Download or read book Generation of Internal Waves Over Idealized 3 D Topography by Tidal Forcing written by James R. Munroe and published by . This book was released on 2003 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Laboratory and Numerical Studies of Internal Wave Generation and Propagation in the Ocean written by Benjamin Thomas King and published by . This book was released on 2010 with total page 478 pages. Available in PDF, EPUB and Kindle. Book excerpt: Internal waves are generated in the ocean by oscillating tidal flow over bottom topography such as ridges, seamounts, and continental slopes. They are similar to the more familiar surface waves, but not being constrained to move on the surface, propagate throughout the bulk of the world oceans. Internal waves transmit energy over thousands of kilometers, ultimately breaking and releasing their energy into turbulence and mixing. Where these internal waves are generated, as well as where and how they break and cause mixing, has important effects on the general circulation of the ocean, which is in turn a major component in earth's climate. As a first step in a more thorough understanding of the evolution of internal waves in the ocean, it is important to characterize their generation. The two-dimensional generation problem has been studied for four decades, with ample experimental, numerical, and theoretical results. Most of this past work has also been done using linear, inviscid approximations. However, wave generation in the ocean is three-dimensional (3D), and in many locations, nonlinear and viscous effects can be significant. Recent advances in experimental and numerical techniques are only now making the fully nonlinear, 3D generation process accessible. We utilize these new techniques to perform both laboratory experiments and numerical simulations on internal wave generation in 3D. We find that a significant component of the internal wave field generated by tidal flow over 3D topography is radiated in the direction perpendicular to the tidal forcing direction. This could lead to substantial improvements of global internal wave generation models. In addition, we have developed a new method for statistical analysis of ocean data sets, and have found large regions in the deep ocean where internal waves may not propagate. This will also have important effects on the way researchers study the propagation of internal waves, which, when propagating downward, were previously thought to always reflect from the sea floor.
Download or read book Ocean Mixing written by Michael Meredith and published by Elsevier. This book was released on 2021-09-16 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ocean Mixing: Drivers, Mechanisms and Impacts presents a broad panorama of one of the most rapidly-developing areas of marine science. It highlights the state-of-the-art concerning knowledge of the causes of ocean mixing, and a perspective on the implications for ocean circulation, climate, biogeochemistry and the marine ecosystem. This edited volume places a particular emphasis on elucidating the key future questions relating to ocean mixing, and emerging ideas and activities to address them, including innovative technology developments and advances in methodology. Ocean Mixing is a key reference for those entering the field, and for those seeking a comprehensive overview of how the key current issues are being addressed and what the priorities for future research are. Each chapter is written by established leaders in ocean mixing research; the volume is thus suitable for those seeking specific detailed information on sub-topics, as well as those seeking a broad synopsis of current understanding. It provides useful ammunition for those pursuing funding for specific future research campaigns, by being an authoritative source concerning key scientific goals in the short, medium and long term. Additionally, the chapters contain bespoke and informative graphics that can be used in teaching and science communication to convey the complex concepts and phenomena in easily accessible ways. - Presents a coherent overview of the state-of-the-art research concerning ocean mixing - Provides an in-depth discussion of how ocean mixing impacts all scales of the planetary system - Includes elucidation of the grand challenges in ocean mixing, and how they might be addressed
Download or read book Laboratory and Analytical Modeling of Internal Waves in Uniform and Non uniform Stratifications written by Manikandan Sankaranarayanan Mathur and published by . This book was released on 2011 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: Internal gravity waves are propagating disturbances in a stably stratified fluid. Ubiquitous in geophysical systems, they have significant impact on both fundamental processes and engineering applications. In the ocean, for example, internal waves are a significant means of tidal dissipation, eventually affecting abyssal mixing and the global energy budget. They are also of importance in engineering fields such as deep-water oil drilling, submarine technology and acoustic communications. In the atmosphere, internal waves affect momentum and energy transport processes. While the generation of internal waves in both the ocean and the atmosphere is beginning to be well understood, what is now of great interest is the life of internal waves after their generation. More specifically, how are they dissipated, and what fundamental phenomena occur along the