Combined refraction and diffraction models for sea waves over complicated topography and with currents in shallow water

-Combined refraction and diffraction models in the form of linear parabolic approximation are derived through smallparameter method. More strictly theoretical basis and more accuracy in the models than Lozano's (1980) are obtained. Some theoretical defects in Liu's model (1985) with consideration of current are not only found but also eliminated. More strict and accurate models are, therefore, presented in this paper.The calculation results and analysis in applying the models to actual wave field with consideration of bottom friction will be given in the following paper.

Ocean wave diffraction in near-shore regions observed by Synthetic Aperture Radar

Observation and analysis of ocean wave diffraction in near-shore and near-island region was performed with Synthetic Aperture Radar （SAR） data, using an optimized retrieval method named parameterized first-guess spectrum retrieval method. The results retrieved from ERS-SAR and ENVISAT-ASAR images showed that, in the region sheltered by land jut, the energy of long waves is reduced by 10%-20% and that the propagation direction of long waves is changed due to the effect of topography. In the shadow zone behind the island, ocean wave can propagate along the seashore instead of perpendicular to the coastline, as shown by SAR images.

Cavity effect on Rayleigh wave dispersion and P-wave refraction

Sinkholes and cavities can represent serious hazards to human safety and urban infrastructures,cause roadbed subsidence,and so on.It is therefore essential to evaluate various sinkholes in different depths and sizes to assess the risk of collapse.This paper evaluates the effect of different cavities on Rayleigh-wave propagation and body(P)wave refraction.Rayleigh(R)wave propagation is analyzed according to the classical multi-channel analysis of surface waves(MASW)method also considering the R-wave backscattering.Synthetic seismic traces are computed by means of finite element modeling(FEM)for cavity and intrusion at different depths and sizes.Furthermore,field acquisition data is used to verify the detection effect of a cavity on R-and P-waves.The results show that the presence of backscattered R-waves and the changes in the R-wave velocity spectrum can help in cavity identification.Additional possible evidence is represented by significant changes in the refraction travel times over the cavity location.It can be concluded that the field data are in good agreement with the synthetic,and it could be effective to consider the results of both R-and P-wave analysis in order to efficiently identify the cavities.

Modelling Wave Transmission and Overtopping Based on Energy Balance Equation

Wave transmission and overtopping around nearshore breakwaters can have significant influence on the transmitted wave parameters,which affects wave conditions and sediment transportation and becomes the focus of design in engineering.The objective of this paper is to present a simplified model to estimate these important wave parameters.This paper describes the incorporation of wave transmission and overtopping module into a wave model for multi-directional random wave transformation based on energy balance equation with the consideration of wave shoaling,refraction,diffraction,reflection and breaking.Wen's frequency spectrum and non-linear dispersion relation are also included in this model.The influence of wave parameters of transmitted waves through a smooth submerged breakwater has been considered in this model with an improved description of the transmitted wave spectrum of van der Meer et al.(2000) by Carevic et al.(2013).This improved wave model has been validated through available laboratory experiments.Then the verified model is applied to investigate the effect of wave transmission and overtopping on wave heights behind low-crested breakwaters in a project for nearshore area.Numerical calculations are carried out with and without consideration of the wave transmission and overtopping,and comparison of them indicates that there is a considerable difference in wave height and thus it is important to include wave transmission and overtopping in modelling nearshore wave field with the presence of low-crested breakwaters.Therefore,this model can provide a general estimate of the desired wave field parameters,which is adequate for engineers at the preliminary design stage of low-crested breakwaters.

