Mathematical Models for Combined Refraction-Diffraction of Waves on Non-Uniform Current and Depth

Two mathematical models for combined refraction-diffraction of regular and irregular waves on non-uniform current in water of slowly varying topography are presented in this paper. Model I is derived by wave theory and variational principle separately. It has two kinds of expressions including the dissipation term. Model n is based on the energy conservation equation with energy flux through the wave crest lines in orthogonal curvilinear coordinates and the wave kinematic conservation equation. The analysis and comparison and special cases of these two models are also given.     

Numerical Simulation for Refraction-Diffraction of Waves in Water of Slowly Varying Current and Topography

A new numerical finite difference iteration method for refraction-diffraction of waves in waterof slowly varying current and topography is developed in this paper.And corresponding theoretical modelincluding the dissipation term is briefly described,together with some analysis and comparison ofcomputational results of the model with measurements in a hydraulic scale model(Berkhoff et al.,1982).An example of practical use of the method is given,showing that the present model is useful to engineeringpractice.     

利用波能平衡方程研究波浪折射——绕射的数学模型及数值模拟

波能平衡方程是研究风浪要素及波能传播问题的很有效的方法，计算较为简单，在海洋学及海岸动力学中得到广泛的应用。本文采用考虑波能侧向传递机制和耗损制约的波能平衡方程组作为研究波浪折射——绕射变形的控制方程。对数学模型用差分法进行了数值模拟，并用两个例题进行了验证     

Refraction-Diffraction Model for Irregular Wave and Directional Spectrum Considering Current

- A mild-slope equation for combined refraction and diffraction of random waves in the independent time current is derived using Kirby equation(1984). In the derivation, the frequency of random waves is represented based on the time series concept, by a typical frequency and its deviation part. Numerical results, compared with those of laboratory experiments, demonstrate that new set of irregular mild slope equation with current is of good adaptability.     

Groupiness of Sea Waves and Their Characteristic Parameters

Three methods for studying wave groups and their main parameters for describing wave groupiness are reviewed in this paper. Then they are analyzed and compared combined with field data from both aspects of group height and group length. A method and two parameters that can describe wave groupiness are suggested. The groupiness parameters of sea waves at three field stations are given. The effects of groupiness on both distributions of the wave height and the phase of component waves are investigated. The effects of datum length on the calculated value of grouping parameters are also discussed.     

Numerical Simulated Study on the Separation of Oblique Incident and Reflected Waves

The Goda's method of separating the frequency spectrum of the unidirectional incident and reflected waves is improved. The proposed method can be applied to the separation of oblique incident and reflected waves and the two wave gauges can be arranged in an arbitrary angle in front of a structure. When the projected distance of the two probes on the incident wave direction is the multiple ofthe half length of the incident waves, the singular problem will emerge by using the method. It is advised that when the projected distance of the two measured points on the incident wave direction is 0.05～0.45 times the wave length of peak frequency wave, good results can be obtained. The simulated resultant waves are separated by the method of numerical simulation and the separated wave spectra are basically corresponding to the target spectra input. The wave trains calculated by the separated incident and reflected wave frequency spectrum are approximated to the input wave trains and the reflected coefficient can be derived correctly. Therefore, the method proposed in this paper is reliable.     

Prediction of Height and Period Joint Distributions for Stochastic Ocean Waves

This article proposes a new methodology to predict the wave height and period joint distributions by utilizing a transformed linear simulation method. The proposed transformed linear simulation method is based on a Hermite transformation model where the transformation is chosen to be a monotonic cubic polynomial, calibrated such that the first four moments of the transformed model match the moments of the true process. The proposed new approach is applied for calculating the wave height and period joint distributions of a sea state with the surface elevation data measured at an offshore site, and its accuracy and efficiency are favorably validated by using comparisons with the results from an empirical joint distribution model, from a linear simulation model and from a second-order nonlinear simulation model.     

