Coupled Wave Model Research Articles

Wind–Wave Coupling Model for Wave Energy Forecast

Since waves fluctuate continuously, the forecast of the wave energy is very important for the operation of the power system integrated with large-scale wave energy generations. Waves are driven by wind, so that the relationship between wind and wave is very useful in wave energy forecast. Hence, a wave energy forecast method based on the wind-wave coupling model is proposed in this paper. The wave is first divided into wind waves and swells. The correlation between wind and wind wave is analyzed, and a wind-wave coupling model is established using copula function. Based on the coupling model and the forecasted wind speed, the average wave height of the wind wave can be forecasted, while the time series method is used to forecast the average wave height of the swell. Combining the wind wave and the swell, the average wave height of the integrated wave is obtained and the wave energy can be forecasted. Using the measured wind and wave data from a real ocean, the day-ahead wave energy is forecasted by the proposed method. The forecast result is close to the measured data and the effectiveness of the proposed wave energy forecast method is validated.

Evaluating the Pattern of Monsoon Wind Generated Waves in the Northwest of the Persian Gulf using Coupled Atmospheric and Wave Model

Evaluating the Pattern of Monsoon Wind Generated Waves in the Northwest of the Persian Gulf using Coupled Atmospheric and Wave Model

Deep-subwavelength control of acoustic waves in an ultra-compact metasurface lens

Space-coiling acoustic metasurfaces have been largely exploited and shown their outstanding wave manipulation capacity. However, they are complex in realization and cannot directly manipulate acoustic near-fields by controlling the effective path length. Here, we propose a comprehensive paradigm for acoustic metasurfaces to extend the wave manipulations to both far- and near-fields and markedly reduce the implementation complexity with a simple structure, which consists of an array of deep-subwavelength-spaced slits perforated in a thin plate. A semi-analytical approach for such a design is established using a microscopic coupled-wave model, which reveals that the acoustic diffractive pattern at every slit exit is the sum of the initial transmission and the secondary scatterings of the coupled fields from other slits. For proof-of-concept, we examine two metasurface lenses for sound focusing within and beyond the diffraction limit. This work provides a feasible strategy for creating ultra-compact acoustic components with versatile potentials.

Dynamic Coupling in Order Book: Quantum Framework

We apply coupled-wave model to describe statistics of imbalance in order book and its impact on price. We find that the model can be related to the observed market data if coupling is dynamic and depends on imbalance in such way that kicks the system out of states with large imbalance. Dynamic coupling has impact on price returns by affecting execution probabilities unless the price settles around the security’s fair value.

Modeling of light coupling effect using tunneling theory based on particle properties of light

Based on the wave-particle duality of light, the Schrodinger equation for a photon as a particle is established to treat the light coupling effect by introducing concepts of the virtual mass and potential for a photon, which is different from the previous method that uses the analogy with quantum mechanics. The virtual mass is physically correlated to the kinetic energy according to Einstein’s energy–momentum relation. As a consequence, this new model has merits of physical simplicity and analytic nature. This new model can well explain the exponential dependence of the light coupling effect on the physical parameters in coupled waveguides on, which can be observed in the experimental and simulation data reported in the literature. Moreover, an explicit expression for the coupling length (coefficient) on the effects of physical parameters can be obtained by virtue of this new model, whereas the previous modal approach and the coupled-wave model resulted in implicit expressions. This new model does not only give a better physical understanding but also offers a possibility to design and fabricate optic devices based on the light coupling effect by optimizing the physical parameters.

Coupling hydrodynamic and wave models: first step and sensitivity experiments in the Mediterranean Sea

This work describes the first step towards a fully coupled modelling system composed of an ocean circulation and a wind wave model. Sensitivity experiments are presented for the Mediterranean Sea where the hydrodynamic model NEMO is coupled with the third-generation wave model WaveWatchIII (WW3). Both models are implemented at 1/16° horizontal resolution and are forced by ECMWF 1/4° horizontal resolution atmospheric fields. The models are two-way coupled at hourly intervals exchanging the following fields: sea surface currents and temperature are transferred from NEMO to WW3 by modifying the mean momentum transfer of waves and the wind speed stability parameter, respectively. The neutral drag coefficient computed by WW3 is then passed to NEMO, which computes the surface stress. Five-year (2009–2013) numerical experiments were carried out in both uncoupled and coupled mode. In order to validate the modelling system, numerical results were compared with coastal and drifting buoys and remote sensing data. The results show that the coupling of currents with waves improves the representation of the wave spectrum. However, the wave-induced drag coefficient shows only minor improvements in NEMO circulation fields, such as temperature, salinity, and currents.

