平缓岸坡上波浪破碎的实验研究

在１／２００的缓坡上进行了规则波与不规则波破碎的实验研究。在本实验条件下,分析了波形的不对称必至波浪破碎指标的影响,并以此对合田良实和Ｎｅｌｓｏｎ关于极平缓坡上规则波破碎指标的分歧作了解释。本文的研究还表明,底坡坡度ｉ、相对水深ｄ／Ｌ。及波形的不对称必至不规则波的破碎指标的影响较小。合田对规则波的破碎指标在不规则波条件下仍然可用,但系数Ａ应取为０．１５。不规则波波长与同周期按线悸理论计算之波长的比     

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。     

珊瑚岸礁破碎带附近波浪演化实验研究

通过波浪水槽实验对珊瑚岸礁破碎带附近波浪演变规律开展研究,实验采用了概化的岸礁模型,测试了4种礁坪水深、4种礁前斜坡坡度和一系列入射波高的组合工况。对破碎带宽度和破碎带附近波浪的入射、反射、透射以及能量耗散进行了测量分析,透射波的计算考虑了礁坪上高次谐波的影响。结果表明:礁坪水深和入射深水波高的比值(即礁坪相对水深)是影响岸礁破碎带附近波浪演化的关键参数,而礁前斜坡坡度的影响在本文测量的范围内可以忽略不计。破碎带宽度与礁坪上浅水波波长为同一数量级,并与礁坪相对水深成反比;透射系数随礁坪相对水深的增大呈线性增长,而反射系数的变化却无类似规律;岸礁能够削弱超过50%入射波能,礁坪相对水深越小,波浪破碎造成的能量耗散越大。     

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。     

三维波浪在岛礁地形上破碎特性试验研究

对三维波浪在岛礁地形上的传播特性进行了物理模型试验研究。为了探究三维波浪在岛礁地形上传播的破碎指标,将岛礁地形简化为1∶5的向海坡与水平礁坪相连的物理模型。对于不同波况下的规则波、不规则波、多向波在该地形上的破碎特性进行了研究。结果表明,在该地形条件下,较大入射波高的波浪均在礁坪上发生破碎,并且随着入射波高的增大,破碎位置向来浪方向移动,破碎指标与入射波陡H_0/L_0相关,斜向波浪传播受入射角度的影响。同时,文中也给出了在该地形下波浪的破碎指标,并将三维结果与二维结果进行了对比。     

礁冠宽度对珊瑚礁坪波浪增水影响的实验研究

通过物理模型实验研究岸礁礁冠宽度变化对礁坪上波浪增水的影响,实验采用概化的岸礁和梯形礁冠模型,在一系列规则波工况下分别测试5种不同宽度的礁冠以及无礁冠模型。实验结果表明:礁冠宽度越大,波浪破碎造成的能量衰减越剧烈;礁冠的存在使礁坪上的波浪增水增大,且礁冠宽度越大,增水值越大;增水随礁冠水深的增大而减小,并引入了一对无量纲参数合理地描述了入射波波要素对增水的影响;运用文献中基于能量守恒的理论模型进一步研究了礁冠宽度对增水的影响,并给出模型中的礁形参数与实测的礁冠相对宽度间的经验关系式;通过分析同一礁冠水深控制下,相对增水随着礁冠相对宽度的变化趋势,发现只有在礁冠充分宽的情况下礁冠水深才是控制礁坪上增水的主要因素。     

波浪非线性对海草消波特性的影响

海草所形成的植物消波体系能有效防止岸线的侵蚀。利用Sánchez-González等的实验数据分析了波浪非线性对海草消波特性的影响。研究结果表明,相对水深和波陡对海草床的波能衰减系数影响依赖于海草淹没度。相对波高一定时,拖曳力系数随相对水深的增大而增大。对给定的相对水深,拖曳力系数随波陡的增大而减小。波浪非线性对于规则波和非规则波海草消波特性的影响并不一致。用无量纲参数（邱卡数、雷诺数、厄塞尔数）表达拖曳力系数的效果取决于拖曳力系数与无量纲参数的关系中是否充分考虑波浪非线性对拖曳力系数的影响。     

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。     

深水破碎波判据的研究：I.破碎波判据的研究概况及计算方法

本文总结了近百年来破碎波判据的研究状况，全面分析了深水波浪破碎的理论与实验研究结果，就深水破碎波判据的研究方法和适用性进行了广泛讨论。给出了各种波浪破碎判据的表达形式及其相互间的换算关系；总结了破碎波实例资料的处理方法。     

海岸波浪多次破碎波能耗散模型

在坡度很缓(接近或小于1∶100)的海岸,波浪在向海岸传播的过程中,可能经历多次破碎,而在两次波浪破碎之间将伴随着波浪恢复(波浪恢复到不破碎状态)。在现有海岸波高计算模型中,波浪破碎是通过波能耗散来模拟的,但所采用的波能耗散模型都不能自动考虑波浪出现多次破碎的过程,特别精确模拟这一过程中出现的波浪恢复。本文提出了解决这一问题的新的波能耗散模型,模型的建立是通过在Dally模型中重新建立稳定波能、饱和波高水深比和波能耗散系数,并引入了波浪恢复的判断条件实现的。该模型的波能耗散在波浪恢复区的值很小故能描述波浪恢复区的波浪运动。与实验结果的对比表明,新模型可以适合缓坡情况波浪多次破碎的波高模拟,而且对不同坡度的平坡和沙坝海岸(1∶100～1∶10)的破碎波模拟都可以给出与实验结果符合的结果,并且可以自动识别多次波浪破碎的存在和波浪恢复的发生。     

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.     

