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A Case Study of Nearshore Wave Transformation Processes along the Coast of Mexico near the Laguna Verde Nuclear Power Plant Using a Fast Simulation Method  [PDF]
Israel-Enrique Herrera-Díaz,Carlos Couder-Casta?eda,Hermilo Ramírez-León
Modelling and Simulation in Engineering , 2010, DOI: 10.1155/2010/690786
Abstract: A numerical model based on the mild-slope equation of water wave propagation over complicated bathymetry, taking into account the combined effects of refraction, diffraction, and reflection due to breakwater, is presented. The numerical method was developed using a split proposed version of the mild-slope equation and solved by an implicit method in a finite volume grid; this technique easily allows model the wave effects caused by the breakwater building in coastal waters, where industrial and other economic activities take place. Controlled case studies have been made and the results match very well with the reference solution. The capability and utility of the model for real coastal areas are illustrated by application to the breakwater of the Laguna Verde Nuclear Power Plant (LVNPP). 1. Introduction Recently a great deal of public concern and interest are being directed towards the coastal waters, where industrial activities take place. As a result engineers are faced with and increasing demand for solutions to coastal problems. Among these is the understanding of the water wave transformation over the complicated bathymetry, from deep water to shallow sloping beaches, which dominates various aspects of coastal hydrodinamic processes, especially the generation of alongshore currents as well as sediment transport. The mild-slope equation- (MSE-) based wave models emerged in late 1960s and have since reached total maturity by early 1990. A number of free and commercially MSE models are available today like CGWAVE and CREDIZ models, but in the field it is not possible to use them because the engineers do not have the enough time to create the meshes and wait for the results in field. The key of the model presented is the previous calculus of some important nearshore wave processes like wave current and wave-wave interactions made with a research hydrodinamic model early developed [1]. The mild-slope equation which describes the propagation of periodic, small amplitude surface gravity waves over a seabed of mild slope was first established by Berkhoff [2]. This original equation takes into account the combined effects of refraction, diffraction and reflection, while the influence of wave breaking, bottom friction, currents and wind is neglected; for this reason we utilize a hydrodinamic model [1] to calculate these effects. The solution of the mild-slope equation was obtained by using the finite-element method [3, 4] and finite-difference schemes [5, 6]. However, this mild-slope equation is essentially of elliptic type and therefore its solution is very
Nearshore wave forecasting and hindcasting by dynamical and statistical downscaling  [PDF]
?yvind Breivik,Yvonne Gusdal,Birgitte R. Furevik,Ole Johan Aarnes,Magnar Reistad
Physics , 2012, DOI: 10.1016/j.jmarsys.2009.01.025
Abstract: A high-resolution nested WAM/SWAN wave model suite aimed at rapidly establishing nearshore wave forecasts as well as a climatology and return values of the local wave conditions with Rapid Enviromental Assessment (REA) in mind is described. The system is targeted at regions where local wave growth and partial exposure to complex open-ocean wave conditions makes diagnostic wave modelling difficult. SWAN is set up on 500 m resolution and is nested in a 10 km version of WAM. A model integration of more than one year is carried out to map the spatial distribution of the wave field. The model correlates well with wave buoy observations (0.96) but overestimates the wave height somewhat (18%, bias 0.29 m). To estimate wave height return values a much longer time series is required and running SWAN for such a period is unrealistic in a REA setting. Instead we establish a direction-dependent transfer function between an already existing coarse open-ocean hindcast dataset and the high-resolution nested SWAN model. Return values are estimated using ensemble estimates of two different extreme-value distributions based on the full 52 years of statistically downscaled hindcast data. We find good agreement between downscaled wave height and wave buoy observations. The cost of generating the statistically downscaled hindcast time series is negligible and can be redone for arbitrary locations within the SWAN domain, although the sectors must be carefully chosen for each new location. The method is found to be well suited to rapidly providing detailed wave forecasts as well as hindcasts and return values estimates of partly sheltered coastal regions.
