Three-dimensional Nearshore Currents and Eddies on an Alongshore-variable Barred Beach PDF Download
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Author: Christine Marie Baker
Publisher:
ISBN:
Category :
Languages : en
Pages : 53
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Book Description
Three-dimensional circulation in the nearshore region is critical for contaminants, sediment, and larvae dispersion along the coast and transport between the surf zone and the inner shelf. In the surf zone, eddies generated by short-crested wave breaking, wave-group forcing, and shear instabilities are associated with energetic vortical motion at very low frequencies (f ~ 0.005 Hz), but the horizontal length scales and vertical structure of these vortical motions are poorly understood. Here, a three-dimensional phase-resolving numerical model, Simulating WAves till SHore (SWASH), simulates wave propagation and three-dimensional circulation patterns on a barred beach near Duck, North Carolina. Modeled wave statistics and nearshore currents are consistent with field measurements collected in Oct. 2015. The model accurately simulates the cross-shore wave height gradient, mean alongshore currents, and offshore-directed meanders within the surf zone for a range of offshore wave conditions. Simulated eddy length scales, quantified using the alongshore wavenumber spectra of vorticity, suggest that large-scale eddies (O(100) m) occur for both alongshore-variable (observed) and alongshore-uniform (alongshore mean of observed) bathymetry, and may be enhanced by surfzone bathymetric variability. Small-scale eddies (O(10) m) generated by short-crested breaking and wave-group forcing have similar eddy variance for simulations with alongshore-uniform and alongshore-variable bathymetry. The depth dependence of the alongshore wavenumber spectra of vorticity magnitude and peak length scales varies with cross-shore location and bathymetric variability. The complex vertical structure of the energy, coherence, and phase of very low-frequency vortical motion for both alongshore-variable and alongshore-uniform bathymetry may be associated with the vertical structure of eddy injection, instabilities, mean shear, and bottom boundary layer dynamics.
Author: Christine Marie Baker
Publisher:
ISBN:
Category :
Languages : en
Pages : 53
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Book Description
Three-dimensional circulation in the nearshore region is critical for contaminants, sediment, and larvae dispersion along the coast and transport between the surf zone and the inner shelf. In the surf zone, eddies generated by short-crested wave breaking, wave-group forcing, and shear instabilities are associated with energetic vortical motion at very low frequencies (f ~ 0.005 Hz), but the horizontal length scales and vertical structure of these vortical motions are poorly understood. Here, a three-dimensional phase-resolving numerical model, Simulating WAves till SHore (SWASH), simulates wave propagation and three-dimensional circulation patterns on a barred beach near Duck, North Carolina. Modeled wave statistics and nearshore currents are consistent with field measurements collected in Oct. 2015. The model accurately simulates the cross-shore wave height gradient, mean alongshore currents, and offshore-directed meanders within the surf zone for a range of offshore wave conditions. Simulated eddy length scales, quantified using the alongshore wavenumber spectra of vorticity, suggest that large-scale eddies (O(100) m) occur for both alongshore-variable (observed) and alongshore-uniform (alongshore mean of observed) bathymetry, and may be enhanced by surfzone bathymetric variability. Small-scale eddies (O(10) m) generated by short-crested breaking and wave-group forcing have similar eddy variance for simulations with alongshore-uniform and alongshore-variable bathymetry. The depth dependence of the alongshore wavenumber spectra of vorticity magnitude and peak length scales varies with cross-shore location and bathymetric variability. The complex vertical structure of the energy, coherence, and phase of very low-frequency vortical motion for both alongshore-variable and alongshore-uniform bathymetry may be associated with the vertical structure of eddy injection, instabilities, mean shear, and bottom boundary layer dynamics.
Author: Antonio Fernando Garcez Faria
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 182
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Book Description
The objective of this dissertation is to develop numerical models and compare their predictions with data acquired during the DUCK94 experiment in order to improve our physical understanding of the hydrodynamic processes governing the vertical and cross shore distributions of both longshore and cross shore currents over a barred beach. The vertical structure of the mean longshore current is found to be well described by a logarithmic profile and a relationship between bed shear stress and bottom roughness, including the influence of ripples and mega-ripples, was also found. The vertical structure of the mean cross shore current (undertow) is modeled using an eddy viscosity closure scheme to solve for the turbulent shear stress and includes contributions from breaking wave rollers. These models of the vertical profiles of longshore and cross shore mean currents are combined to formulate a quasi three dimensional model to describe the cross shore distribution of the longshore current. This model includes turbulent mixing due to the cross shore advection of mean momentum of the longshore current by the mean cross shore current and contributions from wave rollers.
