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1
Firdaus, Nurman, Baharuddin Ali, Mochammad Nasir e M. Muryadin. "The Wave Heights Distribution of Random Wave Based on Ocean Basin". Kapal: Jurnal Ilmu Pengetahuan dan Teknologi Kelautan 17, n. 3 (1 ottobre 2020): 114–22. http://dx.doi.org/10.14710/kapal.v17i3.31021.
Testo completoAbstract (sommario):
The wave height parameter in ocean waves is one of the important information for a marine structure design. The present paper investigates the results of wave heights distribution from laboratory-generated for single sea state. Data of the random wave time series collected at the ocean basin are analyzed using the wave spectrum and compared with the theoretical spectrum in this study. The random wave data is varied with four sea states consisting of sea states 3, 4, 5 and 6 obtained from laboratory measurements. The parameter conditions of generated sea waves are represented by a value of significant wave height and wave peak period in the range of sea states. The individual wave heights data in each sea state are presented in the form of exceedance probability distribution and the predictions using a linear model. This study aims to estimate the wave heights distribution using the Rayleigh and Weibull distribution model. Furthermore, the accuracy of the wave heights distribution data's prediction results in each sea state has been compared and examined for both models. The applied linear models indicate similar and reasonable estimations on the observed data trends.
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Jialei, Lv, Shi Jian, Zhang Wenjing, Xia Jingmin e Wang Qianhui. "Numerical simulations on waves in the Northwest Pacific Ocean based on SWAN models". Journal of Physics: Conference Series 2486, n. 1 (1 maggio 2023): 012034. http://dx.doi.org/10.1088/1742-6596/2486/1/012034.
Testo completoAbstract (sommario):
Abstract Waves are one of the most important dynamic phenomena in the ocean, and thus numerical simulations of ocean wave is of great importance. Based on SWAN wave numerical model, this paper simulates the waves in the Northwest Pacific Ocean and analyzes the wave height field in the sea area. Moreover, A new wave period parameterization scheme is proposed according to the relationship between the wave height and wave period, in addition, the simulation mode of wave period elements in the Northwest Pacific Ocean is optimized by analyzing the difference of wave period under the proposed parameterization scheme.
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Zhang, Huichen, e Markus Brühl. "GENERATION OF EXTREME TRANSIENT WAVES IN EXPERIMENTAL MODELS". Coastal Engineering Proceedings, n. 36 (30 dicembre 2018): 51. http://dx.doi.org/10.9753/icce.v36.waves.51.
Testo completoAbstract (sommario):
The transfer of natural waves and sea states into small- and large-scale model teste contributes to the proper design of offshore and coastal structure. Such shallow-water ocean surface waves are highly nonlinear and subject to wave transformation and nonlinear wave-wave interactions. However, the standard methods of wave generation according to conventional wave theories and wave analysis methods are limited to simple regular waves, simple sea states and low-order wave generation without considering the nonlinear wave-wave interactions. The research project Generation of Extreme Transient Waves in Experimental Models (ExTraWaG) aims to accurately generate target transient wave profile at a pre-defined position in the wave flume (transfer point) under shallow water conditions. For this purpose, the KdV-based nonlinear Fourier transform is introduced as a continuative wave analysis method and is applied to investigate the nonlinear spectral character of experimental wave data. Furthermore, the method is applied to generate transient nonlinear waves as specific locations in the wave flume, considering the nonlinear transformation and interactions of the propagating waves.
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BAL, GUILLAUME, e OLIVIER PINAUD. "IMAGING USING TRANSPORT MODELS FOR WAVE–WAVE CORRELATIONS". Mathematical Models and Methods in Applied Sciences 21, n. 05 (maggio 2011): 1071–93. http://dx.doi.org/10.1142/s0218202511005258.
Testo completoAbstract (sommario):
We consider the imaging of objects buried in unknown heterogeneous media. The medium is probed by using classical (e.g. acoustic or electromagnetic) waves. When heterogeneities in the medium become too strong, inversion methodologies based on a microscopic description of wave propagation (e.g. a wave equation or Maxwell's equations) become strongly dependent on the unknown details of the heterogeneous medium. In some situations, it is preferable to use a macroscopic model for a quantity that is quadratic in the wave fields. Here, such macroscopic models take the form of radiative transfer equations also referred to as transport equations. They can model either the energy density of the propagating wave fields or more generally the correlation of two wave fields propagating in possibly different media. In particular, we consider the correlation of the two fields propagating in the heterogeneous medium when the inclusion is absent and present, respectively. We present theoretical and numerical results showing that reconstructions based on this correlation are more accurate than reconstructions based on measurements of the energy density.
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Pruser, H. H., H. Schaper e W. Zielke. "IRREGULAR WAVE TRANSFORMATION IN A BOUSSINESO WAVE MODEL". Coastal Engineering Proceedings 1, n. 20 (29 gennaio 1986): 205. http://dx.doi.org/10.9753/icce.v20.205.
Testo completoAbstract (sommario):
Numerical wave models for shallow water waves are of particular importance for the calculation of the wave climate in harbours and coastal areas. Especially nonlinear time domain models, which are based on the Boussinesq-Wave- Equations, may be helpful in the future for simulating the interaction of currents with refraction, diffraction, reflection and for simulating shoaling..-of irregular waves in natural areas; a potential which has not yet been fully developed. During the last ten years numerical models, based on these equations, have been published; such as ABBOTT et. al. , HAUGUEL and SCHAPER / ZIELKE . Research on this topic is currently being carried on. Some efforts have been made to verify the capability of the models to describe the various physical phenomena. However, up to now, verification has been limited to regular waves. The aim of this paper therefore is, to consider questions concerning irregular, nonlinear waves.
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Mori, Nobuhito, Joao Morim, Mark Hemer, Xiaolan L. Wang e COWCLIP Project. "ENSEMBLE WAVE CLIMATE PROJECTIONS BASED ON CMIP5 MODELS". Coastal Engineering Proceedings, n. 36v (28 dicembre 2020): 23. http://dx.doi.org/10.9753/icce.v36v.waves.23.
Testo completoAbstract (sommario):
A warming climate has the potential to not only raise sea level but also exacerbate coastal hazards due to changes in storm frequency and intensity. Along open coasts where wave energy is often the dominant process dictating shoreline positions, changes in mean and extreme wave conditions are likely to alter long-term geomorphic evolution patterns. The Coordinated Ocean Wave Climate Project (COWCLIP) is to provide infrastructure to support a systematic, community-based framework that allows for validation and inter-comparison of wave projections. Here, the primary aims are to 1) present quantitative evaluations of projected global scale wave conditions and 2) to present the framework and preliminary results of regional wave modeling that will provide projections of nearshore wave conditions for use in long-term geomorphic change analyzes.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/Y6BEHq5wZXw
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Hernandez-Duenas, Gerardo, Leslie M. Smith e Samuel N. Stechmann. "Investigation of Boussinesq dynamics using intermediate models based on wave–vortical interactions". Journal of Fluid Mechanics 747 (15 aprile 2014): 247–87. http://dx.doi.org/10.1017/jfm.2014.138.
Testo completoAbstract (sommario):
AbstractNonlinear coupling among wave modes and vortical modes is investigated with the following question in mind: can we distinguish the wave–vortical interactions largely responsible for formation versus evolution of coherent, balanced structures? The two main case studies use initial conditions that project only onto the vortical-mode flow component of the rotating Boussinesq equations: (i) an initially balanced dipole and (ii) random initial data in the vortical modes. Both case studies compare quasi-geostrophic (QG) dynamics (involving only nonlinear interactions between vortical modes) to the dynamics of intermediate models allowing for two-way feedback between wave modes and vortical modes. For an initially balanced dipole with symmetry across the$\hat{\boldsymbol {x}}$-axis, the QG dipole will propagate along the$\hat{\boldsymbol {x}}$-axis while the trajectory of the Boussinesq dipole exhibits a cyclonic drift. Compared to a forced linear (FL) model with one-way forcing of wave modes by the vortical modes, the simplest intermediate model with two-way feedback involving vortical–vortical–wave interactions is able to capture the speed and trajectory of the dipole for roughly ten times longer at Rossby$Ro$and Froude$Fr$numbers$Ro = Fr \approx 0.1$. Despite its success at tracking the dipole, the latter intermediate model does not accurately capture the details of the flow structure within the adjusted dipole. For decay from random initial conditions in the vortical modes, the full Boussinesq equations generate vortices that are smaller than QG vortices, indicating that wave–vortical interactions are fundamental for creating the correct balanced state. The intermediate model with QG and vortical–vortical–wave interactions actually prevents the formation of vortices. Taken together these case studies suggest that: vortical–vortical–wave interactions create waves and thereby influence the evolution of balanced structures; vortical–wave–wave interactions take energy out of the wave modes and contribute in an essential way to the formation of coherent balanced structures.