Evaluation of Various Technologies for Wave Energy Conversion in the Portuguese Nearshore  [PDF]
Dina Silva,Eugen Rusu,Carlos Guedes Soares
Energies , 2013, DOI: 10.3390/en6031344
Abstract: The objective of the present work is to perform an evaluation of the performance provided by various technologies for wave energy conversion in the Portuguese continental coastal environment. The wave climate in the target area is first analyzed using the results from three years of simulations with a wave prediction system based on numerical models. Based on the above data, diagrams for the bivariate distributions of the sea states occurrences, defined by the significant wave height and the energy period, are designed for both winters and whole years. On this basis, the output of five different technologies for the conversion of wave energy is assessed in some relevant locations from the Portuguese nearshore. According to the results obtained, the Portuguese continental coastal environment appears to be appropriate for the wave energy extraction. At the same time, the present work shows that the output of the wave energy conversion devices does not depend only on the average wave energy but is also dependent on the distribution of the wave energy among the sea states of different periods. For this reason, a good agreement between the characteristics of the power matrices of the wave energy converters operating in a certain place and the diagrams for the bivariate distributions of the sea states occurrences corresponding to the considered location represents a key issue in selecting the most appropriate technology for wave energy conversion.
Comparison of various methods for estimating wave incident angles in the nearshore zone
AS Ngusaru
Tanzania Journal of Science , 2002,
Abstract: Five different methods were examined for their suitability in estimating the inshore wave incident angles on a nearshore zone with a complex topography. Visual observation provided preliminary estimates. Two frequency independent methods and one frequency dependent method based on current meter measurements were examined. Another frequency dependent method based on collocated bottom pressure and current meter measurements was also examined. The results from all the methods provided a reasonably consistent estimate of the inshore wave incident angles. The frequency independent methods gave exactly the same results while the frequency dependent methods had a 5% relative error among themselves. Between frequency independent and frequency dependent methods, the relative error was 11%. However, since the frequency dependent methods involve smoothing of the velocity spectra, this method was found to be rather subjective. The frequency independent method based on high passed velocity vectors seems to be easy to apply and to provide unambiguous estimate of inshore wave incident angles. Tanzanian Journal of Science Vol. 28(1) 2002: 47-62
Relationships between coastal processes and properties of the nearshore sea bed dynamic layer:  [cached]
Rafa? Ostrowski,Zbigniew Pruszak
Oceanologia , 2011,
Abstract: The paper discusses the notion of a layer of sandy sediments overlying a substratum of cohesive deposits in the coastal zone. This layer of sand is generally more mobile and is therefore conventionally referred to as the dynamic layer. Its parameters are important to coastal lithodynamic and morphodynamic processes caused by waves and currents. On the other hand, the dynamic layer is formed by nearshore hydrodynamic impact. The variability of the features of the dynamic layer on the southern Baltic dune and cliff shores in Poland is analysed on the basis of selected geological data supported by local seismo-acoustic field investigations. It appears that the conventional notion of the dynamic layer makes sense only in specific geomorphologic conditions. In such cases, mostly related to cliff shores, theoretical modelling of sediment transport should take the properties of the dynamic layer into account.
Power Collection from Wave Energy Farms  [PDF]
Jonas Sjolte,Gaute Tjensvoll,Marta Molinas
Applied Sciences , 2013, DOI: 10.3390/app3020420
Abstract: Most Wave Energy Converters (WECs) produce highly distorted power due to thereciprocal motion induced by ocean waves. Some WEC systems have integrated energystorage that overcomes this limitation, but add significant expenses to an already costlysystem. As an alternative approach, this article investigates the direct export option thatrelies on aggregate smoothing among several WECs. By optimizing the positioning of theWEC devices with respect to the incoming waves, fluctuations may be mutually canceledout between the devices. This work is based on Fred. Olsen’s WEC system Lifesaver, anda WEC farm consisting of 48 devices is designed in detail and simulated. The major costdriver for the electrical export system is the required oversize factor necessary for transferof the average power output. Due to the low power quality, this number can be as high as20 at the entry point of the electrical system, and it is thus crucial to quickly improve thepower quality so that the downstream power system is efficiently utilized. The simulationsundertaken in this work indicate that a high quality power output can be achieved at the farmlevel, but that a significant oversize factor will be required in the intermediate power systemwithin the farm.
