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Nearshore Currents Over a Barred Beach

1997 Science
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Release : 1997
Genre : Science
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Book Synopsis Nearshore Currents Over a Barred Beach by : Antonio Fernando Garcez Faria

Download or read book Nearshore Currents Over a Barred Beach written by Antonio Fernando Garcez Faria. This book was released on 1997. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Wind and Wave Forcing of Longshore Currents Across a Barred Beach

1988 Banks (Oceanography)
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Release : 1988
Genre : Banks (Oceanography)
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Book Synopsis Wind and Wave Forcing of Longshore Currents Across a Barred Beach by : Dennis James Whitford

Download or read book Wind and Wave Forcing of Longshore Currents Across a Barred Beach written by Dennis James Whitford. This book was released on 1988. Available in PDF, EPUB and Kindle. Book excerpt: 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).

Three-dimensional Nearshore Currents and Eddies on an Alongshore-variable Barred Beach

2019
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Release : 2019
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Book Synopsis Three-dimensional Nearshore Currents and Eddies on an Alongshore-variable Barred Beach by : Christine Marie Baker

Download or read book Three-dimensional Nearshore Currents and Eddies on an Alongshore-variable Barred Beach written by Christine Marie Baker. This book was released on 2019. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Mechanics Of Coastal Sediment Transport

1992-11-02 Technology & Engineering
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Release : 1992-11-02
Genre : Technology & Engineering
Kind : eBook
Book Rating : 688/5 ( reviews)

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Book Synopsis Mechanics Of Coastal Sediment Transport by : Jorgen Fredsoe

Download or read book Mechanics Of Coastal Sediment Transport written by Jorgen Fredsoe. This book was released on 1992-11-02. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Literature Review on the Geologic Aspects of Inner Shelf Cross-shore Sediment Transport

1995 Continental shelf
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Release : 1995
Genre : Continental shelf
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Book Synopsis Literature Review on the Geologic Aspects of Inner Shelf Cross-shore Sediment Transport by : J. Bailey Smith

Download or read book Literature Review on the Geologic Aspects of Inner Shelf Cross-shore Sediment Transport written by J. Bailey Smith. This book was released on 1995. Available in PDF, EPUB and Kindle. Book excerpt:

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