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1.
The main purpose of this article is to systematically investigate the influence of offshore fringing reef topography on the infragravity-period harbor oscillations. The infragravity (IG) period oscillations inside an elongated harbor induced by normally-incident bichromatic wave groups are simulated using a fully nonlinear Boussinesq model, FUNWAVE 2.0. Based on an IG wave decomposition method, effects of plane reef-face slopes, reef-face profile shapes and the existence of reef ridge on bound and free IG waves and their relative components inside the harbor are comprehensively studied. For the given harbor and reef ridge, the range of the reef-face slopes and the various profile shapes studied in this paper, results show that the amplitude of the free IG waves inside the harbor increases with the increasing of the reef-face slope; while the bound IG waves inside the harbor seem insensitive to it. The effects of the profile shapes on the IG period waves inside the harbor are closely related to the width of the reef face. The existence of the reef ridge can relieve the bound IG waves to some extent when the incident short wave amplitudes are relatively large, while its effects on the free IG waves are negligible. 相似文献
2.
为准确模拟孤立波在岸礁地形上的传播和爬坡,采用基于完全非线性Boussinesq方程开发的Funwave-TVD模型,探究模型的可行性,并利用验证后的模型进一步研究岸礁各地形因素对孤立波爬高的影响。研究结果表明:模型能准确模拟孤立波在岸礁陡变地形上的传播及变形,摩擦系数对礁前陡坡及礁坪上的波浪传播模拟影响不大,但对爬坡预测的敏感性较强;模型空间步长可适当增大,提高计算效率;随着礁坪宽度的增大以及礁后斜坡的变缓,孤立波爬坡高度下降明显,而礁前陡坡坡度变化对孤立波爬坡高度影响不大。 相似文献
3.
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
4.
通过在波浪水槽中进行一系列物理模型实验, 研究珊瑚礁礁坪宽度变化对珊瑚礁海岸附近波浪传播变形及礁坪上波浪增水的影响。物理实验采用理想化的珊瑚礁模型, 测试了3种礁坪宽度下的一系列不规则波工况。实验结果分析表明: 波浪沿礁传播过程中, 短波持续衰减; 低频长波波高沿礁逐渐增大, 直到海岸线附近达到最大; 随着礁坪宽度的增加, 海岸线附近的短波波高呈下降趋势, 低频长波波高的变化规律不显著; 礁坪上的波浪增水受礁坪宽度变化的影响不明显; 通过对海岸线附近的波浪进行频谱分析发现, 礁坪上低频长波的运动存在着一阶共振模式, 且共振放大效应强度受礁坪水深、入射波峰周期和礁坪宽度共同影响。 相似文献
5.
Many low-lying tropical and sub-tropical atolls fringed by coral reefs are susceptible to coastal inundation during extreme wave events. Previous studies have shown that the infragravity (IG) wave is the dominant component of shoreline run-up compared to the sea and swell (SS) wave and the wave-induced setup. To better understand both the SS and IG wave dynamics over a fringing reef with various morphologies, a series of laboratory experiments were conducted in a wave flume based on an idealized fringing reef profile. The shoreline responses of waves to different reef morphologies with/without the reef crest, the lagoon and the reef surface roughness were examined. IG wave resonance on the reef flat was identified by a spectral analysis of the shoreline wave records. Subsequently, a numerical model based on the Boussinesq equations was validated by the experimental data. The model was then applied to investigate the impacts of varying reef morphologic features (fore-reef slope, reef-crest width, lagoon width, and reef roughness coefficient) on the shoreline wave motions. 相似文献
6.