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Gogin, Aleksandr G., e Izmail G. Kantarzhi. "Numerical simulation of sea-wave diffraction with random phases on breakwaters". Vestnik MGSU, n. 4 (aprile 2023): 615–26. http://dx.doi.org/10.22227/1997-0935.2023.4.615-626.
Testo completoAbstract (sommario):
Introduction. Numerical simulation of sea gravity waves interaction with seaport barriers using modern numerical wave models is considered. The predictive power of some commonly used models is examined in relation to the diffraction of sea waves with a random phase in comparison with known analytical methods and experimental data.
Materials and methods. Numerical simulation is carried out using modern numerical wave models implemented in the DHI MIKE 21 software package. A spectral wave model with a function for correcting wave diffraction in shallow water and a phase-resolving wave model based on the Boussinesq equations are used.
Results. Distribution of diffraction coefficients behind the breakwaters of the conventional port water area has been obtained for all models. As a result of the comparison, it was found that models of irregular waves (waves with random phases) have better wave energy distribution behind the breakwaters as compared to regular (monochromatic) wave models. It is noted that the type of frequency distribution of random waves has almost no effect on the diffraction coefficients of the water area, while the angular distribution, on the contrary, has a significant effect.
Conclusions. The wave model based on the Boussinesq equations in the irregular wave approximation is determined as the numerical wave model with the best predictive ability. The spectral wave model with diffraction correction function, which is less demanding on computer power, also made it possible to obtain results close to the reference ones. It is confirmed that regular wave propagation modelling of sea waves can give incorrect results in those seaport water areas where wave diffraction effects are strong.
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SU, MING, GARY G. YEN e R. R. RHINEHART. "GA-BASED TIME SERIES MODELS WITH THRESHOLD IN TWO DOMAINS". Journal of Circuits, Systems and Computers 18, n. 04 (giugno 2009): 801–23. http://dx.doi.org/10.1142/s021812660900537x.
Testo completoAbstract (sommario):
A new threshold time series model is proposed whose submodels are extended from AR to SARIMA and whose domains having thresholds are extended to two. By these two extensions, the newly proposed models offer more flexibility to piecewisely approximate nonstationary time series by a finite number of local stationary models. A genetic algorithm is applied to simultaneously search for appropriate model structures, estimate the optimal model coefficients, as well as partition space by finding appropriate thresholds. The resulting model is applied to a synthetic multi-frequency sine wave and two financial time series with improved modeling quality. The proposed model is also applied to seismogram analysis in order to recognize earthquake wave pattern related to locate arrival time of different waves.
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Zhang, Jun. "Hybrid Wave Models and Their Applications for Steep Ocean Waves". Marine Technology Society Journal 33, n. 3 (1 gennaio 1999): 15–26. http://dx.doi.org/10.4031/mtsj.33.3.3.
Testo completoAbstract (sommario):
Bound-wave components resulting from inter-actions among free-wave components have significant effects on resultant wave properties, especially in a steep ocean wave field. Hybrid Wave Models (HWM) distinguish the bound-wave from free-wave components in the decomposition of an irregular wave field as well as the prediction of its resultant proper-ties. To ensure the convergence, the HWMs selectively use the conventional and phase modulation approaches to address the nonlinear interactions between-free-wave components of different frequency ratios. The models are able to predict resultant wave properties accurately and deterministically based on the time-series measurements at fixed points. Four examples of their applications to the prediction of wave properties and wave-structure interactions are presented, which demonstrate the usefulness of HWMs to the studies of ocean surface waves.
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Londhe, S. N., e Vijay Panchang. "One-Day Wave Forecasts Based on Artificial Neural Networks". Journal of Atmospheric and Oceanic Technology 23, n. 11 (1 novembre 2006): 1593–603. http://dx.doi.org/10.1175/jtech1932.1.
Testo completoAbstract (sommario):
Abstract Sophisticated wave models like the Wave Model (WAM) and Simulating Waves Nearshore (SWAN)/WAVEWATCH are used nowadays along with atmospheric models to produce forecasts of ocean wave conditions. These models are generally run operationally on large ocean-scale domains. In many coastal areas, on the other hand, operational forecasting is not performed for a variety of reasons, yet the need for wave forecasts remains. To address such cases, the production of forecasts through the use of artificial neural networks and buoy measurements is explored. A modeling strategy that predicts wave heights up to 24 h on the basis of judiciously selected measurements over the previous 7 days was examined. A detailed investigation of this strategy using data from six National Data Buoy Center (NDBC) buoys with diverse geographical and statistical properties demonstrates that 6-h forecasts can be obtained with a high level of fidelity, and forecasts up to 12 h showed a correlation of 67% or better relative to a full year of data. One limitation observed was the inability of the artificial neural network model to correctly predict the magnitude of the highest waves; although the occurrence of high waves was predicted, the peaks were underestimated. The inclusion of several years of data and the judicious selection of the training set, especially the inclusion of extreme events, were shown to be crucial for the model to recognize interannual variability and provide more reliable forecasts. Real-time simulations performed for April 2005 demonstrate the efficiency of this technology for operational forecasting.
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Kyaw, Thit Oo, Tomoya Shibayama, Yoko Shibutani e Yasuo Kotake. "DEVELOPMENT OF A DEEP-LEARNING BASED WAVE FORECASTING MODEL USING LSTM NETWORK". Coastal Engineering Proceedings, n. 36v (28 dicembre 2020): 31. http://dx.doi.org/10.9753/icce.v36v.waves.31.
Testo completoAbstract (sommario):
Forecasting of wave conditions plays an essential role for offshore construction and maintenance. Recently, machine learning-based wave forecasting models have been developed and their integrated usage with physics-based numerical models has become popular. These studies mostly apply Feed Forward Neural Networks (FFNNs) with an emphasis on prediction of time-series of waves, tides and storm surges. As a particularly different approach, we develop a deep learning-based wave forecasting model using Long Short-Term Memory (LSTM) network under Recurrent Neural Networks. As a case study, the model will be utilized to predict the wave conditions (low or high) near the Tottori Port, Japan.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/oMvIS9zkIOs
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Vogel, J. A., A. C. Radder e J. H. De Reus. "VERIFICATION OF NUMERICAL WAVE PROPAGATION MODELS IN TIDAL INLETS". Coastal Engineering Proceedings 1, n. 21 (29 gennaio 1988): 30. http://dx.doi.org/10.9753/icce.v21.30.
Testo completoAbstract (sommario):
The performance of two numerical wave propagation models has been investigated by comparison with field data. The first model is a refractiondiffraction model based on the parabolic equation method. The second is a refraction model based on the wave action equation, using a regular grid. Two field situations, viz. a tidal inlet and a river estuary along the Dutch coast, were used to determine the influence of the local wind on waves behind an island and a breaker zone. It may be concluded from the results of the computations and measurements that a much better agreement is obtained when wave growth due to wind is properly accounted for in the numerical models. In complicated coastal areas the models perform well for both engineering and research purposes.
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Penalba, Markel, e John V. Ringwood. "Linearisation-based nonlinearity measures for wave-to-wire models in wave energy". Ocean Engineering 171 (gennaio 2019): 496–504. http://dx.doi.org/10.1016/j.oceaneng.2018.11.033.
Testo completo
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Saprykina, Yana, Burak Aydogan e Berna Ayat. "MODELLING OF SPILLING AND PLUNGING BREAKING WAVES IN SPECTRAL MODELS". Coastal Engineering Proceedings, n. 37 (1 settembre 2023): 15. http://dx.doi.org/10.9753/icce.v37.papers.15.
