Large Eddy Simulation for Wave Breaking in the Surf Zone

In this paper, (he large eddy simulation method is used combined with the marker and cell method to study the wave propagation or shoaling and breaking process. As wave propagates into shallow water, the shoaling leads lo the increase of wave height, and then at a certain position, the wave will be breaking. The breaking wave is a powerful agent for generating turbulence, which plays an important role in most of the fluid dynamic processes throughout the surf zone, such as transformation of wave energy, generation of near-shore current and diffusion of materials. So a proper numerical model for describing the turbulence effect is needed. In this paper, a revised Smagorinsky subgrid-scale mode! is used to describe the turbulence effect. The present study reveals that the coefficient of the Smagorinsky model for wave propagation or breaking simulation may be taken as a varying function of the water depth and distance away from the wave breaking point. The large eddy simulation model presented in this pape     

On Radiation Boundary Conditions and Wave Transformation Across the Surf Zone

The purpose of this paper is to extend the validity of Li's parabolic model (1994) by incorporating a combined energy factor in the mild-slope equation and by improving the traditional radiation boundary conditions. With wave breaking and energy dissipation expressed in a direct form in the equation, the proposed model could provide an efficient numerical scheme and accurate predictions of wave transformation across the surf zone. The radiation boundary conditions are iterated in the model without use of approximations. The numerical predictions for wave height distributions across the surf zone are compared with experimental data over typical beach profiles. In addition, tests of waves scattering around a circular pile show that the proposed model could also provide reasonable improvement on the radiation boundary conditions for large incident angles of waves.     

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.     

北戴河海滩泥沙捕获实验及其初步结果分析

介绍了利用泥沙捕获器观测破波带泥沙垂直分布结构的现场实验方法和基本程序，以及利用实验结果计算泥沙通量的方法。研究表明，近岸带泥沙运移通量及其在垂向上的分布受破波带相对位置和海滩地形变化的影响。在破波点附近，波浪的搅动和流场作用强，泥沙运移通量增大，泥沙在波浪的作用下可以大量进入垂直水体以悬移和跃移的方式运移。在本实验中，破波点附近的泥沙在距海底100cm的垂直水体中运移，通量垂向向上逐渐减小。远离破波点，泥沙运移通量和进入垂直水体的高度明显下降。在地形变化复杂的有坝海滩，沙坝顶部的泥沙运移通量最大，泥沙进入垂直水体运移的机率增加，而在沙坝问的沟槽内，波浪和海流作用减弱，泥沙通量和垂向进入水体运移的比例下降。     

潜堤上规则波辐射应力的数值研究

在近岸波浪相关研究中,辐射应力是波动在水体中引起的剩余动量流,是波浪运动的重要物理量.在波浪从深水逐渐传向浅水的过程中,波浪的非线性逐渐增强,甚至会发生破碎等剧烈变形,引起辐射应力的强烈变化,对次重力波生成等有重要贡献.应用OpenFOAM精细模拟波浪在潜堤上的传播,得出波浪运动的详细流场信息,计算了有波浪破碎情况下潜...     

Approach to Calculating Methods of Wave Breaking Depth and Height

- Engineers in coastal engineering have been paying much attention to the research subject on wave breaking. In this paper, previous research results on the calculating methods of wave breaking depth and height are enumerated, the laws of wave transformation before and after wave breaking are investigated, an adequate supposition is made, and the effect of beach slope, bed friction and breaking turbulence on wave breaking is considered. By applying the theory of wave energy dissipation rate and combining with proper formulas of solitary waves, a new calculating formula of wave breaking depth and height on the movable bed is derived and examined with the data from experimental pools of different sizes, and it is proved to be of practicability.     

One-Dimensional Horizontal Boussinesq Model Enhanced for Non-Breaking and Breaking Waves

Based on a set of fully nonlinear Boussinesq equations up to the order of O（μ^2, ε^3μ^2） （where ε is the ratio of wave amplitude to water depth and ,μ is the ratio of water depth to wave length） a numerical wave model is formulated. The model＇s linear dispersion is acceptably accurate to μ ≌ 1.0, which is confirmed by comparisons between the simulat- ed and measured time series of the regular waves propagating on a submerged bar. The moving shoreline is treated numer- ically by replacing the solid beach with a permeable beach. Run-up of nonbreaking waves is verified against the analytical solution for nonlinear shallow water waves. The inclusion of wave breaking is fulfilled by introducing an eddy term in the momentum equation to serve as the breaking wave force term to dissipate wave energy in the surf zone. The model is applied to cross-shore motions of regular waves including various types of breaking on plane sloping beaches. Comparisons of the model test results comprising spatial distribution of wave height and mean water level with experimental data are presented.     

