Nearshore Currents Over a Barred Beach PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download Nearshore Currents Over a Barred Beach PDF full book. Access full book title Nearshore Currents Over a Barred Beach by Antonio Fernando Garcez Faria. Download full books in PDF and EPUB format.
Author: Antonio Fernando Garcez Faria
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 182
Get Book Here
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: Antonio Fernando Garcez Faria
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 182
Get Book Here
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: Dennis James Whitford
Publisher:
ISBN:
Category : Banks (Oceanography)
Languages : en
Pages : 238
Get Book Here
Book Description
Previous investigations of longshore currents have included simplifying assumptions and restriction (such as a planar beach, a steady and depth uniform flow, spatially-variant bed shear stress and turbulent momentum exchange, and the exclusion of surface wind stress. These assumptions are quantitatively investigated by calculating the relative importance of each term in the longshore momentum balance with an emphasis on the relative importance of wind forcing across the barred nearshore. Wind and wave forcing of longshore currents across a barred beach are examined using both a numerical model and field measurements. A local momentum balance was measured at various locations across the surf zone during the SUPERDUCK experiment held at the USACE CERC Field Research Facility, Duck, N.C. in October 1986. A moveable sled was instrumented with pressure, current, and wind sensors to measure the various terms in the longshore momentum equation. Stability-dependent atmospheric drag coefficients for the surf zone are determined from wind stress measurements acquired just beyond the surf zone and wind speed measurements acquired from an anemometer atop the 9 m sled mast. Breaking waves were visually identified and electronically marked on the data tapes. Keywords: Ocean currents; Air water interactions; Nearshore surf zone; Wind stress; Theses. (EDC).
Author: Christine Marie Baker
Publisher:
ISBN:
Category :
Languages : en
Pages : 53
Get Book Here
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: Jorgen Fredsoe
Publisher: World Scientific Publishing Company
ISBN: 9814365688
Category : Technology & Engineering
Languages : en
Pages : 390
Get Book Here
Book Description
This book treats the subject of sediment transport in the marine environment, covering transport of noncohesive sediment by waves and currents in- and outside the surf zone. It can be read independently, but a background in hydraulics and basic wave mechanics is required.The primary aim of the book is to describe the physical processes of sediment transport and how to represent them in mathematical models. The book can be divided in two main parts; in the first, the relevant hydrodynamic theory is described. This part contains a review of elementary theory for water waves, chapters on the turbulent wave boundary layer and the turbulent interaction between waves and currents, and finally, surf zone hydrodynamics and wave driven currents.The second part covers sediment transport and morphological development.The part on sediment transport introduces the basic concepts (critical bed shear stress, bed load, suspended load and sheet layer, near-bed concentration, effect of sloping bed); it treats suspended sediment in waves and current and in the surf zone, and current and wave-generated bed forms. Finally, the modelling of cross-shore and long-shore sediment transport is described together with the development of coastal profiles and coastlines.
Author: J. Bailey Smith
Publisher:
ISBN:
Category : Continental shelf
Languages : en
Pages : 168
Get Book Here
Book Description
Author: Jane Mckee Smith
Publisher: World Scientific
ISBN: 9814480525
Category : Science
Languages : en
Pages : 4836
Get Book Here
Book Description
This comprehensive and up-to-date volume contains 367 papers presented at the 29th International Conference on Coastal Engineering, held in Lisbon, Portugal, 19-24 September 2004. It is divided into five parts: waves; long waves, nearshore currents, and swash; sediment transport and morphology; coastal management, beach nourishment, and dredging; coastal structures. The contributions cover a broad range of topics including theory, numerical and physical modeling, field measurements, case studies, design, and management. Coastal Engineering 2004 provides engineers, scientists, and planners state-of-the-art information on coastal engineering and coastal processes.The proceedings have been selected for coverage in:
Author: John Casey Church
Publisher:
ISBN:
Category : Littoral drift
Languages : en
Pages : 140
Get Book Here
Book Description
The momentum equation governing mean longshore currents on straight beaches is a balance of forcing from the momentum transfer of the oscillatory wave motion, turbulent momentum transfer (mixing), and bottom stress. Of these, the wave's contribution is well understood, but the remaining two are not, principally due to the complicated hydrodynamics of the surf-zone. Addressing the bottom stress term, a longshore current model is developed which includes a modification of the bottom stress due to the effects of breaking-wave induced turbulence. A one-dimensional turbulent kinetic energy equation is used to model this breaking-wave induced turbulence, producing a spatially varying bottom friction coefficient. The modeled longshore current cross-shore profiles show improved agreement with field observations. In a second bottom stress study, vertical profiles of mean longshore currents are examined using field data obtained with vertically stacked electromagnetic current meters with the goal of measuring the bottom stress and its associated drag coefficient. The profiles are observed to become vertically uniform whenever the ratio of wave height to depth exceeds 0.3, indicating that nearly all of the waves passing a given location are breaking. Finally, horizontal turbulent momentum transfer (mixing) is examined for the case of shear instabilities of the longshore current.
Author: Gerard P. Lennon
Publisher:
ISBN:
Category : Ocean currents
Languages : en
Pages : 232
Get Book Here
Book Description
Author: Jane Mckee Smith
Publisher: World Scientific
ISBN: 9814467561
Category : Technology & Engineering
Languages : en
Pages : 5136
Get Book Here
Book Description
This proceedings contains papers presented at the 31st International Conference on Coastal Engineering, which has held in Hamburg, Germany (31 August - 5 September 2008). The proceeding is divided into five parts: Waves; Long Waves, Nearshore Currents, and Swash; Sediment Transport and Morphology; Coastal Management, Environment, and Risk; and Coastal Structures. The papers cover a broad range of topics including theory, numerical and physical modeling, field measurements, case studies, design, and management. Coastal Engineering 2008 provides coastal engineers, scientists, and planners, with state-of-the-art information on coastal engineering and coastal processes.
Author: Jane Mckee Smith
Publisher: World Scientific
ISBN: 9814486973
Category : Technology & Engineering
Languages : en
Pages : 4007
Get Book Here
Book Description
This book contains more than 300 papers presented at the 28th International Conference on Coastal Engineering, held in Cardiff, Wales, in July 2002. It is divided into five parts: coastal waves; nearshore currents, swash, and long waves; coastal structures; sediment transport; and coastal morphology, beach nourishment, and coastal management. The papers cover a broad range of topics, including theory, numerical and physical modeling, field measurements, case studies, design, and management. Coastal Engineering 2002 provides engineers, scientists, and planners with state-of-the-art information on coastal engineering and coastal processes.
