风对二维极值波作用的数值研究

实际海域中风浪往往共存,当极值波浪出现时,风会对其特性产生很大影响。为了研究风对极值波浪特性的影响规律,该文基于势流理论建立自由水面满足完全非线性边界条件的风浪混合作用数值水槽模型,通过实时模拟造波板运动产生入射波,并基于波群聚焦原理定点产生极值波浪,利用改进的杰弗里斯遮蔽原理(Jeffreys'sheltering mechanism)将风压引入到自由水面动力边界条件中。在时域模拟中,采用混合欧拉-拉格朗日方法追踪瞬时水面,利用格林第二定理建立了边界积分方程,采用高阶边界元方法进行离散求解。通过与已发表实验结果对比验证模型的准确性,进而开展数值实验研究风对极值波浪水动力特性的影响,包括聚焦幅值、聚焦位置和极值波高随风速的变化以及波群聚焦和解焦过程波浪演变特性等。     

机械式造波机的机构设计及其运动性能分析

为满足实验室进行水槽试验时对波浪的要求，在机械式造波机机构简图的基础上进行了严格的理论分析，并提出了机构设计所遵循的一般原则：①涡轮电机输出转盘的半径r0应尽可能小；②系数比ι2／ι3（涡轮电机输出转盘中心至造波机摇板转动点的距离ι2与摇板转动力臂ι3之比）尽可能大。通过数值计算研究了造波机摇板的运动特性，表明造波机摇板的运动规律是简谐的，造出的波浪也符合简谐规律。同时指出，造波机摇板平衡位置的偏移角与系数比相关，系数比越大，则偏移角越小。     

基于动量源方法的黏性流数值波浪水槽

以N-S方程为控制方程,采用VOF方法追踪自由面,通过在动量方程中添加附加源项的方法,发展了黏性流数值造波和消波的方法。基于Fluent求解器,建立了同时具有造波和消波功能的二维数值波浪水槽。进行了数值模拟分析,表明了数值造波和消波的有效性,并成功地数值模拟了在黏性流理论框架中水波与两个垂直刚性薄板相互作用产生的驻波等现象。     

无反射不规则波造波机系统的研究

水槽不规则波的波浪试验中，造波机和建筑物之间波浪的多次反射是影响试验精度的重要方面，本文给出了水槽中不规则波造波机无反射造波的方法，提出了不规则波代表频率的确定方法，长时间造波试验研究结果表明，该文提出的方法是有效的。     

规则波中弧形返浪墙的非线性水动力载荷数值模拟

运用基于FLUENT软件平台的二维数值波浪水槽,采用流体体积(VOF)方法处理波浪自由面,应用"解析松弛"方法实现了数值造波-消波。模拟规则波下不同返浪墙断面形式情况下的流场和水动力。应用直墙驻波理论解和物理模型试验结果验证了数值波浪水槽的可行性。比较波浪力的数值模拟与物理模型试验结果可以发现,水动力冲量的均方差小于水动力最大值的均方差,且水动力冲量的误差也小于水动力最大值,说明以冲量作为特征量能更好地描述水动力载荷的变化。在给定堤顶超高的条件下,不同堤脚超高和弧形返浪墙高度的组合对越浪量有明显影响:低弧趾超高和大半径弧面组合有利于降低越浪量,但水动力载荷也较大;高弧趾超高和小半径弧面组合越浪量较大。     

黏性波浪场与半潜平台相互作用的数值模拟

以N-S方程为控制方程,采用动量源方法,结合追踪自由面的VOF方法,基于FLUENT求解器,建立了同时具有造波和消波功能的数值波浪水槽.利用该数值水槽对黏性波浪场与半潜平台的相互作用问题进行了数值模拟,获得了黏性波浪场作用下半潜平台水动力载荷及其立柱表面波浪爬高的时历特性.研究表明,利用所建立的数值波浪水槽来研究黏性波浪场与深海平台非线性相互作用是一条有效的途径.     

VOF方法模拟波浪槽中二维非线性波

造波板运动生成非线性波问题是研究物体与波浪非线性相互作用的典型例子。本文研究了用ＶＯＦ方法模拟波浪水槽生成非线性波（孤立波和椭圆余弦波）的问题，为实现造波板在计算中可以做穿越网格的大幅值运动，本文采用在压力迭代中调整造波板邻近单元中压力来满足造波板上流体运动条件。对开路边界条件和自由表面与物面交点处边界条件也提出了处理方法，计算结果与实验结果和解析结果进行了对比。     

造波板运动造波的实时模拟

基于势流理论和时域高阶边界元方法,建立了完全非线性数值波浪水槽模型,通过实时模拟造波板运动来产生波浪.采用混合欧拉-拉格朗日方法追踪流体瞬时水面,运用四阶Runga-Kutta方法更新下一时间步的波面和速度势,同时应用镜像格林函数消除了水槽两个侧面和底面上的积分,在水槽末端布置人工阻尼层消除反射波浪,通过加速势的方法准确计算速度势的时间导数.利用所建模型分别对规则波和不规则波进行了模拟研究,得到了稳定的波形,与试验结果、理论结果和已发表结果均吻合良好,同时计算了造波板做单一频率运动产生的非线性波浪力.     

