scholarly journals A NUMERICAL INVESTIGATION OF THE LONGSHORE CURRENT PROFILE FOR MULTIPLE BAR/TROUGH BEACHES

1986 ◽  
Vol 1 (20) ◽  
pp. 73 ◽  
Author(s):  
Steven K. Baum ◽  
David R. Basco
Keyword(s):  
Numerical Model ◽  
Wave Height ◽  
Water Depth ◽  
Balance Equation ◽  
Surf Zone ◽  
Momentum Balance ◽  
Longshore Current ◽  
Current Profile ◽  
Momentum Balance Equation ◽  
Wave Decay

A numerical model is developed which calculates the longshore current profile for an arbitrary bottom profile. The basis of the model is the use of radiation stress theory in a longshore momentum balance equation which includes a driving stress, a bottom stress, and a lateral mixing stress. Each of the stresses is derived from previously developed formulations, rederiving them to take into account separate cross shore variations in the wave height and the water depth, as well as the wave approach angle. This is done to dispense with the constant wave breaking index assumption used to model wave decay in the surf zone, which is rejected as unrealistic for natural beaches. A numerical model is used to calculate distributions of the wave height and water depth across the surf zone for arbitrary, yet realistic, bottom profiles. A numerical model of the theoretically derived longshore momentum balance equation is developed and solved using the distributions obtained from the wave decay model. The profiles calculated are compared to previous theoretical models and to laboratory and field measurements.

Surf zone transformation of wave height to water depth ratios

1992 ◽  
Vol 17 (1-2) ◽  
pp. 49-70 ◽  
Author(s):  
R.C. Nelson ◽  
J. Gonsalves
Keyword(s):  
Wave Height ◽  
Water Depth ◽  
Surf Zone

scholarly journals Electromagnetic momentum balance equation and the force density in material media

2012 ◽  
Vol 34 (2) ◽  
Author(s):  
I. Campos ◽  
J.L. Jiménez ◽  
M.A. López-Mariño
Keyword(s):  
Graduate Students ◽  
Lorentz Force ◽  
Balance Equation ◽  
Momentum Balance ◽  
Force Density ◽  
External Fields ◽  
Momentum Balance Equation ◽  
Current Distributions ◽  
Electromagnetic Momentum ◽  
Arbitrary Charge

We present a momentum balance equation derived directly from Maxwell's equations. This equation contains a force density, which we call Maxwell's force density, which generalizes the Lorentz force density, now including total fields rather than only external fields, and arbitrary charge and current distributions. As a test for this balance equation we derive for gases the electrostatic and magnetostatic Helmholtz force densities. This deduction will be useful for advanced undergraduates and graduate students, as well as for specialists interested in the conceptual aspects of electromagnetism.

scholarly journals THREE DIMENSIONAL FLOW PROFILES ON LITTORAL BEACHES

1988 ◽  
Vol 1 (21) ◽  
pp. 52 ◽  
Author(s):  
Ib A. Svendsen ◽  
Rene S. Lorenz
Keyword(s):  
Perturbation Method ◽  
Poisson Equation ◽  
Surf Zone ◽  
Three Dimensional ◽  
Longshore Current ◽  
Current Profile ◽  
Three Dimensional Flow ◽  
Flow Profiles ◽  
Current Variation ◽  
Averaged Models

The problem of combined cross-shore and longshore currents generated by waves in and around a surf zone is considered in its full three-dimensional formulation. The equations for the two current components are decoupled and it is found that for a cylindrical coast with no longshore variations the longshore current variation with depth and distance from the shoreline satisfies a Poisson equation. This equation is solved by a perturbation method and it is shown that the longshore velocities are always larger than the velocities found by classical theory. In the simple uncoupled case, the full 3-D current profile is constructed by combining the results with cross - shore velocities determined in previous publications. Also, the total velocities are larger than velocities found from simple depth averaged models.

scholarly journals AN HEURISTIC MODEL OF WAVE HEIGHT DISTRIBUTION IN SURF ZONE

1980 ◽  
Vol 1 (17) ◽  
pp. 15 ◽  
Author(s):  
Masaru Mizuguchi
Keyword(s):  
Surf Zone ◽  
Experimental Result ◽  
Height Distribution ◽  
Heuristic Model ◽  
Longshore Current ◽  
Current Profile ◽  
Beach Profile ◽  
Wave Height Distribution ◽  
Constant Slope ◽  
Step Type