Food and Feeding Habits of the Surf Zone Penaeid Prawn Macropetasma africanus (Balss)

Abstract. Macropetasma africanus is an important component of the nearshore macrofauna in South African marine waters. Juveniles utilize high energy surf zones as nursery and maturation areas before offshore migration to spawning areas. Samples were taken from two surf zone areas and an offshore spawning area over a two year period. Spatial, seasonal, and diel variations in diet, established from stomach content analysis (N = 1020), indicate that M. africanus is an omnivorous feeder with a diet reflecting general food availability in the environment. Five major food groups were identified. Detritus was the most important food group identified in a medium energy surf zone and offshore spawning area. Phytoplankton was the major food group utilized in a high energy surf area characterized by phytoplankton blooms. Crustaceans were an important component of the diet in all three areas sampled and the remains of copepods, ostracods, isopods, amphipods, and mysids were identified. Benthic macrofauna and meiofauna are not important components of the M. africanus diet in the turbulent surf zone areas but appear more important in the offshore area. Feeding behaviour is adapted to turbulent conditions found in surf areas and the passage of food through the foregut is rapid.     

Determining the Onset and Strength of Unforced Wave Breaking in A Numerical Wave Tank

A numerical wave tank is used to investigate the onset and strength of unforced wave breaking, and the waves have three types of initial spectra: constant amplitude spectrum, constant steepness spectrum and Pierson-Moscowitz spectrum. Numerical tests are performed to validate the model results. Then, the onset of wave breaking is discussed with geometric, kinematic, and dynamic breaking criteria. The strength of wave breaking, which is always characterized by the fractional energy loss and breaking strength coefficient, is studied for different spectra. The results show how the energy growth rate is better than the initial wave steepness on estimating the fractional energy losses as well as breaking strength coefficient.     

Application of VOF in Calculating Wave Energy Loss due to Spilling Breaker

- A large amount of experimental analysis and systematical theoretical calculation has been done by the authors to solve the problem of wave transformation and breaking, considering the effect of both current and topography, but only the wave energy loss due to spilling breaker in the surf zone has been discussed in this paper. Based on test result analysis and calculation with the Stream Function Wave Theory, the wave velocity field at breaking points has been obtained, and it is used to calculate the wave heights after breaking by the VOF (Volume of Fluid) method, in which the governing equations are continuity equation and Navier-Stokes Equation for imcompressible fluids. In the present paper, the improved VOF technique is used to calculate the wave heights of stable regular waves after breaking. Results fit the test data well, which shows that the VOF method is suitable to numerical simulation of regular waves after breaking. Besides, the breaker coefficient B of regular waves in the bore model is a     

初始倾斜跃层所致内波的数值研究

The pycnocline in a closed domain is tilted by external wind forcing and tends to restore to a level posi- tion when the wind falls. An internal seiche oscillation exhibits if the forcing is weak, otherwise internal surge and internal solitary waves emerge, which serve as a link to cascade energy to small-scale processes. A two-dimensional non-hydrostatic code with a turbulence closure model is constructed to extend previous laboratory studies. The model could reproduce all the key phenomena observed in the corresponding labo- ratory experiments. The model results further serve as a comprehensive and reliable data set for an in-depth understanding of the related dynamical process. The comparative analyses indicate that nonlinear term favors the generation of internal surge and subsequent internal solitary waves, and the linear model predicts the general trend reasonably well. The vertical boundary can approximately reflect all the incoming waves, while the slope boundary serves as an area for small-scale internal wave breaking and energy dissipation. The temporal evolutions of domain integrated kinetic and potential energy are also analyzed, and the results indicate that about 20% of the initial available potential energy is lost during the first internal wave breaking process. Some numerical tactics such as grid topology and model initialization are also briefly discussed.     

Improved representation of breaking wave energy dissipation in parametric wave transformation models

An improved formulation to describe breaking wave energy dissipation is presented and incorporated into a previous parametric cross-shore wave transformation model [Baldock, T.E., Holmes, P., Bunker, S., Van Weert, P., 1998. Cross-shore hydrodynamics within an unsaturated surf zone. Coastal Engineering 34, 173–196]. The new formulation accounts for a term in the bore dissipation equation neglected in some previous modelling, but which is shown to be important in the inner surf zone. The only free model parameter remains the choice of γ, the ratio of wave height to water depth at initial breaking, and a well-established standard parameter is used for all model runs. The proposed model is compared to three sets of experimental data and a previous version of the model which was extensively calibrated against field and laboratory data. The model is also compared to the widely used model presented by Thornton and Guza (1983) [Thornton, E.B., Guza, R.T., 1983. Transformation of wave height distribution. Journal of Geophysical Research 88 (No.C10), 5925–5938].     