Testo completoAbstract (sommario):
Based on the data of field experiments and modeling was revealed that the dissipation of the energy of the high-frequency part of the wave spectrum due to wave breaking should compensate the nonlinear growth of higher wave harmonics, which occurs in different ways both for waves breaking with different types and for different methods of modeling a nonlinear source term. The effect of the dissipative term type used on the estimates of sediment transport is discussed.
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Ern, Manfred, Quang Thai Trinh, Peter Preusse, John C. Gille, Martin G. Mlynczak, James M. Russell III e Martin Riese. "GRACILE: a comprehensive climatology of atmospheric gravity wave parameters based on satellite limb soundings". Earth System Science Data 10, n. 2 (27 aprile 2018): 857–92. http://dx.doi.org/10.5194/essd-10-857-2018.
Testo completoAbstract (sommario):
Abstract. Gravity waves are one of the main drivers of atmospheric dynamics. The spatial resolution of most global atmospheric models, however, is too coarse to properly resolve the small scales of gravity waves, which range from tens to a few thousand kilometers horizontally, and from below 1 km to tens of kilometers vertically. Gravity wave source processes involve even smaller scales. Therefore, general circulation models (GCMs) and chemistry climate models (CCMs) usually parametrize the effect of gravity waves on the global circulation. These parametrizations are very simplified. For this reason, comparisons with global observations of gravity waves are needed for an improvement of parametrizations and an alleviation of model biases. We present a gravity wave climatology based on atmospheric infrared limb emissions observed by satellite (GRACILE). GRACILE is a global data set of gravity wave distributions observed in the stratosphere and the mesosphere by the infrared limb sounding satellite instruments High Resolution Dynamics Limb Sounder (HIRDLS) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER). Typical distributions (zonal averages and global maps) of gravity wave vertical wavelengths and along-track horizontal wavenumbers are provided, as well as gravity wave temperature variances, potential energies and absolute momentum fluxes. This global data set captures the typical seasonal variations of these parameters, as well as their spatial variations. The GRACILE data set is suitable for scientific studies, and it can serve for comparison with other instruments (ground-based, airborne, or other satellite instruments) and for comparison with gravity wave distributions, both resolved and parametrized, in GCMs and CCMs. The GRACILE data set is available as supplementary data at https://doi.org/10.1594/PANGAEA.879658.
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Khoirunnisa, H., G. R. Pasma e G. Gumbira. "Numerical modeling of return period waves based on non-linear Boussinesq wave models to support tidal flood studies in the Kedungsepur area". IOP Conference Series: Earth and Environmental Science 1224, n. 1 (1 agosto 2023): 012020. http://dx.doi.org/10.1088/1755-1315/1224/1/012020.
Testo completoAbstract (sommario):
Abstract A number of rapid developments and negative effects of climate change in coastal areas have forced its equilibrium system. As a result, tidal floods, high waves, and storms occur more frequently. The goal of this research is to examine nearshore hydrodynamic conditions by using results from the hindcasting procedure. A non-linear Boussinesq (BW) and Spectral Wave (SW) models are used in this study. The models use the manning coefficient, bathymetry data (BATNAS), significant wave height, and wave period calculated by using the hindcasting method. This research commenced by processing wind data from the European Center for Medium-Range Weather Forecasts (ECMWF) from the years 2009 to 2021 with an interval of 3 hours. Then, wave height for return periods 1-, 50- and 100-years are calculated using Gumbel and Fisher-Tippett type I distribution, respectively. The aforementioned approach produced wave heights of 4.23; 6.16; and 6.49 m for return periods 1, 50, and 100 years, respectively. By using this series of wave data, the models predicted that 1.2 m waves propagate close to the nearshore regions.
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Sidler, Rolf. "A porosity-based Biot model for acoustic waves in snow". Journal of Glaciology 61, n. 228 (2015): 789–98. http://dx.doi.org/10.3189/2015jog15j040.
Testo completoAbstract (sommario):
AbstractPhase velocities and attenuation in snow cannot be explained by the widely used elastic or viscoelastic models for acoustic wave propagation. Instead, Biot’s model of wave propagation in porous materials should be used. However, the application of Biot’s model is complicated by the large property space of the underlying porous material. Here constant properties for ice and air, and empirical relationships are used to estimate unknown porous properties from snow porosity. Using this set of equations, phase velocities and plane wave attenuation of shear- and compressional waves are predicted as functions of porosity or density. For light snow the peculiarity was found that the velocity of the first compressional wave is lower than that of the second compressional wave that is commonly referred to as the ‘slow’ wave. The reversal of the velocities comes with an increase of attenuation for the first compressional wave. This is in line with the common observation that sound is strongly absorbed in light snow. The results have important implications for the use of acoustic waves to evaluate snow properties and to numerically simulate wave propagation in snow.
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Luo, Feng, Yao Feng, Guisheng Liao e Linrang Zhang. "The Dynamic Sea Clutter Simulation of Shore-Based Radar Based on Stokes Waves". Remote Sensing 14, n. 16 (12 agosto 2022): 3915. http://dx.doi.org/10.3390/rs14163915.
Testo completoAbstract (sommario):
The sea clutter model based on the physical sea surface can simulate radar echo at different times and positions and is more suitable for describing dynamic sea clutter than the traditional models based on statistical significance. However, when applying the physical surface model to shore-based radar, the effects of wave nonlinearity, breaking wave, shadow, and radar footprint size must be considered. In this paper, a dynamic sea clutter simulation scheme based on a nonlinear wave is proposed that uses random Stokes waves instead of linear superposition waves to simulate the nonlinear dynamic sea surface and then calculates echo in the form of scattering cells. In this process, the relationship between wind speed and the nonlinear factor of the Stokes wave is derived, a simple model of shadow modulation is provided, and a method for appending the sea clutter spikes formed by breaking waves is developed. The experimental results show that the simulated sea clutter and the real measured clutter have good consistency in intensity, amplitude statistical distribution, Doppler spectrum, and spatiotemporal correlation. The proposed scheme is suitable for the sea clutter simulation of shore-based radar and can also adjust the relevant parameters to extend to other types of sea clutter simulation.
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Guérin, Charles-Antoine, Nicolas Desmars, Stéphan T. Grilli, Guillaume Ducrozet, Yves Perignon e Pierre Ferrant. "An improved Lagrangian model for the time evolution of nonlinear surface waves". Journal of Fluid Mechanics 876 (1 agosto 2019): 527–52. http://dx.doi.org/10.1017/jfm.2019.519.
Testo completoAbstract (sommario):
Accurate real-time simulations and forecasting of phase-revolved ocean surface waves require nonlinear effects, both geometrical and kinematic, to be accurately represented. For this purpose, wave models based on a Lagrangian steepness expansion have proved particularly efficient, as compared to those based on Eulerian expansions, as they feature higher-order nonlinearities at a reduced numerical cost. However, while they can accurately model the instantaneous nonlinear wave shape, Lagrangian models developed to date cannot accurately predict the time evolution of even simple periodic waves. Here, we propose a novel and simple method to perform a Lagrangian expansion of surface waves to second order in wave steepness, based on the dynamical system relating particle locations and the Eulerian velocity field. We show that a simple redefinition of reference particles allows us to correct the time evolution of surface waves, through a modified nonlinear dispersion relationship. The resulting expressions of free surface particle locations can then be made numerically efficient by only retaining the most significant contributions to second-order terms, i.e. Stokes drift and mean vertical level. This results in a hybrid model, referred to as the ‘improved choppy wave model’ (ICWM) (with respect to Nouguier et al.’s J. Geophys. Res., vol. 114, 2009, p. C09012), whose performance is numerically assessed for long-crested waves, both periodic and irregular. To do so, ICWM results are compared to those of models based on a high-order spectral method and classical second-order Lagrangian expansions. For irregular waves, two generic types of narrow- and broad-banded wave spectra are considered, for which ICWM is shown to significantly improve wave forecast accuracy as compared to other Lagrangian models; hence, ICWM is well suited to providing accurate and efficient short-term ocean wave forecast (e.g. over a few peak periods). This aspect will be the object of future work.
