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Accurate and significant wave height prediction with a couple of hours of warning time should offer major safety improvements for coastal and ocean engineering applications. However, significant wave height phenomenon is nonlinear and nonstationary, which makes any prediction simulation a non-straightforward task. The aim of the research presented in this paper is to improve predicted significant wave height via a hybrid algorithm. Firstly, empirical mode decomposition (EMD) is used to preprocess the nonlinear data, which are decomposed into several simple signals. Then, least square support vector machine (LSSVM) with nonlinear learning ability is used to predict the significant wave height, and particle swarm optimization (PSO) is implemented to automatically perform the parameter selection in LSSVM modeling. The EMD-PSO-LSSVM model is used to predict the significant wave height for 1, 3 and 6 hours leading times of two stations in the offshore and deep-sea areas of the North Atlantic Ocean. The results show that the EMD-PSO-LSSVM model can remove the lag in the prediction timing of the single prediction models. Furthermore, the prediction accuracy of the EMD-LSSVM model that has not been optimized in the deep-sea area has been greatly improved, an improvement of the prediction accuracy of Coefficient of determination (푅??) from 0.991, 0.982 and 0.959 to 0.993, 0.987 and 0.965, respectively, has been observed. The proposed new hybrid model shows good accuracy and provides an effective way to predict the significant wave height for the deep-sea area. [ABSTRACT FROM AUTHOR]

We reformulate a three‐dimensional theory for wave‐ice interactions for flexible ice floes and present a comparison of this new formulation with selected recent parameterizations for the scattering of ocean surface waves due to individual ice floes. The formulation is based on single flow scattering and a transport equation for energy, which fits with the paradigm used in wave prediction code. These parameterizations are implemented as source terms in the action balance equation for a modern version of the phase‐averaging wave model WAVEWATCH III® (denoted WW3). In this comparison, a simple experiment is performed with regularly distributed ice floes in a marginal ice zone. With the new wave‐ice formulation, results show that attenuation in the direction of propagation is less intense than for the other considered formulations, scattering is more isotropic, and the wave energy is attenuated in the region of the original spectral peak. Thus, a new spectral peak is developed, which is shifted to higher frequencies. The wave scattering and subsequent attenuation are related to the floe response amplitude and the dimensions of the ice floes. Plain Language Summary: We present a model for the propagation of ocean waves in the marginal ice zone, a region of broken ice floes, by introducing a three‐dimensional scattering term based on the physics of a flexible ice floe in waves. This formulation is incorporated into a global wave prediction model WAVEWATCH III. We test this model by a series of simple test cases. Results show that the scattering effect is less intense than other formulations and that the wave spreads out eventually propagating in all directions far into the ice pack. Key Points: We implement a new parameterization for wave‐ice interactions for the three‐dimensional attenuation and scattering of waves due to flexible ice floes into a modern operational wave modelThe model is compared with three other models for three‐dimensional attenuation and scattering of waves due to ice floes in an idealized marginal ice zone (MIZ)While the four models exhibit quite different rates of attenuation near the MIZ edge, far within the MIZ, scattering is isotropic, and the wave energy is most attenuated in the lower spectral frequency region [ABSTRACT FROM AUTHOR]

SWAN (Simulating Wave Near-shore) is a numerical wave model for hindcasting/forecasting wave parameters in coastal areas. This numerical model is chosen because is suitable for shallow water. This study was conducted to verify the results of wave height hindcasting in Jepara coastal waters. This is expected to support wave characteristic research based on wave forecasting for 10 years in the waters between Java, Sumatera and Kalimantan. The model is run with the third-generation mode (GEN3), which allow wind input, quadruplet and triad interactions, whitecapping, and breaking. Wind data is obtained from ECMWF (European Centre for Medium-Range Weather Forecasts) and the bathymetry from GEBCO (General Bathymetric Chart of The Oceans). The validation of the model and buoy data during July - December 1993 shows a good result (Root Mean Square Error = 0.166 and correlation/ linear regression = 0.807). Based on the literature, qualitatively the model has been verified with other simulation from another model in the same location. [ABSTRACT FROM AUTHOR]

ABSTRACT Yuk, J.-H.; Park, J.H., and Joh, M., 2018. Modelling of Storm-induced Seawater Flooding in the Suyeong River Area, South Korea: A Case Study due to the Storm Surge and Waves during Typhoon Sanba. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 746–750. Coconut Creek (Florida), ISSN 0749-0208. The Suyeong River Area (SRA), located in Busan, a major city on the southeastern coast of South Korea, is frequently damaged by storm-induced seawater flooding. One of the main reasons for seawater flooding is the propagation of storm surges and wind waves through the Suyeong River in the SRA. In this study, a series of prediction systems of storm tides, surges, waves and resultant seawater flooding for the SRA based on unstructured meshes with a high resolution of approximately 10 m covering the entire flood plain and a HPC-based parallel tide-surge-wave model were developed. Meteorological forcing variables such as wind and air pressure calculated by the parametric tropical cyclone model based on typhoon information were used in the storm-surge and wave models. The modeled meteorological data were in good agreement with observations of both the wind and air pressure. The simulated surge heights and wave properties showed good agreement with the observations as well. Waves reached the mid-stream area of the SRA, likely affecting the duration of seawater flooding. The prediction system in this study can reasonably simulate tide-surge-wave and resultant seawater flooding (coastal inundation) during extreme conditions, e.g., storms in the SRA of Busan, South Korea. [ABSTRACT FROM AUTHOR]

