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1.
根据Kjeldsen对畸形波的定义：波高大于有效波高的2倍（H/H1/3＞2）,基于实测波浪资料,统计分析了江苏射阳海域和广东南澳海域的畸形波个数和波浪要素。江苏射阳海域畸形波发生概率为0.005 7%,广东南澳海域畸形波发生概率为0.007%。用Rayleigh分布、双参数Weibull 分布和MER分布对实测数据得到的特征波高进行了拟合,研究了海域内畸形波发生的概率分布。拟合结果表明：MER分布更适合描述两个海域畸形波的发生概率,两个海域畸形波的发生概率均高于Rayleigh分布和Weibull分布。在测量数据期间,台风在海域过境可能增加畸形波的发生概率;同时两个海域的双峰谱占比为22.7%和5.8%,可能也是导致畸形波发生概率增加的原因之一。 相似文献
2.
跨海大桥桥墩基础施工若采用双壁钢围堰,则在其外壁进行开孔可有效减小波浪力,有利于降低钢围堰的制作造价和提高基础施工的安全性。以某跨海大桥基础施工采用的双壁圆形钢吊箱围堰为研究对象,引入波浪力折减系数Kd对消波效果进行评价,采用数值方法着重分析波浪参数和围堰自身结构设计参数对消波效果的影响规律。结果表明:Kd随波陡增大呈先快后缓的增大趋势,波陡超过0.032后,消波效果基本不再变化;随着相对水深的增大,Kd呈先减小后增大并趋缓的规律,在相对水深d/L约为0.455时取得最小值;Kd随开孔率的增大呈线性减小,开孔率越大,消波效果越好。随着双壁间距s的增大,Kd总体上呈减小趋势,且减小速率先快后慢;双壁间距较小时,开孔的消波作用较弱。开孔率和双壁间距两种因素间存在耦合作用,两者越大,其耦合作用也越强。围堰设计中可适当增大开孔率并选取合适的双壁间距以得到最佳消波效果。 相似文献
3.
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。 相似文献
4.
本文提出了一种倾斜挡浪板式桩基透空型防波堤,通过物理模型试验对规则波作用下防波堤的消浪性能进行了研究。试验中观测了桩基透空型防波堤迎浪侧和背浪侧波面的变化过程,探讨了不同入射波浪条件下防波堤挡浪板的开孔率ε和布置形式B对其消浪性能的影响,分析了防波堤的反射系数Kr、透射系数Kt以及波能耗散系数Kd随着相对波高H/D和相对堤宽W/L的变化关系,并从波浪能量分布的角度分析此种防波堤的消浪机理。研究结果表明,单层挡浪板的开孔率自30%降低至10%,平均透射系数可减小约24.3%,平均耗散系数可增长约12.8%;双层挡浪板防波堤的反射系数取决于前排挡浪板的开孔率,透射系数取决于挡浪板组合中的最小开孔率。 相似文献
5.
南沙群岛珊瑚岛礁众多,大多数岛礁具有向海坡陡峭、外礁坪比较平缓的特征。将南沙群岛岛礁的迎浪向地形概化为陡坡和缓坡组成的双斜坡,采用FUNWAVE-TVD模式数值模拟概化地形上的波浪,根据模拟的破碎波高分析其拍岸浪特征。对拍岸浪数值模拟结果进行比较分析,向海坡的坡度对拍岸浪影响不大,外礁坪上拍岸浪高随地形坡度增大而略有增大;向海坡和外礁坪交界位置(即坡折点)水深对拍岸浪有比较明显的影响,拍岸浪高随坡折点水深增大而减小;拍岸浪高随入射波高和波周期增大而增大。利用大量的拍岸浪数值模拟数据对国内外5种统计模型进行检验,并且基于拍岸浪数值模拟数据建立了3种南沙群岛岛礁拍岸浪统计模型,计算结果显示这些模型适用性较好。 相似文献
6.
