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Abstract: This paper presents the new active absorption wave basin, named Hydrodynamic Calibrator (HC), constructed at the University of São Paulo (USP), in the Laboratory facilities of the Numerical Offshore Tank (TPN). The square (14m×14m) tank is able to generate and absorb waves from 0.5Hz to 2.0Hz, by means of 148 active hinged flap wave makers. An independent mechanical system drives each flap by means of a 1HP servo-motor and a ball-screw based transmission system. A customized ultrasonic wave probe is installed in each flap, and is responsible for measuring wave elevation in the flap. A complex automation architecture was implemented, with three Programmable Logic Computers (PLCs), and a low-level software is responsible for all the interlocks and maintenance functions of the tank. Furthermore, all the control algorithms for the generation and absorption are implemented using higher level software (MATLAB®/Simulink block diagrams). These algorithms calculate the motions of the wave makers both to generate and absorb the required wave field by taking into account the layout of the flaps and the limits of wave generation. The experimental transfer function that relates the flap amplitude to the wave elevation amplitude is used for the calculation of the motion of each flap. This paper describes the main features of the tank, followed by a detailed presentation of the whole automation system. It includes the measuring devices, signal conditioning, PLC and network architecture, real-time and synchronizing software and motor control loop. Finally, a validation of the whole automation system is presented, by means of the experimental analysis of the transfer function of the waves generated and the calculation of all the delays introduced by the automation system. [Copyright &y& Elsevier]

Abstract: The present paper and its companion (Higuera et al., 2012) introduce OpenFOAM® as a tool to consider for coastal engineering applications as it solves 3D domains and considers two-phase flow. In this first paper, OpenFOAM® utilities are presented and the free surface flow solvers are analysed. The lack of specific boundary conditions for realistic wave generation is overcome with their implementation combined with active wave absorption. Wave generation includes all the widely used theories plus specific piston-type wavemaker replication. Also standalone active wave absorption implementation is explained for several formulations, all of which are applicable to 3D cases. Active wave absorption is found to enhance stability by decreasing the energy of the system and to correct the increasing water level on long simulations. Furthermore, it is advantageous with respect to dissipation zones such as sponge layers, as it does not increase the computational domain. The results vary depending on the theory (2D, Quasi-3D and 3D) but overall performance of the implemented methods is very good. The simulations and results of the present paper are purely theoretical. Comparisons with laboratory data are presented in the second paper (Higuera et al., 2012). [Copyright &y& Elsevier]

A two-dimensional (2D) numerical model is developed for the wave simulation and propagation in a wave flume. The fluid flow is assumed to be viscous and incompressible, and the Navier-Stokes and continuity equations are used as the governing equations. The standard k- ɛ model is used to model the turbulent flow. The Navier-Stokes equations are discretized using the staggered grid finite difference method and solved by the simplified marker and cell (SMAC) method. Waves are generated and propagated using a piston type wave maker. An open boundary condition is used at the end of the numerical flume. Some standard tests, such as the lid-driven cavity, the constant unidirectional velocity field, the shearing flow, and the dam-break on the dry bed, are performed to valid the model. To demonstrate the capability and accuracy of the present method, the results of generated waves are compared with available wave theories. Finally, the clustering technique (CT) is used for the mesh generation, and the best condition is suggested. [ABSTRACT FROM AUTHOR]

Researchers who study in-situ internal waves like to obtain first hand knowledge and data about the natural phenomenon from the ocean and river estuaries. However, it is difficult to obtain information from in-situ data. Scientists examine well-defined factors such as the topography, angular magnitude of slope and wave energy and the relationship between such factors. Aside from collecting in-situ data, researchers design water tank systems that imitate the real ocean environment where they can carry out sensitive investigations. In recent decades, such laboratory experiments have made a significant contribution to the exploration of the following: the variation of incident wave frequency with rotational effects, the quantification of the degree of internal wave reflection, as well as vortex formation and evolution on the lee side. Experimental studies have helped understand the movement of a natural internal wave in the ocean, and the mechanisms of wave generation, propagation, circulation, dissipation, evolution etc. We review the latest work related to laboratory experiments and the theoretical kinematics needed for a better understanding of a natural internal solitary wave. Finally, we summarize the characteristics of the governing equations and related experimental information for advanced connection in further study. [ABSTRACT FROM PUBLISHER]