Retrieving capillary-gravity wave spectrum from polarimetric microwave radiation of ocean surface

A new simple two-scale model on the polarimetric microwave emission of ocean surface is derived at first, which can be ex-pressed as an integral of weighting functions (M0 and M2) and ocean surface curvature spectrum coefficients (C0 and C2). This provides a simple way to investigate the effect of curvature spectrum on ocean emission. It is found that ocean waves with wavelengths both comparable to and much greater than the electromagnetic wavelength can contribute to the harmonics of ocean surface microwave emission, depending on the magnitude of the ocean surface spectrum in these length scales. Bright-ness temperature predictions differ significantly due to present diverse spectrum models, and thus a study on wave spectrum obtained inversely from brightness temperature measurements is necessary. From the ocean surface radiation data measured by polarimetric microwave radiometer, we derived an ocean wave spectrum with a wider wave number range, using the proposed two-scale model and constrained linear least-squares method. The derived ocean wave spectrum is useful for comparing with present diverse models.

基于Matlab的不规则海浪三维仿真

讨论了二维不规则长峰波海浪和三维不规则短峰波海浪的模型的建立,并在海浪谱分析的基础上进行了仿真研究。在Matlab仿真系统中为了得到较为真实理想的海浪模拟效果,作者提出了对仿真图形进行了波面细化,海浪颜色和光照等加工处理的方法。

基于海浪谱的Gerstner波浪模拟

本文从海洋学现有的观测和研究成果出发,结合海浪的Gerstner模型,提出一种风力作用下的基于海浪谱的三维Gerstner海浪模型。首先,通过分析Gerstner模型各个参数的随机性,利用海浪谱和方向谱相关公式,获得固定风速下模型各随机参数值,建立固定风速下的海浪模型;然后,在此基础上进一步构造了基于海浪谱的风力模型,模拟了风力作用下的海浪;最后,采用基于视点的网格拓扑结构,实现了海浪的实时绘制。实验结果表明,该模型不仅能更真实地模拟海浪,还具有较好的交互性。

海岸悬沙运移数学模型

根据适合大范围缓变地形情况下 ,不恒定、非均匀流场中随机波折绕射联合数值模式及波浪作用下的二维浅水环流方程和悬沙扩散方程 ,建立了波浪、潮流共同作用下二维悬沙数学模型 ,并将该模型应用于渤海湾北部海域 ,进行了波、流共同作用下航道疏浚弃土的悬沙扩散、运移及海床演变的数值模拟 。

不恒定非均匀流场中随机波的折绕射联合数学模型

根据考虑流影响的缓坡方程 ,运用波动叠加原理 ,导出了一种适合大范围缓变地形情况下 ,不恒定非均匀流场中随机波的折绕射联合的数值模式 .应用该模式进行了概化的半椭圆斜坡海底及渤海湾西部海域不恒定非均匀流场中随机波传播的折绕射联合的数值计算 。

瓯江口海区波浪数学模型研究

建立了考虑复杂地形造成的折射、绕射、底摩擦波能损失、波浪破碎及岛屿影响的多向不规则波传播变形的数学模型 。

利用波浪折绕射模型和风浪成长公式计算临港重现期波要素

本文通过波浪折绕射模型和浅水风浪成长公式的联合计算得到了杭州湾北岸海域的不同方向、不同重现期和不同水位条件下的波浪场分布,结果表明该海域以东向浪为主。描述了50年一遇、不同方向、不同水位条件下的波浪特征。

多方向不规则波传播变形数值模拟

在推广的缓坡方程数学模型基础上建立了多方向不规则波数学模型,综合考虑了波浪折射、绕射、反射、底摩擦和风能输入等因素。基于线性波浪理论,将波浪方向谱在频率和方向上按等能量分割法离散后,分别计算各组成波的传播变形,再计算合成波要素。缓坡方程数学模型采用改进的ADI法求解,计算效率高,稳定性好。采用椭圆形浅滩不规则波模型试验结果和单突堤不规则波绕射理论解对数学模型进行了验证,数值模拟结果和试验值及理论解符合良好。利用该模型进行了某港港内波浪折射、绕射和反射的联合数值模拟,给出了合理的港内波高分布。

