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A series of three-dimensional laboratory experiments on beach nourishment behavior are described and analyzed. The experiments were designed to isolate the influences of berm height, beachfill median grain size, wave height, and wave period. The results have not been scaled up to prototype conditions, but many features of the laboratory evolution have also been observed in previous field studies. Laboratory results indicate that beachfill half-life (time required for half of the added volume to leave the nourished footprint) is inversely correlated with wave height, and positively correlated with berm height. A weak positive correlation with grain size was found. The influence of wave period was inconclusive. A coupled model describing the effects of both longshore and cross-shore sediment transport was developed and applied. The model accounts for the rapid loss of nourishment material offshore via cross-shore sediment transport, followed by a more gradual redistribution up- and downcoast of the project via longshore sediment transport. The influence of cross-shore sediment transport decreases as the beach slope approaches that of the prenourishment beach. The new model has not been calibrated for application at field scales, but it does reproduce the salient features of the laboratory dataset, and previous field data sets, such as the flattening of the beach profile as the project evolves. By describing the position of three elevation contours (berm crest, waterline, and beachfill toe), it thus provides a more realistic alternative to the “one-line” models often applied to beach nourishment problems by accounting for cross-shore sediment transport. [ABSTRACT FROM AUTHOR]

This study employs an existing finite-difference model based on the hyperbolic form of the modified mild slope equation (MMSE) to investigate wave reflection near bathymetric depressions such as dredged borrow pits and nearshore canyons. First, the model is tested for numerical limitations on the higher order bottom slope and curvature terms using idealized cases of a simple depth transition and a symmetric trapezoidal trench, with comparisons of the MMSE to both the traditional mild slope equation (MSE) solution and a shallow water analytic solution. It is demonstrated that the model gives accurate solutions on slopes as steep as 1:1, and that the solutions from all three models agree in the shallow water region. However, for waves in intermediate depths, predicted wave reflection from nearshore depressions is shown to differ significantly between the MMSE and MSE models. Next, geometrical data from a wide range of existing and proposed borrow pits and a submarine canyon are gathered and analyzed for whether wave reflection is an important process near realistic nearshore depressions. The geometric data show that realistic nearshore depressions lie within the tested range of the MMSE model and that borrow pits are generally not in shallow water, which means it is important to use a MMSE-type model to calculate reflection from these features. In addition, storm conditions on average lead to a 50% increase in reflection coefficient in comparison to the mean wave conditions, due to the increase in wave period. Finally, the results also indicate borrow pit design criteria that can be used to ensure minimal reflection. [ABSTRACT FROM AUTHOR]

The paper presents the results of model scale experiments for the study of wave attenuation by horizontal interlaced, multilayer, moored floating pipe breakwater. A review of some significant floating breakwater models proposed by earlier investigators is included. For a floating breakwater the transmission coefficient (Kt) is influenced by relative width of the breakwater (W/L). Nondimensional graphs indicating the variation of Kt with respect to W/L (with Hi/L as a parameter for different Hi/d values) and Kt versus Hi/L (for a range of d/L values from 0.09 to 0.24) have been plotted. Further variation of Kt with relative depth d/L for different W/L values is also studied. From the experimental study and results obtained, it is found that the transmission coefficient decreases with an increase in relative breakwater width W/L and wave steepness Hi/L for all Hi/d values. In the present study it was observed that performance was better for breakwater configurations of W/L>=0.7 when compared with configurations of W/L<0.7. Further, the experimental results obtained were compared with the output of a mathematical model. From the comparison for Hi/L=0.04, values of Kt obtained from the present experiments were in agreement with those obtained from the mathematical model. [ABSTRACT FROM AUTHOR]

The accuracy of using high-order Boussinesq-type models as compared to the typical order models is examined in this paper. The high-order model used is the two-layer model of Lynett and Liu in 2004, which captures both linear and nonlinear wave evolution up to kh≈6. The physical situations examined all involve nearshore breaking, and an eddy-viscosity type breaking model is adopted for the two-layer model. One-horizontal dimension setups are the focus of this paper. It is shown that high-order models show significant benefit very near to the breaker line. For regular incident waves, the overshoaling seen in the one-layer (“fully nonlinear” extended Boussinesq) model is due to rapid increase of energy in the fifth and higher harmonics. These high-order nonlinear components are captured well in the two-layer model. The two-layer model also exhibits a noticeable accuracy increase for cnoidal waves breaking on a slope. For regular wave evolution over a bar, the high-order models are in good agreement with experiment, correctly modeling the free short waves behind the step. Under irregular wave conditions, it is likewise shown that high-order nonlinearity is important near the breaker line and the outer surf zone. Using SwashX field data, spectral comparisons are made and discussed. [ABSTRACT FROM AUTHOR]