way ? To investigate these issues, this thesis presents the results of internal wave studies using a combination of experimental and analytical modeling, with a focus on internal wave scattering in the ocean. In the first part of the thesis, the effectiveness of a novel wave generator, which comprises a series of vertically stacked plates that oscillate horizontally, in generating unidirectional plane waves/wave beams and distinct vertical modes is discussed and demonstrated in experiments. The experimental results show excellent agreement with corresponding numerical simulations, which model the wave generator as a vertical boundary on which desired velocity fields are enforced. Finally, it is shown that the Fourier transform of the spatial structure of the wave generator is a useful predictive tool for the emitted wave field. This novel technique of wave generation is then used in the experiments discussed in the remainder of the thesis. The second part of the thesis considers the viscous propagation of internal wave beams in nonuniform stratifications, and uses laboratory observations of wave beam ducting to explain the apparent vanishing of an internal wave beam at the Keana ridge, Hawaii. Furthermore, an analogy between internal wave transmission in nonuniform stratifications and light transmission in optical interferometry is established. Constructing an internal wave interferometer in the lab, selective transmission of wavelengths by nonuniform stratifications is demonstrated. In the final part of the thesis, an investigation of internal wave scattering by ocean-floor topography is carried out. An existing Green function method for internal tide generation is advanced to account for arbitrary two-dimensional topography in arbitrary nonuniform stratifications. The analytical model is then utilized to study the scattering of a mode-I internal tide by idealized topographic shapes in uniform and nonuniform stratifications. The thesis concludes with a case study of the scattering of mode-1 internal tide at the Line Islands Ridge at Hawaii, the location of an upcoming NSF field study, the EXperiment on Internal Tide Scattering (EXITS).
Download or read book Master s Theses Directories written by and published by . This book was released on 2004 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Education, arts and social sciences, natural and technical sciences in the United States and Canada".
Download or read book Importance of Topography in Generation and Preparation of Internal Waves written by Helmuth Sandstrom and published by . This book was released on 1966 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Turbulence and Internal Waves in Tidal Flow Over Topography written by Bishakhdatta Gayen and published by . This book was released on 2012 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES) are used to investigate and quantify the dynamical processes underlying turbulence formed during the generation of an internal wave beam and its subsequent interaction with a realistically stratified upper ocean. As a part of the thesis, a three-dimensional mixed spectral/finite difference code was developed, parallelized, validated and employed to study several geophysical problems relevant to internal tide generation and its nonlinear breaking. The thesis research has four phases. In the first phase, a study of a stratified non-sloping bottom boundary layer under an oscillating tide was completed. The focus is on the boundary layer response to an external stratification based on LES. Flow instabilities and turbulence in the bottom boundary layer are found to excite internal gravity waves that propagate away into the ambient with phase angle varying over the tidal cycle. Subsequent studies as part of the second phase consider a stratified oscillating flow over a sloping bottom wall to mimic the generation of baroclinic internal waves (IW) from the tide-topography interaction at a model continental slope. The DNS study shows transition to turbulence, which is present along the entire extent of the near-critical region of the slope in the regime of low background excursion number and Reynolds number. The transition is found to be initiated by a convective instability, which is closely followed by shear instability. The peak value of the near-bottom velocity is found to increase with increasing length of the critical region of the topography. The scaling law that is observed to link the near-bottom peak velocity to slope length is explained by an analytical boundary layer solution that incorporates an empirically obtained turbulent viscosity. As an extension of the second phase, the objective of the third phase work is to numerically model a near-bottom beam with a larger, more realistic width using LES and characterize its turbulence statistics. Maximum turbulent kinetic energy and dissipation rate are found just after the zero velocity point when flow reverses from downslope to upslope motion. The phasing and other characteristics of the turbulent mixing in the present simulations show remarkable similarity with that observed off Kaena Ridge in Hawaii taken during the hawaiian ocean mixing experiment (HOME), and may be explained by the beam-scale convective overturns found here. The objective of the final phase is to understand the interaction process between an IW beam and an upper ocean pycnocline and to further characterize the cascade to small scales in the context of IW beam degradation observed in the ocean.