Landslide-generated tsunami predictions are commonly based on two-dimensional (2D) wave channel or three-dimensional (3D) wave basin experiments with considerably different outcomes. It is not fully understood which idealized water body geometry applies best to a specific prototype. Hence, a physical small-scale model study has been conducted that, for the first time, systematically investigates the effect of geometry on landslide-generated tsunami height, amplitude, period, and celerity. A rigid slide generated tsunamis propagating in various geometries characterized by the basin side angle. Considered were 2D (= 0°), 3D (= 90°), and six intermediate geometries. The differences between 2D and 3D wave heights were found to be about 20% at a distance of five times the water depth from the slide impact zone, but increased with increasing distance. It is shown that the 3D case applies on a much wider prototype range than the 2D case because it approximates the wave features on the slide axis for all investigated geometries with > 30°. The energy flux conservation based on the given 2D results can predict wave heights for the remaining geometries with ℸ 30°. The implications of the present results in practice are discussed and an example illustrates how the results support tsunami hazard assessment despite significant scale effects. [ABSTRACT FROM AUTHOR]

Land-based high-frequency (HF) radars have the unique capability of continuously monitoring ocean surface environments at ranges up to 200 km off the coast. They provide reliable data on ocean surface currents and under slightly stricter conditions can also give information on ocean waves. Although extraction of wind direction is possible, estimation of wind speed poses a challenge. Existing methods estimate wind speed indirectly from the radar derived ocean wave spectrum, which is estimated from the second-order sidebands of the radar Doppler spectrum. The latter is extracted at shorter ranges compared with the first-order signal, thus limiting the method to short distances. Given this limitation, we explore the possibility of deriving wind speed from radar first-order backscatter signal. Two new methods are developed and presented that explore the relationship between wind speed and wave generation at the Bragg frequency matching that of the radar. One of the methods utilizes the absolute energy level of the radar first-order peaks while the second method uses the directional spreading of the wind generated waves at the Bragg frequency. For both methods, artificial neural network analysis is performed to derive the interdependence of the relevant parameters with wind speed. The first method is suitable for application only at single locations where in situ data are available and the network has been trained for while the second method can also be used outside of the training location on any point within the radar coverage area. Both methods require two or more radar sites and information on the radio beam direction. The methods are verified with data collected in Fedje, Norway, and the Ligurian Sea, Italy using beam forming HF WEllen RAdar (WERA) systems operated at 27.68 and 12.5 MHz, respectively. The results show that application of either method requires wind speeds above a minimum value (lower limit). This limit is radar frequency dependent and is 2.5 and 4.0 m/s for 27.68 and 12.5 MHz, respectively. In addition, an upper limit is identified which is caused by wave energy saturation at the Bragg wave frequency. Estimation of this limit took place through an evaluation of a year long database of ocean spectra generated by a numerical model (third generation WAM). It was found to be at 9.0 and 11.0 m/s for 27.68 and 12.5 MHz, respectively. Above this saturation limit, conventional second-order methods have to be applied, which at this range of wind speed no longer suffer from low signal-to-noise ratios. For use in operational systems, a hybrid of first- and second-order methods is recommended. [ABSTRACT FROM AUTHOR]

Abstract: A numerical model, which can simulate wave generation and propagation is developed to simulate oscillations induced by seafloor movements inside a harbor of constant slope, and once verified and then validated through comparison with experimental results, the numerical results are used to examine the analytic solutions presented in Wang et al. (Wang, G., Dong, G., Perlin, M., Ma, X., Ma, Y., 2011. An analytic investigation of oscillations within a harbor of constant slope. Ocean Engineering 38, 479–486). Small-scale seafloor movement usually induces small longitudinal oscillations, but evident larger transverse oscillations. These transverse oscillations are sensitive to the location of the moveable seafloor. The numerical result of each transverse eigen frequency compares well with the theoretical solution; in addition the spatial structure of each mode is also well-captured by the theory. Furthermore, evident/larger longitudinal oscillations induced by large-scale seafloor movements are simulated, and the numerical resonant frequencies agree favorably with the analytical solutions. These longitudinal oscillations are sensitive to the horizontal location of the moveable seafloor. [Copyright &y& Elsevier]