Estimation of a wave spectrum from specified values of significant wave heights and average zero cross periods is traditionally made through empirical equations like those of Pierson–Moskowitz and Jonswap. This technical note discusses an alternative scheme based on artificial neural network. Wave spectral distribution over various wave frequencies was obtained for given values of significant wave height and period using feedforward back-propagation network. The rider buoy data at a site off the United States coast monitored by the National Data Buoy Center was used as a basis for network development. Qualitative as well as quantitative comparisons of the network-yielded spectra with target spectra indicated that the developed network could model the wave spectral shapes in a better way than commonly used theoretical spectra. [ABSTRACT FROM AUTHOR]

This article comments on the article "Predictions of Missing Wave Data by Recurrent Neuronets," by Can Elmar Balas, Levent Koç and Lale Balas. Several methods for estimating missing wave data recorded by directional wave bouys are compared by the authors. The authors developed several mathematical models for estimating missing wave. The data from 12 months of noncontinuous measurements at the directional wave buoy of Alanya, Thurkey were the only data used for training the models. The less than two weeks of data used for training the models is an unacceptably low volume of wave-climate information to properly characterize any wave measurement station, according to the reviewers.

A vertical two-dimensional numerical model for local scour beneath an offshore pipeline exposed to waves is developed in this study. Waves are modeled as sinusoidally oscillatory flows, and the phase-resolved velocity field around the pipeline is simulated by solving the Reynolds-averaged Navier-Stokes equations with a k-ω turbulence closure. Both suspended and bed loads of sediment transport are considered in the model. A special technique for coupling the solution of the flow field to the scour calculation is developed to accommodate different timescales of the flow and morphological changes. The seabed morphology calculation is based on the period-averaged sediment transport rate with a morphological time step that is chosen by designating a maximum allowable bed deformation in each update. Numerical tests indicate that this technique significantly reduces the computational costs and is of acceptable accuracy. A sand-slide method is employed after each bed update to smooth out small bed irregularities. The model is applied to simulate three cases of wave-induced scour below a pipeline where laboratory measurements were published in the literature. The predicted scour-hole profiles compare favorably with the laboratory observations. [ABSTRACT FROM AUTHOR]

Recent advances in the Boussinesq modeling of nearshore hydrodynamics offer a platform for the study of wind effects on wave transformation and breaking-generated nearshore circulation. The paper documents: (1) the new parameterization of the momentum flux transferred from the wind to surface gravity waves in the coastal region on the basis of the field observations; (2) the implementation of the parameterized wind stress into phase-resolving Boussinesq wave models; (3) the development of empirical breaking criteria with the wind effect based on the existing laboratory data; and (4) the tests of the extended Boussinesq model against field observations and empirical results with respect to wind drag coefficients over shoaling waves and wave growth on a shallow lake. Fairly good agreement between the model results and measurements is observed. The methodology for the parameterization of the wind stress as a function of wave steepness and wind speed as well as the extended Boussinesq model incorporating the wind forcing can be used as a tool to improve our understanding of wind effects on nearshore wave propagation and horizontal circulation. [ABSTRACT FROM AUTHOR]

A 3D numerical solution was derived to determine the wave field in a physical wave tank equipped with a porous wave absorber of variable width and draft. The solution was achieved by applying the boundary element method. The model was applied to analyze the effect of the geometry and material of wave absorbers on wave reflection to eventually equip a wave tank with a proper wave absorber. The results show that absorber geometry has a complex, often surprising and nonintuitive effect on wave reflection. A more pronounced effect on wave reflection possesses physical and hydraulic properties of the material used to build a wave absorber. A reduction of wave reflection can usually be achieved by increasing absorber length and simultaneously decreasing its slope, and often a reduction of wave reflection can be achieved by increasing absorber draft or width. Moreover, a reduction of wave reflection, often substantial, can be achieved by increasing porosity and the damping coefficient. The results and additional analysis show that a reasonable wave reflection level can already be achieved for fairly short absorbers, and the model can be applied to select an optimal wave absorber for any prespecified conditions. Theoretical results are in reasonable agreement with experimental data. [ABSTRACT FROM AUTHOR]

Presents information on a study which developed a local two-phase nonlinear hydrodynamic numerical model to simulate oil containment by a fixed boom under open-water conditions. General equations; Simulation of free-surface elevation under current and wave conditions; Effect of nonhydrostatic pressure on oil slick shape.

Presents information on a study which applied a numerical model that numerically predicts the relationship between oil containment failure velocity and wave/wind parameters. Influence of wind on failure velocity; Effect of viscosity and density on failure velocity; Effects of oil volume and boom draft on the failure velocity under wave conditions.

This article presents a closure to the article "Predictions of Missing Wave Data by Recurrent Neuronets," by Can Elmar Balas, Levent Koç and Lale Balas. The authors address each issues discussed by the reviewers including how the number of data used for training is low to characterize wave measurement station, and the charts and statistics are showing poor prediction capacity of the proposed multistep method. The possibility of overlearning taking place in training because the number of free parameters of the proposed mathematical models is similar to or higher than the number of data points used for training.