Author: John Casey Church
Publisher:
ISBN:
Category : Littoral drift
Languages : en
Pages : 140
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.
Topics in Longshore Currents
Author: John Casey Church
Publisher:
ISBN:
Category : Littoral drift
Languages : en
Pages : 140
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.
Publisher:
ISBN:
Category : Littoral drift
Languages : en
Pages : 140
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.
Wind and Wave Forcing of Longshore Currents Across a Barred Beach
Author: Dennis James Whitford
Publisher:
ISBN:
Category : Banks (Oceanography)
Languages : en
Pages : 238
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).
Publisher:
ISBN:
Category : Banks (Oceanography)
Languages : en
Pages : 238
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).
Experimental Study of Longshore Currents on a Plane Beach
Author: Cyril Jerome Galvin
Publisher:
ISBN:
Category : Beaches
Languages : en
Pages : 96
Book Description
Publisher:
ISBN:
Category : Beaches
Languages : en
Pages : 96
Book Description
Longshore Current Velocity
Author: Cyril Jerome Galvin
Publisher:
ISBN:
Category : Ocean currents
Languages : en
Pages : 18
Book Description
Publisher:
ISBN:
Category : Ocean currents
Languages : en
Pages : 18
Book Description
Compilation of Longshore Current Data
Author: Cyril Jerome Galvin
Publisher:
ISBN:
Category : Littoral drift
Languages : en
Pages : 32
Book Description
Publisher:
ISBN:
Category : Littoral drift
Languages : en
Pages : 32
Book Description
Longshore Current Observations in Southern California
Author: United States. Beach Erosion Board
Publisher:
ISBN:
Category : Beach erosion
Languages : en
Pages : 60
Book Description
Publisher:
ISBN:
Category : Beach erosion
Languages : en
Pages : 60
Book Description
Technical Memorandum - U.S. Army Corps of Engineers, Coastal Engineering Research Center
Author: Coastal Engineering Research Center (U.S.)
Publisher:
ISBN:
Category : Beach erosion
Languages : en
Pages : 1082
Book Description
Publisher:
ISBN:
Category : Beach erosion
Languages : en
Pages : 1082
Book Description
Saving America's Beaches
Author: Scott L. Douglass
Publisher: World Scientific
ISBN: 9789812776907
Category : Science
Languages : en
Pages : 114
Book Description
This book tells you where beach sand comes from, how waves are formed and how they break and move sand down the coast, how OC works of manOCO have blocked this movement and caused beach erosion, and what can be done to save the beaches for future generations of Americans. A three-part prescription for healthy beaches is proposed: OC backing offOCO, OC bypassing sandOCO, and OC beach nourishmentOCO. So if you love waves and beaches, and care about the future of your favorite beach spot, then read this book while you enjoy the beach."
Publisher: World Scientific
ISBN: 9789812776907
Category : Science
Languages : en
Pages : 114
Book Description
This book tells you where beach sand comes from, how waves are formed and how they break and move sand down the coast, how OC works of manOCO have blocked this movement and caused beach erosion, and what can be done to save the beaches for future generations of Americans. A three-part prescription for healthy beaches is proposed: OC backing offOCO, OC bypassing sandOCO, and OC beach nourishmentOCO. So if you love waves and beaches, and care about the future of your favorite beach spot, then read this book while you enjoy the beach."
Littoral Sand Transport from Longshore Currents
Author: Todd E. Walton
Publisher:
ISBN:
Category : Littoral drift
Languages : en
Pages : 24
Book Description
Publisher:
ISBN:
Category : Littoral drift
Languages : en
Pages : 24
Book Description
Technical Memorandum
Author:
Publisher:
ISBN:
Category : Beach erosion
Languages : en
Pages : 844
Book Description
Publisher:
ISBN:
Category : Beach erosion
Languages : en
Pages : 844
Book Description