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Smit, P. B., T. T. Janssen e T. H. C. Herbers. "Stochastic Modeling of Coherent Wave Fields over Variable Depth". Journal of Physical Oceanography 45, n. 4 (aprile 2015): 1139–54. http://dx.doi.org/10.1175/jpo-d-14-0219.1.
Testo completoAbstract (sommario):
AbstractRefractive focusing of swell waves can result in fast-scale variations in the wave statistics because of wave interference, which cannot be resolved by stochastic wave models based on the radiative transport equation. Quasi-coherent statistical theory does account for such statistical interferences and the associated wave inhomogeneities, but the theory has thus far been presented in a form that appears incompatible with models based on the radiative transfer equation (RTE). Moreover, the quasi-coherent theory has never been tested against field data, and it is not clear how the coherent information inherent to such models can be used for better understanding coastal wave and circulation dynamics. This study therefore revisits the derivation of quasi-coherent theory to formulate it into a radiative transport equation with a forcing term that accounts for the inhomogeneous part of the wave field. This paper shows how the model can be nested within (or otherwise used in conjunction with) quasi-homogeneous wave models based on the RTE. Through comparison to laboratory data, numerical simulations of a deterministic model, and field observations of waves propagating over a nearshore canyon head, the predictive capability of the model is validated. The authors discuss the interference patterns predicted by the model through evaluation of a complex cross-correlation function and highlight the differences with quasi-homogeneous predictions. These results show that quasi-coherent theory can extend models based on the RTE to resolve coherent interference patterns and standing wave features in coastal areas, which are believed to be important in nearshore circulation and sediment transport.
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Pierson, Willard J., e Azed Jean-Pierre. "Monte Carlo Simulations of Nonlinear Ocean Wave Records with Implications for Models of Breaking Waves". Journal of Ship Research 43, n. 02 (1 giugno 1999): 121–34. http://dx.doi.org/10.5957/jsr.1999.43.2.121.
Testo completoAbstract (sommario):
A Monte Carlo method for simulating nonlinear ocean wave records as a function of time is described. It is based on a family of probability density functions developed by Karl Pearson and requires additional knowledge of the dimensionless moments of a postulated nonlinear wave record, which are the skewness and kurtosis. A frequency spectrum is used to simulate a linear record. It is then transformed to a nonlinear record for the chosen values of the skewness and kurtosis. The result is not a perturbation expansion of the nonlinear equations that describe unbroken waves. It yields a simulated wave record that reproduces the chosen values for the skewness and, if needed, the kurtosis of a wave record so that the statistical properties are modeled. A brief history of the development of the linear model, presently in use, is given along with a survey of wave data that show the variability of the nonlinear properties of wave records. The need for a nonlinear model of waves for naval architecture, remote sensing and other design problems is shown. This method cannot provide any information on whether a particular wave will break. Some of the recent results on breaking waves and "green water" are reviewed. The possibility that this method can be extended based on the concept of a "local absorbing patch" is described.
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Diaz Loaiza, Manuel Andres, Jeremy D. Bricker, Remi Meynadier, Trang Minh Duong, Rosh Ranasinghe e Sebastiaan N. Jonkman. "Development of damage curves for buildings near La Rochelle during storm Xynthia based on insurance claims and hydrodynamic simulations". Natural Hazards and Earth System Sciences 22, n. 2 (8 febbraio 2022): 345–60. http://dx.doi.org/10.5194/nhess-22-345-2022.
Testo completoAbstract (sommario):
Abstract. The Delft3D hydrodynamic and wave model is used to hindcast the storm surge and waves that impacted La Rochelle, France, and the surrounding area (Aytré, Châtelaillon-Plage, Yves, Fouras, and Île de Ré) during storm Xynthia. These models are validated against tide and wave measurements. The models then estimate the footprint of flow depth, speed, unit discharge, flow momentum flux, significant wave height, wave energy flux, total water depth (flow depth plus wave height), and total (flow plus wave) force at the locations of damaged buildings for which insurance claims data are available. Correlation of the hydrodynamic and wave results with the claims data generates building damage functions. These damage functions are shown to be sensitive to the topography data used in the simulation, as well as the hydrodynamic or wave forcing parameter chosen for the correlation. The most robust damage functions result from highly accurate topographic data and are correlated with water depth or total (flow plus wave) force.
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Gagarina, E., J. van der Vegt e O. Bokhove. "Horizontal circulation and jumps in Hamiltonian wave models". Nonlinear Processes in Geophysics 20, n. 4 (12 luglio 2013): 483–500. http://dx.doi.org/10.5194/npg-20-483-2013.
Testo completoAbstract (sommario):
Abstract. We are interested in the modelling of wave-current interactions around surf zones at beaches. Any model that aims to predict the onset of wave breaking at the breaker line needs to capture both the nonlinearity of the wave and its dispersion. We have therefore formulated the Hamiltonian dynamics of a new water wave model, incorporating both the shallow water and pure potential flow water wave models as limiting systems. It is based on a Hamiltonian reformulation of the variational principle derived by Cotter and Bokhove (2010) by using more convenient variables. Our new model has a three-dimensional velocity field consisting of the full three-dimensional potential velocity field plus extra horizontal velocity components. This implies that only the vertical vorticity component is nonzero. Variational Boussinesq models and Green–Naghdi equations, and extensions thereof, follow directly from the new Hamiltonian formulation after using simplifications of the vertical flow profile. Since the full water wave dispersion is retained in the new model, waves can break. We therefore explore a variational approach to derive jump conditions for the new model and its Boussinesq simplifications.
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Follett, R. K., A. Colaïtis, D. Turnbull, D. H. Froula e J. P. Palastro. "Validation of ray-based cross-beam energy transfer models". Physics of Plasmas 29, n. 11 (novembre 2022): 113902. http://dx.doi.org/10.1063/5.0123462.
Testo completoAbstract (sommario):
Ray-based cross-beam energy transfer (CBET) models have become a common feature of the radiation-hydrodynamic codes used to simulate inertial confinement fusion experiments. These models are necessary for achieving better agreement with experimental measurements, but their detailed implementation can vary widely between the codes and often rely on artificial multipliers. To address this, a series of 2D and 3D test cases has been developed with validated solutions from wave-based calculations. Comparisons of various ray-based CBET models to the wave-based calculations highlight the essential physics that is required for accurate ray-based CBET modeling. Quantitative comparison metrics and/or field data from the wave-based calculations have been made available for use in the validation of other ray-based CBET codes.
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Holman, Kathleen D., David J. Lorenz e Michael Notaro. "Influence of the Background State on Rossby Wave Propagation into the Great Lakes Region Based on Observations and Model Simulations*". Journal of Climate 27, n. 24 (10 dicembre 2014): 9302–22. http://dx.doi.org/10.1175/jcli-d-13-00758.1.
Testo completoAbstract (sommario):
Abstract The authors investigate the relationship between hydrology in the Great Lakes basin—namely, overlake precipitation and transient Rossby waves—using the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis data and historical output from phase 3 of the Coupled Model Intercomparison Project (CMIP3). The preferred path of observed Rossby wave trains associated with overlake precipitation on Lake Superior depends strongly on season and appears to be related to the time-mean, upper-level flow. During summer and fall, the Northern Hemisphere extratropical jet is relatively narrow and acts as a waveguide, such that Rossby wave trains traversing the Great Lakes region travel along the extratropical Pacific and Atlantic jets. During other months, the Pacific jet is relatively broad, which allows more wave activity originating in the tropics to penetrate into the midlatitudes and influence Lake Superior precipitation. Analysis is extended to CMIP3 models and is intended to 1) further understanding of how variations in the mean state influence transient Rossby waves and 2) assess models’ ability to capture observed features, such as wave origin and track. Results indicate that Rossby wave train propagation in twentieth-century simulations can significantly differ by model. Unlike observations, some models do not produce a well-defined jet across the Pacific Ocean during summer and autumn. In these models, some Rossby waves affecting the Great Lakes region originate in the tropics. Collectively, observations and model results show the importance of the time-mean upper-level flow on Rossby wave propagation and therefore on the relative influence of the tropics versus the extratropics on the hydroclimate of the Great Lakes region.