To meet the growing global demand for carbon neutral electricity, wave energy is increasingly being identified for its global prevalence and the emerging clean technologies that can harness it. To provide the scale of electricity needed, Wave Energy Converters (WECs) will need to be deployed in large arrays. However, the effects of a WEC array's layout on the surrounding wave conditions in both the near and far fields is poorly understood. The published literature describes numerous methods to model interactions of incident waves and WEC arrays. Yet, none of the published methods provide a methodology which spectrally resolves the individual WEC's energy conversion characteristics, and has the flexibility to be applied to any emerging WEC design. This study develops and implements two novel candidate high-fidelity representations of a Backwards Bent Duct Buoy Oscillating Water Column (BBDB) WEC within a Simulating WAves Nearshore (SWAN) coastal model. Each candidate representation is developed by post-processing time series data generated from a time domain numerical simulation to form a meta-model, referred to as an obstacle case, consistent with the SWAN governing equations and discretization scheme. The study is executed within the framework of SNL-SWAN – a modified version of SWAN that includes a WEC obstacle case that is built on the established concept of using SWAN's transmission coefficient to emulate the wave-WEC interactions. The two new WEC obstacle cases build on SNL-SWAN by considering the WEC's intercepted power , the rate of energy extraction from the waves, instead of the captured power , the rate of energy conversion by the power-take-off. The two new candidates differ in their level of spectral resolution: one homogenizes the intercepted power across the frequency domain while the other attempts to spectrally resolve the energy transfer mechanisms. The two new candidate obstacle cases were compared by considering up to 5 BBDB devices subject to irregular wave conditions. For an individual device, a region of significantly perturbed wave heights, referred to as a wake, stretched 200 m in the lee of the WEC, with the maximum impact on wave heights seen 50 m behind the device. The wake behind five devices is largely dependent on the device spacing. The five unit WEC array only presented decreases of wave height between 0.2 and 0.7 m 200 m behind the last device in the array. A five unit WEC array model showed that estimates of individual WEC power performance was reduced by 2.3% and 6.0% when implementing the two new obstacle cases. [ABSTRACT FROM AUTHOR]

Outliers are considerably inconsistent and exceptional objects in the data set that do not adapt to expected normal condition. An outlier in wave measurements may be due to experimental and configuration errors, technical defects in equipment, variability in the measurement conditions, rare or unknown conditions such as tsunami, windstorm and etc. To improve the accuracy and reliability of an built ocean wave model, or to extract important and valuable information from collected wave data, detecting of outlying observations in wave measurements is very important. In this study, three typical outlier detection algorithms:Box-plot (BP), Local Distance-based Outlier Factor (LDOF), and Local Outlier Factor (LOF) methods are used to detect outliers in significant wave height (Hs) records. The historical wave data are taken from National Data Buoy Center (NDBC). Finally, those data points are considered as outlier identified by at least two methods which are presented and discussed. Then, Hs prediction has been modelled with and without the presence of outliers by using Regression trees (RTs). [ABSTRACT FROM AUTHOR]

This study shows that storm surge model performance in the North Sea is mostly unaffected by the application of temporal variations of surface drag due to changes in sea state provided the choice of a suitable constant Charnock parameter in the sea-state-independent case. Including essential meteorological features on smaller scales and minimising interpolation errors by increasing forcing data resolution are shown to be more important for the improvement of model performance particularly at the high tail of the probability distribution. This is found in a modelling study using WAQUA/DCSMv5 by evaluating the influence of a realistic air-sea momentum transfer parameterization and comparing it to the influence of changes in the spatial and temporal resolution of the applied forcing fields in an effort to support the improvement of impact and climate analysis studies. Particular attention is given to the representation of extreme water levels over the past decades based on the example of the Netherlands. For this, WAQUA/DCSMv5 is forced with ERA-Interim reanalysis data. Model results are obtained from a set of different forcing fields, which either (i) include a wave-state-dependent Charnock parameter or (ii) apply a constant Charnock parameter (αCh = 0.032) tuned for young sea states in the North Sea, but differ in their spatial and/or temporal resolution. Increasing forcing field resolution from roughly 79 to 12 km through dynamically downscaling can reduce the modelled low bias, depending on coastal station, by up to 0.25 m for the modelled extreme water levels with a 1-year return period and between 0.1 m and 0.5 m for extreme surge heights. [ABSTRACT FROM AUTHOR]

The two-phase flow instability in heated channels is an important phenomenon in industrial facilities. The effect of ocean motions upon the flow instability should be predicted accurately for the heat exchangers in floating platform. The reduced order model with drift-flux approach is developed to analyze the density wave oscillation in a uniformly heated channel in ocean motions. The density variation of coolant flow is considered. The stability maps can be predicted precisely on experimental data. The effect of ocean motions on the stability boundary is investigated quantitatively by the defining of the degree of instability. The subcritical Hopf bifurcation in ocean motions is also studied. [ABSTRACT FROM AUTHOR]

In this paper, a preliminary study of wave-induced oscillatory seabed response around twin-pile group is performed using a three-dimensional (3D) model, and meanwhile comparative analysis with mono-pile is conducted. In the proposed model, Reynolds-Averaged Navier-Stokes (RANS) equations with k−ε turbulence model is applied to simulate the wave motion, while Biot's poro-elastic theory for the porous seabed is employed to govern the seabed response. Validation against available experiment data and analytical solution demonstrates that the present model has the capacity of simulating wave-structure-seabed interaction (WSSI) around pile structures. Results show that magnitudes of wave-induced oscillatory pore pressure and liquefaction depth around twin-pile group tend to attenuate along the pile-pile centerline, presenting significant difference from that around mono-pile. [ABSTRACT FROM AUTHOR]