On the instabilities of a potential vortex with a free surface

In this paper, we address the linear stability analysis of a confined potential vortex with a free surface. This particular flow has been recently used by Tophøj et al. (Phys. Rev. Lett., vol. 110(19), 2013, article 194502) as a model for the swirling flow of fluid in an open cylindrical container, driven by rotating the bottom plate (the rotating bottom experiment) to explain the so-called rotating polygons instability (Vatistas J. Fluid Mech., vol. 217, 1990, pp. 241–248; Jansson et al., Phys. Rev. Lett., vol. 96, 2006, article 174502) in terms of surface wave interactions leading to resonance. Global linear stability results are complemented by a Wentzel–Kramers–Brillouin–Jeffreys (WKBJ) analysis in the shallow-water limit as well as new experimental observations. It is found that global stability results predict additional resonances that cannot be captured by the simple wave coupling model presented in Tophøj et al. (2013). Both the main resonances (thought to be at the root of the rotating polygons) and these secondary resonances are interpreted in terms of over-reflection phenomena by the WKBJ analysis. Finally, we provide experimental evidence for a secondary resonance supporting the numerical and theoretical analysis presented. These different methods and observations allow to support the unstable wave coupling mechanism as the physical process at the origin of the polygonal patterns observed in free-surface rotating flows.

Analytical coupled-wave model for photonic crystal surface-emitting quantum cascade lasers.

An analytical coupled-wave model is developed for surface-emitting photonic-crystal quantum cascade lasers (PhC-QCLs). This model provides an accurate and efficient analysis of full three-dimensional device structure with large-area cavity size. Various laser properties of interest including the band structure, mode frequency, cavity loss, mode intensity profile, and far field pattern (FFP), as well as their dependence on PhC structures and cavity size, are investigated. Comparison with numerical simulations confirms the accuracy and validity of our model. The calculated FFP and polarization profile well explain the previously reported experimental results. In particular, we reveal the possibility of switching the lasing modes and generating single-lobed FFP by properly tuning PhC structures.

Wave setup properties in the surge-wave coupled simulation: a case study of Typhoon Khanun

The accurate prediction of surge height is vitally important in designing coastal defense structures. With the advancement of computation efficiency, many researchers have studied the wave-current interaction on surge height by coupling hydrodynamic and wave models. In this study, Deflt3D Flow model was interacted dynamically with Delft3D Wave model to simulate the storm surge process caused by typhoon Khanun to obtain the spatiotemporal properties on wave setup induced by storm wind. Simulations with and without wave model have been conducted, revealing that the spatiotemporally varying wave setup distribute along the coastal line when typhoon is in the open sea with large wave height and surge height around. The spatial distribution of nearshore wave setup at landfall moment was obtained. Nevertheless the contribution of wave effects on storm surge increases slightly under intensive storm wind, with the maximum wave setup near typhoon center accounting for 10% of the peak surge height.

Parallel Analysis to Simulate an Experiment of Tsunami Open Flume Based on 2D-3D One-way Coupling Wave Model

Parallel Analysis to Simulate an Experiment of Tsunami Open Flume Based on 2D-3D One-way Coupling Wave Model

Risk Valuation for Securities with Limited Liquidity

Professional market participants have to deal with illiquid securities on a constant basis. For such securities traditional risk assessment techniques fail. This can lead to underestimated and distorted results for the entire investment portfolio, and ultimately to inadequate risk management. We present a framework, based on coupled-wave model, that allows to model securities with low liquidity and evaluate impact of various risk sources, associated with liquidity. In addition to risk management, this framework should be helpful to firms and trading desks in evaluating cost of liquidity and selecting liquidation tactics for their oversize positions.