Soft computing tools in the form of combination of multiple nonlinear regression and M5'' model tree were used for estimation of overtopping rate at the vertical coastal structures. For reliable and precise estimation of overtopping rate, the experimental data available in the database CLASH were used. The dimensionless overtopping rate was estimated in terms of conventional dimensionless parameters including the relative crest freeboard Rc/Hs, seabed slope tanθ, deep water wave steepness Som, surf similarity ξom and local relative water depth ht/Hs. The accuracy of the new model was compared with other existing models and also evaluated with some field measurements. The results indicated that the model presented in this paper is more accurate than other existing models. With statistical parameters, it is shown that the accuracy of predictions in the new model is better than that of other models. 相似文献
7.
真江蓠是原产于西北太平洋的重要经济红藻。我们利用10对微卫星引物检测中国黄渤海地区真江蓠的群体遗传多样性和结构。10个微卫星位点在12个群体中共检测到65个等位基因，每个位点的等位基因（Na）为1~28，有效等位基因（Ne）为1.0~9.6。每个群体的平均等位基因（Na）、平均有效等位基因（Ne）、平均香浓指数（I）、平均观察杂合度（Ho）和平均预期杂合度（He）分别为2.4、1.6、0.419、0.133和0.227，显示较低的群体遗传多样性。中国黄渤海12个真江蓠群体间遗传分化较大（Fst=0.398 7），基因流有限（Nm=0.377 1），近交系数为正（Fis=0.391 3，Fit=0.634 0），表明可能存在近交和杂合子缺失现象。Structure和UPGMA系统进化分析一致将12个群体分为两个遗传组，并在黑石礁群体（HS）和石岛群体（SD）中发现明显的遗传混杂现象。AMOVA分析显示遗传变异主要来自于群体内（73.27%）。该研究可为黄渤海地区真江蓠自然资源保护和管理提供科学依据。 相似文献
8.
瓯江口是一个径流量变化剧烈的强潮河口。本文基于非结构网格FVCOM模型，建立瓯江口海域大范围三维数学模型，研究不同时间尺度（潮周期、大-小潮）的盐度变化，并利用势能异常动力方程对数值模拟结果分析了瓯江口层化过程的动力机制。同时，利用河口Ri数和层化参数△s/<s>研究了不同时间尺度的层化稳定性及其空间变化，得出决定层化状态的潮差和径流量的阈值。结果显示：瓯江北口上段、中段和口门在潮差分别超过3.8m、4.0m和4.6m时呈完全混合状态。当径流量小于280 m3/s或大于510 m3/s，北口上段持续完全混合；而在口门附近，完全混合和层化的临界径流量约为280 m3/s。研究认为瓯江河口北口存在周期性的层化，北口下段在落潮和涨潮初期呈部分混合状态，而其它时段为完全混合。上段只在落潮初期存在层化。层化增强主要是纵向对流与横向速度剪切导致，而湍混合和纵向潮应力是层化减弱的主要因素。 相似文献
9.
为了探究岛屿周围珊瑚礁在抵御海啸灾害中的作用,采用激波捕捉类Boussinesq模型FUNWAVE-TVD,对孤立波在理想化三维岛礁地形上的传播及爬坡开展了现场尺度的平面二维数值模拟,分析了入射波高、礁坪水深、礁坪宽度、礁前斜坡坡度、礁后斜坡坡度、珊瑚礁糙率对岛屿四周孤立波爬高分布的影响。结果表明,珊瑚礁的存在总体上可有效降低岛屿四周孤立波的最大爬坡高度;入射波高、礁坪水深、礁坪宽度、珊瑚礁糙率是影响珊瑚岛礁四周孤立波爬坡分布的主要因素,岛礁四周最大爬坡高度会随入射波高和礁坪水深的增大、礁坪宽度和珊瑚礁糙率的减小而不断增大;当礁坪水深增大到一定程度时,珊瑚礁主要会对岛屿背浪面的爬高失去影响,而当礁坪宽度和珊瑚礁糙率减小至一定程度时,会出现岛礁四周最大爬高高于无珊瑚礁时爬高的现象;礁后斜坡的变缓会使岛礁周围的最大爬高有所减小,而礁前斜坡坡度对珊瑚岛礁周围的最大爬高几乎没有影响。 相似文献
10.
