Download or read book Longshore Current Velocity written by Cyril Jerome Galvin and published by . This book was released on 1967 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Field Investigation of the Spatial and Temporal Structure of Longshore Currents written by Guy Allen Meadows and published by . This book was released on 1978 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: This field investigation was conducted to obtain simultaneous and continuous measurements of the horizontal, vertical and temporal variability of the longshore current flow field. The present study has resulted in a two-dimensional mapping, across the surf zone and with depth, of the longshore current field. The vertical structure of the mean longshore current flow field is nearly uniform with depth, with a narrow bottom boundary layer and sharp velocity gradients at the water-sediment interface. This investigation has also shown that the total longshore current velocity vector, at any point across the surf zone, is composed of three distinct velocity components. These components are: (1) a steady longshore current velocity component; (2) a long-period fluctuating velocity component which tends to be out-of-phase with the incident wave field and; (3) a short-period fluctuating longshore current velocity component which tends to be in-phase with the incident wave field. The results of this study have further indicated that neither the deterministic radiation stress approach to the prediction of longshore currents, nor a probabilistic formulation, provide adequate prediction of the magnitude or distribution of the longshore current velocity across the surf zone. In addition, the existence of a low velocity zone in the longshore current flow field has been isolated over the submarine bar. It appears that existing analytical formulations for longshore current flow prediction must be re-evaluated in light of the findings of this study. (Author).

Download or read book Longshore current velocity written by Cyril Jerome Galvin and published by . This book was released on 1967 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Compilation of Longshore Current Data written by Cyril Jerome Galvin and published by . This book was released on 1967 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Topics in Longshore Currents written by John Casey Church and published by . This book was released on 1993 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book The Prediction of Longshore Currents written by John A. Putnam and published by . This book was released on 1949 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Simple Quasi three Dimensional Model of Longshore Currents Over Arbitrary Profile written by Antonio Fernando Garcez Faria and published by . This book was released on 1995 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: The long shore current maximum observed in the trough of a barred beach during the nearshore dynamics experiment DELILAH at Duck, North Carolina, is not predicted by present theory. The simplest longshore curren models balance cross-shore changes in the alongshore wave momentum (radiation stress) with the alongshore bottom shear stress. Waves break over the bar, reform in the trough and again break on the foreshore resulting in changes in the radiation stress, which predicts two jets, one over the bar and the other at the foreshore, which does not agree with the observed current maximum in the trough. The advection of the momentum of the longshore current by mean cross-shore currents as a source of momentum mixing is investigated. The longshore current is strongest toward the surface and decreasing to zero at the bottom. The cross-shore mean current has an onshore transport in the wave crest/trough region and an offshore transport beneath (undertow). The net interaction can induce significant lateral mixing of the alongshore momentum of the mean currents, which is shown using a simplified three- dimension model of nearshore currents to explain much of the differences with observations.

Download or read book Compilation of Longshore Current Data written by Cyril Jerome Galvin and published by . This book was released on 1967 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The paper is a compilation of published longshore current data available from North American sources as of January 1966. The data comprise 352 separate observations; of these 225 were obtained from four laboratory studies and 127 from four field studies. Each observation includes (at least) measured longshore current velocity, in feet per second; wave direction; a wave height, in feet; wave period, in seconds; and beach slope. Values of breaker height and breaker angle were computed for those observations lacking measured values. Longshore current velocity is usually less than 2 feet per second under both field and laboratory conditions. The maximum velocity observation from the field is 5.5 feet per second; from the laboratory 3.8 feet per second. (Author).

Download or read book Experimental Study of Longshore Currents on a Plane Beach written by Cyril Jerome Galvin and published by . This book was released on 1965 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Littoral Sand Transport from Longshore Currents written by Todd E. Walton and published by . This book was released on 1980 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Shear Instability of Longshore Currents and Their Interaction with Gravity Waves written by Ye Li and published by . This book was released on 2004 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Longshore Currents and Nearshore Topographies written by Choule J. Sonu and published by . This book was released on 1966 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Validity of seven analytical formula as well as linear and non-linear multiple regressive schemes was tested using field data from the Outer Banks, North Carolina. Generally, agreement proved unsatisfactory. Field experiences indicate that the longshore current is a velocity field consisting of a multitude of velocity vectors whose basic pattern varies depending upon the regimes of wave-current-topography interaction. The need to recognize topography as a responding variable as well as a process variable in the physical scheme of longshore current is emphasized.

Download or read book An Investigation of Longshore Currents written by J. A. Putnam and published by . This book was released on 1948 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Longshore Current and Sediment Transport written by Edward Bennett Thornton and published by . This book was released on 1969 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt: On the basis of a simplified model, an attempt is made to completely describe littoral processes including both longshore current and sand transport. Emphasis is placed on formulating usable predictive equations for engineering practice. Abstract.

Download or read book Vertical Profiles of Longshore Currents written by Carlos Manuel da Costa Ventura Soares and published by . This book was released on 1995 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimental Study of Longshore Currents on a Plane Beach written by Cyril Jerome Galvin and published by . This book was released on 1965 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Wind and Wave Forcing of Longshore Currents Across a Barred Beach written by Dennis James Whitford and published by . This book was released on 1988 with total page 238 pages. 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).