带异形块体海堤越浪的数值模拟

该文在FLUENT软件平台上，发展了数值消波-造波技术，通过在动量方程里添加多孔介质源项，建立了带有多孔介质模型的二维数值波浪水槽。应用该数值波浪水槽，数值模拟了在斜坡堤坡面上铺设异形块体情况下的越浪过程，给出了越浪量。为了率定异形块体的等效惯性阻力系数，进行了典型工况的物理模型实验，给出了在斜坡堤坡面上不同位置处铺设一层异形块体情况下多孔介质模型的等效阻力系数。     

基于VOF方法的数值波浪水槽以及造波、消波方法研究

该文基于不可压缩黏性流体的N-S方程和VOF方法,利用CFD商业软件FLUENT及其二次开发功能,发展和提出了动边界造波、多孔介质消波等多种数值方法,建立了可有效模拟弱非线性波的数值波浪水槽.同时对现有的几种造波-消波方法进行了详细的分析,综合比较了不同方法的优劣性,指出了本文提出的多孔介质消波法可更有效的吸收波能,给出了造波-消波的最优配置.     

THREE-DIMENSIONAL NUMERICAL SIMULATION OF WAVE SLAMMING ON AN OPEN STRUCTURE

The three-dimensional numerical simulation of wave slamming on an open structure in the splash zone is carried out based upon the Volume Of Fluid (VOF) method.A wave basin is established by solving the...     

Comparison between wave generation methods for numerical simulation of bimodal seas

This paper describes an investigation of the generation of desired sea states in a numerical wave model. Bimodal sea states containing energetic swell components can be coastal hazards along coastlines exposed to large oceanic fetches. Investigating the effects of long-period bimodal seas requires large computational domains and increased running time to ensure the development of the desired sea state. Long computational runs can cause mass stability issues due to the Stokes drift and wave reflection, which in turn affect results through the variation of the water level. A numerical wave flume, NEWRANS, was used to investigate two wave generation methods: the wave paddle method, allowing for a smaller domain; and the internal mass source function method, providing an open boundary allowing reflected waves to leave the domain.The two wave generation methods were validated against experimental data by comparing the wave generation accuracy and the variance of mass in the model during simulations. Results show that the wave paddle method not only accurately generates the desired sea state but also provides a more stable simulation, in which mass fluctuation has less of an effect on the water depth during the long-duration simulations. As a result, it is suggested that the wave paddle method with active wave absorption is preferable to the internal wave maker option when investigating intermediate-depth long-period bimodal seas for long-duration simulations.     

THE LONG WAVE OSCILLATIONS IN HARBORS WITH ABSORBING BOUNDARY CONDITIONS

This paper employs finite element method to solve shallow water equations withabsorbing boundary conditions(the third kind,mixed boundary conditions).It is of practicalimportance in the cases that the land boundaries of the coastal area are made of porous mediumallowing sea water flow in or out.The absorbing boundary conditions are treated as naturalboundary conditions in wave equation finite element model.The numerical results for rectangu-lar and quarterly annular harbors indicate that the numerical solutions agree very well with ana-lytic solutions,which are also given in this paper.It is found that the land boundary absorbabili-ty may be significant to long wave oscillations,such as tidal waves in coastal harbors.     

改进的非线性波传播数值模型的验证和应用

基于吸收入射边界上反射波的方法,并通过将统一边界条件表达式推广到适应不规则波的情况,改进了非线性波传播的数值模型.将利用模型的线性版本(略去非线性项)所计算得到的台阶地形上波浪的反射和透射系数与相应的解析解进行了定量比较.在斜坡地形上数值模拟了不规则波的传播,并将数值结果和物理模型实验值进行了比较.在下游边界分别为开边界和全反射边界的等水深的水槽内数值模拟了不规则波的传播变形,讨论了非线性作用的影响.在侧边界和下游边界均为全反射的固壁边界、二维的等水深水域内,数值模拟了波浪斜向入射时所产生的波浪变形.计算结果表明,对上述各种算例,改进后的非线性波传播数值模型均能进行有效地数值模拟.     

REFLECTION AND TRANSMISSION OF WATER WAVES BY POROUS VERTICAL PLATES

The reflection and transmission of small amplitude surface waves by two verticalporous plates with spacing L fixed in the middle of an infinitely long channel of constant depthare studied.Analytical solutions in closed forms are obtained for the surface wave profiles.It isfound that,when the spacing L is a quarter-wavelength plus a multiple of the half-wavelength ofthe incident wave,not only the reflected wave amplitude but also the transmitted wave amplitudereduce to minima.On the other hand,when the spacing L is a multiple of the half-wavelengthof the incident wave,both the reflected wave amplitude and the transmitted wave amplitude havethe maximum values.For these two special cases,the energy dissipation caused by the twoporous plates and the water between them are also discussed.     