潮汐河口桥墩群对波浪传播影响的数值研究

为研究河口桥墩群的消波作用,以李村河口段胶州湾快速路桥墩群为例,建立了基于波作用守恒方程的二维波浪模型,精细模拟了100年一遇高潮耦合100年一遇波高情况下,波浪通过河口桥墩群后波浪变化及波高分布,并利用物理模型试验结果对其进行了验证,二者吻合较好。数值模拟结果显示:桥墩群对河口波浪具有明显的消减作用,其透射系数随桥墩挤压面积比的增大呈线性减小趋势。     

A Numerical Model for Edge Waves on A Compound Slope

An edge wave is a kind of surface gravity wave basically travelling along a shoaling beach. Based on the periodic assumption in the longshore direction, a second order ordinary differential equation is obtained for numerical simulation of the cross-shore surface elevation. Given parameters at the shoreline, a cross-shore elevation profile is obtained through integration with fourth-order Runge-Kutta technique. For a compound slope, a longshore wavenumber is obtained by following a geometrical approach and solving a transcendental equation with an asymptotic method. Numerical results on uniform and compound sloping beaches with different wave periods, slope angles, modes and turning point positions are presented. Some special scenarios, which cannot be predicted by analytical models are also discussed.     

A 2D Mathematical Model for Sediment Transport by Waves and Tidal Currents

In this study, the combined actions of waves and tidal currents in estuarine and coastal areas are considered and a 2D mathematical model for sediment transport by waves and tidal currents has been established in orthogonal curvilinear coordinates. Non-equilibrium transport equations of suspended load and bed load are used in the model. The concept of background concentration is introduced, and the formula of sediment transport capacity of tidal currents for the Oujiang River estuary is obtained. The Dou Guoren formula is employed for the sediment transport capacity of waves. Sediment transport capacity in the form of mud and the intensity of back silting are calculated by use of Luo Zaosen＇ s formula. The calculated tidal stages are in good agreement with the field data, and the calculated velocities and flow directions of 46 vertical lines for 8 cross sections are also in good agreement with the measured data. On such a basis, simulations of back silting after excavation of the waterway with a sand bar under complicated boundary conditions in the navigation channel induced by suspended load, bed load and mud by waves and tidal currents are discussed.     

Profile Evolution and Energy Dissipation for Internal Soliton Transmitting over Different Submarine Ridges

1 .IntroductionWhile surface solitary waves arefoundin many physical phenomena (Chouand Shih,1996 ;Chouand Quyang,1999 ;Chouet al .,2003 ; Chenet al .,2004 ; Wang,2004 ;Tsenget al .,2005) ,internal solitary waves (ISWs) have been observed since the beginning of the 20th century.In fact ,some internal waves have alarge enoughamplitudeto cause consequence onthe surface .Hence obser-vation of the oceansurface may helpto detect the activities of internal waves . We require observationsthrough…     

Numerical Simulation of Wave Height and Wave Set-Up in Nearshore Regions

Based on the time dependent mild slope equation including the effect of wave energy dissipation, an expression for the energy dissipation factor is derived in conjunction with the wave energy balance equation, and then a practical method for the simulation of wave height and wave set-up in nearshore regions is presented. The variation of the complex wave amplitude is numerically simulated by use of the parabolic mild slope equation including the effect of wave energy dissipation due to wave breaking. The components of wave radiation stress are calculated subsequently by new expressions for them according to the obtained complex wave amplitude, and then the depth-averaged equation is applied to the calculation of wave set-up due to wave breaking. Numerical results are in good agreement with experimental data, showing that the expression for the energy dissipation factor is reasonable and that the new method is effective for the simulation of wave set-up due to wave breaking in nearshore regions.     

Numerical Study on the Effect of Submerged Depth on the Horizontal Plate Wave Energy Converter

The growing search for clean and renewable energy sources has given rise to the studies of exploring sea wave energy. This paper is concerned with the numerical evaluation of the main operational principle of a submerged plate employed for the conversion of wave energy into electrical one. The numerical model used to solve the conservation equations of mass, momentum and transport of volume fraction is based on the finite volume method (FVM). In order to tackle with the flow of mixture of air-water and its interaction with the device, the multiphase model volume of fluid (VOF) is employed. The purpose of this study is the evaluation of a numerical model for improvement of the knowledge about the submerged plate wave energy converter, as well as the investigation of the effect of the distance from the plate to the bottom of the sea (HP) on the performance of the converter. The simulations for several distances of the plate from the seabed show that the optimal efficiency is 64%, which is obtained for HP=0.53 m (88% of the depth). This efficiency is 17% larger than that found in the worst case (HP=0.46 m, 77% of the depth).     