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Shi, Jiao, Tianyun Su, Xinfang Li, Fuwei Wang, Jingjing Cui, Zhendong Liu e Jie Wang. "A Machine-Learning Approach Based on Attention Mechanism for Significant Wave Height Forecasting". Journal of Marine Science and Engineering 11, n. 9 (19 settembre 2023): 1821. http://dx.doi.org/10.3390/jmse11091821.
Testo completoAbstract (sommario):
Significant wave height (SWH) is a key parameter for monitoring the state of waves. Accurate and long-term SWH forecasting is significant to maritime shipping and coastal engineering. This study proposes a transformer model based on an attention mechanism to achieve the forecasting of SWHs. The transformer model can capture the contextual information and dependencies between sequences and achieves continuous time series forecasting. Wave scale classification is carried out according to the forecasting results, and the results are compared with gated recurrent unit (GRU) and long short-term memory (LSTM) machine-learning models and the key laboratory of MArine Science and NUmerical Modeling (MASNUM) numerical wave model. The results show that the machine-learning models outperform the MASNUM within 72 h, with the transformer being the best model. For continuous 12 h, 24 h, 36 h, 48 h, 72 h, and 96 h forecasting, the average mean absolute errors (MAEs) of the test sets were, respectively, 0.139 m, 0.186 m, 0.223 m, 0.254 m, 0.302 m, and 0.329 m, and the wave scale classification accuracies were, respectively, 91.1%, 99.4%, 86%, 83.3%, 78.9%, and 77.5%. The experimental results validate that the transformer model can achieve continuous and accurate SWH forecasting, as well as accurate wave scale classification and early warning of waves, providing technical support for wave monitoring.
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Stephan, Claudia, M. Joan Alexander e Jadwiga H. Richter. "Characteristics of Gravity Waves from Convection and Implications for Their Parameterization in Global Circulation Models". Journal of the Atmospheric Sciences 73, n. 7 (24 giugno 2016): 2729–42. http://dx.doi.org/10.1175/jas-d-15-0303.1.
Testo completoAbstract (sommario):
Abstract Characteristic properties of gravity waves from convection over the continental United States are derived from idealized high-resolution numerical simulations. In a unique modeling approach, waves are forced by a realistic thermodynamic source based on observed precipitation data. The square of the precipitation rate and the gravity wave momentum fluxes both show lognormal occurrence distributions, with long tails of extreme events. Convectively generated waves can give forces in the lower stratosphere that at times rival orographic wave forcing. Throughout the stratosphere, zonal forces due to convective wave drag are much stronger than accounted for by current gravity wave drag parameterizations, so their contribution to the summer branch of the stratospheric Brewer–Dobson circulation is in fact much larger than models predict. A comparison of these forces to previous estimates of the total drag implies that convectively generated gravity waves are a primary source of summer-hemisphere stratospheric wave drag. Furthermore, intermittency and strength of the zonal forces due to convective gravity wave drag in the lower stratosphere resemble analysis increments, suggesting that a more realistic representation of these waves may help alleviate model biases on synoptic scales. The properties of radar precipitation and gravity waves seen in this study lead to a proposed change for future parameterization methods that would give more realistic drag forces in the stratosphere without compromising mesospheric gravity wave drag.
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Stosic, Biljana. "Wave-based digital models of different branch-line couplers". Serbian Journal of Electrical Engineering 17, n. 2 (2020): 149–69. http://dx.doi.org/10.2298/sjee2002149s.
Testo completoAbstract (sommario):
Microwave and millimeter-wave communication systems require couplers in different applications. The aim of this paper is to construct simple wave digital models of directional couplers with two or three parallel lines. The idea behind this aim is to be able to model a microstrip structure and to simulate it using Simulink platform which has already been used extensively by researchers. Advanced Design System (ADS) software and MATLAB/Simulink environment are used to design, implement and simulate the investigated microstrip circuits and their models. Validity and accuracy of the presented digital models are fully demonstrated through several benchmark problems.
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Drzewiecki, Marcin. "The Propagation of the Waves in the CTO S.A. Towing Tank". Polish Maritime Research 25, s1 (1 maggio 2018): 22–28. http://dx.doi.org/10.2478/pomr-2018-0018.
Testo completoAbstract (sommario):
Abstract The paper presents the results of research focused on the wave propagation in the CTO S.A. deepwater towing tank. In the scope of paper, the wavemaker transfer function was determined for regular waves, based on the Biésel Transfer Function and further for irregular waves, based on Hasselman model of nonlinear energy transfer. The phenomena: wave damping, wave breakdown and wave reflection, were measured, analyzed and mathematically modeled. Developed mathematical models allow to calculate the impact of mentioned phenomena on the wave propagation and furthermore to calculate the wave characteristics along the whole measurement area in the CTO S.A. deepwater towing tank, based on wavemaker flap motion control.
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Mohapatra, Sarat Chandra, Hafizul Islam, Thiago S. Hallak e C. Guedes Soares. "Solitary Wave Interaction with a Floating Pontoon Based on Boussinesq Model and CFD-Based Simulations". Journal of Marine Science and Engineering 10, n. 9 (5 settembre 2022): 1251. http://dx.doi.org/10.3390/jmse10091251.
Testo completoAbstract (sommario):
A mathematical model of solitary wave interaction with a pontoon-type rigid floating structure over a flat bottom is formulated based on Boussinesq-type equations under weakly nonlinear dispersive waves. Based on the higher-order Boussinesq equations, the solitary wave equation is derived, and a semi-analytical solution is obtained using the perturbation technique. On the other hand, brief descriptions of the application of wave2Foam and OceanWave3D on the aforementioned problem are presented. The analytical solitary wave profiles in the outer region are compared with Computational Fluid Dynamics (CFD) and OceanWave 3D model simulations in different cases. The comparison shows a good level of agreement between analytical, wave2Foam, and OceanWave3D. In addition, based on the wave2Foam and coupled OceanWave3D model, the horizontal, vertical wave forces, and the pressure distributions around the pontoon are analysed. Further, the effect of the Ursell number, pontoon length, and water depth on the solitary wave profiles are analysed based on the analytical solution. The paper validates each of the three models and performs intercomparison among them to assess their fidelity and computational burden.
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Weymouth, Gabriel D., e Dick K. P. Yue. "Physics-Based Learning Models for Ship Hydrodynamics". Journal of Ship Research 57, n. 01 (1 marzo 2013): 1–12. http://dx.doi.org/10.5957/jsr.2013.57.1.1.
Testo completoAbstract (sommario):
We present the concepts of physics-based learning models (PBLM) and their relevance and application to the field of ship hydrodynamics. The utility of physics-based learning is motivated by contrasting generic learning models for regression predictions, which do not presume any knowledge of the system other than the training data provided with methods such as semi-empirical models, which incorporate physical insights along with data-fitting. PBLM provides a framework wherein intermediate models, which capture (some) physical aspects of the problem, are incorporated into modern generic learning tools to substantially improve the predictions of the latter, minimizing the reliance on costly experimental measurements or high-resolution high-fidelity numerical solutions. To illustrate the versatility and efficacy of PBLM, we present three wave-ship interaction problemsat speed waterline profiles;ship motions in head seas; andthree-dimensional breaking bow waves. PBLM is shown to be robust and produce error rates at or below the uncertainty in the generated data at a small fraction of the expense of high-resolution numerical predictions.
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Uday A. Alturfi e Abdul-Hassan K. Shukur. "Investigation of Energy Dissipation for Different Breakwater Based on Computational Fluid Dynamic Model". CFD Letters 16, n. 1 (29 novembre 2023): 22–42. http://dx.doi.org/10.37934/cfdl.16.1.2242.