THE STATISTIC CHARACTERISTICS OF IRREGULAR BREAKING WAVE FORCES ON VERTICAL WALLS

ＴＨＥＳＴＡＴＩＳＴＩＣＣＨＡＲＡＣＴＥＲＩＳＴＩＣＳＯＦＩＲＲＥＧＵＬＡＲＢＲＥＡＫＩＮＧＷＡＶＥＦＯＲＣＥＳＯＮＶＥＲＴＩＣＡＬＷＡＬＬＳ￥ＬｉＹｕ－ｃｈｅｎｇ；ＬｉｕＤａ－ｚｈｏｎｇ（Ｄｅｐｔ．ｏｆＣｉｖｉｌＥｎｇｉｎｅｅｒｉｎｇ，Ｄａｌｉａｎ...     

海啸波引起的近岸房屋局部冲刷试验

基于波浪水槽,分别考虑独栋和房屋群两种情况,开展海啸波引起的近岸房屋局部冲刷试验研究,分别建立了独栋房屋情况下相对最大冲刷深度与海啸波相对越顶高度关系式和房屋群情况下局部最大冲刷深度与海啸波波高、房屋宽度、房屋高度、房屋数量、房屋间的中心间距的关系式。试验结果表明在海啸波越顶水流产生的水跌以及海啸波通过房屋时产生的扰流共同作用下,房屋周围,特别是海侧会产生明显的局部冲刷坑;回落水流水跌是局部冲刷坑产生的主要因素,扰流是次要因素。所建立的关系式揭示了最大局部冲刷深度与海啸波、房屋尺寸、房屋布局的内在联系。     

NUMERICAL SIMULATION OF IRREGULAR WAVE-SIMULATING IRREGULAR WAVE TRAIN

In real sea states, damage incidents on offshore floating structures are not due to the whole time series of wave elevation characterized as statistical one but due to few extreme waves or wave groups in irregular wave train. So, using CFD tools to precisely simulate predetermined irregular wave train will lay sound basis for understanding the local characteristic of the flow field and impact loads on offshore floating structures when damage incidents occur. In this article, the generation of single extreme wave is investigated in a numerical wave tank. First, experimental irregular wave train is decomposed into certain number of small-amplitude waves. The Fourier series expansion is performed to determine the amplitude and initial phase angle of each wave component. A hydrodynamic transfer function is used to calculate the amplitude of wave-maker motion associated with each wave component. Then superposition is carried out on all of the wave-maker motion components to get the final wave-maker motion. With the wave-maker motion as input, simulation of the single extreme irregular wave train is modeled successfully. Then the method is applied to simulating a much more complicated irregular wave train. Once again main features of the complicated irregular wave train are reproduced compared with experiment carried out in the new deepwater experimental basin at Shanghai Jiao Tong University. In the simulation, dynamic mesh method is enabled to model the piston-type wave-maker, the Volume Of Fluid (VOF) method is employed to capture the free surface and a dissipation zone is introduced to deal with wave reflection.     

水平多孔板导致之近岸陷波

在本文中，利用线性水波理论和本征函数展开方法，我们研究了附有一沉放在一定深度水下的水平多孔介质板之垂直岸壁的水波反射问题，数值模拟了水平多孔板的消浪特性，我们发现，通过在岸会加一水平的多孔人质薄板之后，将增加近岸处波浪反射和散射过程的复杂性，导致陷波现象发生，具有恰当可渗性能的多孔介质薄板将具有消浪特性，这时板的行为就象一个波浪吸收器一样，从而减少了岸壁的反射能力，降低了岸壁处及其临近的波高，板越     

ANALYTICAL STUDY OF WAVE MAKING IN A FLUME WITH A PARTIALLY REFLECTING END-WALL

Based on the eigenfunction expansion technique, the wave generation by a piston wave maker in a wave flume with a partially reflecting end-wall is studied. The corresponding velocity potential and wave elevation in the flume are obtained. The present analytical solution is verified by the numerical results obtained from a time-domain higher-order boundary element method in a closed flume. Numerical experiments are further carried out to study the difference between the partial/full reflection boundary and the transmission boundary and the effects of the reflection coefficient and the motion period of the wave maker on the wave height. Meanwhile, the natural frequency of the wave flume can be obtained from the analytical expression. The resonance occurs when the motion frequency is equal to the natural frequency. Even the partial reflection of the end-wall in the wave flume experiments has a great influence on the wave height, therefore, inaccurate measurements would be resulted in long-time simulations, especially when the wave frequency approaches the wave flume natural frequency. The present study can serve as a guidance for the physical experiment in wave flumes.