通过波浪水槽实验对大糙率礁面存在下珊瑚礁海岸附近规则波非线性特征参数(偏度、不对称度和厄塞尔数)的变化规律进行了研究。实验采用圆柱体阵列来模拟礁面的粗糙度,测试了一系列规则波工况。结果表明:偏度、不对称度和厄塞尔数的幅值分别在珊瑚礁破碎带结束位置、破碎带内和破碎带开始位置达到最大。3个参数的幅值均随着入射波波高的增大而增大;偏度值随着波浪周期的增大而减小,不对称度幅值和厄塞尔数随着周期的增大而增大;偏度值随着礁坪水深的增大而增大,不对称度幅值和厄塞尔数随着礁坪水深的增大而减小。深水厄塞尔数可以用来描述礁坪上波浪非线性参数的变化,最后给出了用其预测礁坪上3个非线性特征参数的经验关系式。 相似文献
11.
Numerical simulations of gravity waves with high-order nonlinearities in two-dimensional domain are performed by using the pseudo spectral method. High-order nonlinearities more than third order excite apparently chaotic evolutions of the Fourier energy in deep water random waves. The high-order nonlinearities increase kurtosis, wave height distribution and Hmax/H1/3 in deep water and decrease these wave statistics in shallow water. Moreover, they can generate a single extreme high wave with an outstanding crest height in deep water. High-order nonlinearities (more than third order) can be regarded as one cause of freak waves in deep water. 相似文献
12.
The Edgeworth’s form of a cumulative expansion of the probability density function (PDF) of surface elevation expands the maximum wave height distribution to predict the occurrence probability of freak waves. This study investigated the enhancement of the occurrence probability of freak waves due to the fourth order moment of surface elevation, kurtosis, change and found that the nonlinear effects on the occurrence probability of a freak wave linearly depends on kurtosis for a small number of waves N=250. The statistical theory was compared with field data, and freak waves sometimes appear when not expected by the Rayleigh theory, but they were predicted by the proposed theory. 相似文献
13.
Long time series of wave field are experimentally simulated by JONSWAP spectra with random phases in a 2D wave flume. Statistic properties of wave surface, such as significant wave height, skewness and kurtosis, are analyzed, and the freak wave occurrence probability and its relations with Benjamin-Feir index （BFI） are also investigated. The results show that the skewness and the kurtosis are significantly dependent on the wave steepness, and the kurtosis increases along the flume when BFI is large. The freak waves are observed in random wave groups. They occur more frequently than expected, especially for the wave groups with large BFI. 相似文献
14.
A nonlinear model for nonbreaking shoaling random waves 总被引：1，自引：0，他引：1
ＡｎｏｎｌｉｎｅａｒｍｏｄｅｌｆｏｒｎｏｎｂｒｅａｋｉｎｇｓｈｏａｌｉｎｇｒａｎｄｏｍｗａｖｅｓＬｉｕＸｉｎ＇ａｎ,ＨｕａｎｇＰｅｉｊｉ,ＣｈｅｎＸｕｅｙｉｎｇ,ＨｕＺｅｊｉａｎ（ＲｅｃｅｉｖｅｄＯｃｔｏｂｅｒ１５,１９９６,ａｃｃｅｐｔｅｄＡｕｇｕ... 相似文献
15.
M. R. Gourlay 《Coastal Engineering》1996,27(3-4)
Wave set-up may be significant in determining water levels on coral reefs particularly in microtidal environments and hence is an important factor for the design of reef-top structures and for the stability of reef-top islands. Laboratory experiments have been made on a two dimensional model of an idealised horizontal reef under two different conditions corresponding to a fringing reef (or closed lagoon) situation and a platform reef (or open lagoon) situation. Both wave set-up on the reef-top and the wave-generated flow across the reef were measured and related to wave and tide level conditions.All other factors being the same, wave set-up is greatest at low tide levels whereas wave-generated flow is greater at higher tide levels. The magnitude of the set-up on a platform reef with a wave-generated flow is less than on a fringing reef without any net flow by an amount equal to the velocity head of the flow across the reef. Dimensionless parameters
and q/√gHo3 are found to be functions of relative submergence parameters hr/Ho or
. For values of (
) Ho > 1 waves break on the reef-top and radiation stress theory can be used to calculate set-up. For (
)Ho < 0.7 waves break on the reef-face and set-up is determined by broadcrested weir control at the reef-edge. (The symbols are defined as follows: g is gravitational acceleration; hr is still water depth over horizontal reef-top; Ho is offreef wave height (equivalent deep water value); q is discharge per unit length of reef edge; T is wave period and
is maximum wave set-up on reef-top.) 相似文献
16.