Large Eddy Simulation for Plunge Breaker and Sediment Suspension

Breaking waves are a powerful agent for generating turbulence that plays an important role in many fluid dynamical processes, particularly in the mixing of materials. Breaking waves can dislodge sediment and throw it into suspension, which will then be carried by wave-induced steady current and tidal flow. In order to investigate sediment suspension by breaking waves, a numerical model based on large-eddy-simulation (LES) is developed. This numerical model can be used to simulate wave breaking and sediment suspension. The model consists of a free-surface model using the surface marker method combined with a two-dimensional model that solves the flow equations. The turbulence and the turbulent diffusion are described by a large-eddy-simulation (LES) method where the large turbulence features are simulated by solving the flow equations, and a subgrid model represents the small-scale turbulence that is not resolved by the flow model. A dynamic eddy viscosity subgrid scale stress model has been used for the     

Variation in Surf-zone Fish Community Structure Across a Wave-exposure Gradient

Fluctuations in various attributes of a surf-zone fish community were examined by beach seining at a series of sites spanning a wave-exposure gradient in the Saldanha Bay–Langebaan Lagoon system, on the South African west coast. During April 1994, 24 species, totalling 25 676 individuals and 434 kg, were captured. Three teleosts,Atherina breviceps, Liza richardsoniiandPsammogobius knysnaensis, dominated numerically, while three elasmobranchs,Rhinobatos annulatus, Mustelus mustelusandMyliobatis aquila, dominated the biomass. Elasmobranchs displayed no discernible distribution patterns. Two important trends were, however, evident in the teleost catches: overall teleost abundance (mean density) increased markedly as wave exposure decreased; and highest species richness and diversity, and lowest dominance were both recorded at intermediate levels of exposure. A positive relationship between fish size and exposure was also evident for at least two of the species. These trends were attributed primarily to the availability and abundance of suitable food resources, and to physical disturbance introduced by breaking waves.     

Physical Investigation of Directional Wave Focusing and Breaking Waves in Wave Basin

An experimental scheme for the generation of directional focusing waves in a wave basin is established in this paper. The effects of the directional range, frequency width and center frequency on the wave focusing are studied. The distrihution of maximum amplitude and the evolution of time series and spectra during wave packet propagation and the variation of water surface parameters are extensively investigated. The results reveal that the characteristics of focusing waves are significantly influenced hy wave directionality and that that breaking criteria for directional waves are distinctly different from those for unidirectional waves.     

Effects of Wave Breaking on Freak Wave Generation in Random Wave Train

The experimental studies of the wave breaking effects on freak wave generation are presented within a finite-depth random wave train in a laboratory wave tank. The main attention is paid to the abnormal index,AI=Hmax/Hs,being used to characterize the freak waves,and the changes of the coefficient due to wave breaking. The results show that the occurrence probability of freak wave events in non-breaking waves is much larger than that in breaking waves and such occurrence in deep water is larger than that in ...     

近岸波浪破碎区不规则波浪的数值模拟

基于近岸不规则波浪传播的抛物型缓坡方程和两类波浪破碎能量损耗因子,对近岸波浪破碎区不规则波浪的波高分布进行了数值模拟,并结合实验结果对数值模拟结果进行了验证分析,结果表明采用两类波浪破碎能量损耗因子所模拟的破碎区波高与实测值均吻合良好,波浪破碎能量损耗因子及波浪破碎指标对破碎区波浪波高分布影响较明显。     

冲流带海滩高频振动探讨

在粤东汕尾寮嘴口岬间海滩冲流带设置两条剖面,利用2003年10月13日一个潮周期实测高频剖面数据(采样间隔为1min和6min),分析了海滩的高频振动特征。并结合同期实测碎波带水位波动,探讨了海滩高频振动的动力原因。分析表明,此海滩过程主要以堆积为主,并表现有显著周期的振动：其日内变化受潮汐控制,表现为涨潮堆积、落潮侵蚀;波能对海滩高频振动过程有着重要的影响。     

Information System for Ocean Wave Resources and Its Application to Wave Power Utilization

An information system for ocean wave resources and its application to wave power utilizationare indtroduced.It can manage,analyze and process the data in the monthly report of ocean wave observa-tion records of the State Ocean Administration,and can provide various kinds of curves and numericalcharacters of statistics.This system has been put into utility in Guangzhou Institute of Energy Conversion(GIEC),the Chinese Academy of Sciences since 1996.An application example is given of theinverstigation and analysis on ocean wave resource of the Nan Ao Island,Guangdong Province,where a100 kW onshore OWC(oscillating water column)wave power station will be built.The wave power distri-bution is obtained in different wave directions for different wave periods.It is found that 70 percent of thewave power comes from the direction of ENE,and more than 95 percent of the wave power is related withdirection E.The average wave power density is about 3 kW/m,and more than 80 percent of the wavepower is distributed in the     

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…