Until now, almost every study on coastal processes has considered the basic type of two-dimensional beach profile as being of constant slope. However, as our knowledge on this problem advances, we realize the importance of the influences of the bottom configuration on the hydrodynamic phenomena in a given area. Figure 1 shows a recent experimental result on the longshore current profile on a step type beach. ( Here the step type beaches are defined as those which have a step in the bottom profile, whether the beaches are of accretion type or not.)

scholarly journals Sea-ice mechanical energy balance: nearshore Chukchi Sea, 1982

1991 ◽  
Vol 15 ◽  
pp. 63-72
Author(s):  
Robert S. Pritchard
Keyword(s):  
Energy Balance ◽  
Sea Ice ◽  
Balance Equation ◽  
Driving Forces ◽  
Chukchi Sea ◽  
Mechanical Energy ◽  
Power Input ◽  
Energy Balance Equation ◽  
Momentum Balance ◽  
Momentum Balance Equation

The mechanical energy balance of sea ice provides information about ice dynamic behavior, driving forces and the constitutive law. The energy balance equation, formed as the product of ice velocity with the ice momentum balance equation, describes changes to the kinetic and potential energy densities as power is input to the ice by wind and current. The momentum balance equation may also be used to describe the ice-stress divergence, air stress, and water stress, but the scalar form of the energy balance is simpler to understand. This paper provides new interpretations of several terms in the energy balance equation, in particular power input by air and water stress and by sea-surface tilt. Barometric pressure fields and drifting buoys deployed on the Chukchi Sea ice cover during 1982 provide wind, ice motion and current measurements that allow each term in the energy balance equation to be evaluated as a function of time. Magnitudes of power input by wind and current show how the energy balance is decomposed and help describe the relative importance of these driving forces. In the nearshore Chukchi Sea during February, March and April 1982, both wind and current provided significant forcing of the ice. Ice stress was also important and, at times, dominated other terms in the mechanical energy balance.

Assessment of the wave attenuation capacity of a mangrove forest based on its age and the incident wave conditions

2020 ◽  
Author(s):  
Maria Maza ◽  
Javier L. Lara ◽  
Iñigo J. Losada
Keyword(s):  
Wave Height ◽  
Water Depth ◽  
Mangrove Forest ◽  
Wave Attenuation ◽  
Volume Fraction ◽  
Coastal Protection ◽  
Local Flow ◽  
Ecosystem Properties ◽  
Wave Decay ◽  
Wave Conditions

<p>Although mangroves reduce annual flooding to millions of people there is not a methodology to implement these solutions and it is still difficult to estimate the protection provided by them under different environmental conditions and ecosystem properties. To move forward in the consecution of an engineering approach when implementing these solutions for coastal defense, the first step to make is to better understand and parameterize the basic physical processes involved in flow-mangroves interaction. With the aim of getting a new formulation for wave decay provided by Rhizophora mangrove forests based on flow and ecosystem properties, an experimental campaign was carried out where both wave attenuation and forces on mangrove individuals were measured under different wave conditions. Both, the hydrodynamic conditions and the mangrove forest, were scaled according to field conditions for short waves. The detailed wave attenuation and drag force measurements obtained in these experiments allowed to obtain new formulations of wave decay produced by the forest depending on the flow, i.e.: water depth, wave height and period, and on the forest characteristics, i.e.: individuals submerged solid volume fraction and density. These formulations are used to get attenuation rates under different flow and ecosystem conditions. The resultant curves provide with the wave decay produced by a specific Rhizophora forest subjected to the defined wave conditions. The forest is defined on the basis of its age, considering the differences in individual trees depending on their maturity and the density of the forest as the number of trees per unit area. Wave conditions are defined by the root mean square wave height and the peak period and water depth is also considered. The obtained curves allow to estimate the width of the forest necessary to reach a certain level of protection considering the local flow conditions and the forest age. This can assist in the inclusion of nature-based solutions in the portfolio of coastal protection measures.</p>

scholarly journals The FENE Dumbbell Polymer Model: Existence and Uniqueness of Solutions for the Momentum Balance Equation

2014 ◽  
Vol 26 (2) ◽  
pp. 217-241 ◽  
Author(s):  
Adriana Valentina Busuioc ◽  
Ionel Sorin Ciuperca ◽  
Dragoş Iftimie ◽  
Liviu Iulian Palade
Keyword(s):  
Balance Equation ◽  
Existence And Uniqueness ◽  
Momentum Balance ◽  
Polymer Model ◽  
Uniqueness Of Solutions ◽  
Momentum Balance Equation ◽  
Model Existence
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