Author: Kristen D. Splinter
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
ABSTRACT: Our study introduced a new 3D, time dependent, non-hydrostatic, Large Eddy Simulation (LES) nearshore circulation model. It was wave phase averaged, in a curvilinear, bottom conforming, [sigma]-coordinate system; with a rigid lid that was capable of examining depth dependent, low-frequency, and nearshore current response to breaking waves in the surf zone. A principal advantage of our model was that it included dynamics of the undertow and vertical mixing that led to enhanced cross shore mixing. Uncertainties associated with modeling bottom friction were reduced because bottom stress was modeled with the no slip condition by using a high resolution vertically clustered grid with O (1-10 cm) scales near the seabed. The LES turbulence closure scheme produced reasonable time averaged alongshore and cross shore vertical velocity profiles.
Author: Bruce J. Morris
Publisher:
ISBN: 9781423525349
Category :
Languages : en
Pages : 100
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Book Description
Mean cross-shore wave height transformation and alongshore currents observed on near-planar and barred beaches are compared with predictions based on the nearshore numerical model Delft3D. Delft3D solves the two-dimensional, depth-averaged, momentum balance (2-DH) between forcing (by breaking waves and variations in mean surface elevation), changes in momentum flux, bottom stress and lateral mixing. The observations were acquired on the near-planar California beaches at Torrey Pines and Santa Barbara and the barred beach at Duck, N.C., and include a wide range of conditions with maximum mean currents of 1.5 m/s. The model has two free parameters, a depth dependent breaking term, gamma, and the bed roughness length, k sub s. An empirical formula to determine gamma a priori from the deep-water wave steepness and bed slope is developed, showing good agreement in the wave height transformation. Including rollers in the wave forcing results in improved predictions of the observed alongshore current structure by shifting the predicted velocity maxima shoreward and increasing the velocity in the trough of the bar compared with model predictions without rollers. On near-planar beaches and high-energy events on barred beaches, a one- dimensional (alongshore uniform bathymetry) model performs as well as 2-DH. On barred beaches under moderate conditions when alongshore non-uniform bathymetry prevails, the 2-DH model performs better than the 1-D model, particularly in the bar-trough region. Wave forcing balances the bottom stress with a second balance between alongshore variation in the mean surface elevation (pressure gradients) and the inertia of the alongshore current.
Author: Charles W. Finkl
Publisher: Springer
ISBN: 9783319938059
Category : Science
Languages : en
Pages : 0
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Book Description
This thoroughly revised and expanded edition of the much acclaimed Encyclopedia of Coastal Science edited by M. Schwarz (Springer 2005), presents an interdisciplinary approach that includes biology, ecology, engineering, geology, geomorphology, oceanography, remote sensing, technological advances, and anthropogenic impacts on coasts. Within its covers the Encyclopedia of Coastal Science, 2nd ed. brings together and coordinates many aspects of coastal and related sciences that are widely dispersed in the scientific literature. The broadly interdisciplinary subject matter of this volume features contributions by over 280 well-known international specialists in their respective fields and provides an abundance of figures in full-color with line drawings and photographs, and other illustrations such as satellite images. Not only does this volume offer a large number of new and revised entries, it also includes an illustrated glossary of coastal geomorphology, extensive bibliographic citations, and cross-references. It provides a comprehensive reference work for students, scientific and technical professionals as well as administrators, managers, and informed lay readers. Reviews from the first edition: Awarded for Excellence in Scholarly and Professional Publishing: “Honorable Mention”, in the category Single Volume/Science from the Association of American Publishers (AAP) 2005. "The contents and approach are interdisciplinary and, under a single cover, one finds subjects normally scattered throughout scientific literature." "The topics cover a broad spectrum, so does the geographic range of the contributors. ... besides geomorphologists, biologists, ecologists, engineers, geographers, geologists, oceanographers and technologists will find information related to their respective fields ... . Inclusion of appendices ... is very useful. The illustrated glossary of geomorphology will prove very useful for many of us ... ." Roger H. Charlier, Journal of Coastal Research, Volume 21, Issue 4, Page 866, July 2005. "It is an excellent work that should be included