Probabilistic Models for the Probability of Wave Breaking and Whitecap Coverage Based on Kinematic Breaking Criterion

More and more researches show that neither the critical downward acceleration nor the critical slope of water waves is a universal constant. On the contrary, they vary with particular wave conditions. This fact moders the models either for the probability of wave breaking B or for the whitecap coverage W based on these criteria difficult to apply. In this paper and the one which follows we seek to develop models for the prediction of both B and W based on the kinematical criterion. First, several joint probabihstic distribution functions (PDFs) of wave characteristics are derived, based on which the breaking properties B and W are estimated. The estimation is made on the assumption that a wave breaks ff the horizontal velocity of water particles at its crest exceeds the local wave celerity, and whitecapping occurs in regions of fluid where water particles travel faster than the waves. The consequent B and W depend on wave spectral moments of orders 0 to 4.Then the JONSWAP spectrum is used to represent the fetch-limited sea waves in deep water, so as to relate the probahility of wave breaking and the whitecap coverage with wind parameters. To this end, the time-averaging technique proposed by Glazman (1986) is applied to the estimation of the spectral moments involved, and furthermore, the theoretical models are compared with available observations collected from published literature. From the comparison, the averaging time scale is determined. The final models show that the probability of wave breaking as well as the whitecap coverage depends on the dimensionless fetch. The agreement between these models and the database is reasonable.     

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。     

Experimental Study of Wave Breaking on Gentle Slope

—An experimental study of regular wave and irregular wave breaking is performed on a gentleslope of 1:200.In the experiment,asymmetry of wave profile is analyzed to determine its effect on wavebreaker indices and to explain the difference between Goda and Nelson about the breaker indices of regu-lar waves on very mild slopes.The study shows that the breaker index of irregular waves is under less influ-ence of bottom slope i,relative water depth d/L_0 and the asymmetry of wave profile than that of regularwaves.The breaker index of regular waves from Goda may be used in the case of irregular waves, whilethe coefficient A should be 0.15.The ratio of irregular wavelength to the length calculated by linear wavetheory is 0.74.Analysis is also made on the waveheight damping coefficient of regular waves after break-ing and on the breaking probability of large irregular waves.     

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.     

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.     

Numerical Prediction of Regular Wave Breaking on Very Gentle Slopes

Regular wave deformation and breaking on very gende slopes is calculated by Mixed-Eulerian-Lagrangian procedure. The velocity potentials and their normal derivatives on the boundary are calculated through the mixed 0-1 boundary element method. The wave elevation and the potentials of time-stepping integration are detertnined by the 2nd-order Taylor expansion at the nodes of free surface boundary elements. During calculation the x-coordinates of the free surface element nodes are supposed to remain unchanged, i.e. the partial derivatives of wave elevation and potentials with respect to x are considered as zero. The numerical results of asymmetric parameters of breaking waves are verified by experimental study. It is shown that when the wave asymmetry is weak, the maximum horizontal velocity of water particales occurs at the wave peak and, the average ratio of this maximum velocity to wave celerity is 0.96. However, when the wave asymmetry is strong, the maximum horizontal velocity of water particles occu     

The wave transformation and breaking phenomena in shallow water

Ｔｈｅｗａｖｅｔｒａｎｓｆｏｒｍａｔｉｏｎａｎｄｂｒｅａｋｉｎｇｐｈｅｎｏｍｅｎａｉｎｓｈａｌｌｏｗｗａｔｅｒ￥ＬｉＹｕｃｈｅｎｇ（１．ＤａｌｉａｎＵｎｉｖｅｒｓｉｔｙｏｆＴｅｃｈｎｏｌｏｇｙ，Ｄａｌｉａｎ１１６０２３，Ｃｈｉｎａ）Ａｂｓｔｒａｃｔ：...     

关于波浪破碎特性的研究

有关波浪破碎问题的研究是海岸工程界十分关注的课题。本文列举了前人有关波浪破碎特性方面的研究成果；分析了波浪破碎前后波高的变化规律，作出了适当的假定；并考虑了动床海滩坡度、底摩擦以及紊动对波浪破碎特性的影响。应用波动能量耗散率理论，并结合孤立波理论的有关公式，作者推导了计算动床海滩上破碎指标ｒ_ｂ的公式，并进而给出破碎水深ｈ_ｂ与破碎波高Ｈ_ｂ的计算公式。通过不同规模实验水槽的资料验证表明，这组计算式具有广泛的实用性。     

波群内单个波的波陡分布与波破碎

对波群内单个波的波陡分布和波破碎进行了实验研究。研究结果是,波群中波动的最大振幅出现在波群前部而不是出现在波群中央,这种不对称性导致波群前部单个波出现大波陡的概率大于后部单个波出现大波陡的概率;进一步的波破碎统计发现波群前部单个波破碎的频率是后部单个波破碎频率的4倍。因此认为,波群结构的不对称性能够导致单个波发生破碎的...