scholarly journals LATERAL MIXING AND WAVE DIRECTION IN THE WAVE-CURRENT INTERACTION REGICN

1986 ◽  
Vol 1 (20) ◽  
pp. 29
Author(s):  
Kyoung Ho Kim ◽  
Sawaragi Toru ◽  
Deguchi Ichiro
Keyword(s):  
Surf Zone ◽  
Three Dimensional ◽  
Electromagnetic Current ◽  
Wave Direction ◽  
Wave Energy Dissipation ◽  
Wave Flume ◽  
Mixing Coefficient ◽  
Lateral Mixing ◽  
Current Interaction ◽  
Wave Angle

The lateral mixing coefficient, in which the wave energy dissipation by wave breaking is taken account and the assumption of Richardson's 4/3 power law is involved, is derived for the surf zone and the diffusion of tracers injected in the wave-current interaction region is discussed experimentally to investigate the proposed lateral mixing coefficient. Furthermore measurements of velocity field on the three dimensional sloping beach of plane wave flume have been made by a bidirectional electromagnetic current meter. The results were used to investigate the characteristics of the structure of on-offshore and alongshore mean currents arid the techniques for the determination of wave angle in the surf zone.

scholarly journals ABOUT THE ENERGY DISSIPATION OVER BARRED BEACH

1988 ◽  
Vol 1 (21) ◽  
pp. 20
Author(s):  
Johannes Oelerich ◽  
Hans-Henning Dette
Keyword(s):  
Stochastic Process ◽  
Energy Dissipation ◽  
Surf Zone ◽  
Field Measurements ◽  
The West ◽  
Wave Energy Dissipation ◽  
Wave Flume ◽  
Moderate Energy ◽  
Empirical Approaches ◽  
Spilling Breaker

Since wave energy dissipation in the surf zone is a stochastic process closed mathematical formulations cannot be expected. The dissipation was computed using several analytical and/or empirical approaches and compared with prototype measurements in the Big Wave Flume (GWK) in Hannover as well as with field measurements from the west coast, of the Island of Sylt/North Sea. Generally good agreements were found for moderate energy dissipation conditions (spilling-breaker), whereas in the case of plunging breakers, however, the fitting is not solved satisfactory.

Nearshore mixing and dispersion

1994 ◽  
Vol 445 (1925) ◽  
pp. 561-576 ◽  
Keyword(s):  
Surf Zone ◽  
Three Dimensional ◽  
Dispersion Effect ◽  
Longshore Current ◽  
Turbulent Length Scale ◽  
Interaction Terms ◽  
Longshore Currents ◽  
Order Of Magnitude ◽  
Lateral Mixing ◽  
The One

Longshore currents have in the past been analysed assuming that the lateral mixing could be attributed to turbulent processes. It is found, however, that the mixing that can be justified by assuming an eddy viscosity v t = l√k where l is the turbulent length scale, k the turbulent kinetic energy, combined with reasonable estimates for l and k is at least an order of magnitude smaller than required to explain the measured cross-shore variations of longshore currents. In this paper, it is shown that the nonlinear interaction terms between cross-and longshore currents represent a dispersive mechanism that has an effect similar to the required mixing. The mechanism is a generalization of the one-dimensional dispersion effect in a pipe discovered by Taylor (1954) and the three-dimensional dispersion in ocean currents on the continental shelf found by Fischer (1978). Numerical results are given for the dispersion effect, for the ensuing cross-shore variation of the longshore current and for the vertical profiles of the longshore currents inside as well as outside the surf zone. It is found that the dispersion effect is at least an order of magnitude larger than the turbulent mixing and that the characteristics of the results are in agreement with the sparse experimental data material available.

scholarly journals THEORETICAL MODEL FOR NEARSHORE CIRCULATIONS

1988 ◽  
Vol 1 (21) ◽  
pp. 28
Author(s):  
Mikio Sasaki ◽  
Akira Ozaki ◽  
Hiroshi Saeki
Keyword(s):  
Surf Zone ◽  
Perturbation Expansion ◽  
Break Point ◽  
Bottom Friction ◽  
First Order ◽  
Maximum Value ◽  
Lateral Mixing ◽  
Current Interaction ◽  
The Mean ◽  
Offshore Region

The dynamics of nearshore circulations is investigated using mass, momentum and energy conservation equations with bottom friction, lateral mixing and wave-current interaction. By means of introducing a perturbation expansion for the mean variables, the first-order solutions are found in the surf and offshore zones according to the boundary conditions at the coast. It is found that:(l) The rip velocity attains a maximum value in the offshore region near the break point as Yr* becomes larger. (2) The longshore velocities become higher in the surf zone and lower in the offshore region with increasing Yr*. (3) The rip and longshore velocities in the surf zone become relatively smaller due to the effects of the bottom friction, and that the rip and longshore velocities in the surf zone become smaller due to the wave-current interaction.

scholarly journals Development and Validation of Quasi-Eulerian Mean Three-Dimensional Equations of Motion Using the Generalized Lagrangian Mean Method