Testo completoAbstract (sommario):
In this research, the hydraulic performance of the combined shape breakwaters was investigated through a laboratory study supported by a numerical mathematical model CFD to examine the different model shapes depending on the transmissions wave coefficient Ct. In order to stabilize the incident wave Hi with the same characteristics, waves were defined through the UDF file for CFD model. To investigated the performance of breakwaters base on energy dissipations, different models were tested under various wave condition, water depth, and relative submerged depth. Result of this study are showed that the Transmission coefficient are increased with increased of incident wave high for all type of breakwater model, and for all models of breakwater, transmission wave height (Ht) are increased with increased relative submerged depth (Hs/Hi). The highest value for energy dissipations (1 - Ct) % are received for zero submerged depth in model of sloped steps model (M2) is 80 %. Ansys Fluent solver are adopted to modelling the transit flow condition with dynamic mesh to represent the flap motion type to generate wave. Numerical beach plays an important role in CFD model to prevent the reflection wave in lee side of breakwater and represent the absorbing shoreline. 240 grid per wave length are selected for Mesh independent solution and make acceptable result comparison with experimental.
34
Babanin, Alexander V., e AndréJ van der Westhuysen. "Physics of “Saturation-Based” Dissipation Functions Proposed for Wave Forecast Models". Journal of Physical Oceanography 38, n. 8 (1 agosto 2008): 1831–41. http://dx.doi.org/10.1175/2007jpo3874.1.
Testo completoAbstract (sommario):
Abstract The dissipation term is one of the three most important source functions of the radiative transfer equation employed by all spectral wave models to predict the wave spectrum. In this paper, the issue of physics of such dissipation functions is discussed. It is argued that the physics presently utilized in the models do not adequately describe currently known features of the wave dissipation process, and the dissipation functions, to a great extent, remain a residual tuning term in spite of important experimental progress in wave breaking studies. A recently suggested “saturation-based” dissipation function and its connections with the experimental physics are analyzed in detail.
35
Cova, Raul, David Henley e Kristopher A. Innanen. "Computing near-surface velocity models for S-wave static corrections using raypath interferometry". GEOPHYSICS 83, n. 3 (1 maggio 2018): U23—U34. http://dx.doi.org/10.1190/geo2017-0340.1.
Testo completoAbstract (sommario):
A near-surface velocity model is one of the typical products generated when computing static corrections, particularly in the processing of PP data. Critically refracted waves are the input usually needed for this process. In addition, for the converted PS mode, S-wave near-surface corrections must be applied at the receiver locations. In this case, however, critically refracted S-waves are difficult to identify when using P-wave energy sources. We use the [Formula: see text]-[Formula: see text] representation of the converted-wave data to capture the intercept-time differences between receiver locations. These [Formula: see text]-differences are then used in the inversion of a near-surface S-wave velocity model. Our processing workflow provides not only a set of raypath-dependent S-wave static corrections, but also a velocity model that is based on those corrections. Our computed near-surface S-wave velocity model can be used for building migration velocity models or to initialize elastic full-waveform inversions. Our tests on synthetic and field data provided superior results to those obtained by using a surface-consistent solution.
36
Van Duin, Cornelis A. "Rapid-distortion turbulence models in the theory of surface-wave generation". Journal of Fluid Mechanics 329 (25 dicembre 1996): 147–53. http://dx.doi.org/10.1017/s0022112096008877.
Testo completoAbstract (sommario):
Turbulent air flow over a surface gravity wave of small amplitude is studied analytically on the basis of a family of rapid-distortion turbulence models. Results for the wave growth rate do not depend sensitively on the specific choice of these models. However, the agreement with results based on a so-called truncated mixing-length model (Belcher & Hunt 1993) is poor, despite physical similarity of the models. The present analysis also shows that the use of turbulence models based on rapid-distortion theory leads to significant underestimation of observed growth rates of high-frequency waves.
37
YANG, DI, e LIAN SHEN. "Direct-simulation-based study of turbulent flow over various waving boundaries". Journal of Fluid Mechanics 650 (24 marzo 2010): 131–80. http://dx.doi.org/10.1017/s0022112009993557.
Testo completoAbstract (sommario):
We use direct numerical simulation of stress-driven turbulent Couette flows over waving surfaces to study turbulence in the vicinity of water waves. Mechanistic study is performed through systematic investigation of different wavy surface conditions including plane progressive Airy and Stokes waves with and without wind-induced surface drift, as well as stationary wavy walls and vertically waving walls for comparison. Two different wave steepness values ak = 0.1 and 0.25 are considered, where a is the wave amplitude and k is the wavenumber. For effects of wave age, defined as the ratio between the wave phase speed c and the turbulence friction velocity u*, we consider three values, namely c/u* = 2, 14 and 25, corresponding to slow, intermediate and fast waves, respectively. Detailed analysis of turbulence structure and statistics shows their dependence on the above-mentioned parameters. Our result agrees with previous measurement and simulation results and reveals many new features unreported in the literature. Over progressive waves, although no apparent flow separation is found in mean flow, considerable intermittent separations in instantaneous flow are detected in slow waves with large steepness. The near-surface coherent vortical structures are examined. We propose two conceptual vortex structure models: quasi-streamwise and reversed horseshoe vortices for slow waves and bent quasi-streamwise vortices for intermediate and fast waves. Detailed examination of Reynolds stress with quadrant analysis, turbulent kinetic energy (TKE) and TKE budget with a focus on production shows large variation with wave phase; analysis shows that the variation is highly dependent on wave age and wave nonlinearity. Comparison between Airy waves and Stokes waves indicates that although the nonlinearity of surface water waves is a high-order effect compared with the wave age and wave steepness, it still makes an appreciable difference to the turbulence structure. The effect of wave nonlinearity on surface pressure distribution causes substantial difference in the wave growth rate. Wind-induced surface drift can cause a phase shift in the downstream direction and a reduction in turbulence intensity; this effect is appreciable for slow waves but negligible for intermediate and fast waves. In addition to providing detailed information on the turbulence field in the vicinity of wave surfaces, the results obtained in this study suggest the importance of including wave dynamics in the study of wind–wave interaction.
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Nguyen, Thao Danh, e Duy The Nguyen. "SIMULATION OF WAVE PRESSURE ON A VERTICAL WALL BASED ON 2-D NAVIER-STOKES EQUATIONS". Science and Technology Development Journal 12, n. 18 (15 dicembre 2009): 59–68. http://dx.doi.org/10.32508/stdj.v12i18.2384.
Testo completoAbstract (sommario):
This paper applies and develops a numerical model based on the two-dimensional vertical Navier-Stokes equations to simulate the temporal and spatial variations of wave parameters in front of vertical walls. A non-uniform grids system is performed in the numerical solution of the model by transforming a variable physical domain to a fixed computational domain. Through present model, beside some basic hydrodynamic problems of water waves such as wave profile and water particle velocities, standing wave pressures at the wall are examined. Numerical results of the present model are compared with laboratory data and with existing empirical and theoretical models. The comparisons show that the model can simulate reasonably the wave processes of the waves in front of vertical walls as well as the wave pressures on the wall.
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Pawlak, Dawid, e Jan M. Kelner. "Directional link attenuation in millimeter-wave range based on empirical model modification". Bulletin of the Military University of Technology 71, n. 3 (30 settembre 2022): 69–92. http://dx.doi.org/10.5604/01.3001.0053.6745.
Testo completoAbstract (sommario):
The upcoming fifth and next generation mobile phone systems will use not only the frequencybands of sub-6 GHz but also the millimeter-wave and terahertz bands. From a practical viewpoint,this approach requires the use of directional antennas or beamforming systems. To ensure greaterenergy efficiency of the wireless link, the radio beams on the transmitting and receiving sides shouldbe aligned ones. Path loss models are commonly used for designing the radio communication systemsand networks. However, in the literature, there are no adequate methods of attenuation modellingavailable for the cases of misalignment of antenna beams. In this paper, a method of modifying the pathloss model, based on a multi-elliptical propagation model, is proposed. For this purpose, dedicatedsoftware was developed in the MATLAB environment, which was used to conduct simulation tests.In the remainder of the paper, exemplary results of the adaptation of empirical path loss models inthe range of millime-ter-waves are presented, which were obtained using the developed program.Keywords: wireless communication, radio wave propagation, path loss models, multi-ellipticalpropagation model, directional antennas, directional radio link, millimeter waves, 5G systems,simulation studies
40
Bennetts, L. G., e T. D. Williams. "Water wave transmission by an array of floating discs". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 471, n. 2173 (gennaio 2015): 20140698. http://dx.doi.org/10.1098/rspa.2014.0698.