This study presents the principles of the new coupling interface based on the SURFEX multi-surface model and the OASIS3-MCT coupler. As SURFEX can be plugged into several atmospheric models, it can be used in a wide range of applications, from global and regional coupled climate systems to high-resolution numerical weather prediction systems or very fine-scale models dedicated to process studies. The objective of this development is to build and share a common structure for the atmosphere–surface coupling of all these applications, involving on the one hand atmospheric models and on the other hand ocean, ice, hydrology, and wave models. The numerical and physical principles of SURFEX interface between the different component models are described, and the different coupled systems in which the SURFEX OASIS3-MCT-based coupling interface is already implemented are presented. [ABSTRACT FROM AUTHOR]

We investigate the extended nonlinear Schrödinger equation with higher-order odd and even terms. The model includes additional higher-order dispersion and nonlinear terms that are most important for applications in fiber optics, in the case of the Heisenberg spin chain, and for ocean waves. Special exact solutions in the form of a dipole soliton is obtained, by adopting a complex amplitude ansatz composed of the product of bright and dark solitary waves. The conditions on the system parameters for the existence of this localized structure are also reported. The derived solution characteristically exists due to a balance among physical effects of different nature. Numerical results and discussions are also presented. [ABSTRACT FROM AUTHOR]

In this study we develop a formulation to model the effect of a thin porous plate of arbitrary geometry in a fluid flow. This underlying model is based on the 1D pressure drop in the normal direction to the plate and is easily used for 2D and 3D flows. Our primary interest lies in perforated plates for use in ocean wave damping applications, although other porous media such as woven gauze or slotted screens can be handled in an identical manner. We implement the model in a Smoothed Particle Hydrodynamics (SPH) framework which is an intrinsically suitable method for the interaction between complex geometries and ocean waves. We compare predictions of the method to theory and available experimental data in a set of simulations including 2D steady-state flow normal and inclined to a screen. In all cases the results from the SPH implementation are in very satisfactory agreement. The method is then demonstrated on solitary wave interaction with a porous barrier and the transmission, reflection and absorption of wave energy is predicted as a function of permeability. [ABSTRACT FROM AUTHOR]

This paper develops a new two-stage approach for accurate modeling and prediction of tidal current. The proposed method makes use of a novel fuzzy feature selection to extract the most preferable features from the tidal current speed and direction data set. The selected features are further used to train a support vector regression for accurate prediction. The setting parameters of the proposed model are trained by a new optimization algorithm based on the harmony search algorithm to get to the most optimal training targets. The proposed optimization algorithm makes use of the crossover and mutation operators from genetic algorithm to escape from the local optima and find the global solutions. Experimental tidal data from Persian Gulf, Iran, are used to assess the accuracy and performance of the proposed model. The results show the appropriate performance and high precision of the proposed model in comparison with other famous methods. [ABSTRACT FROM PUBLISHER]

Ocean wave loading is in most cases the largest environmental force acting on offshore structures. For floating structures in particular, sea waves may induce considerable motions that the design practice must account for. This paper deals with the dynamics and vibration control of floating structures due to wave loading, with particular focus on heave motion of offshore production units. A semisubmersible model is considered. The design optimization of different structural arrangements is obtained first with the proposed simplified approaches considering the platform heave motion. Different model configurations are analysed with the purpose of mitigating the vessel vibrations, in particular the heave response. The fluid structure interaction is considered and FE-CFD techniques are employed for a comprehensive analysis of the performance of the models. The worked examples and the respective interpretation of the results shine lights on the scope and application of the structural arrangements and computation techniques presented here. [ABSTRACT FROM AUTHOR]

Chun, H. and Ahn, K., 2017. Storm waves on the east coast of Korea: 20 years of wave hindcasting. This paper presents 20 years of wave hindcasting in the East Sea (Sea of Japan) to estimate return periods of storm waves at the east coast of South Korea for coastal risk management. The numerical results were validated against the measured data obtained at eight wave stations in the East Sea. The comparison of correlation coefficients of significant wave heights and wave periods, 0.81-0.95 and 0.70-0.88, respectively, between the numerical results and the measured data shows good agreement. Note that the numerical results agree well with the measurements despite the large computational grid size used. The storm waves on February 2008 were successfully simulated in the present study, and the computed peak periods at Gangneung Port showed good agreement with those measured, even though the coefficients of whitecapping dissipation were not modified. On the basis of 20 years of wave hindcasting results, extreme wave analysis was carried out using the peak-over-threshold method and the generalized Pareto distribution function. According to the extreme wave analysis, significant wave heights occurred at Sokcho and Gangneung on 23 October 2006, and were estimated to have a return period of 100 years. It was found that the waves generated by Typhoon Nabi (T0514) were the most severe in the East Sea during the simulation period. During this typhoon period, a 50-year wave appeared at Pohang, the southern East Sea. [ABSTRACT FROM AUTHOR]

A shallow-water equation (SWE) is used to simulate earthquake-induced water waves in this study. A finite-difference method is used to calculate the SWE. The model is verified against the models of Sato and of Demirel and Aydin with three kinds of seismic waves, and the numerical results of earthquake-induced water waves calculated using the proposed model are reasonable. It is also demonstrated that the proposed model is reliable. Finally, an empirical equation for the maximum water elevation of earthquake-induced water waves is developed based on the results obtained using the model, which is an improvement on former models. [ABSTRACT FROM AUTHOR]