Download or read book Issues in General Physics Research 2011 Edition written by and published by ScholarlyEditions. This book was released on 2012-01-09 with total page 13957 pages. Available in PDF, EPUB and Kindle. Book excerpt: Issues in General Physics Research / 2011 Edition is a ScholarlyEditions™ eBook that delivers timely, authoritative, and comprehensive information about General Physics Research. The editors have built Issues in General Physics Research: 2011 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about General Physics Research in this eBook to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Issues in General Physics Research: 2011 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.
Download or read book Tidally Generated Internal Waves from Asymmetric Topographies written by Kyle Jeffrey Hakes and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Investigation of the Spatial and Temporal Structure of Internal Waves written by Andy I. Pickering and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A collection of field experiments and model simulations are used to investigate the spatial and temporal aspects of internal waves, with a focus on near-inertial waves and internal tides. First, the near-inertial wave field in the North Pacific is investigated using an array of 5 profiling moorings and shipboard ADCP transects. The ship transects reveal the horizontal structure of near-inertial shear, which is coherent over large distances (~ 80 km) and exhibits a change in character crossing 28.9°N. Second, the spatial structure of internal tidal beams is studied with repeated shipboard ADCP transects across Kaena Ridge, Hawaii. Harmonic fits are used to isolate the M2 component of velocity, revealing a beam structure that compares well with theoretical ray paths and numerical simulations. Third, internal tides are investigated with moorings deployed in Luzon Strait, a major internal tide generation site with complex bathymetry and mesoscale variability. The coherence of internal tides over 4 spring-neap tidal cycles is quantified, and a model is used to diagnose the mechanisms responsible. Intrusions of the Kuroshio current shift large-scale patterns of internal tide pressure, leading to lower coherence and possibly affecting the wave field radiated from Luzon Strait. Finally, the turbulent mixing caused by tidal flow over topography in southern Luzon Strait is investigated with a profiling mooring and model simulations. Depth-integrated turbulent dissipation varies by an order of magnitude between spring and neap tides. Model simulations show that turbulence is due to the formation and breaking of lee waves. Dissipation varies for similar barotropic forcing over the 50 day record, suggesting that mesoscale variability is important in modulating mixing.
Download or read book The Importance of Topography in Generation and Propogation of Internal Waves written by Helmuth Sandstrom and published by . This book was released on 1966 with total page 105 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Internal Wave Generation Over Rough Sloped Topography written by Lauren E. Eberly and published by . This book was released on 2012 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: Internal waves exist everywhere in stratified fluids - fluids whose density changes with depth. The two largest bodies of stratified fluid are the atmosphere and ocean. Internal waves are generated from a variety of mechanisms. One common mechanism is wind forcing over re- peated sinusoidal topography, like a series of hills. When modeling these waves, linear theory has been employed due to its ease and low computational cost. However, recent research has shown that non-linear effects, such as boundary layer separation, may have a dramatic impact on wave generation. This research has consisted of experimentation on sloped, sinusoidal hills. As of yet, no experimental research has been done to characterize internal wave generation when repeated sinusoidal hills lie on a sloped surface such as a continental slope or a foothill. In order to perform this experiment, a laboratory was built which employed the synthetic schlieren method of wave visualization. Measurements were taken to find wind speed, boundary layer thickness, and density perturbation. From these data, an analysis was performed on wave propagation angle, wave am- plitude, and pressure drag. The result of the analysis shows that when wind blows across a series of sloped sinusoidal hills, fluid becomes trapped in the troughs of the hills resulting in a lower apparent forcing amplitude. The generated waves contain less energy than linear predictions. Ad- ditionally, the sloped hills produce waves which propagate at an angle away from the viewer. A necessary correction, which shifts from the reference frame of the observer to the reference plane of the waves is described. When this correction is applied, it is shown that linear theory may only be applied for low Froude numbers. At high Froude numbers, the effect of the boundary layer is great enough that the wave characteristics deviate significantly from linear theory predictions. The analyzed data agrees well with previous studies which show a similar deviation from linear theory.