Abstract: In the past years the existence of freak waves has been affirmed by observations, registrations, and severe accidents. One of the famous real-world registrations is the so-called “New Year Wave” recorded in the North Sea at the Draupner jacket platform on January 1, 1995. Since there is only a single point registration available, it is not possible to draw conclusions on the spatial development in front of and behind the point of registration, which is indispensable for a complete understanding of this phenomenon. This paper presents the temporal and spatial development of the “New Year Wave” generated in a seakeeping basin. This extreme sea state is measured at different locations in the tank, in a range from 2163m (full scale) ahead of to 1470m behind the target position—520 registrations altogether. The focus lies on the detailed description of a possible evolution of the “New Year Wave” over a large area. The group velocity, wave propagation and energy flux of this wave group as well as the wave kinematics and dynamics are analysed. As a case study a Ro/Ro vessel has been investigated in the “New Year Wave”, with special emphasis on the vertical bending moment. [Copyright &y& Elsevier]

Abstract: Subaerial landslide generated impulse waves were investigated in a prismatic wave channel. Seven governing parameters, namely the still water depth, slide impact velocity, slide thickness, bulk slide volume, bulk slide density, slide impact angle, and grain diameter, were systematically varied. The generated impulse waves are nonlinear, intermediate- to shallow-water waves involving a small to considerable fluid mass transport. The Stokes wave, cnoidal wave, solitary wave, and bore theories were applied to describe the observed maximum waves. The theoretical and observed features of these four wave types are highlighted. A diagram allows to predict the wave type directly as a function of the slide parameters, the slide impact angle, and the still water depth. [Copyright &y& Elsevier]

The cooperative motion of a fluid and a parabolic tank is modeled. Use is made of a discrete model based on the Hamilton-Ostrogradsky principle for an arbitrary body of revolution and a non-Cartesian parametrization of the domain occupied by the fluid. A set of coordinate functions satisfying kinematic boundary conditions and solvability conditions is set up. The discrete model is used to study the transients in the system. It is shown that the model adequately describes the nonlinear dynamic properties of the system [ABSTRACT FROM AUTHOR]

series of carefully controlled experiments on the wave-generation characteristics of a model of a compartmented surface-effect ship has been conducted in a towing tank. Configurations of the model included cases encompassing one subcushion and two subcushions, as well as differing values of the pressures in the subcushions. It was shown that a reduced wave generation in the appropriate Froude number range could be achieved in this manner. Furthermore, a previously developed theory for the wave generation of marine vessels was verified for the model for a Froude number greater than 0.40. [ABSTRACT FROM AUTHOR]

Subaerial landslide generated impulse waves were investigated in a prismatic wave channel based on Froude similitude and granular slide material. The tests included the following seven governing parameters: still water depth, slide impact velocity, slide thickness, bulk slide volume, bulk slide density, slide impact angle, and grain diameter. All governing parameters, except for the grain diameter with a negligible effect, are included in the impulse product parameter P allowing for a simple application. Empirical equations based on 211 experiments for all relevant wave features in practice including the maximum wave height, the maximum wave amplitude with its location and period in the slide impact zone, and both the wave height and amplitude decay and the period increase in the wave propagation zone are a simple function of P. The presented equations were validated with 223 runs resulting in improved goodness of fit. The limitations of the herein derived empirical equations are also highlighted. The wave height and amplitude equations based on a wave channel (2D) agree well with the 1958 Lituya Bay case. [ABSTRACT FROM AUTHOR]

Abstract: Wave generation and absorption are analyzed in a closed basin, within the framework of linear potential theory. Wavemakers on the sides of the basin are used for both generating and absorbing the waves. Relations are derived governing the control of the absorbers, to reduce or eliminate reflected waves from the walls of the basin. These relations are tested by showing numerical examples of wave systems in square and circular basins, first without a body in the basin and then with a floating hemisphere. Computations of the added mass, damping, and exciting forces on the hemisphere are presented to indicate the effectiveness of the wave absorbers. Two-dimensional results are shown in the time domain to illustrate some of the transient effects associated with different types of absorber controls. [Copyright &y& Elsevier]