We have developed a numerical model, which is a combination of ray-tracing and optical propagation, to study underwater downwelling irradiance fluctuations, which occur due to the focusing of light by wind-driven surface waves, at different depths and under various conditions. In particular, to have more realistic results, we utilized the Gerstner model to simulate sea surface waves and to take account of water effects such as scattering and absorption, the point spread function (PSF) of water is used. The effects of physical factors such as wind speed, water depth, and light wavelength on the underwater irradiance spatial distribution, probability density function (PDF) and coefficient of variation (CV) of the irradiance are investigated. Irradiance fluctuations occur at high frequencies immediately below the surface, which means they are related to surface waves with short wavelengths. As we look deeper, the effect of surface waves with longer wavelengths becomes apparent. The simulation also shows the dependence of the average of the downwelling irradiance on the surface profile, depth and incident wavelength. The variance of the irradiance reaches a maximum at a certain depth and then rapidly decreases. [ABSTRACT FROM AUTHOR]

Internal Solitary Wave (ISW) normally converts its polarity from depression wave to elevation wave during shoaling process. This phenomenon has been verified by model studies and field observations. However, through the comparison between theoretical studies and observations, we find that Extended Kortweg-de Vries (EKdV) theory, often used by numerical simulations, cannot well predict the polarity conversion area of shoaling ISWs. Here we trace seismic reflectors within the water column, captured by exploration seismic data, and systematically analyze the polarity conversion area of the shoaling ISWs in the northeastern South China Sea (SCS). The results show that the ISWs in the northeastern SCS generally begin to convert their polarities from depression to elevation waves at the seafloor depth of about 200 m, and turn into elevation waves at the seafloor depth of about 100 m. The ISWs between depression and elevation waves are newly defined as transition waves, which are distributed between the seafloor depth of 130 m and 220 m; while elevation waves are distributed between 80 m and 120 m. We compared the observation with the theoretical critical conversion depth estimation by the two-layer model based on EKDV equation. The result suggests that the depth of the upper layer in the two-layer model can be selected as the depth of the maximum buoyancy frequency not the base of the mixing layer. Such selection can get better estimation of critical conversion depth of shoaling ISWs. Our analysis also suggests that the polarity conversion process is amplitude-dependent. The ratio of amplitude to depth for elevation waves is more than two times larger than that of the transition waves. This implies that the seafloor plays a more important role in shallow water than in deep water in controlling the amplitudes of ISWs during shoaling process. [ABSTRACT FROM AUTHOR]

A complete facet model for the backscattering from rough sea surface with breaking waves is proposed in this paper. In consideration of the spatial distribution of breaking waves on sea surface, the model is able to give a good interpretation to the “super events” under high sea states, such as sea spikes and high polarization ratios. Based on the proposed model, normalized radar cross section plots of sea surface under backscattering configuration are calculated and compared with measured data. The comparisons show that the proposed model is tractable to estimate the scattering from electrically large ocean surface under high sea states with accuracy and efficiency. In addition, the non-Gaussian statistics and spatial correlation properties of sea clutter are analyzed under different range resolutions and incident angles. The results show that high kurtosis value, which means a sea spike phenomenon, mostly happens in lower grazing angle and higher range resolution cases. The comparisons of simulated SAR images of sea surface with and without breaking waves also reveal that sea spikes and high polarization ratios are caused by breaking waves. All the simulation results prove that our model not only is able to explain the physical mechanism of the scattering but also can be applied to the analyses of statistical properties of sea clutter under high sea states. [ABSTRACT FROM PUBLISHER]

Kim, K.O.; Yuk, J.-H.; Jung, K.T., and Choi, B.H., 2017. Swell propagation caused by typhoon passage to the Yellow and East China Seas. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 144-148. Coconut Creek (Florida), ISSN 0749-0208. Typhoons generate big swells frequently propagating over the East China Sea, the wide continental shelf sea with depth shallower than 200 m. The characteristic features of swell propagation into the Yellow and East China Seas caused by typhoon Herb in 1996 has been investigated applying a ray-tracing technique and a spectral wave model (SWAN) with an unstructured-mesh grid system. This study discusses the generation and propagation of the swells into the Yellow and East China Seas using the integration of ray trajectories and model-based simulated wave. Calculated and observed wave heights and periods at Gadeokdo, Korea are found to be in reasonable agreement with each other. [ABSTRACT FROM AUTHOR]

Ha, T.; Heo, K.-Y.; Jeon, J.S., and Kang, S., 2017. Numerical modelling of large swell waves using different atmospheric reanalysis data in East Sea. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 164-168. Coconut Creek (Florida), ISSN 0749-0208. Recently, large swell waves have been attracted by many engineers and scientists in South Korea since the eastern coast of the Korean Peninsula has been frequently damaged by large swell waves for several years during winter season. These waves were occasionally higher than 3 m and could be very dangerous for people in beach areas. It has been identified that these waves originated from a certain cyclone passing over East Sea in recent researches. However, an apparent developing mechanism of large swell waves in East Sea is still remained unidentified. Numerical modelling of water waves using the third generation wave model is a convenient source for analysis of wave behaviors in the ocean. In this study, two well-known global atmospheric reanalysis data (ERA-Interim and NCEP FNL) were employed to simulate large swell waves in East Sea. Since sea surface wind is generally regarded as the most important source to wave models, different global reanalysis data should be carefully applied to wave models for better performance. Numerical results of wave models using two different reanalysis data were compared with available observational data and their performance reproducing large swell waves was evaluated both qualitatively and quantitatively. Both simulated wave products using ERA-Interim and NCEP FNL data were reasonably agreeable with corresponding observational data while wave products employing ERA-Interim data qualitatively represented development of observed wave profiles slightly better at certain locations than those employing NCEP FNL data. On the other hand, wave products using NCEP FNL data quantitatively represented observational wave heights slightly better than those using ERA-Interim data during the extreme events. [ABSTRACT FROM AUTHOR]