Download or read book Internal Wave Generation in the Presence of Turning Depths written by Matthew C. Drake and published by . This book was released on 2012 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the ocean, internal gravity waves are generated by tidal flow over sea floor topography. An internal gravity wave is only able to freely propagate if the buoyancy frequency is greater than the driving frequency, where the buoyancy frequency is proportional to the square root of the density gradient. A turning depth is defined as a height below which the buoyancy frequency is less than the driving frequency. King et al. showed that turning depths for internal waves generated by lunar tidal flow exist in the ocean, at varying heights from the sea floor [11]. The present study is the first to examine the generation and propagation of internal waves by tidal flow over topography that lies below a turning depth. I use laboratory experiments and numerical simulations to examine the effect of these turning depths on energy flux of the internal waves generated by tidal flow over topography. I find excellent agreement between numerical and laboratory work, and I show that the internal wave energy is strongly damped by the presence of a turning depth above the topography. Further, this has strong implications for ocean energy budget calculations.
Download or read book Numerical Simulations of Internal Waves Generated by Flow Over a Ridge written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: QIAN, HUI. Numerical Simulations of Internal Waves Generated by Flow over a Ridge. (Under the direction of Dr. Ping-Tung Shaw). A three-dimensional nonhydrostatic numerical model is used to study the generation of internal wave energy by barotropic tidal flow over a steep ridge. Numerical experiments are carried out over ridges of three different heights in an ocean with strong stratification at shallow depths. The topographic width, stratification, and amplitude of the barotropic tide are varied to examine the dependence of the normalized energy flux on the slope parameter, the ratio of the ridge slope to that of the wave beam. Over a tall ridge reaching the strongly stratified depths of the water column, the non-dimensional energy flux increases with the slope parameter and becomes constant when the slope parameter exceeds a critical value. For a small ridge confined at weakly stratified depths, the non-dimensional energy flux reaches a maximum with increase in the slope parameter but decreases with further increase in the slope parameter. The two regimes of dependence on the slope parameter can be described in terms of a local Froude number. The results show that internal wave generation is most efficient when the ridge is steep and the ridge top reaches the strongly stratified upper ocean. Comparison between the parameterization scheme and the estimated energy flux at several locations in the ocean shows reasonable agreement. The non-dimensional relation provides a way to estimate the baroclinic energy flux using topographic scales, stratification, and strength of the barotropic tides in the ocean.
Download or read book The Effect of Asymmetrical Topography on the Generation of Internal Waves written by Michael Peter Angus and published by . This book was released on 2012 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Tidal Dynamics and Mixing Over Steep Topography written by Emanuel Ferreira Coelho and published by . This book was released on 1994 with total page 213 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coastal currents and water column stratification frequently are determined by local phenomena that interact to produce complex dynamics. A process study was designed to assess the role of tides over a coastal shelf break as a local source of internal waves spatially-inhomogeneous, baroclinic residual currents, and internal mixing. The temporal evolution of three dimensional stratification and currents were characterized within a 4Kmx4Km box close to the mouth of Monterey Canyon, California. Strong, baroclinic, unidirectional, spatially inhomogeneous jet-like currents were observed with 24 hour periods, together with the occurrence of semidiurnal thermocline oscillations and vertically mixed layers. The linear theory of Baines predicts the existence of significant tidally forced internal waves in the area, with an interfacial mode at the thermocline decoupled from the internal waves propagating in the weaker stratification below. A ray tracing method is developed to study the nonlinear propagation of these tidally forced internal waves by considering wave advection and straining by the topographically controlled barotropic tidal flow while neglecting internal wave-wave interactions. It is found that nonlinear interaction of tidally forced internal waves with the topographically controlled barotropic tidal flow is a mechanism capable of forcing residual currents and internal wave shear instabilities that are capable of creating internal mixed layers similar to those observed at the mouth of Monterey Canyon.
Download or read book Digital Terrain Modeling written by Zhilin Li and published by CRC Press. This book was released on 2004-11-29 with total page 337 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by experts, Digital Terrain Modeling: Principles and Methodology provides comprehensive coverage of recent developments in the field. The topics include terrain analysis, sampling strategy, acquisition methodology, surface modeling principles, triangulation algorithms, interpolation techniques, on-line and off-line quality control in data a