Free-wave contamination is a non-desirable but frequent characteristic in many wave tank experiments. Higher-order wave generation is not widely implemented yet, whereas the effectiveness of active wave absorption systems is frequency-dependent, and usually unknown. The resulting free-wave contamination usually remains unnoticed, but may have important consequences especially at low frequencies. We present a Generation–Separation–Compensation (GSC) procedure to identify, quantify and attenuate the free-wave contamination. The resulting wave field behaves as expected from a higher-order wave generation with no re-reflections at the wave paddle. The attenuation ratio of the unwanted energy content is relatively high (between 60% to 90%). The GSC procedure uses the general framework for wave separation proposed by Padilla and Alsina (2020) with an array of in-line probes. The application of this technique over experimental data is presented with excellent results. The robustness of the qualitative analysis is guaranteed for experimental settings fulfilling a minimum distance between the first and the last probe and a maximum spacing between probes. The stability of the quantitative analysis is guaranteed when P , number of probes forming the array, is above five, and Δ x s e p / λ , ratio between the spacing of the probes forming the array and the wavelength, is within the recommended range 0.1–0.45. • Free-wave contamination is detected using the qualitative analysis of Padilla and Alsina (2020). • The Generation–Separation–Compensation (GSC) procedure is to (1) identify and quantify and (2) attenuate, if needed, the existing free-wave contamination. • The applicability over experimental data of the GSC procedure is discussed. • The GSC procedure minimizes the free-wave contamination with satisfactory results, especially at the low frequencies. [ABSTRACT FROM AUTHOR]

In this paper, the effect of flow on the theoretical model and experimental performance of a plunger-type wavemaker has been investigated. Through a variance-based global sensitivity analysis, the influence of the input parameters on the output variance of the wavemaker model was explored. For a uniform flow, the first order and total effect sensitivity indices were estimated to be 1. 29 ± 0. 32 % and 6. 00 ± 0. 14 % , respectively. While the flow is less influential compared to the other parameters, it was established that including flow in the model is essential for application to experimental systems. To validate the experimental wavemaker, wave profiles were generated and measured under a variety of test conditions in relation to the sensitivity analysis. It was observed that the error between the experimental results and the theoretical model increased as both frequency and flow increased. To address the observed error, three correction methods were applied to the model which included a case specific, general case, and operational correction. While the case specific correction improved the average a / s percent error by 94.27%, 94.07%, and 96.60% for three different plunger wedges, it was established that the operational correction is more applicable to experimental plunger systems. The operational correction improves the average a / s percent error by 33.14%, 36.63%, and 37.23% respectively for the three wedges. Finally, to further reduce the error between experimental observations and the corrected model, the operational range of the experimental system was established with respect to frequency and flow rate limits. • An extension to the plunger-type wavemaker model was proposed to include flow. • A sensitivity analysis evaluated the influence of the model's six input parameters. • A plunger system was experimentally validated for the inclusion of flow. • Three correction methods to address the observed errors were proposed. • The operational range of the experimental plunger system was established. [ABSTRACT FROM AUTHOR]

Abstract: In this work, a combined immersed boundary (IB) and volume of fluid (VOF) methodology is developed to simulate the interactions of free-surface waves and submerged solid bodies. The IB method is used to account for the no-slip boundary condition at solid interfaces and the VOF method, utilizing a piecewise linear interface calculation, is employed to track free surfaces. The combined model is applied in several case studies, including the propagation of small-amplitude progressive waves over a submerged trapezoidal dike, a solitary wave traveling over a submerged rectangular object, and wave generation induced by a moving bed. Numerical results depicting the free-surface evolutions and velocity fields are in good agreement with either experimental data or numerical results obtained by other researchers. In addition, the simplification of the initial free-surface deformation used in most tsunami earthquake source study is justified by the present model application. The methodology presented in the paper serves as a good tool for solving many practical problems involving free surfaces and complex boundaries. [Copyright &y& Elsevier]

The water wave generation by a freely falling rigid body is examined in this paper. Two different two-dimensional numerical approaches have been utilized to simulate the time histories of fluid motion, free surface deformation, and the vertical displacement of a rectangular-shape rigid body. While the first approach is based on the Reynolds-averaged Navier–Stokes (RANS) equations, with the k-ε closure model to compute the turbulence intensity, the second uses the smoothed particle hydrodynamics (SPH) method. Numerical simulations using several different initial elevations of the rigid body and different water depths have been performed. The displacement of the moving rigid body is determined by dynamic equilibrium of the forces acting on the body. Numerical results obtained from both approaches are discussed and compared with experimental data. Images of the free surface profile and falling rigid body recorded from the laboratory tests are compared with numerical results. Good agreement is observed. Numerical solutions for the velocity fields, pressure distributions, and turbulence intensities in the vicinity of the falling rigid body are also presented. The similarity and discrepancy between the solutions obtained by the two approaches are discussed. [ABSTRACT FROM AUTHOR]

A meshless numerical model for nonlinear free surface water waves is presented in this paper. Using the fundamental solution of the Laplace equation as the radial basis functions and locating the source points outside the computational domain, the problem is solved by collocation of boundary points. The present model is first applied to simulate the generation of periodic finite-amplitude waves with high wave steepness and then is employed to simulate the modulation of monochromatic waves passing over a submerged obstacle. Very good agreements are observed when comparing the present results with an analytical solution, experimental data, and other numerical results. [ABSTRACT FROM AUTHOR]