Ryu, Y.; Jung, T.-H., and Kim, Y.-T., 2017. Kinematics of overtopping flow on breakwater top. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 234-238. Coconut Creek (Florida), ISSN 0749-0208. This study carried out experiments to investigate the behavior of overtopping flows in the vicinity of a caisson breakwater with dissipating blocks. Overtopping flows over a breakwater show horizontal momentum that causes significant damage to objects such as buildings, vehicles, or persons on the top. There is a need to understand overtopping flows on the top related to wave conditions to mitigate damage. This study measured front velocity and impinging distance of overtopping flows by monochromatic waves to examine flow behavior on the top and estimate overtopping flows over the rear slope of the breakwater model in varying wave conditions. Relationships among the parameters were also used to induce empirical equations through dimensionless analysis. [ABSTRACT FROM AUTHOR]

This paper presents the formulation and validation of a shock‐capturing hybrid method using the WENO (weighted essential non‐oscillatory)‐HLL (Harten–Lax–Van Leer) scheme for the solution of the two-dimensional extended Boussinesq-type equations. The governing equations are reformulated in a conservative form, using high-order finite volume WENO schemes with HLL Riemann solver to handle the flux terms. The efficient third-order Runge–Kutta time-stepping scheme is used to advance the numerical solution through time. Wave breaking is predicted by applying a wave breaking criterion to automatically degenerate the Boussinesq equations into nonlinear shallow water equations. In order to test whether the present numerical model could accurately reproduce the processes of transformation, breaking, and run-up of nonlinear dispersive waves under different wave conditions in the nearshore region, five test cases have been simulated. The numerical results show that the present shock-capturing model could simulate the nearshore wave processes very well. [ABSTRACT FROM AUTHOR]

We derive an asymptotic equation governing the trans-ocean propagation of tsunami from source to the continental shelf. Focus is on disturbances originated from a slender fault of finite length. The variable sea depth is assumed to consist of a slowly varying mean and random fluctuations. The method of multiple scales is used to derive a Kadomtsev-Petviashvili equation with variable coefficients. Modifications by one- and two-dimensional random irregularities are shown to affect the wave speed, dissipation and additional dispersion. The result can be used to facilitate physical insight with modest numerical efforts. [ABSTRACT FROM AUTHOR]

The evolution of unidirectional nonlinear sea surface waves is calculated numerically by means of solution of the Euler equations. The wave dynamics corresponds to quasi-equilibrium states characterized by JONSWAP spectra. The spatiotemporal data are collected and processed providing information about the wave height probability and typical appearance of abnormally high waves (rogue waves). The waves are considered at different water depths ranging from deep to relatively shallow cases ( k h > 0.8, where k is the peak wavenumber, and h is the local depth). The asymmetry between front and rear rogue wave slopes is identified; it becomes apparent for sufficiently high waves in rough sea states at all considered depths k h ≥ 1.2. The lifetimes of rogue events may reach up to 30-60 wave periods depending on the water depth. The maximum observed wave has a height of about three significant wave heights. A few randomly chosen in situ time series from the Baltic Sea are in agreement with the general picture of the numerical simulations. [ABSTRACT FROM AUTHOR]

Here we discuss some of the progresses that have been made in the last 20 years in the field of oceanic rogue waves, focusing on the role played by leading order equations such as the nonlinear Schrödinger and the Korteweg-De Vries equations. For such equations, it is possible, as shown in Onorato et al. (Origin of heavy tail statistics in equations of the nonlinear Schrödinger type: an exact result, 2016. arXiv:1601.04317), to derive a very simple relation in which the variation of the third (for the Kd V) and fourth (for the NLS) moment of the probability density function of the wave field can be related to the variation of the spectral bandwidth. These relations give some new perspectives on the formation of rogue waves in a random sea state. [ABSTRACT FROM AUTHOR]

Although tsunamis in the deep ocean are very long waves of quite small amplitudes, as they propagate shorewards into shallow water, nonlinearity becomes important and the structure of the leading waves depends on the polarity of the incident wave from the deep ocean. In this paper, we use a variable-coefficient Korteweg-de Vries equation to examine this issue, for an initial wave which is either elevation, or depression, or a combination of each. We show that the leading waves can be described by a reduction of the Whitham modulation theory to a solitary wave train. We find that for an initial elevation, the leading waves are elevation solitary waves with an amplitude which varies inversely with the depth, with a pre-factor which is twice the maximum amplitude in the initial wave. By contrast, for an initial depression, the leading wave is a depression rarefaction wave, followed by a solitary wave train whose maximum amplitude of the leading wave is determined by the square root of the mass in the initial wave. [ABSTRACT FROM AUTHOR]

