作用在大直径圆柱墩上不规则波波浪力的试验研究

本文介绍大直径圆柱墩不规则波波浪力的确定方法,本法基于波浪绕射理论及随机海浪的极值分布理论而建立,经过不规则波波力试验,证实它是合理并可靠的。文中讨论了波力谱的表达式,波力及波力矩的统计分布特征及波力谱(或波力矩谱)与波浪谱峰频值ω_0的关系。     

斋堂岛东南海域波浪特征及海浪谱分析

利用斋堂岛东南海域2013年至2014年的实测波浪资料,统计分析了本海域波浪特征,为波浪能资源评估提供基本波浪参数。统计结果表明,本海域年平均有效波高为0.60 m,最大波高为5.30 m,平均周期为3.3 s,最大周期为8.3 s,常浪向为E-SE向。本文亦讨论了本海域波高分布和波高与周期的关系,并基于JONSWAP谱谱型的基本结构,拟合得到适用于本海域的海浪谱谱型,可为海洋能发电装置的布设及相应的工程建设提供一定的参考。     

复杂地形下海浪数值模式的特征线计算格式

LAGFD-WAM海浪数值模式是一种第三代海浪数值模式，通过求解波数谱平衡方程，并考虑风输入、波浪破碎耗散、底摩擦耗散、波波非线性相互作用和波流相互作用等源函数，模拟波数空间下的海浪方向谱，并依此获得海浪的波高、周期和平均波向。该模式的一个显著特点是采用特征线嵌入格式求解海浪的传播。在进行浅水区域的海浪模拟时，特征线嵌入格式的数值计算方案是否合理对海浪数值模拟结果产生直接的影响。为此LAGFD-WAM海浪数值模式提出了一种新的特征线混合数值计算格式，并应用于浅水海浪数值模拟。结果表明，采用该计算方法，能够使数值模拟结果与实测结果很好符合。     

欧洲北海海域波高区间分布概率研究

为了研究欧洲北海海域的波高全区域概率分布情况,从而为海洋平台等海洋浮式结构物的选址和结构设计提供依据。首先基于Global Waves Statistics(GWS)提供的实测数据,确定典型计算工况的发生概率;同时考虑实测数据中极端波浪环境下的数据缺失导致大波高分布概率偏小的问题,利用三参数Weibull分布确定不同重现期下的极值风速,作为典型计算工况的补充。以不同风速、风向的定常风场为输入项,利用第三代海浪数值模型SWAN模型,对北海全区域波高进行数值模拟。将数值模拟的稳态形式依照各工况的发生概率进行归一化累加处理,认为其结果可以表征全区域的波高概率分布情况。以波高概率分布的计算结果为依据,分析北海海域波浪环境的统计学特征,发现有效波高为7 m以上的大波高频发区在北海北部区域有大范围分布;有效波高4～5 m为北海东北区域的多发海况,极端海况下的有效波高主要分布于7～14 m区间,在地形突变区域的波高发生显著变化。     

运用SWAN数值模拟对渤海波浪极值参数的研究(英文)

本文以高分辨率后报风场资料为输入,采用SWAN波浪模式,模拟了渤海海域1985年至2004年共20年间的波浪场。通过有效波高数据的比较,可看出波浪数值结果与实测资料符合较好,可以用数值结果分析渤海海域的波浪特征。利用计算的年极值波要素,本文给出并分析了渤海海域不同重现期下的极值参数分布情况。     

广西沿海年极值波高分析

经分析发现广西沿海极值波高不符合用的P－Ⅲ型分布，并分析了其符合的分布函数，结果表明对Weibull分布符合最好，为解决Weibull分布参数难于确定的问题，引入了共轭梯度法计算其参数，最终计算了多年一遇极值波高。     

海浪同化预报模型理论基础

将共轭变分同化方法应用于LAGFD－WAM海浪数值模式，导出了海浪谱能量平衡方程的共轭方程以及风输入、破碎、底摩擦、波波非线性相互作用和波流相互作用的相庆共轭源函数，建立了海浪同化模型，数值计算仍采用特征线嵌入计算格式，为合成孔径雷达波谱反演资料和卫星高度计有效波高资料同化奠定理论基础。     

岛屿岛礁海域海浪能谱模型研究进展

波浪能谱模型在岛屿岛礁海域的波浪预报研究和海洋工程中应用广泛,但存在模式计算格点无法充分体现岛屿岛礁的复杂地形特征和很难刻画波浪受到岛屿岛礁影响发生变形物理过程等两个关键问题。多重网格嵌套方案、岛屿次网格地形效应计算方案以及非结构网格、无网格、动态自适应四叉树网格等技术在体现岛屿岛礁复杂地形方面取得了较好的效果;将相位解析模型与波浪能谱模型优势互补是提高能谱模型对岛屿近岸波浪变形物理过程计算能力的一个有效方法。开展球坐标系下波作用密度谱方程的自适应四叉树网格求解方法研究,借鉴相位解析模型最新成果完善能谱模式的绕射、反射、底摩擦等物理过程,是提高岛屿岛礁海域海浪精细预报技术水平的前沿性、探索性研究方向。     