Testo completoAbstract (sommario):
An experimental validation of theoretical models of regular-water-wave transmission through arrays of floating discs is presented. The experiments were conducted in a wave basin. The models are based on combined potential-flow and thin-plate theories, and the assumption of linear motions. A low-concentration array, in which discs are separated by approximately a disc diameter in equilibrium, and a high-concentration array, in which adjacent discs are almost touching in equilibrium, were used for the experiments. The proportion of incident-wave energy transmitted by the discs is presented as a function of wave period, and for different wave amplitudes. Results indicate the models predict wave-energy transmission accurately for small-amplitude waves and low-concentration arrays. Discrepancies for large-amplitude waves and high-concentration arrays are attributed to wave overwash of the discs and collisions between discs. Validation of model predictions of a solitary disc's rigid-body motions are also presented.
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Wei, Chih-Chiang, e Hao-Chun Chang. "Forecasting of Typhoon-Induced Wind-Wave by Using Convolutional Deep Learning on Fused Data of Remote Sensing and Ground Measurements". Sensors 21, n. 15 (2 agosto 2021): 5234. http://dx.doi.org/10.3390/s21155234.
Testo completoAbstract (sommario):
Taiwan is an island, and its economic activities are primarily dependent on maritime transport and international trade. However, Taiwan is also located in the region of typhoon development in the Northwestern Pacific Basin. Thus, it frequently receives strong winds and large waves brought by typhoons, which pose a considerable threat to port operations. To determine the real-time status of winds and waves brought by typhoons near the coasts of major ports in Taiwan, this study developed models for predicting the wind speed and wave height near the coasts of ports during typhoon periods. The forecasting horizons range from 1 to 6 h. In this study, the gated recurrent unit (GRU) neural networks and convolutional neural networks (CNNs) were combined and adopted to formulate the typhoon-induced wind and wave height prediction models. This work designed two wind speed prediction models (WIND-1 and WIND-2) and four wave height prediction models (WAVE-1 to WAVE-4), which are based on the WIND-1 and WIND-2 model outcomes. The Longdong and Liuqiu Buoys were the experiment locations. The observatory data from the ground stations and buoys, as well as radar reflectivity images, were adopted. The results indicated that, first, WIND-2 has a superior wind speed prediction performance to WIND-1, where WIND-2 can be used to identify the temporal and spatial changes in wind speeds using ground station data and reflectivity images. Second, WAVE-4 has the optimal wave height prediction performance, followed by WAVE-3, WAVE-2, and WAVE-1. The results of WAVE-4 revealed using the designed models with in-situ and reflectivity data directly yielded optimal predictions of the wind-based wave heights. Overall, the results indicated that the presented combination models were able to extract the spatial image features using multiple convolutional and pooling layers and provide useful information from time-series data using the GRU memory cell units. Overall, the presented models could exhibit promising results.
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Lowe, Ryan J., Corrado Altomare, Mark Buckley, Renan da Silva, Jeff Hansen e Dirk Rijnsdorp, Jose Dominguez, Alejandro Crespo. "NONHYDROSTATIC AND MESH-FREE COMPUTATIONAL FLUID DYNAMICS MODEL COMPARISONS OF SURF ZONE HYDRODYNAMICS BY PLUNGING IRREGULAR WAVES". Coastal Engineering Proceedings, n. 37 (1 settembre 2023): 11. http://dx.doi.org/10.9753/icce.v37.currents.11.
Testo completoAbstract (sommario):
Wave breaking over steep bathymetry often generates plunging waves where the free surface overturns and violent water motion is triggered. Simulating these complex surf zone processes poses significant challenges for conventional mesh-based hydrodynamic models, due to the rapidly-deforming nature of the free surface and underlying turbulent flows. Yet accurate prediction of these hydrodynamics is essential to characterize the wide range of nearshore processes driven by wave breaking. In this study we rigorously compare the ability of two different classes of phase-resolving wave-flow models to predict a wide range of hydrodynamic processes driven by irregular wave breaking over a fringing reef using data from Buckley et al. (2015). These two models were: 1) the mesh-based nonhydrostatic wave-flow model SWASH, having vertical resolution but only providing a single-value representation of the free-surface; and 2) the mesh-free, Lagrangian particle-based approach Smoothed Particle Hydrodynamics (SPH) using DualSPHysics (DSPH), which directly resolves the overturning free surface. Both models were applied in 2DV mode.
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Poghosyan, Ruben, e Yuan Luo. "Random Convolutional Kernels for Space-Detector Based Gravitational Wave Signals". Electronics 12, n. 20 (20 ottobre 2023): 4360. http://dx.doi.org/10.3390/electronics12204360.
Testo completoAbstract (sommario):
Neural network models have entered the realm of gravitational wave detection, proving their effectiveness in identifying synthetic gravitational waves. However, these models rely on learned parameters, which necessitates time-consuming computations and expensive hardware resources. To address this challenge, we propose a gravitational wave detection model tailored specifically for binary black hole mergers, inspired by the Random Convolutional Kernel Transform (ROCKET) family of models. We conduct a rigorous analysis by factoring in realistic signal-to-noise ratios in our datasets, demonstrating that conventional techniques lose predictive accuracy when applied to ground-based detector signals. In contrast, for space-based detectors with high signal-to-noise ratios, our method not only detects signals effectively but also enhances inference speed due to its streamlined complexity—a notable achievement. Compared to previous gravitational wave models, we observe a significant acceleration in training time while maintaining acceptable performance metrics for ground-based detector signals and achieving equal or even superior metrics for space-based detector signals. Our experiments on synthetic data yield impressive results, with the model achieving an AUC score of 96.1% and a perfect recall rate of 100% on a dataset with a 1:3 class imbalance for ground-based detectors. For high signal-to-noise ratio signals, we achieve flawless precision and recall of 100% without losing precision on datasets with low-class ratios. Additionally, our approach reduces inference time by a factor of 1.88.
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Sansón, L. Zavala. "Simple Models of Coastal-Trapped Waves Based on the Shape of the Bottom Topography". Journal of Physical Oceanography 42, n. 3 (1 marzo 2012): 420–29. http://dx.doi.org/10.1175/jpo-d-11-053.1.
Testo completoAbstract (sommario):
Abstract Solutions of barotropic coastal-trapped waves in the shallow-water context are discussed for different shapes of the bottom topography. In particular, an infinite family of topographic waves over continental shelves characterized by a shape parameter is considered. The fluid depth is proportional to xs, where x is the offshore coordinate and s is a real, positive number. The model assumes the rigid-lid approximation and a semi-infinite domain 0 ≤ x ≤ ∞. The wave structure and the dispersion relation depend explicitly on the shape parameter s. Essentially, waves over steeper shelves possess higher frequencies and phase speeds. In addition, the wave frequency is independent of the alongshore wavenumber k, implying a zero group velocity component along the coast. The advantages and limitations of this formulation, as well as some comparisons with other models, are discussed in light of numerical simulations for waves over arbitrary topography within a finite domain. The numerical calculations show that the frequency of the waves present a nondispersive regime at small wavenumbers (observed by several authors), followed by a constant value predicted by the analytical solutions for larger k. It is concluded that these frequencies can be considered as an upper limit reached by barotropic coastal-trapped waves over the infinite family of xs-bottom profiles, regardless of the horizontal and vertical scales of the system. The modification of the dispersion curves in a stratified ocean is briefly discussed.
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Protsenko, S. V. "Modelling Turbulent Flows near Coastal Structures Using Various Turbulence Models". Computational Mathematics and Information Technologies 8, n. 1 (2 aprile 2024): 55–62. http://dx.doi.org/10.23947/2587-8999-2024-8-1-55-62.