in any carefully selected list of best science reference books of the year "Summing Up: Highly recommended. " M.L. Larsgaard, Choice, Volume 43, Issue 6, Page 989, February 2006. "This volume is a comprehensive collection of articles covering all aspects of the subject: social and economic, engineering, coastal processes, habitats, erosion, geological features, research and observation." ... "As with similar works reviewed, I chose to read articles on familiar topics to see if they covered the expected, and some on unfamiliar topics to see if they could be readily understood. The book passed both tests, but the style is denser and more fact-filled than most of the encyclopedias I have reviewed." John Goodier, Reference Reviews, Volume 20, Issue 2, pages 35-36, 2006
Author: Benoit Cushman-Roisin
Publisher: Academic Press
ISBN: 0080916783
Category : Science
Languages : en
Pages : 850
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Book Description
Introduction to Geophysical Fluid Dynamics provides an introductory-level exploration of geophysical fluid dynamics (GFD), the principles governing air and water flows on large terrestrial scales. Physical principles are illustrated with the aid of the simplest existing models, and the computer methods are shown in juxtaposition with the equations to which they apply. It explores contemporary topics of climate dynamics and equatorial dynamics, including the Greenhouse Effect, global warming, and the El Nino Southern Oscillation. Combines both physical and numerical aspects of geophysical fluid dynamics into a single affordable volume Explores contemporary topics such as the Greenhouse Effect, global warming and the El Nino Southern Oscillation Biographical and historical notes at the ends of chapters trace the intellectual development of the field Recipient of the 2010 Wernaers Prize, awarded each year by the National Fund for Scientific Research of Belgium (FNR-FNRS)
Author: National Research Council
Publisher: National Academies Press
ISBN: 0309172225
Category : Technology & Engineering
Languages : en
Pages : 112
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Book Description
Environmental information is important for successful planning and execution of naval operations. A thorough understanding of environmental variability greatly increases the likelihood of mission success. To ensure that naval forces have the most up-to-date capabilities, the Office of Naval Research (ONR) has an extensive environmental research program. This research, to be of greatest use to the warfighter, needs to be directed towards assisting and solving battlefield problems. To increase research community understanding of the operational demands placed on naval operators and to facilitate discussion between these two groups, the National Research Council's (NRC) Ocean Studies Board (OSB), working with ONR and the Office of the Oceanographer of the Navy, convened five previous symposia on tactical oceanography. Oceanography and Mine Warfare examines the following issues: (1) how environmental data are used in current mine warfare doctrine, (2) current procedures for in situ collection of data, (3) the present capabilities of the Navy's oceanographic community to provide supporting information for mine warfare operations, and (4) the ability of oceanographic research and technology developments to enhance current mine warfare capabilities. This report primarily concentrates on the importance of oceanographic data for mine countermeasures.
Author: Robin Davidson-Arnott
Publisher: Cambridge University Press
ISBN: 1108424279
Category : Science
Languages : en
Pages : 541
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Book Description
Grounded in current research, this second edition has been thoroughly updated, featuring new topics, global examples and online material. Written for students studying coastal geomorphology, this is the complete guide to the processes at work on our coastlines and the features we see in coastal systems across the world.
Author: Richard Soulsby
Publisher: Thomas Telford
ISBN: 9780727725844
Category : Science
Languages : en
Pages : 280
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Book Description
The practical engineer looking for an urgent solution to a sediment-related project often finds that the results of the relevant academic research are published in unfamiliar language in publications that are not easily available. Dynamics of marine sands bridges the gap between academic research and practical applications by summarising the research results in a unified form, backed up with worked examples and case studies. This comprehensive new book presents methods for calculating the various hydrodynamic and sediment dynamic quantities necessary for marine sediment transport applications, and recommends the most appropriate methods to use for engineering projects.
Author:
Publisher:
ISBN:
Category : Geodesy
Languages : en
Pages : 1476
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Book Description