Abstract: Modulational, Benjamin-Feir, instability is studied for the down-stream evolution of surface gravity waves. An explicit solution, the soliton on finite background, of the NLS equation in physical space is used to study various phenomena in detail. It is shown that for sufficiently long modulation lengths, at a unique position where the largest waves appear, phase singularities are present in the time signal. These singularities are related to wave dislocations and lead to a discrimination between successive ‘extreme’ waves and much smaller intermittent waves. Energy flow in opposite directions through successive dislocations at which waves merge and split, causes the large amplitude difference. The envelope of the time signal at that point is shown to have a simple phase plane representation, and will be described by a symmetry breaking unfolding of the steady state solutions of NLS. The results are used together with the maximal temporal amplitude MTA, to design a strategy for the generation of extreme (freak, rogue) waves in hydrodynamic laboratories. [Copyright &y& Elsevier]

Abstract: An approximate Stream Function wavemaker theory for highly non-linear regular waves in flumes is presented. This theory is based on an ad hoc unified wave-generation method that combines linear fully dispersive wavemaker theory and wave generation for non-linear shallow water waves. This is done by applying a dispersion correction to the paddle position obtained for non-linear long waves. The method is validated by a number of wave flume experiments while comparing with results of linear wavemaker theory, second-order wavemaker theory and Cnoidal wavemaker theory within its range of application. [Copyright &y& Elsevier]

Abstract: We deal with the problem of a caisson breakwater embodying an OWC which is connected to the sea through a small opening. Waves cannot enter this OWC and the oscillations of the water column are due to the wave pressure on the small opening. The problem is solved through two alternative approaches. First alternative: we assume that the plant generates a progressive wave which is superimposed on the standing wave yielded by the reflection of the incident wave. Second alternative: a priori before the breakwater there may be every periodic waveform with the given frequency and a mean energy flux smaller than (or equal to) the mean energy flux of the incident waves, and we look for the waveform satisfying the equations of wave–OWC interaction, and giving the largest value of (mean energy flux/mean energy per unit surface). In some cases the solutions obtained through the two alternative approaches prove to be coincident with each other. In other cases the solution giving the largest value of proves to be a sum of two standing waves with phase angles in space and time. In these cases (sum of two standing waves) the plant may absorb up to the 100% of the incident wave energy. [Copyright &y& Elsevier]

Abstract: A deterministic combination of numerical and physical models for coastal waves is developed. In the combined model, a Boussinesq model MIKE 21 BW is applied for the numerical wave computations. A piston-type 2D or 3D wavemaker and the associated control system with active wave absorption provides the interface between the numerical and physical models. The link between numerical and physical models is given by an ad hoc unified wave generation theory which is devised in the study. This wave generation theory accounts for linear dispersion and shallow water non-linearity. Local wave phenomena (evanescent modes) near the wavemaker are taken into account. With this approach, the data transfer between the two models is thus on a deterministic level with detailed wave information transmitted along the wavemaker. [Copyright &y& Elsevier]

Abstract: This paper analyses 10 years of wave data from the Mediterranean Spanish (Catalan) coast considering the mean wave climate and storm events from the standpoint of wind-wave momentum transfer and wave prediction. The data, registered by a buoy at about 12km from the coastline, revealed two main groups of wave storms, with NW and E directions. NW storms correspond to a fetch-limited situation since the intense wind blows from land. Low-pressure centres located over the Mediterranean Sea produce easterly storms. Near the coast the eastern winds from the sea are replaced by NW winds coming from meteorological patterns over northern Spain and south-western France. Wave storms are classified and studied to obtain their main features (including spectral width, wave length, wave age and bimodality) and discussed in terms of wind-wave momentum transfer for operational wave predictions. Observations show a complex coastal wave climate. Fetch-limited storms presented smaller spectral widths while varying wind situations presented larger widths due to the presence of bimodal spectra. These wave features are highly relevant for wind–ocean momentum transfer and, thus, for current and wave predictions. The spectral width proved to be a good indicator of sea complexity and is thus applicable for improved wind drag estimations. A new drag coefficient formulation is proposed, based on existing wind dependent drag expressions, but including also spectral wave properties (a spectral width parameter) that highlights the characteristics of wind-wave generation under pre-existing swell. Such a formulation, once properly validated with field observations, is expected to improve wind-wave predictions. [Copyright &y& Elsevier]