Testo completoAbstract (sommario):
Introduction. The reduction in beach width due to erosion is a significant issue that can either be mitigated or exacerbated by coastal protection structures. Modelling breaking waves near the coast and around coastal structures can be used to determine their impact on the dynamics of the coastal zone. The objective of this study is to model and analyze the dynamics of turbulent structures around a single breakwater, obtained using two turbulence modelling schemes: RANS and LES.Materials and Methods. Turbulence induced by breaking waves was investigated. The modelling was based on bathymetric measurements conducted along the Azov Sea coast and a three-dimensional wave hydrodynamics model supplemented with various turbulence calculation configurations.Results. Modelling results of wave processes generating turbulent flows in the presence of coastal protection structures using different turbulence models were obtained. Results obtained based on Reynolds-averaged Navier-Stokes (RANS) equations are compared with the results of Large Eddy Simulation (LES) approach with Smagorinsky dynamic subgrid-scale model (DSM).Discussion and Conclusions. The results showed that wave heights simulated by LES were higher than those simulated by RANS in the front and leeward regions of the coastal protection structure and were lower in its upper part. Thus, according to LES, a greater amount of wave energy was preserved after passing over the breakwater. Velocity vectors of the water medium showed the formation of a vortex when LES was used, whereas no evidence of such turbulent vortices was detected in the case of RANS, confirming the better performance of LES for turbulence modelling in the coastal zone. According to the presented results, LES is the preferred tool for generating turbulence under incoming wave conditions in engineering practices.
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Früh, W. G. "Low-order models of wave interactions in the transition to baroclinic chaos". Nonlinear Processes in Geophysics 3, n. 3 (30 settembre 1996): 150–65. http://dx.doi.org/10.5194/npg-3-150-1996.
Testo completoAbstract (sommario):
Abstract. A hierarchy of low-order models, based on the quasi-geostrophic two-layer model, is used to investigate complex multi-mode flows. The different models were used to study distinct types of nonlinear interactions, namely wave- wave interactions through resonant triads, and zonal flow-wave interactions. The coupling strength of individual triads is estimated using a phase locking probability density function. The flow of primary interest is a strongly modulated amplitude vacillation, whose modulation is coupled to intermittent bursts of weaker wave modes. This flow was found to emerge in a discontinuous bifurcation directly from a steady wave solution. Two mechanism were found to result in this flow, one involving resonant triads, and the other involving zonal flow-wave interactions together with a strong β-effect. The results will be compared with recent laboratory experiments of multi-mode baroclinic waves in a rotating annulus of fluid subjected to a horizontal temperature gradient.
47
Chen, Qin, Ling Zhu, Fengyan Shi e Steve Brandt. "BOUSSINESQ MODELING OF COMBINED STORM SURGE AND WAVES OVER WETLANDS FORCED BY WIND". Coastal Engineering Proceedings, n. 36v (28 dicembre 2020): 6. http://dx.doi.org/10.9753/icce.v36v.waves.6.
Testo completoAbstract (sommario):
Coastal wetlands protect the shoreline and infrastructure by attenuating wind waves and reducing storm surge. It is of importance to accurately quantify the flood protection provided by vegetation. Existing numerical models for hurricane waves and storm surge are based on the phase-averaged wave action balance equation and the nonlinear shallow water equations, respectively, with the wind forcing and vegetal drag as the free surface and bottom boundary conditions. To consider the interaction of waves and surge, the phase-averaged short wave and long wave (storm surge) models can be coupled in a staggered fashion. If the time step of the wave model and storm surge model are 30 minutes and 1 s, respectively, both models would exchange information every 30 minutes. There is no iteration between the wave and surge models at each coupling interval. An alternative to this state-of-the-practice of hurricane wave and storm surge modeling is to simulate the combined wave and surge motion driven by wind and attenuated by wetland vegetation using a phase-resolving Boussinesq model. The objective of this study is threefold: 1) to demonstrate the capability of modeling wave growth by wind, wave reduction by vegetation, and the total water level (wave setup, wind setup and wave runup) using the extended FUNWAVE-TVD model; 2) to analyze the energy balance of the combined wave and surge motion; 3) to examine the momentum balance with an emphasis on the vegetal drag owing to the combined wave orbital velocity and wind-driven current velocity.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/-o_kx4hPvC8
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Rhee, Shin Hyung, e Fred Stern. "RANS Model for Spilling Breaking Waves". Journal of Fluids Engineering 124, n. 2 (28 maggio 2002): 424–32. http://dx.doi.org/10.1115/1.1467078.
Testo completoAbstract (sommario):
A RANS model for spilling breaking waves is developed, which can be implemented with ship hydrodynamics RANS CFD codes. The model is based on the Cointe & Tulin theory of steady breakers. The breaker cross section is assumed triangular with maximum height determined by the theoretical/experimental linear relationship with following wave height. Pressure and velocity boundary conditions are imposed on the dividing streamline between the breaker and underlying flow based on the hydrostatic and mixing layer models. An iterative solution procedure provides a unique solution for specified breaking criteria and simulation conditions. The model is implemented using CFDSHIP-IOWA and validated using spilling breaking wave benchmark data for two-dimensional submerged hydrofoils. As with other current RANS codes, wave elevations are under-predicted. However, for the first time in literature, the breaking wave wake is predicted. Results for total head, mean velocities, and Reynolds stresses are in agreement with available spilling breaking wave benchmark data.
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Nose, Takehiko, Takuji Waseda, Tsubasa Kodaira e Jun Inoue. "Satellite-retrieved sea ice concentration uncertainty and its effect on modelling wave evolution in marginal ice zones". Cryosphere 14, n. 6 (24 giugno 2020): 2029–52. http://dx.doi.org/10.5194/tc-14-2029-2020.
Testo completoAbstract (sommario):
Abstract. Ocean surface waves are known to decay when they interact with sea ice. Wave–ice models implemented in a spectral wave model, e.g. WAVEWATCH III® (WW3), derive the attenuation coefficient based on several different model ice types, i.e. how the model treats sea ice. In the marginal ice zone (MIZ) with sea ice concentration (SIC) < 1, the wave attenuation is moderated by SIC: we show that subgrid-scale processes relating to the SIC and sea ice type heterogeneity in the wave–ice models are missing and the accuracy of SIC plays an important role in the predictability. Satellite-retrieved SIC data (or a sea ice model that assimilates them) are often used to force wave–ice models, but these data are known to have uncertainty. To study the effect of SIC uncertainty ΔSIC on modelling MIZ waves during the 2018 R/V Mirai observational campaign in the refreezing Chukchi Sea, a WW3 hindcast experiment was conducted using six satellite-retrieved SIC products based on four algorithms applied to SSMIS and AMSR2 data. The results show that ΔSIC can cause considerable wave prediction discrepancies in ice cover. There is evidence that bivariate uncertainty data (model significant wave heights and SIC forcing) are correlated, although off-ice wave growth is more complicated due to the cumulative effect of ΔSIC along an MIZ fetch. The analysis revealed that the effect of ΔSIC can overwhelm the uncertainty arising from the choice of model ice types, i.e. wave–ice interaction parameterisations. Despite the missing subgrid-scale physics relating to the SIC and sea ice type heterogeneity in WW3 wave–ice models – which causes significant modelling uncertainty – this study found that the accuracy of satellite-retrieved SIC used as model forcing is the dominant error source of modelling MIZ waves in the refreezing ocean.
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Guinot, Vincent, Sandra Soares-Frazão e Carole Delenne. "Experimental validation of transient source term in porosity-based shallow water models". E3S Web of Conferences 40 (2018): 06033. http://dx.doi.org/10.1051/e3sconf/20184006033.
Testo completoAbstract (sommario):
Porosity-based shallow water models for the simulation of urban floods incorporate additional energy dissipation terms compared to the usual two-dimensional shallow water equations. These terms account for head losses stemming from building drag. They are usually modelled using turbulence-based equations of state (drag proportional to the squared velocity). However, refined numerical simulations of wave propagation in periodic urban layouts indicate that such drag models do not suffice to reproduce energy dissipation properly. Correct wave propagation speeds, energy dissipation rates and flow fields are obtained by incorporating a new type of source term, active only under transient situations involving positive waves. This source term does not take the form of an equation of state. It can be modelled as an artificial increase in water inertia. In this communication, an experimental validation of this source term model is presented by means of new dam-break flow experiments in idealized, periodic urban layouts. The experimental results validate both the existence and the proposed formulation of this new source term.