The paper reports unique high-resolution observations of meteotsunami by a large array of oceanographic instruments deployed on the Atchafalaya Shelf (Louisiana, USA) in 2008 with the primary aim to study wave dissipation in muddy environments. The meteotsunami event on March 7, 2008, was caused by the passage of a cold front which was monitored by the NOAA NEXRAD radar. The observations of water surface elevations on the shelf show a highly detailed textbook picture of an undular bore (solibore) in the process of its disintegration into a train of solitons. The picture has a striking feature never reported before not only for the meteotsunamis but in other contexts of disintegration of a long-wave perturbation into a sequence of solitons as well-the persistent presence of a single soliton, well ahead of the solibore. Data analysis and simulations based on the celebrated variable-coefficient KdV (vKdV) equation first proposed by Ostrovsky and Pelinovsky (Izv Atmos Ocean Phys 11:37-41, 1975) explain the physics of this phenomenon and suggest that the formation of the lone soliton ahead of the solibore is very likely to be the result of the specific interplay of natural meteotsunami forcing and nearshore bathymetry. The analysis strongly suggests that the patterns of coexisting lone solitons and packets of cnoidal waves should be quite common for meteotsunamis. They were not observed before only because of the scarcity of high-resolution observations. The results highlight the effectiveness of the vKdV equation in providing understanding of the fundamental mechanisms of the complex natural phenomenon that would otherwise require computationally very expensive numerical models. [ABSTRACT FROM AUTHOR]

Ocean waves can be explained in terms of many factors, including wave spectrum, which has the characteristics of wave height and periodicity, directional spreading function, which has a directional property, and random phase, which randomly represents a certain property. Under the assumption of a linear system, ocean waves show irregular behaviours, which can be observed in the forms of wave spectrum, directional spreading function, and complex phase calculations using the method of linear superposition. Ocean waves, which include a variety of periodic elements, exhibit direct proportionality between their period and propagation velocity. The purpose of this study was to understand the phase components of the period and to make exact calculations on the deterministic phase in order to make predictions on ocean waves. However, measurements of actual ocean waves exist only in the form of information on wave elevation, so we faced an inverse problem of having to analyse this information and calculate the deterministic phase. Regularization was used as part of the solution, and various methods were used to obtain stable values. [ABSTRACT FROM AUTHOR]

Both parametric roll and added resistance in head seas are hot topics in ship hydrodynamics. Parametric roll with half the encounter frequency is usually not taken into account in the calculation of added resistance in regular head seas. In order to study the correlation between parametric roll and added resistance, firstly, a formula of added resistance in regular head seas with parametric roll taken into account based on Maruo theory is developed to investigate the effect of parametric roll on added resistance in regular head seas. Secondly, partially restrained free running experiments with and without roll motions are carried out respectively to investigate the effects of parametric roll on added resistance in regular head seas. The results of experiments and simulations using the C11 containership show that added resistance is affected by parametric roll, and the results of experiments also show that heave and pitch motions are distinctly affected by parametric roll. [ABSTRACT FROM AUTHOR]

The impact of fast-propagating swell on the air-sea momentum exchange and the marine boundary layer is examined based on multiple large-eddy simulations over a range of wind speed and swell parameters in the light-wind-fast-wave regime. A wave-driven supergeostrophic jet forms near the top of the wave boundary layer when the forwarding-pointing (i.e., negative) form drag associated with fast wind-following swell overpowers the positive surface shear stress. The magnitude of the form drag increases with the wavelength and slope and decreases with increasing wind speed, and the jet intensity in general increases with the magnitude of the surface form drag. The resulting negative vertical wind shear above the jet in turn enhances the turbulence aloft. The level of the wind maximum is found to be largely determined by the wavenumber and the ratio of the surface shear stress and form drag: the larger the magnitude of this ratio, the higher the altitude of the wind maximum. Although the simulated wind profile often closely follows the log law in the wave boundary layer, the surface stress derived from the logarithmic wind profile is significantly larger than the actual total surface stress in the presence of swell. Therefore, the Monin-Obukhov similarity theory is generally invalid over swell-dominated ocean. This is attributed to the wave-induced contribution to momentum flux, which decays roughly exponentially in the vertical and is largely independent of local wind shear. [ABSTRACT FROM AUTHOR]

A force action caused by the generation of internal waves in the vicinity of a density jump layer in a marine medium and exerted on underwater obstacles streamlined by a two-layer flow has been studied as part of a theoretical model. A horizontal element of an engineering structure, for example, a transport pipeline, which is modeled by a point dipole, is selected as an underwater obstacle. The integral representations for the wave resistance and the lift force are obtained. The characteristic features of variation in the hydrodynamic reactions to the streamlined obstacle, as well as the conditions of their significant intensification are revealed. [ABSTRACT FROM AUTHOR]

In this study, a new numerical scheme with variable-coefficient dispersive conditions was developed to simulate tsunamis over slowly varying topography. The new model was developed using a novel time-space decoupled numerical scheme that used the classic wave equation. By adapting this model to simulate tsunamis, a variable-coefficient dispersive condition was derived to consider the dispersive effects using a numerical truncation error from the numerical scheme. The stability condition and range of the variable coefficient were analyzed using a stability analysis. Using the specific dispersive condition and the modified time-space decoupled scheme, a uniform grid system can be used to simulate a dispersive tsunami over slowly varying topography. Numerical experiments for wave propagation with Gaussian humps and dipolar sources in uniform and varying topography demonstrate that the scheme is efficient for simulating tsunami propagation over slowly varying water depths with dispersive effects. [ABSTRACT FROM AUTHOR]