Abstract: An analytical model is developed for the initial stage of surface wave generation at an air–water interface by a turbulent shear flow in either the air or in the water. The model treats the problem of wave growth departing from a flat interface and is relevant for small waves whose forcing is dominated by turbulent pressure fluctuations. The wave growth is predicted using the linearised and inviscid equations of motion, essentially following Phillips [Phillips, O.M., 1957. On the generation of waves by turbulent wind. J. Fluid Mech. 2, 417–445], but the pressure fluctuations that generate the waves are treated as unsteady and related to the turbulent velocity field using the rapid-distortion treatment of Durbin [Durbin, P.A., 1978. Rapid distortion theory of turbulent flows. PhD thesis, University of Cambridge]. This model, which assumes a constant mean shear rate Γ, can be viewed as the simplest representation of an oceanic or atmospheric boundary layer. For turbulent flows in the air and in the water producing pressure fluctuations of similar magnitude, the waves generated by turbulence in the water are found to be considerably steeper than those generated by turbulence in the air. For resonant waves, this is shown to be due to the shorter decorrelation time of turbulent pressure in the air (estimated as∝1/Γ), because of the higher shear rate existing in the air flow, and due to the smaller length scale of the turbulence in the water. Non-resonant waves generated by turbulence in the water, although being somewhat gentler, are still steeper than resonant waves generated by turbulence in the air. Hence, it is suggested that turbulence in the water may have a more important role than previously thought in the initiation of the surface waves that are subsequently amplified by feedback instability mechanisms. [Copyright &y& Elsevier]

Abstract: This paper is concerned with breaking criteria for generated waves. An input in the form of a time signal is prescribed to a wave maker located at one end of a wave tank as used in hydrodynamic laboratories. The motion of this wave maker produces waves propagating into initially still water in the tank. The spatial evolution of the wave train is referred to as the signaling problem to distinguish from an initial value problem that investigates the temporal evolution of a given initial wave profile. A numerical simulation of the nonlinear propagation of time traces along the tank is investigated to see if breaking occurs and, if so, at which location in the tank. A quantity is proposed as a breaking indicator that is based on a modification of a mean convergence rate of the squared steepness, recently suggested by Song and Banner for the initial value problem. Two classes of waves, namely Benjamin–Feir and bichromatic waves, are considered as influx to the wave maker. A comparison between the signaling problem and the initial value problem for these two classes is presented. The result of the investigations is that, for both classes, the initial steepness can be more extreme in the signaling case than in the case of the initial value problem such that there is no breaking during their evolution. Furthermore, the modified quantity shows the existence of a threshold value for breaking, below which no breaking can occur. [Copyright &y& Elsevier]

In comparison with wave modeling on an open coast, the complex geometry and bathymetry of estuaries, the unsteady conditions associated with estuarine circulation generated by tides and winds, and the relatively inadequate field data present a unique challenge. This study utilizes an unsteady, curvilinear spectral wave model that has the flexibility to resolve large geometric and bathymetric gradients and allows for consideration of unsteady forcing and currents to predict wind waves in Mobile Bay, Alabama. First, a laboratory data set on wave transformation over a circular shoal is chosen to test the curvilinear wave model. Excellent agreement is found between the numerical results and the laboratory measurements with a directional wave input and fine spatial resolution. Second, a three-dimensional circulation model is used to predict the varying current field and water levels that serve as the input to the wave model. The predictions of the wave model under unsteady forcing and ambient currents are then compared with the existing field measurement of wind waves in Mobile Bay. Numerical experiments are carried out to examine the effects of estuarine circulation and grid resolution on the model result. The study shows that the technique of linking a spectral wave model to a hydrodynamic model on curvilinear grids is an effective tool for wave prediction in estuaries. [ABSTRACT FROM AUTHOR]

Based on the Navier-Stokes Equations (NSE), numerical simulation with fine grids is conducted to simulate the coastal surface wave changes, including wave generation, propagation, transformation and interactions between waves and structures. This numerical model has been tested for the generation of the desired incident waves, including both regular and random waves. Some numerical results of this model are compared with available experimental data. In order to apply this model to actual cases, boundary conditions are considered in detail for different shoreline types (beach or breakwater, slope or vertical wall, etc.). Finally, the utility of the model to a real coastal area is shown by applying it to a fishing port located in Shidao, Rongcheng, Shandong Province, P. R. China. [ABSTRACT FROM AUTHOR]

