基于水槽实验的近岸波浪破碎计算研究

将前人波浪破碎计算及判定公式进行汇总、整理并分成3类;同时,为了对选取公式进行比较,文还将上述公式分为两类破碎波高计算模型,一类是直接计算模型;另一类是联立拍岸浪波高计算模型与破碎判据,建立的间接计算模型。在此基础上,结合实验数据,对破碎波高和破碎指标进行误差分析得出,间接计算模型中,Goda提出的破碎判据效果最好,为下一步拍岸浪精细化预报以及其区域计算模型的建立提供参考。     

直墙前破波波浪力──对修正过的Gota方法的探讨

对被重新修正后的Goat在墙波压力计算方法进行了分析，主要是对其无因次波浪力随基床肩宽和相对波高的变化进行分析，结果发现，Goat法计算的无因次波浪力随基床肩宽的变化，有一最不利肩宽，此不利肩宽与相对波高无关；在同一水深条件下，Goat法计算的无因次波浪力随相对波高的增大而增大。此两点与试验数据不符。     

可控深水破碎波的实验室生成方法研究

实验室一般采用波浪聚焦方法生成深水破碎波,通过各组分波浪的波幅叠加生成一个波高显著增大的大波,使其波陡超过极限波陡发生破碎。利用该方法生成深水破碎波浪的破碎次数通常并不唯一,导致波浪破碎后的流场特征不明显;造波参数不易于选取导致研究工况的设置难度大,直接影响深水破碎精细化实验的效果和效率。本文采用聚焦波理论计算波面,并利用上跨零点法定义的波高和波长计算理论波陡,结合物理模型实验统计波浪沿程破碎次数与剧烈程度,研究以JONSWAP谱为造波输入谱型时,聚焦波幅、谱峰频率、频宽等造波输入参数对于波浪破碎情况的影响,从而建立深水波浪破碎次数与造波输入参数之间的近似定量关系,为实验造波参数的选取提供参考,提高实验效率。     

波浪在珊瑚礁地形上破碎特性试验研究

对波浪在珊瑚礁地形上的传播特性进行了物理试验研究,将珊瑚礁地形简化为坡度为1∶5的陡坡(向海坡)加较长水平礁坪段的地形,对规则波和不规则波在该地形条件下的波浪破碎及波高沿程衰减进行了研究。结果表明,波高较小时,波浪破碎发生在礁坪上,但随着入射波高的增大,破碎位置逐渐向来浪方向移动,直至在向海坡段破碎。对于在礁坪上破碎的波浪,相对水深db/L0一定的条件下,破碎波高与入射波陡H0/L0相关,且变化趋势受相对水深db/L0的影响。同时给出了该地形条件下波浪破碎指标以及礁坪段破碎后沿程波高的计算公式。     

珊瑚礁地形上破碎波高试验研究

破碎波高是珊瑚礁地形上波浪演化的重要参数之一,对工程安全和海岸变形具有重要影响。通过二维波浪水槽,对珊瑚礁地形上破碎波高进行试验研究,分析破碎波高随波陡、礁坪水深以及礁前斜坡坡度的变化。研究表明,相对破碎波高随相对礁坪水深的增大而增大,随入射波陡的增大而减小,但礁前斜坡坡度对相对破碎波高的影响并不明显。通过引入相对礁坪水深,将经典的破碎波高计算公式拓展至珊瑚礁地形上破碎波高的计算。该公式计算值与前人的试验值进行对比验证,吻合较好。研究成果可为工程实践和数值模拟提供参考与借鉴。     

直墙前破波波浪力

对被重新修正后的Ｇｏａｔ直墙波压力计算方法进行了分析，主要是对其无因次波浪力随基床肩宽和相对波变的变化进行分析，结果发现，Ｇｏａｔ法计算的无因次波浪力随基床肩宽的变化有一最不利肩宽，此不利肩宽与相对波高无关；在同一水深条件下，Ｇｏａｔ法计算的无因次波浪力随对波高的增大而增大。此两点与试验数据不符。     

近岸破碎波高概率分布研究

引入极限波高是随机变量的概念，将近岸破碎波的波高概率分布用形式不同的未破碎波高的概率密度和已破碎波高的概率密度的相加来表示，提出了一种新的破碎波高概率分布形式。认为破碎带内的波高总体上服从瑞利分布，其中已破碎波高的概率密度按总波高的概率密度等比例分布于整个波高范围，破碎概率和当地均方根波高与极限特征波高之比有关。实验表明，本文提出的近岸破碎波高概率分布较好地体现了近岸波浪的破碎特征。     

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。     

岛礁地形上斜坡堤前破碎波流场数值模拟研究

基于SPH方法建立波浪数值水槽,对岛礁地形上的波浪传播变形进行了数值模拟,分析了岛礁地形上波浪破碎过程的波高和水质点波动流速分布,并采用波浪水槽物理模型试验数据进行对比验证。结果表明,该模型可以较准确地模拟岛礁地形上波浪破碎引起的波高和波动流场沿程变化。在此基础上模拟了礁坪上建设斜坡堤后的波动流场,分析了斜坡堤对礁坪上流场形态、沿程波高、波动流速垂向分布及近底流速的影响。结果表明：在建设斜坡堤后,礁坪上波浪破碎更加猛烈,波浪破碎点前移;沿程波高与波动流速受反射波影响明显,沿程波高变化呈现为先增大、再减小、再增大,最后在防波堤堤脚处减小,近底流速变化趋势则与之相反;在堤前半倍波长范围内反向近底流速峰值较非岛礁地形上规范公式计算值增幅较大。     

近岸波浪数值计算中两种动边界处理的比较

在近岸波浪数值计算中,动边界处理是不可避免的问题。文章基于Boussinesq方程的FUNWAVE-TVD模式,引入窄缝法对波浪水槽实验进行数值模拟,比较窄缝法和干湿网格法的波浪数值计算结果;设计多种周期和波高的波浪数值试验,分析两种动边界处理下数值计算结果的差异。结果表明,两种动边界处理对近岸波浪破碎的数值模拟有影响,对波浪漫滩区的计算影响尤为显著。     

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.     