近岸多向不规则波传播变形的数学模型

开发了考虑非线性弥散作用的缓坡多向不规则波传播变形的数学模型,首先,根据线性波动的叠加原理和波浪方向谱理论,以考虑非线性弥散影响的规则波缓坡方程为基础,推导出考虑非线性弥散影响的缓坡多向不规则波传播变形的微分方程;其次,基于以上方程使用有限差分方法建立数学模型;然后,采用实验室波浪试验资料对本数学模型进行验征计算;最后,对非线性弥散对波浪传播的影响进行研究．研究结果表明:开发的数学模型合理、可信;在浅水区,非线性弥散作用明显,考虑非线性弥散作用十分必要．

海浪谱折绕射联合模型在障碍物后水域的应用

本文应用海浪谱折绕射模型计算了不规则波传播至有障碍物(如半岛)的水域的海浪要素。文中给出了障碍物背风面边值的处理方法,比较了理论值和实测值的结果,符合良好。说明缓坡上海浪谱折绕射联合模型和文中给出的边值处理方法,对障碍物后遮拦区波要素计算是有效的。

二维水波数学模型的实验验证

为了验证基于缓坡方程的波浪折射和绕射综合问题的数学模型，在波浪水池中，对缓坡地形上的双突堤在规则波、单向不规则波和多向不规则波作用下的折射、绕射综合影响进行了实验研究，并将实验得到的结果和数值计算结果进行了比较。

海浪谱的选择对海面电磁波散射建模的影响

海浪谱的选择对Bragg共振散射建模的影响是海面电磁波散射建模的关键问题。首先简介了海浪谱的概念,然后选择RA(Romeiser-Alpers)谱进行了Bragg共振散射建模,最后选择另一种具有代表性的PM(Pierson-Moskowitz)谱进行了Bragg共振散射建模,并通过仿真实验对两种海浪谱及其用于Bragg共振散射建模的效果进行了比较分析。获得的结论对合理地选择海浪谱具有指导意义。

海浪建模方法综述

海浪建模作为海浪模拟的重要组成部分,直接影响海浪模拟的逼真度和效率。侧重于虚拟现实和海面回波仿真的角度对海浪建模进行综述。介绍了海浪的形成过程;详细总结了海浪建模的主要方法及其优缺点;并对今后海浪建模技术的研究重点进行了预测。

海浪能量方向分布形式对近岸波折绕射计算的影响

本文考虑海浪能量在方向上的分布,结合组成波折绕射控制方程组,建立了海浪方向谱的折绕射联合模型,并在简单地形上实施数值计算.比较简单波及能量谱折绕射的计算结果,表明:考虑海浪能量的方向分布,能减弱波动能量辐聚、辐散的程度,改变辐聚、辐散的位置.方向分布形式不同,这种影响表现出的程度也不一样.

基于AR模型功率谱估计的海浪水压场特性研究

海浪水压场是水压引信的主要干扰源．通过自行研制的高精度海浪水压场自动测量系统进行了海上测量试验，获取了大量的海浪水压场原始数据．采用基于AR模型功率谱估计对实测数据进行了分析，详细研究了不同水深、不同浪级下的海浪水压场特性，得出了海浪水压场在短时间内可视为平稳随即过程，其主要能量集中在0．05～0．2Hz，且随着海况级别的升高，最大能谱频率向低频方向移动等重要结论，为新型水压引信提高抗海浪水压场干扰能力提供了设计依据．

基于拟层流风波生成机制的海浪谱模型

海浪谱的能量可以视为由具有不同相速度的谐波携带的能量所组成。基于对风波形成、发展过程的认识,认为各组成谐波的能量由谐波自平均风摄取而来,由此根据拟层流模型推导出谐波能量密度的计算公式,建立以等效风速和峰值频率等为基本参数的海浪谱模型——随机Fourier函数模型,并给出了确定谐波频率、波长、相速度、振幅以及等效风速等模型参数的原则和计算方法。在59个实测样本谱基础上,采用随机建模方法确定模型参数的取值及其概率分布。结果表明,海浪谱模型可以很好地预测谱能,所计算的物理谱与实测谱均值吻合良好。