浪流耦合数值模式在苏北辐射沙洲海域的应用研究

采用三角形网格海洋模式ADCIRC-2DDI和海浪模式SWAN双向耦合模式,建立了苏北辐射沙洲海域高精度水动力模型,用以研究该海域天文潮-风暴潮-海浪相互作用。以2012年15号台风"布拉万"为例,分别采用WRF气象模型后报风场和台风模型风场进行台风期间水位和波浪场的数值模拟,与实测资料的对比结果显示模型较准确地模拟出了"布拉万"台风期间的风暴增水与海浪过程,但模拟的极值增水和二次增水时间较实测资料提前了3 h左右。对"布拉万"台风期间模拟结果的分析表明:在浅滩及浅滩前沿水域,水位和海流对海浪模拟结果具有显著影响,是否耦合计算的有效波高差异可达1 m以上;波浪对水位的影响具有空间差异,在水深大于15 m的区域,波浪引起的水位变化小于5 cm,在浅滩区域,波浪引起的水位变化在4～10 cm,是否考虑波浪耦合对漫滩区域的模拟结果影响较大,进行浅滩及浅滩前沿的水动力计算,有必要考虑浪流耦合过程。     

南麂海域海浪分布基本特征

根据１９６０－１９８９年南麂海洋站的实测风浪资料，分析了该海域的风浪特征，结果认为：这个海域的浪通常是混合浪，常见浪是三级波高的浪；海浪要素的均值分布比较平稳，极值具有不均匀分布的特性，本区的波高和周期的联合分布表明，波高在０．５－１．９ｍ，周期为４．０－６．９ｓ类型的浪在该海域出现频率最高，此外，引用最大熵谱方法找出了本区波高，周期和风速的主要变化周期，还讨论了台风浪的周期与最大波高的经验关系。     

特征线计算格式下共轭方程两种导出途径的比较

共轭方程的导出是建立资料同化模型的关键，其导出方式有两种途径：AFD形式与FDA形式。在特征线计算格式基础上针对一类较广泛海洋动力控制方程分析了其两种共轭方程（AFD形式与FDA形式）之间的关系，并将理论结果应用于波谱共轭方程的讨论。     

利用共轭方程研究海洋对于大气局域气温的作用

提出了利用共轭方程研究海洋对于局域大气平均气温的作用的方法。在现今海洋基本动力方程基础上导出了球坐标系下的海水温度共辊方程。分析了海水共轭温度的意义，其量值(或垂直梯度量值)表征了不同区域海洋对于局域气温的相应贡献，它在全球海洋中的分布对于局域气候形成与变化研究具有重要意义。     

Euler–Lagrange equations for the spectral element shallow water system

We present the derivation of the discrete Euler–Lagrange equations for an inverse spectral element ocean model based on the shallow water equations. We show that the discrete Euler–Lagrange equations can be obtained from the continuous Euler–Lagrange equations by using a correct combination of the weak and the strong forms of derivatives in the Galerkin integrals, and by changing the order with which elemental assembly and mass averaging are applied in the forward and in the adjoint systems. Our derivation can be extended to obtain an adjoint for any Galerkin finite element and spectral element system.We begin the derivations using a linear wave equation in one dimension. We then apply our technique to a two-dimensional shallow water ocean model and test it on a classic double-gyre problem. The spectral element forward and adjoint ocean models can be used in a variety of inverse applications, ranging from traditional data assimilation and parameter estimation, to the less traditional model sensitivity and stability analyses, and ensemble prediction. Here the Euler–Lagrange equations are solved by an indirect representer algorithm.     

海浪同化预报模型理论基础

将共轭变分同化方法应用于 LAGFD- WAM海浪数值模式 ,导出了海浪谱能量平衡方程的共轭方程以及风输入、破碎、底摩擦、波波非线性相互作用和波流相互作用的相应共轭源函数 ,建立了海浪同化模型 ,数值计算仍采用特征线嵌入计算格式 ,为合成孔径雷达波谱反演资料和卫星高度计有效波高资料同化奠定理论基础     

Approximate Variational Method for Ocean Data Assimilation

An approximate variational method is proposed to assimilate an oceanographic data set with a numerical ocean model. In the approximate method, the adjoint equation to a governing equation is derived and then converted to a finite difference form, in contrast to the ordinary, exact variational method which is composed of a finite difference equation adjoint to the finite difference governing equation. A cumbersome derivation of the adjoint equation is avoided, and finite difference schemes used for the original governing equation are easily utilized for the adjoint equation. This method has been verified with twin experiments. The flow field in the twin experiments is composed of dipole eddies in a two-layer quasi-geostrophic model. Initial and boundary conditions are control variables. The descent converges towards the exact field within 50 iterations, showing that the fundamental problem of the method (an unstable descent with a large number of iterations) does not appear. The approximate method is promising and should be tried with real data. This revised version was published online in July 2006 with corrections to the Cover Date.     