One of the possible methods to deal with the reflecting waves at the incident boundary in numerical modeling is to generate waves in the computation domain and absorb the outgoing waves at the incident boundary. A source function is introduced into the momentum equation of Boussinesq equations for generating wave in a computation domain in this paper. Typical numerical examples are given for the verification of the proposed method. Numerical examination for the wave diffraction through a breakwater gap shows that the proposed method is especially useful for multidirectional waves. [Copyright &y& Elsevier]

Landslide generated impulse waves were investigated in a two-dimensional physical laboratory model based on the generalized Froude similarity. The recorded wave profiles were extremely unsteady and nonlinear. Four wave types were determined: weakly nonlinear oscillatory wave, non-linear transition wave, solitary-like wave and dissipative transient bore. Most of the generated impulse waves were located in the intermediate water depth wave regime. Nevertheless the propagation velocity of the leading wave crest closely followed the theoretical approximations for a solitary wave. Between 4 and 50% of the kinetic slide impact energy propagated outward in the impulse wave train. The applicability ranges of the classical nonlinear wave theories to landslide generated impulse waves were determined. The main wave characteristics were related to the landslide parameters driving the entire wave generation process. The slide Froude number was identified as the dominant parameter. The physical model results were compared to the giant rockslide generated impulse wave which struck the shores of the Lituya Bay, Alaska, in 1958. [ABSTRACT FROM AUTHOR]

The finite-element model for modified Boussinesq equations developed in Part I of this paper is used to study harbor resonance problems. The internal wavemaker technique is implemented on an unstructured finite-element mesh, and a sponge layer is used as an open boundary condition. Both linear and nonlinear harbor oscillations in rectangular and circular basins are examined, and experimental measurements and analytical solutions are used to validate the model. Finally, the wavelet transform is employed to analyze transient features of the nonlinear resonance problem. [ABSTRACT FROM AUTHOR]

The present paper develops the complete second-order wavemaker theory for the generation of multidirectional waves in a semi-infinite basin. The theory includes superharmonics and subharmonics and is valid for a rotational as well as a translatory serpent-type wave-board motion. The primary goal is to obtain the second-order motion of the wave paddles required to get a prescribed multidirectional irregular wave field correct to second order, i.e. to suppress spurious free-wave generation. The wavemaker theory is a 3D extension of the full second-order wavemaker theory for wave flumes by . [Copyright &y& Elsevier]

The moon pool opened in a floating structure significantly affects its wave attenuating performance. In this paper, the hydrodynamic behaviors of several floating breakwaters with moon pool were investigated preliminarily by the Smoothed Particle Hydrodynamics (SPH) method. For a comparative study, wave interactions with a rectangular floating breakwater and a cylindrical dual pontoon floating breakwater were also simulated. The wave was generated with a relaxation zone method which had displayed its accuracy as well as applicability. In addition, the lumped mass method was adopted to provide mooring forces for the floating breakwater. The coupling SPH model was validated by a physical model test and the numerical results were in good agreement with the experimental data. After that, the wave coefficients, such as transmitted wave coefficient, reflected wave coefficient and dissipated wave coefficient, were computed to evaluate the wave attenuating performance of floating body models. Meanwhile, for each model, the motion responses, including sway, heave and pitch, were analyzed to investigate their hydrodynamic performance. The numerical results and analysis are useful for the design of floating breakwaters, and the conclusions could be further applied in the design of wave energy converters. • A coupling SPH model is utilized to investigate the hydrodynamic behavior of floating breakwaters with moon pool. • A relaxation zone technique is adopted for wave generation in an SPH wave flume. • SPH results show good agreement with experimental data for the floating breakwater with mooring lines. • The shapes of the floating breakwater and its moon pool are shown to be important. [ABSTRACT FROM AUTHOR]