Effects of Rotor Solidity on the Performance of Impulse Turbine for OWC Wave Energy Converter

Impulse turbine, working as a typical self-rectifying turbine, is recently utilized for the oscillating water column (OWC) wave energy converters, which can rotate in the same direction under the bi-directional air flows. A numerical model established in Fluent is validated by the corresponding experimental results. The flow fields, pressure distribution and dimensionless evaluating coefficients can be calculated and analyzed. Effects of the rotor solidity varying with the change of blade number are investigated and the suitable solidity value is recommended for different flow coefficients.     

Wave Numerical Model for Shallow Water

The history of forecasting wind waves by wave energy conservation equation is briefly des-cribed.Several currently used wave numerical models for shallow water based on different wave theoriesare discussed.Wave energy conservation models for the simulation of shallow water waves are introduced,with emphasis placed on the SWAN model,which takes use of the most advanced wave research achieve-ments and has been applied to several theoretical and field conditions.The characteristics and applicabilityof the model,the finite difference numerical scheme of the action balance equation and its source termscomputing methods are described in detail.The model has been verified with the propagation refractionnumerical experiments for waves propagating in following and opposing currents;finally.the model is ap-plied to the Haian Gulf area to simulate the wave height and wave period field there,and the results arecompared with observed data.     

Determination of wave energy dissipation factor and numerical simulation of wave height in the surf zone

Based on the time-dependent mild slope equation including the effect of wave energy dissipation, an expression for the energy dissipation factor is derived in conjunction with the wave energy balance equation. The wave height of regular and irregular waves is numerically simulated by use of the parabolic mild slope equation considering the energy dissipation due to wave breaking. Comparison of numerical results with experimental data shows that the expression for the energy dissipation factor is reasonable. The effects of the wave breaking coefficient on the breaking point and the distribution of wave height after breaking are discussed through the study of a specific experimental topography.     

振荡水柱波能发电装置气室的三维数值模拟研究

振荡水柱装置是目前世界上应用最为广泛的岸式波能发电装置.气室作为该装置的主要结构可将入射波浪的能量转换为往复振荡的气流动能,是完成能量一次转换的关键结构.为了建立用于考察入射波浪、气室内的波面振荡变化,准确预测气室工作性能的三维数值模拟模型,构建了基于VOF模型的三维数值波浪水槽.通过与物理模型试验的结果对比发现,该模...     

龙口市人工岛周边海域波浪场和水动力场的数值模拟

为了科学的分析离岸人工岛群对周边海岸动力的影响,本文以龙口市人工岛为例,运用MIKE21数值模拟软件建立了龙口离岸人工岛及附近海域的水动力模型和波浪模型,根据波浪的生成、成长和传播原理,针对最有可能形成较大波浪的W、WNW、NW三个方向,采用频率为0.5%(重现期为200a)的高潮位叠加频率为0.5%(重现期为200a)的W、WNW和NW向风作用下的波浪场和水动力场进行数值模拟研究,给出了高潮位条件下人工岛周边不同波向对应的有效波高和最大波高值,以及最大流速和流向数据,可为人工岛群的地坪标高确立和防浪建筑物的布设提供科学依据。     

Calibration and verification of a spectral wind–wave model for Lake Okeechobee

A spectral wind wave model SWAN (Simulation WAves Nearshore) that represents the generation, propagation and dissipation of waves was applied to Lake Okeechobee. This model includes the effects of refraction, shoaling, and blocking in wave propagation. It accounts for wave dissipation by whitecapping, bottom friction, and depth-induced wave breaking. The wave–wave interaction effect also is included in this model. Measurements of wind and wave heights were made at different stations and different time periods in Lake Okeechobee. Significant wave height values were computed from the recorded data. The correlation between wind stress and significant wave height also was analyzed. A 6-day simulation using 1989 data was conducted for model calibration. Another 6-day simulation using 1996 data was conducted for model verification. The simulated significant wave heights were found to agree reasonably well with measured significant wave heights for calibration and verification periods. Agreement between observed and simulated values was based on graphical comparisons, mean, absolute and root mean square errors, and correlation coefficient. Comparisons showed that the model reproduced both general observed trends and short term fluctuations.