非线性波波相互作用共轭源函数守恒量的分析

海浪组成波中的四波共振时满足谱作用量、谱能量及动量守恒，在变分同化所建立的波谱共轭方程中，对应于非线性波波相互作用源函数Boltzman积分形式，本文建立了其共轭源函数满足的守恒关系；实际海浪计算时广泛采用Hasselmann et al．(1985)的参数化方法，本文给出其综合作用表示式，证明也满足谱作用量、谱能量及动量守恒，并进一步导出了其共轭源函数中存在的守恒量。所有的共轭源函数守恒量只是对共轭算子而言的，对于共轭波谱则不存在相应的守恒关系。     

Wave Refraction-Diffraction in the Presence of a Current

-Wave refraction-diffraction due to a large ocean structure and topography in the presence of a 'current are studied numerically. The mathematical model is the mild-slope equation developed by Kirby (1984). This equation is solved using a finite and boundary element method. The physical domain is devid-ed into two regions: a slowly varying topography region and a constant water depth region. For waves propagating in the constant water depth region, without current interfering, the mild- slope equation is then reduced to the Helmholtz equation which is solved by boundary element method. In varying topography region, this equation will be solved by finite element method. Conservation of mass and energy flux of the fluid between these two regions is required for composition of these two numerical methods. The numerical scheme proposed here is capable of dealing with water wave problems of different water depths with the main characters of these two methods.     

Stochastic simulations of ocean waves: An uncertainty quantification study

The primary objective of this study is to introduce a stochastic framework based on generalized polynomial chaos (gPC) for uncertainty quantification in numerical ocean wave simulations. The techniques we present can be easily extended to other numerical ocean simulation applications. We perform stochastic simulations using a relatively new numerical method to simulate the HISWA (Hindcasting Shallow Water Waves) laboratory experiment for directional near-shore wave propagation and induced currents in a shallow-water wave basin. We solve the phased-averaged equation with hybrid discretization based on discontinuous Galerkin projections, spectral elements, and Fourier expansions. We first validate the deterministic solver by comparing our simulation results against the HISWA experimental data as well as against the numerical model SWAN (Simulating Waves Nearshore). We then perform sensitivity analysis to assess the effects of the parametrized source terms, current field, and boundary conditions. We employ an efficient sparse-grid stochastic collocation method that can treat many uncertain parameters simultaneously. We find that the depth-induced wave-breaking coefficient is the most important parameter compared to other tunable parameters in the source terms. The current field is modeled as random process with large variation but it does not seem to have a significant effect. Uncertainty in the source terms does not influence significantly the region before the submerged breaker whereas uncertainty in the incoming boundary conditions does. Considering simultaneously the uncertainties from the source terms and boundary conditions, we obtain numerical error bars that contain almost all experimental data, hence identifying the proper range of parameters in the action balance equation.     

Wave dispersion equation in a porous seabed

The wave dispersion equation has played a very important role in the development of ocean surface wave theories. The evaluation of the length of a water wave is an essential example of solving the dispersion relation. Conventional ocean wave theories have been based on an assumption of a rigid impermeable seabed. Thus, the conventional wave dispersion equation can only be used in the case of a wave propagating over a rigid impermeable seabed. For waves propagating over a porous seabed (such as a sandy bed), the conventional dispersion relation is no longer valid because of the absence of the characteristics of the porous seabed. The objective of this study is to establish a new wave dispersion equation for waves propagating over a porous seabed. Based on the new relation, the effects of a porous seabed on wave characteristics (such as the wavelength and wave profile) are discussed in detail.     

Marine geodesy— a direction for the future

The sensitivity of the ocean mixed layer response to different parameters such as model horizontal resolution, vertical temperature gradient and eye size is investigated in response to moving Indian Ocean cyclone. For this, a one and one-half layer wind-driven reduced-gravity ocean model is forced with synthetic cyclonic vortex. The sensitivity studies are carried out for a cyclone moving along idealized tracks, initially and then for three observed cyclones (TC 01A), (TC02B) and (TC04A) during 2004. Increasing model resolution resulted in stronger ocean response. The role of initial vertical temperature gradient in modulating the ocean response is found to be important.