Scalable parallel self-assembly of nanoparticle anti-reflection coatings

Here we report a simple, inherently parallel, and scalable bottom-up approach for fabricating nanoparticle anti-reflection coatings on large glass substrates. Negatively charged silica nanoparticles are electrostatically adsorbed onto a surface-functionalized glass substrate with positive surface charges to form a disordered monolayer nanoparticle coating. Systematic experiments have been conducted to optimize the critical process parameters, including the dispersing dielectric media, nanoparticle concentration of the colloidal suspensions, and the coating time, that significantly affect the uniformity and the anti-reflection properties of the final coatings. Specular reflection and transmission measurements demonstrate that good anti-reflection performance (with <1% two-sided reflection) and high optical transmission (>99%) can be achieved by the self-assembled nanoparticle coatings. This innovative technology also enables the simultaneous coating of multiple 5-in.-sized glass substrates with high and reproducible qualities. Importantly, we combine experiments with theoretical calculations to address a fundamental question faced by the fabrication of monolayer nanoparticle-based anti-reflection coatings — what is the optimal nanoparticle surface area coverage for best anti-reflection performance? Our optical simulations based on a rigorous coupled-wave analysis model indicate that the optimal nanoparticle coverage is ~60% which is readily achievable by this electrostatics-assisted bottom-up technology.

Coastal flooding: impact of waves on storm surge during extremes – a case study for the German Bight

Abstract. This study addresses the impact of wind, waves, tidal forcing and baroclinicity on the sea level of the German Bight during extreme storm events. The role of wave-induced processes, tides and baroclinicity is quantified, and the results are compared with in situ measurements and satellite data. A coupled high-resolution modelling system is used to simulate wind waves, the water level and the three-dimensional hydrodynamics. The models used are the wave model WAM and the circulation model GETM. The two-way coupling is performed via the OASIS3-MCT coupler. The effects of wind waves on sea level variability are studied, accounting for wave-dependent stress, wave-breaking parameterization and wave-induced effects on vertical mixing. The analyses of the coupled model results reveal a closer match with observations than for the stand-alone circulation model, especially during the extreme storm Xaver in December 2013. The predicted surge of the coupled model is significantly enhanced during extreme storm events when considering wave–current interaction processes. This wave-dependent approach yields a contribution of more than 30 % in some coastal areas during extreme storm events. The contribution of a fully three-dimensional model compared with a two-dimensional barotropic model showed up to 20 % differences in the water level of the coastal areas of the German Bight during Xaver. The improved skill resulting from the new developments justifies further use of the coupled-wave and three-dimensional circulation models in coastal flooding predictions.

Modeling Bed Evolution Using Weakly Coupled Phase-Resolving Wave Model and Wave-Averaged Sediment Transport Model

In this paper, we propose a model for the simulation of the bed evolution dynamics in coastal regions characterized by articulated morphologies. An integral form of the fully nonlinear Boussinesq equations in contravariant formulation, in which Christoffel symbols are absent, is proposed in order to simulate hydrodynamic fields from deep water up to just seaward of the surf zones. Breaking wave propagation in the surf zone is simulated by integrating the nonlinear shallow water equations with a high-order shock-capturing scheme. The near-bed instantaneous flow velocity and the intra-wave hydrodynamic quantities are calculated by the momentum equation integrated over the turbulent boundary layer. The bed evolution dynamics is calculated starting from the contravariant formulation of the advection-diffusion equation for the suspended sediment concentration in which the advective sediment transport terms are formulated according to a quasi-three-dimensional approach, and taking into account the contribution given by the spatial variation of the bed load transport. The model is validated against several tests by comparing numerical results with experimental data. The ability of the proposed model to represent the sediment transport phenomena in a morphologically articulated coastal region is verified by numerically simulating the long-term bed evolution in the coastal region opposite Pescara harbor (in Italy) and comparing numerical results with the field data.

Surface wave effects on water temperature in the Baltic Sea: simulations with the coupled NEMO-WAM model

Coupled circulation (NEMO) and wave model (WAM) system was used to study the effects of surface ocean waves on water temperature distribution and heat exchange at regional scale (the Baltic Sea). Four scenarios—including Stokes-Coriolis force, sea-state dependent energy flux (additional turbulent kinetic energy due to breaking waves), sea-state dependent momentum flux and the combination these forcings—were simulated to test the impact of different terms on simulated temperature distribution. The scenario simulations were compared to a control simulation, which included a constant wave-breaking coefficient, but otherwise was without any wave effects. The results indicate a pronounced effect of waves on surface temperature, on the distribution of vertical temperature and on upwelling’s. Overall, when all three wave effects were accounted for, did the estimates of temperature improve compared to control simulation. During the summer, the wave-induced water temperature changes were up to 1 °C. In northern parts of the Baltic Sea, a warming of the surface layer occurs in the wave included simulations in summer months. This in turn reduces the cold bias between simulated and measured data, e.g. the control simulation was too cold compared to measurements. The warming is related to sea-state dependent energy flux. This implies that a spatio-temporally varying wave-breaking coefficient is necessary, because it depends on actual sea state. Wave-induced cooling is mostly observed in near-coastal areas and is the result of intensified upwelling in the scenario, when Stokes-Coriolis forcing is accounted for. Accounting for sea-state dependent momentum flux results in modified heat exchange at the water-air boundary which consequently leads to warming of surface water compared to control simulation.

