipation rate. The remaining dissipation is due to fluid drag (interfacial shear, pressure drag and mixing) and was quantified by a drag coefficient. The drag coefficient varies with the inverse of the cube root of densimetric factor.
41
Simonin, David. "Automatic detection and analysis of internal waves on SAR images". Thesis, University of Southampton, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420213.
Testo completo
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Westlake, P. C. "Interfacial and internal waves generated by a submerged prolate spheroid". Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242629.
Testo completo
43
Oikonomou, Emmanouil Konstantiou. "Stationary phase internal waves generated by flow along sloping topography". Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242690.
Testo completo
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Yuan, Chunxin. "The evolution of oceanic nonlinear internal waves over variable topography". Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10053741/.
Testo completoAbstract (sommario):
This thesis is concerned with the evolution of oceanic nonlinear internal waves over variable one-dimensional and two-dimensional topography. The methodology is based on a variable-coefficient Korteweg-de Vries (vKdV) equation and its vari- ants, including the Ostrovsky equation which takes rotation into account and a Kadomtsev-Petviashvili (KP) equation which extends these one-dimensional models to two space dimensions. In addition, a fully nonlinear and non-hydrostatic three- dimensional primitive equation model, MIT general circulation model (MITgcm), is invoked to provide supplementary analyses. First, the long-time combined effect of rotation and variable topography on the evolution of internal undular bore is stud- ied; then an initial mode-2 internal solitary wave propagating onto the continental shelf-slope in a three-layer fluid is investigated. After that, the research is extended to two-dimensional space in which submarine canyon and plateau topography are implemented to examine a mode-1 internal solitary wave propagating over these topographic features. Finally, the topographic effect on internal wave-wave interac- tions is examined using an initial ‘V-shape’ wave representing two interacting waves in the framework of the KP equation.
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Alias, Azwani B. "Mathematical modelling of nonlinear internal waves in a rotating fluid". Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/15861.
Testo completoAbstract (sommario):
Large amplitude internal solitary waves in the coastal ocean are commonly modelled with the Korteweg-de Vries (KdV) equation or a closely related evolution equation. The characteristic feature of these models is the solitary wave solution, and it is well documented that these provide the basic paradigm for the interpretation of oceanic observations. However, often internal waves in the ocean survive for several inertial periods, and in that case, the KdV equation is supplemented with a linear non-local term representing the effects of background rotation, commonly called the Ostrovsky equation. This equation does not support solitary wave solutions, and instead a solitary-like initial condition collapses due to radiation of inertia-gravity waves, with instead the long-time outcome typically being an unsteady nonlinear wave packet. The KdV equation and the Ostrovsky equation are formulated on the assumption that only a single vertical mode is used. In this thesis we consider the situation when two vertical modes are used, due to a near-resonance between their respective linear long wave phase speeds. This phenomenon can be described by a pair of coupled Ostrovsky equations, which is derived asymptotically from the full set of Euler equations and solved numerically using a pseudo-spectral method. The derivation of a system of coupled Ostrovsky equations is an important extension of coupled KdV equations on the one hand, and a single Ostrovsky equation on the other hand. The analytic structure and dynamical behaviour of the system have been elucidated in two main cases. The first case is when there is no background shear flow, while the second case is when the background state contains current shear, and both cases lead to new solution types with rich dynamical behaviour. We demonstrate that solitary-like initial conditions typically collapse into two unsteady nonlinear wave packets, propagating with distinct speeds corresponding to the extremum value in the group velocities. However, a background shear flow allows for several types of dynamical behaviour, supporting both unsteady and steady nonlinear wave packets, propagating with the speeds which can be predicted from the linear dispersion relation. In addition, in some cases secondary wave packets are formed associated with certain resonances which also can be identified from the linear dispersion relation. Finally, as a by-product of this study it was shown that a background shear flow can lead to the anomalous version of the single Ostrovsky equation, which supports a steady wave packet.
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Kesari, Pradhan Himansu. "Numerical modelling of internal waves the western bay of bengal". Thesis, IIT Delhi, 2016. http://localhost:8080/xmlui/handle/12345678/7003.
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47
Jung, Seongyu. "Implementation of internal wave apparatus for copepod behavioral assays". Thesis, Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54377.