2021 ◽  
Vol 9 (1) ◽  
pp. 76
Author(s):  
Duoc Nguyen ◽  
Niels Jacobsen ◽  
Dano Roelvink
Keyword(s):  
Surface Waves ◽  
Deep Water ◽  
Surf Zone ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Breaking Waves ◽  
Successful Implementation ◽  
Random Waves ◽  
Mean Motion ◽  
Generalized Lagrangian

This study aims at developing a new set of equations of mean motion in the presence of surface waves, which is practically applicable from deep water to the coastal zone, estuaries, and outflow areas. The generalized Lagrangian mean (GLM) method is employed to derive a set of quasi-Eulerian mean three-dimensional equations of motion, where effects of the waves are included through source terms. The obtained equations are expressed to the second-order of wave amplitude. Whereas the classical Eulerian-mean equations of motion are only applicable below the wave trough, the new equations are valid until the mean water surface even in the presence of finite-amplitude surface waves. A two-dimensional numerical model (2DV model) is developed to validate the new set of equations of motion. The 2DV model passes the test of steady monochromatic waves propagating over a slope without dissipation (adiabatic condition). This is a primary test for equations of mean motion with a known analytical solution. In addition to this, experimental data for the interaction between random waves and a mean current in both non-breaking and breaking waves are employed to validate the 2DV model. As shown by this successful implementation and validation, the implementation of these equations in any 3D model code is straightforward and may be expected to provide consistent results from deep water to the surf zone, under both weak and strong ambient currents.

scholarly journals TOWARD AN IMPROVED EMPIRICAL FORMULA FOR LONGSHORE SAND TRANSPORT

1988 ◽  
Vol 1 (21) ◽  
pp. 88 ◽  
Author(s):  
Nicholas C. Kraus ◽  
Kathryn J. Gingerich ◽  
Julie Dean Rosati
Keyword(s):  
Oscillatory Flow ◽  
Field Experiments ◽  
Surf Zone ◽  
Transport Rate ◽  
Sand Transport ◽  
Longshore Current ◽  
Wave Energy Dissipation ◽  
Total Transport ◽  
Local Wave ◽  
Correction Terms

This paper presents results of two field experiments performed using portable traps to obtain point measurements of the longshore sand transport rate in the surf zone. The magnitude of the transport rate per unit width of surf zone is found to depend on the product of the local wave height and mean longshore current speed, but correlation is much improved by including two correction terms, one accounting for local wave energy dissipation and the other for the fluctuation in the longshore current. The field transport rates are also found to be compatible with laboratory rates obtained under combined unidirectional and oscillatory flow. Total transport rates previously reported for this experiment program are revised with recently determined sand trapping efficiencies.

scholarly journals STORM INDUCED PERIODICITIES OF SUSPENDED SAND MOVEMENT

1978 ◽  
Vol 1 (16) ◽  
pp. 105 ◽  
Author(s):  
Jay E. Leonard ◽  
Benno M. Brenninkmeyer
Keyword(s):  
Surf Zone ◽  
Normal Wave ◽  
Low Frequency ◽  
Sediment Concentration ◽  
Frequency Component ◽  
High Frequency Component ◽  
Computational Technique ◽  
Electromagnetic Current ◽  
Discrete Fourier Analysis ◽  
Sediment Movement

An array of electronic sensors was installed on Nauset Light Beach, Cape Cod, Massachusetts, U.S.A., in order to provide a description of the sediment movement during storm conditions. These sensors included two sediment concentration indicators (almometers) which monitor sediment movement as a function of elevation and time, one bidirectional electromagnetic current meter, and a resistive wave staff. Prior field studies performed during "normal" conditions have indicated that surf-zone suspended sediment movement is a low-frequency phenomenon, with the relatively high-frequency component (normal wave period) contributing little to the amount of total sediment transported. Development of a computational technique based upon discrete Fourier analysis and digital filtering called Spectrally Filtered Integration (SFI) provides the calculation and filtering of true units of sediment change in grams-per-liter. Moreover, the SFI technique eliminates the possibility spurious sediment information created by the presence of air bubbles in the water column. Generally, higher-frequency sediment movement is more common during storm conditions than during normal non-storm conditions. This movement is controlled not by the prevailing wave and swell periods, but by a longer period which may be due to water interactions below the surface.

scholarly journals WAVE RUN-UP AT SEA DIKES UNDER OBLIQUE WAVE APPROACH

1982 ◽  
Vol 1 (18) ◽  
pp. 50
Author(s):  
E. Tautenhain ◽  
S. Kohlhase ◽  
H.W. Partenscky
Keyword(s):  
Irregular Waves ◽  
Wave Direction ◽  
Wave Runup ◽  
Natural Conditions ◽  
Wave Impact ◽  
Oblique Wave ◽  
Wave Flume ◽  
Wave Approach ◽  
Impact Forces ◽  
Run Up

Besides wave impact forces, erosion of the inner side of a sea dike is a serious cause of destruction. Therefore, wave run-up and overtopping effects have to be considered with respect to the safety of a dike. Strong relations were found between both these influences (TAUTENHAIN et.al., 1980, 1981, 1982), based on experiments in a wave flume and using an energy conservation concept. However, under natural conditions, an oblique wave approach has to be considered. This paper deals with the influence of wave direction on wave runup on a smooth dike slope in order to provide a basis for calculating the overtopping rates for both regular and irregular waves.

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.

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