Using the parallel stacked mirror model to analytically describe diffraction in the planar volume reflection grating with finite absorption

The parallel stacked mirror (PSM) model of grating diffraction is extended to include a complex refractive index for the case of an unslanted reflection geometry at oblique incidence and for the &#x3C3;-polarization. The well-known theoretical upper diffraction efficiency limit applicable to reflective absorption gratings described by Kogelnik&#x2019;s coupled-wave theory, is shown to be directly derivable from the PSM model. Analytical formulae for the diffraction efficiency of phase, absorption, and mixed harmonic-index gratings are compared with numerical computations using a rigorous coupled-wave description. A conventional truncated coupled-wave description, similar to Kogelnik&#x2019;s approach, is also derived from the harmonic-index rigorous coupled-wave equations by limiting the propagating modes to a signal and reference wave and by ignoring second-order derivatives. At low to moderate average loss the PSM theory is observed to provide a somewhat better fit to the rigorous coupled-wave calculations, and this is particularly evident for gratings that are dominated by phase modulation. As the average absorption coefficient is increased, all three models show the diffractive response sharpening around Bragg resonance and the characteristic sideband structure attenuating and then disappearing altogether, giving rise to a broader spectral behavior away from resonance. At high average loss, the truncated coupled-wave model is observed to very marginally outperform PSM. However, overall the PSM model is found to provide an exceedingly good description of the general mixed-phase-absorption unslanted reflection grating with finite average loss.

Polarization-coupled polariton pairs in a birefringent microcavity

We demonstrate a clear anticrossing between two polarization-orthogonal exciton-polariton modes in ZnO microwires. The strong coupling between exciton polaritons with orthogonal polarization is evidenced by using angle-resolved photoluminescence spectroscopy. The evolution of the coupling strength with the detuning between the two coupled polariton modes is studied by scanning the excitation spot on a tapered ZnO microwire. Steady oscillations are established between the two differently polarized polariton modes with resonant wave vectors and frequencies, which is well described by the plane wave coupling model.

Enhanced transmission band in periodic media with loss modulation

We study the propagation of waves in a periodic array of absorbing layers. We report an anomalous increase of wave transmission through the structure related to a decrease of the absorption around the Bragg frequencies. The effect is first discussed in terms of a generic coupled wave model extended to include losses, and its predictions can be applied to different types of waves propagating in media with periodic modulation of the losses at the wavelength scale. The particular case of sound waves in an array of porous layers embedded in air is considered. An experiment designed to test the predictions demonstrates the existence of the enhanced transmission band.

Wave heights in the 21st century Arctic Ocean simulated with a regional climate model

AbstractWhile wave heights globally have been growing over recent decades, observations of their regional trends vary. Simulations of future wave climate can be achieved by coupling wave and climate models. At present, wave heights and their future trends in the Arctic Ocean remain unknown. We use the third‐generation wave forecast model WAVEWATCH‐III forced by winds and sea ice concentration produced within the regional model HIRHAM, under the anthropogenic scenario SRES‐A1B. We find that significant wave height and its extremes will increase over different inner Arctic areas due to reduction of sea ice cover and regional wind intensification in the 21st century. The opposite tendency, with a slight reduction in wave height appears for the Atlantic sector and the Barents Sea. Our results demonstrate the complex wave response in the Arctic Ocean to a combined effect of wind and sea ice forcings in a climate‐change scenario during the 21st century.

Stretching and compressing of short laser pulses by chirped volume Bragg gratings: analytic and numerical modeling

The theory of stretching and compression of short light pulses by chirped volume Bragg gratings (CBGs) is reviewed based on spectral decomposition of short pulses and on wavelength-dependent coupled wave equations. Analytic theory of diffraction efficiency of CBG with constant chirp and approximate theory time- delay dispersion is presented. Comparison of approximate analytic results with exact numeric coupled-wave modeling shows excellent agreement for smooth heterogeneities of CBGs. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. (DOI: 10.1117/1.OE.53.5.051509)