Most tsunamis are triggered by seismic events, involving an underwater earthquake with a sharp vertical displacement of the seafloor. Generally, seabed deformations are not unipolar, but instead bipolar or even more complex. To model tsunamis generated by segmented seafloor deformations, an analytical model and a numerical model including source kinematics are presented. Specifically, a parametric analysis, varying the number of segments and the relative sizes of each segment, is performed to investigate their influence on the wave generation process. Destructive interference is observed between the free surface waves generated by adjacent segments moving in opposite directions. The relatively large horizontal velocities compared to vertical velocities within the rotating flow generated in the case with two opposing segments correspond to relatively low wave amplitudes and the shift in the location of the largest wave. When the net uplift or subsidence volume is smaller, the associated destructive interference is more pronounced. In addition, a larger number of opposing segments produce a more complex velocity field within the tsunamigenic region, causing more destructive interference on the free surface. The role of destructive interference induced by segmented seabed deformations should be considered in assessing tsunami hazards caused by complex fault ruptures. • We use an analytical and a numerical model to study waves generated by segmented seabed motions. • When adjacent segments move in opposing directions, the wave groups exhibit destructive interference. • The destructive interference is most pronounced when the amounts of elevation and subsidence are equal. • A larger number of segments cause a stronger destructive interference of waves. • The effects of wave nonlinearity for the impulsive cases become less important with more segments. [ABSTRACT FROM AUTHOR]

The paper presents a novel wave boundary model, namely Wavy Interface model, abbreviated as WI, for the particle methods by directly modelling the target wave fronts. In practical engineering problems, the information of the design waves as an input boundary is limited to only the wave heights and periods. To accommodate the situations, the proposed Wavy Interface model is designed to omit a usual tuning process by keeping the desired wave front through generation/removal of the particles around the free surface. The good reproducibility of the Wavy Interface model is shown through benchmarks targeting regular, irregular and solitary waves. Verification is made in terms of reproduced free-surface profile, velocity and energy fields. In addition, simulations of overtopping waves show the good conservation of the water level by the Wavy Interface model. The Wavy Interface model is shown to be a proper wave generation model in a numerical wave flume to generate waves as precise as the conventional wave paddle model and with considerable reduction of CPU time. • A Wavy Interface model is proposed for numerical wave flumes by particle methods. • Only a time series of wave height is used as input to generate waves. • Desired waves are generated with the same level of accuracy as wave paddle model. • Verification is made in terms of free-surface profile, velocity and energy fields. • The proposed Wavy Interface model drastically reduces the computational time. [ABSTRACT FROM AUTHOR]

This paper investigates the optimization of second-order control signals required to produce stable non-linear, deep-water waves using a wedge-shaped, plunger-type wave generator. Both numerical and experimental methods are utilized. A fully non-linear and dispersive potential flow (FNPF) solver developed at DTU is used for the numerical work, following improvements that reduce reflection to 1%. The numerical solver is validated against theoretical and experimental data. A defect correction optimization scheme is employed, resulting in optimized control signals for non-dimensional wave numbers of 2.04-8.17 and steepness of 3-7%. These control signals produce waves that are within 2% of stream function theory solutions for the fundamental harmonic component, and within 10% for the second-order harmonic component. The results demonstrate both the applicability of this optimization procedure and the suitability of a heaving wedge for generating stable non-linear deep-water waves. [ABSTRACT FROM AUTHOR]

In this paper, we revisit the hydrodynamics supporting the design and development of the RiverCat class of catamaran ferries operating in Sydney Harbor since 1991. More advanced software is used here. This software accounts for the hydrodynamics of the transom demisterns that experience partial or full ventilation, depending on the vessel speed. This ventilation gives rise to the hydrostatic drag, which adds to the total drag of the vessel. The presence of the transom also creates a hollow in the water. This hollow causes an effective hydrodynamic lengthening of the vessel, which leads to a reduction in the wave resistance. Hence, a detailed analysis is required in order to optimize the size of the transom. It is demonstrated that the drag of the vessel and the wave generation can be predicted with good accuracy. Finally, the software is also used to optimize the vessel further by means of affine transformations of the hull geometry. [ABSTRACT FROM AUTHOR]

Channel flow turbulence exhibits interesting spatiotemporal complexities at transitional Reynolds numbers. In this paper, we investigated some aspects of the kinematics and dynamics of fully localized turbulent bands in large flow domains. We discussed the recent advancement in the understanding of the wave-generation at the downstream end of fully localized bands. Based on the discussion, we proposed a possible mechanism for the tilt direction selection. We measured the propagation speed of the downstream end and the advection speed of the low-speed streaks in the bulk of turbulent bands at various Reynolds numbers. Instead of measuring the tilt angle by treating an entire band as a tilted object as in prior studies, we proposed that, from the point of view of the formation and growth of turbulent bands, the tilt angle should be determined by the relative speed between the downstream end and the streaks in the bulk. We obtained a good agreement between our calculation of the tilt angle and the reported results in the literature at relatively low Reynolds numbers. [ABSTRACT FROM AUTHOR]