Concerning the Wave equation on Asymptotically Euclidean Manifolds  [PDF]
Christopher D. Sogge,Chengbo Wang
Mathematics , 2008, DOI: 10.1007/s11854-010-0023-2
Abstract: We obtain KSS, Strichartz and certain weighted Strichartz estimate for the wave equation on $(\R^d, \mathfrak{g})$, $d \geq 3$, when metric $\mathfrak{g}$ is non-trapping and approaches the Euclidean metric like $ x ^{- \rho}$ with $\rho>0$. Using the KSS estimate, we prove almost global existence for quadratically semilinear wave equations with small initial data for $\rho> 1$ and $d=3$. Also, we establish the Strauss conjecture when the metric is radial with $\rho>0$ for $d= 3$.
Nearshore sticky waters  [PDF]
Juan M. Restrepo,Shankar C. Venkataramani,Clint Dawson
Physics , 2013, DOI: 10.1016/j.ocemod.2014.06.003
Abstract: Wind- and current-driven flotsam, oil spills, pollutants, and nutrients, approaching the nearshore will frequently appear to park just beyond the break zone, where waves break. Moreover, the portion of these tracers that beach will do so only after a long time. Explaining why these tracers park and at what rate they reach the shore has important implications on a variety of different nearshore environmental issues, including the determination of what subscale processes are essential in computer models for the simulation of pollutant transport in the nearshore. Using a simple model we provide an explanation for the underlying mechanism responsible for the parking of tracers, the role played by the bottom topography, and the non-uniform dispersion which leads, in some circumstances, to the eventual landing of all or a portion of the tracers. We refer to the parking phenomenon in this environment as nearshore sticky waters.
Natural Geography in Nearshore areas (NaGISA): The Nearshore component of the Census of Marine Life
Iken,Katrin; Konar,Brenda;
Gayana (Concepción) , 2003, DOI: 10.4067/S0717-65382003000200004
Abstract: the natural geography in shore areas (nagisa, the japanese word for beach) project is the nearshore component of the census of marine life program. nagisa targets nearshore marine biodiversity in large macrophyte communities (hard bottom macroalgal communities and soft sediment sea grass beds) in a depth zonation from high intertidal to 15 m water depth. the overall goal of nagisa is to quantify nearshore biodiversity on a global scale by conducting a longitudinal and latitudinal gradient. outreach to the public, involvement of local communities in the sampling, and education are important components of the nagisa program.
Iteration Coupling Simulation of Random Waves and Wave-Induced Currents
Jinhai Zheng,Tianwen Wang,Gang Wang,Chenming Zhang,Chi Zhang
Journal of Applied Mathematics , 2012, DOI: 10.1155/2012/205376
Abstract: A two-way coupling algorithm for wave-current interaction is developed and implemented into a nearshore circulation model to investigate the effects of fully wave-current interaction on irregular wave transformation over an elliptic shoal. The wave field is simulated by a spectral wave model WABED, and the wave-induced current is solved by a quasi-three-dimensional model WINCM. The surface roller effects are represented in the formulation of surface stress, and the roller characteristics are solved by a roller evolution model. The proposed two-way coupling algorithm can describe both the generation of wave-induced current and the current-induced wave transformation, which is more physically reasonable than the one-way approaches. The model test with a laboratory experiment shows that wave-induced currents have an important influence on the wave transformation, for example, the wave energy defocusing due to the strong jet-like current along the centerline of the shoal. It is revealed that the accuracy of simulated wave field can be significantly improved by taking into account the two-way wave-current interaction.
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