This study applies the numerical model GPUSPH, an implementation of the weakly compressible smoothed particle hydrodynamics (SPH) method on graphics processing units, to simulate nearshore tsunami processes. Two sets of laboratory experiments that involve violent wave breaking are simulated by the three-dimensional numerical model. The first set of experiments addresses tsunamilike solitary wave breaking on and overtopping an impermeable seawall. Comparison with free-surface profiles and laboratory images shows that GPUSPH satisfactorily reproduces the complicated wave processes involving wave plunging, collapsing, splash-up, and overtopping. The other set of experiments investigates tsunamilike solitary wave breaking and inundation over shallow water reefs. The performance of GPUSPH is evaluated by comparing its results with (1) experimental data including free-surface measurements and cross-shore velocity profiles, and (2) published numerical results obtained in two mesh-based wave models: the nonhydrostatic wave model CCHE2D and the Boussinesq-type wave model FUNWAVE. The capability of GPUSPH to simulate nonlinear wave phenomena, such as wave shoaling, reflection, and refraction, is confirmed by comparing the wave field predicted by CCHE2D. Although all three models correctly simulate the solitary wave propagation offshore and the bore due to the broken wave run-up nearshore, GPUSPH outperforms CCHE2D and FUNWAVE in terms of resolving wave plunging and collapsing. The conducted two case studies show that the meshless SPH method is reliable for predicting tsunami breaking in the nearshore zone. [ABSTRACT FROM AUTHOR]

The possibility of reconstructing sea surface wave fields from a noncoherent X-band marine radar return has much potential for maritime operations and ocean engineering. The existing reconstruction method extracts the signal associated with gravity waves that satisfy the dispersion relationship. The process involves parameters related to how the radar signal is modulated by waves of different lengths, propagation directions, amplitudes, and phases. In the absence of independent wave measurements, these reconstruction parameters cannot be rationally adjusted according to wave field conditions, and the predictions are generally of uneven accuracy and reliability. A new reconstruction method based on concurrent phase-resolved wave field simulations is proposed. By maximizing the correlation between the reconstructed and simulated wave fields over time, optimal values of the reconstruction parameters are obtained that are found to vary appreciably with the wave field properties and with the location and size of the subdomain being sensed and reconstructed. With this phase-resolved simulation calibrated (PRSC) approach, the correlation between the evolving reconstructed wave field and that based on phase-resolved simulation, which measures the consistency and fidelity of the reconstruction, is improved significantly (by up to a factor of 2) and is obtained in a substantially broader range of sea states compared to existing methods. [ABSTRACT FROM AUTHOR]

Regression quantile models are proposed to model extreme significant wave height distributions in two Portuguese locations of Figueira da Foz and Azores in the North Atlantic Ocean. A data set from a 44 years hindcast produced in the HIPOCAS project was used in this study. In order to identify trends with time, the data set was divided in 11 samples of 4 year data. Three-parameter Weibull, generalised extreme value and generalised Pareto quantile functions are fitted to data and extrapolated to 50 and 100 year significant wave height return periods. The algorithm of distributional least absolutes is used to estimate the model parameters. The regression quantile models showed the ability to model the historical trends that may subsist in long term data sets, a feature that the traditional fitting of extreme distributions does not account for. [ABSTRACT FROM AUTHOR]

The sea state and environmental sea conditions are basic data for the design of marine structures. Hindcasted wave data have been here applied for the definition of proper environmental conditions at sea, with the aim to estimate the design condition of an innovative quay wall concept, for a more efficient dock design. In this paper the results of a Computational Fluid Dynamic model is used to optimize the design of a non-reflective quay wall of Vlora's harbour and define design loads under the action of extreme conditions. The design wave conditions at the harbour entrance have been estimated analysing 31 years hindcasted waves data simulated through the application of WaveWatch III. Due to the particular geography and topography of the Vlora's Bay wave conditions generated from northwest are transferred to the harbour entrance with application of a 2D spectral wave model. Southern wave states, which are also the most critical for the port structures, are defined by means of a wave generation model, according the available wind measurements. In general hindcasted sea data, after the application of wave models at a proper scale, are the basic data in support of the maritime works through the propagation of design wave condition from off-shore to harbour entrance. The results show that the proposed method based on the numerical modelling allows the identification of the best site specific solution also for a location devoid of any wave measurement. [ABSTRACT FROM AUTHOR]

Accurately estimating the mean and extreme wave statistics and better understanding their directional and seasonal variations are of great importance in the planning and designing of ocean and coastal engineering works. Due to the lack of long-term wave measurement data, the analysis of extreme waves is often based on the numerical wave hind-casting results. In this study, the wave climate in the East China Seas (including the Bohai Sea, the Yellow Sea and the East China Sea) for the past 35 years (1979–2013) is hind-casted using a third generation wave model – WAMC4 (Cycle 4 version of WAM model). Two sets of reanalysis wind data from NCEP (National Centers for Environmental Prediction, USA) and ECMWF (European Centre for Medium-range Weather Forecasts) are used to drive the wave model to generate the long-term wave climate. The hind-casted waves are then analysed to study the mean and extreme wave statistics in the study area. The results show that the mean wave heights decrease from south to north and from sea to land in general. The extreme wave heights with return periods of 50 and 100 years in the summer and autumn seasons are significantly higher than those in the other two seasons, mainly due to the effect of typhoon events. The mean wave heights in the winter season have the highest values, mainly due to the effect of winter monsoon winds. The comparison of extreme wave statistics from both wind fields with the field measurements at several nearshore wave observation stations shows that the extreme waves generated by the ECMWF winds are better than those generated by the NCEP winds. The comparison also shows the extreme waves in deep waters are better reproduced than those in shallow waters, which is partly attributed to the limitations of the wave model used. The results presented in this paper provide useful insight into the wave climate in the area of the East China Seas, as well as the effect of wind data resolution on the simulation of long-term waves. [ABSTRACT FROM AUTHOR]