黄渤海海域波浪时空变化特征分析 总被引：1，自引：0，他引：1
本文利用欧洲中期预报中心(ECMWF)第五代再分析数据集(ECMWF Reanalysis v5 ERA5,ERA5),对中国黄渤海海域2000-2019年的波浪进行了统计分析。得到如下的结论：1.黄渤海海区波浪具有明显的季节性,渤海区域有效波高呈现出周边小,中间大的特点;黄海海域有效波高Hs呈现由南向北降低的趋势;研究区域冬季有效波高均值大于其他季节。2.平均周期T的季节分布类似于有效波高的季节均值分布。渤海仅秋冬季T的均值存在大于4s的区域;黄海海域T的季节分布也呈现由南向北递减的趋势,其中长江口外海区域秋冬季T的季节均值可达6s。3.有效波高距平场EOF分解结果显示,第一模态表明了波浪变化具有明显的季节性特征;第二模态反映了季风的季节转换对有效波高的影响;第三模态代表的可能是地形的变化对有效波高变化的影响。4．代表点统计结果显示：整个渤海地区的常浪向为 NNE~NE,强浪向以 NE和 NNE 为主;黄海海域的常浪向为SSE-SE向,强浪向以 N和 SSE 为主。 相似文献
17.
Experiments were performed in a wave flume to measure the intensity, transmission and reflection of waves breaking over a submerged reef with an offshore gradient of 1:10. The results demonstrate that the relative water depth over the reef crest (hc/Ho) is a dominant factor affecting the breaking characteristics. In particular it is found that as the relative crest submergence is reduced, there is a considerable increase in the intensity of wave breaking over the reef that can be quantified through measurements of the air cavity enclosed beneath the plunging jet. It is also shown that there is a corresponding decrease in wave transmission and reflection as the submergence is reduced. 相似文献
18.
Analysis of freak wave measurements in the Sea of Japan 总被引：3，自引：0，他引：3
This paper presents an analysis of a set of available freak wave measurements gathered from several periods of continuous wave recordings made in the Sea of Japan during 1986–1990 by the Ship Research Institute of Japan. The analysis provides an ideal opportunity to catch a glimpse of the statistics of freak waves in the ocean. The results show that a well-defined freak wave may occur in the developed wind–wave condition: S(f)∝f−4, with single-peak directional spectra. The crest and trough amplitude distributions of the observed sea waves including freak waves are different from the Rayleigh distribution, although the wave height distribution tends to agree with the Rayleigh distribution. Freak waves can be readily identified from the wavelet spectrum where a strong energy density occurs in the spectrum, and is instantly surged and seemingly carried over to the high-frequency components at the instant the freak wave occurs. 相似文献
19.
20.
《Applied Ocean Research》2004,26(1-2):35-48
We present a statistical analysis of some of the largest waves occurring during 793 h of surface elevation measurements collected during 14 severe storms in the North Sea. This data contains 104 freak waves. It is found that the probability of occurrence of freak waves is only weekly dependent on the significant wave height, significant wave steepness and spectral bandwidth. The probability does show a slightly stronger dependency on the skew and kurtosis of the surface elevation data, but on removing the contribution to these measures from the presence of the freakwaves themselves, this dependency largely disappears.Distributions of extreme waves are modelled by fitting Generalised Pareto distributions, and extreme value distributions and return periods are given for freak waves in terms of the empirical fitted parameters. It is shown by comparison with these fits that both the Rayleigh distribution and the fit of Nerzic and Prevosto severely under-predict the probability of occurrence of extreme waves. For the most extreme freak wave in our data, the Rayleigh distribution over-predicts the return period by about 300 times when compared to the fitted model. 相似文献