Testo completoAbstract (sommario):
Internal waves are ubiquitous features in coastal marine environments and have been observed to mediate vertical distributions of zooplankton in situ. Internal waves create fine-scale hydrodynamic cues that copepods and other zooplankton are known to sense, such as fluid density gradients and velocity gradients (quantified as shear deformation rate). The role of copepod behavior in response to cues associated with internal waves is largely unknown. The objective is to provide insight to the bio-physical interaction and the role of biological versus physical forcing in mediating organism distributions. We constructed a laboratory-scale internal wave apparatus to facilitate fine-scale observations of copepod behavior in flows that replicate in situ conditions of internal waves in a two-layer stratification. Three cases were chosen with density jump of 0.75, 1.0, and 1.5 sigma-t units. Analytical analysis of the two-layer system provided guidance to the target forcing frequency needed to generate a standing internal wave with a single dominate frequency of oscillation. Flow visualization and signal processing of the interface location were used to quantify the wave characteristics. The results show a close match to the target wave parameters. Marine copepod (mixed population of Acartia tonsa, Temora longicornis, and Eurytemora affinis) behavior assays were conducted for three different physical arrangements: (1) no density stratification, (2) stagnant two-layer density stratification, and (3) two-layer density stratification with internal wave motion. Digitized trajectories of copepod swimming behavior indicate that in the control (case 1) the animals showed no preferential motion in terms of direction. In the stagnant density jump treatment (case 2) copepods preferentially moved horizontally, parallel to the density interface. In the internal wave treatment (case 3) copepods demonstrated orbital trajectories near the density interface. Further analysis showed that the copepods swim closer to the interface in the presence of internal waves.
48
van, den Bremer T. S. "The induced mean flow of surface, internal and interfacial gravity wave groups". Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:e735afe7-a77d-455d-a560-e869a9941f69.
Testo completoAbstract (sommario):
Although the leading-order motion of waves is periodic - in other words backwards and forwards - many types of waves including those driven by gravity induce a mean flow as a higher-order effect. It is the induced mean flow of three types of gravity waves that this thesis examines: surface (part I), internal (part II) and interfacial gravity waves (part III). In particular, this thesis examines wave groups. Because they transport energy, momentum and other tracers, wave-induced mean flows have important consequences for climate, environment, air traffic, fisheries, offshore oil and other industries. In this thesis perturbation methods are used to develop a simplified understanding of the physics of the induced mean flow for each of these three types of gravity wave groups. Leading-order estimates of different transport quantities are developed. For surface gravity wave groups (part I), the induced mean flow consists of two compo- nents: the Stokes drift dominant near the surface and the Eulerian return flow acting in the opposite direction and dominant at depth. By considering subsequent orders in a separation of scales expansion and by comparing to the Fourier-space solutions of Longuet-Higgins and Stewart (1962), this thesis shows that the effects of frequency dis- persion can be ignored for deep-water waves with realistic bandwidths. An approximate depth scale is developed and validated above which the Stokes drift is dominant and below which the return flow wins: the transition depth. Results are extended to include the effects of finite depth and directional spreading. Internal gravity wave groups (part II) do not display Stokes drift, but a quantity analogous to Stokes transport for surface gravity waves can still be developed, termed the “divergent- flux induced flow” herein. The divergent-flux induced flow it itself a divergent flow and induces a response. In a three-dimensional geometry, the divergent-flux induced flow and the return flow form a balanced circulation in the horizontal plane with the former transporting fluid through the centre of the group and the latter acting in the opposite direction around the group. In a two-dimensional geometry, stratification inhibits a balanced circulation and a second type of waves are generated that travel far ahead and in the lee of the wave group. The results in the seminal work of Bretherton (1969b) are thus validated, explicit expressions for the response and return flow are developed and compared to numerical simulations in the two-dimensional case. Finally, for interfacial wave groups (part III) the induced mean flow is shown to behave analogously to the surface wave problem of part I. Exploring both pure interfacial waves in a channel with a closed lid and interacting surface and interfacial waves, expressions for the Stokes drift and return flow are found for different configurations with the mean set-up or set-down of the interface playing an important role.
49
Dale, Andrew Christopher. "Baroclinic coastal trapped waves above the inertial frequency". Thesis, Bangor University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321385.
Testo completo
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Bastin, Mark E. "Baroclinic waves in containers with sloping end walls". Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670276.
Testo completo