The work presents the implementation and evaluation of a package of free mathematical models proving effectiveness for the western region of the Cuban island. For the driving of the models three sources of winds fields are settled down together with the results of the simulation with the atmospheric mesoescala model MM5, the wind fields obtained from GFS model toasted by the NOAA and those obtained from the parametric wind field calibrated by the author. The models being coupled by means of the nesting technique are WW3 v3.14 by Tolman and SWAN v40.81 by Booij. As a case study six trajectories of selected hurricanes are taken. [ABSTRACT FROM AUTHOR]

The significant increase of the population in coastal areas together with the increment and development of the investments associated to sun and beach tourism, make that every day becomes more important to recognize the behavior of the interaction between wave and coastal defense structures, together with the necessity to predict in a quick and correct way the morphodynamic processes ocurring in sand beaches under extreme situations. The present work evaluates the capacity of the mathematical model Xbeach to correctly simulate the wave-coastal protection structures interaction, mainly its capacity to reproduce the phenomena associated with the hydrodynamic and morphology changes in the presence of groin sand breakwaters. [ABSTRACT FROM AUTHOR]

It is commonly accepted that there is an urgent need for a better understanding of the factors that contribute to the air-sea interaction processes and their feedbacks. In this sense it is absolutely important to develop advanced numerical prediction systems that treat the atmosphere and the ocean as a unified system. The realistic description and understanding of the exchange processes near the ocean surface, requires the exact knowledge of the sea state and its evolution. This can be achieved by considering the sea surface and the atmosphere as a continuously cross talking dynamic system. Therefore, this study aims to present the effort towards developing a new, high-resolution, two-way fully coupled atmosphere-ocean wave model in order to support operational and research activities. A specific issue that it is emphasized here is the determination and parameterization of the air-sea momentum fluxes under conditions of extremely high and time-varying winds. Software considerations, data exchange as well as computational and scientific performance of the coupled system, so-called WEW, are also discussed throughout this study. In a case study of high-impact weather and sea state event, the wind-wave parameterization scheme reduces the resulted wind speed and the significant wave height as a response to the increased aerodynamic drag over rough sea surfaces. Overall, WEW offers a more realistic representation of the momentum exchanges in the ocean wind-wave system and includes the effects of the resolved wave spectrum on the drag coefficient and its feedback on the momentum flux. [ABSTRACT FROM AUTHOR]

This study presents a new method to analyse the properties of the sea-level signal recorded by coastal tide gauges in the long wave range that is in a window between wind/storm waves and tides and is typical of several phenomena like local seiches, coastal shelf resonances and tsunamis. The method consists of computing four specific functions based on the time gradient (slope) of the recorded sea level oscillations, namely the instantaneous slope IS, and three more functions based on IS, that are the sea level SL, the background slope BS and the control function CF. These functions are examined through a traditional spectral FFT analysis and also through a statistical analysis showing that they can be characterised by probability distribution functions PDFs such as the Student's t distribution (IS and SL) and the Beta distribution (CF). As an example, the method has been applied to data from the tide-gauge station of Siracusa, Italy. [ABSTRACT FROM AUTHOR]

The adaptive multiscale moment method (AMMM) was originally developed to solve Fredholm equation. More recently, this method has demonstrated to be effective for scattering problems. In this article, we show that AMMM is a relevant approach to model and to analyze the electromagnetic scattering by coastal breaking sea waves. The shape of breaking wave results from very nonlinear fluid mechanics and is a complex target for electromagnetic scattering. This article presents an efficient hydrodynamic model and, combined with AMMM, a global realistic numerical simulation of the electromagnetic signature induced by breaking sea waves. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The article discusses a study which compares the formulas of the linear throy with the predictions within the framework of the Green-Naghdi model for the bottom pressure caused by the passage of a large-amplitude solitary wave (soliton). The study authors reproduce the basic equations of the model for the waves propagating in one direction. They also used the weak-dispersion approximation when deriving the equations.

This paper presents the results from several experiments aimed at determining the effectiveness of combined caissons with an internal rubble mound to dissipate incident sea wave energy. Techniques for assessing the reflection coefficient from wave tank data are discussed via a comparison between the established two- and three-probe methods and a new method using four probes. It is shown that obtaining reliable results for the incident and reflected waves requires the determinant of the linear system derived from the Fourier transform to be sufficiently greater than zero. This requirement was always satisfied for the three- and four-probe methods, but it was not always satisfied for the two-probe method. The experiments showed that the calculated reflection coefficient decreased when the ratio of the water depth, , to the wavelength, , increased. Increasing the caisson chamber width and the upper frontal opening also substantially decreased the reflection coefficient. Plotting the reflection coefficient as a function of shows that, to keep the reflection coefficient lower than 0.4, the ratio must be greater than 0.15. The effects of a slight variation of the still water level, such as those caused by tides or climate changes, were also analyzed. If the geometrical dimensions are appropriately designed, then the combined caisson can be effective for rising water levels. This occurs when the water level rise leads to an increase of the surface exposed to the armor layer. [ABSTRACT FROM AUTHOR]

A dike erosion model is developed to predict the temporal and cross-shore variations of vertical erosion depth under irregular wave action. The product of the erosion rate and the turf resistance force is related to the rate of erosion work by turbulence generated by wave energy dissipation caused by wave breaking and bottom friction. The turf resistance force is expressed using the turf thickness and the surface and underneath resistance parameters. The empirical parameters are calibrated using available data. The calibrated model is shown to reproduce the relation between the limiting velocity and steady flow duration, the erosion rate on a seaward grassed slope, and the eroded profile evolution of a seaward clay slope. The turf resistance parameters are uncertain and will need to be calibrated for specific dikes. [ABSTRACT FROM AUTHOR]

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