基于波形不对称性的波浪破碎指标

为了探寻波浪破碎与波形不对称性的关系,通过对1/200缓坡上波浪破碎实验研究结果的进一步分析,运用最小二乘法,拟合了波形不对称性参数与相对水深的关系,以及用波形不对称性参数表示的波浪破碎指标表达式。所得规则波的结果与Kjeldsen的深水波结果相同,而不规则波的结果比规则波的小。研究还表明,这一破碎指标与相对水深有关系,随着水深变浅,指标值增大。     

The wave transformation and breaking phenomena in shallow water

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Breaking solitary wave evolution over a porous underwater step

Solitary wave evolution over a shelf including porous damping is investigated using Volume-Averaged Reynolds Averaged Navier–Stokes equations. Porous media induced damping is determined based on empirical formulations for relevant parameters, and numerical results are compared with experimental information available in the literature. The aim of this work is to investigate the effect of wave damping on soliton disintegration and evolution along the step for both breaking and non-breaking solitary waves. The influence of several parameters such as geometrical configuration (step height and still water level), porous media properties (porosity and nominal diameter) or solitary wave characteristics (wave height) is analyzed. Numerical simulations show the porous bed induced wave damping is able to modify wave evolution along the step. Step height is observed as a relevant parameter to influence wave evolution. Depth ratio upstream and downstream of the edge appears to be the more relevant parameter in the transmission and reflection coefficients than porosity or the ratio of wave height–water depth. Porous step also modifies the fission and the solitary wave disintegration process although the number of solitons is observed to be the same in both porous and impermeable steps. In the absence of breaking, porous bed triggers a faster fission of the incident wave into a second and a third soliton, and the leading and the second soliton reduces their amplitude while propagating. This decrement is observed to increase with porosity. Moreover, the second soliton is released before on an impermeable step. Breaking process is observed to dominate over the wave dissipation at the porous bottom. Fission is first produced on a porous bed revealing a clear influence of the bottom characteristics on the soliton generation. The amplitude of the second and third solitons is very similar in both impermeable and porous steps but they evolved differently due to the effect of bed damping.     

Numerical Study on Breaking Criteria for Solitary Waves

Studies of the breaking criteria for solitary waves on a slope are presented in this paper. The boundary element method is used to model the processes of shoaling and breaking of solitary waves on various slopes. Empirical formulae that can be used to characterize the breaking of solitary waves are presented. These include the breaking index, the wave height, the water depth, and the maximum particle velocity at the point of breaking. Comparisons with the results of other researches are given.     

波浪破碎下湍流混合的实验研究

波浪破碎过程产生的湍流动量和能量垂向输运对于加快海洋上混合层中垂向混合具有显著效果.采用二维实验室水槽中对波浪破碎过程进行模拟.对采集的波浪振幅时间序列采用希尔伯特变换定位破碎波位置,波浪的破碎率随有效波高的增加而增大,波浪谱分析得到的波浪基本周期与有效周期结果相似.实验中采用粒子图像测速技术(particle ima...     

Breaking Criteria for Regular Waves on Gentle Slopes

Nelson pointed out that the wave breaking criterion(H/d)_b for gentle slopes(i<1/100),inwhich H is the wave height and d is the water depth at the breaking point,is smaller than that for beachslopes of i>1/100),i.e.,the value of(H/d)_b for gentle slopes may be smaller than 0.6.Goda indicatedthat the wave breaking criterion given by himself is a result based on theoretical study,so it should be alsocorrect and can be used for gentle beaches,i.e.,the value of(H/d)_b for gentle slopes may be still largerthan 0.7.By use of high order nonlinear wave theory,this problem is analyzed in this study and the reasonwhy there is a large difference between different studies is explained.Moreover,the bottom energy loss dur-ing wave propagation is considered and the critical slope for the absence of wave breaking is also analyzed.     

Comparisons of Computational and Experimental Results of Solitary Wave Breaking

- In this paper, the solitary wave deformation along a gentle slope and the impact pressure, on the wall are investigated experimentally and the results are compared with numerical results obtained based on the volume of fluid (VOF) method. The topography used in the experiment consists of three segments. The left segment is a 1:4 slope, the middle segment 1 :SO slope and the right segment a horizontal bed. Both the wave heights and breaking points obtained from numerical simulation and experiments are in good agreement. Numerical results give reasonable pressure distributions of breaking waves on the wall.     

破碎波群的显著特征指标

群发性是风浪破碎的显著特征,最近的研究表明风浪破碎研究应该基于波群而不是单个波。本文探讨破碎波群区别于非破碎波群的显著特征指标。依据一系列风浪破碎实验数据,采用多种判据与实验现场目测的破碎标记信号相结合的原则划分破碎波群与非破碎波群,考查波群特征量、单个波几何特征量、局地破碎判据指标、波包络几何特征量以及波群能量结构特征量等5大类28个指标在破碎波群与非破碎波群上的分布差异。结果表明:波陡、峰前波陡、瞬时波面斜率、运动学判据指标和动力学判据指标等在破碎非破碎波群上的分布几乎没有交叠;后两者尤为理想,分布明显分离,是破碎波群区别于非破碎波群的显著指标;而其它各指标在破碎波群非破碎波群上的分布都有不同程度的交叠,不能单独依据它们区分破碎波群与非破碎波群。