It has been well observed that a reef crest (ridge) may be present at the reef edge, but so far very few published studies focusing on the effects of such reef-crest on the wave dynamics over fringing reefs. To understand the role of a reef-crest configuration in determining breaking-wave induced setup over the reef flat, a series of experiments were carried out in a wave flume using an idealized fringing reef model with a reef crest. Experimental results were reported for a trapezoidal reef crest with five reef-crest widths under a series of monochromatic waves. Also examined was the reef without a reef crest. Data analysis shows that larger energy dissipation associated with smaller surfzone width around the reef edge occurred with a wider reef crest. The maximum wave-induced setup on the reef flat in the presence of the reef crest was significantly larger than that without, and it also increased with increasing reef-crest width. The reef-crest submergence was found to be a primary parameter controlling the magnitude of wave setup on the reef flat provided that the reef crest was sufficient wide. An alternative semi-analytical 1DH model based on the balance of cross-shore momentum was proposed. The model was validated by present laboratory data as well as three existing 1DH laboratory studies. Comparing with other two representative semi-analytical models in the literature showed that the proposed model was capable of better reproducing the maximum wave-induced setup on the reef flat for a variety of reef profiles with/without a reef crest, different reef-crest water levels, as well as both monochromatic and spectral waves. The model parameter was physically related to the two characteristic lengths in the surf zone and its value was dependent on the fore-reef slope as well as the presence of a reef crest. The 1DH model was also satisfactorily applied to a fringing reef in field conditions where the effects of fore-reef friction and back-reef lagoon were not important. 相似文献
7.
Past studies of harbor resonance have mainly been restricted to the quasi-steady oscillations induced by steady wave conditions. This paper investigates the response of a rectangular harbor to subaerial landslide-generated impact waves based on physical models, in order to compare the oscillations induced by steady and transient waves. In response to steady incident waves, oscillations within the harbor need to experience a long process to obtain their maximum value before the input energy and the losses are balanced. Landslide-generated impact waves usually include components with solitary wave characteristics and also components with dispersive wave characteristics. Each component travels with a different celerity. Usually, solitary wave components propagate faster, and arrive in the harbor first. Oscillations attain their maximum status as soon as these components arrive. The subsequently arriving components with dispersive characteristics do not enhance the resonance oscillations. So the waves with solitary characteristics are considered to play an important role in harbor resonance. Numerical experiments, using the FUNWAVE model, were conducted in order to further verify these conclusions. 相似文献
8.
A total variation diminishing Lax–Wendroff scheme has been applied to numerically solve the Boussinesq-type equations. The runup processes on a vertical wall and on a uniform slope by various waves, including solitary waves, leading-depression N-waves and leading-elevation N-waves, have been investigated using the developed numerical model. The results agree well with the runup laws derived analytically by other researchers for non-breaking waves. The predictions with respect to breaking solitary waves generally follow the empirical runup relationship established from laboratory experiments, although some degree of over-prediction on the runup heights has been manifested. Such an over-prediction can be attributed to the exaggeration of the short waves in the front of the breaking waves. The study revealed that the leading-depression N-wave produced a higher runup than the solitary wave of the same amplitude, whereas the leading-elevation N-wave produced a slightly lower runup than the solitary wave of the same amplitude. For the runup on a vertical wall, this trend becomes prominent when the wave height-to-depth ratio exceeds 0.01. For the runup on a slope, this trend is prominent before the strong wave breaking occurs. 相似文献
9.
In the long-wave approximation, we perform the numerical analysis of the plane problem of runup of waves of various shapes
on a sloping beach. We study transformations of the shape of waves flooding the beach and in the course of their subsequent
rundown. The dependence of maximum elevations and lowerings of the sea level on the parameters of the waves approaching the
beach, the depth of the shelf, and the slope of the bottom are investigated. It is shown that the shape of waves affects the
amplitude characteristics of oscillations of the coastline. The heights of the vertical runup of waves incident on a sloping
beach can be several times higher than the amplitude of waves entering the shelf zone. 相似文献
10.
Philip L. -F. Liu 《Coastal Engineering》1986,10(4)
The effects of water depth discontinuity near the harbor mouth on harbor oscillations are examined. Linear long-wave equations are used as the basis of the present study. For simplicity, only the normal incident waves are considered. Assuming that the harbor mouth is small in comparison with wavelength, the method of matched asymptotic expansion is employed to obtain the ocean impedance and the harbor responses. It is found that the incident waves can be trapped over the depth discontinuity which causes large oscillations near the harbor mouth. The radiation damping also decreases because of the appearance of the depth discontinuity, which leads to large amplifications at the lowest mode. 相似文献
11.
Wave elevations and water particle velocities were measured in a laboratory surf zone created by the breaking of a narrow-band irregular wave train on a 1/35 plane slope. The incident waves form wave groups that are strongly modulated. It is found that the waves that break close to the shoreline generally have larger wave-height-to-water-depth ratios before breaking than the waves that break farther offshore. After breaking, the wave-height-to-water-depth ratio for the individual waves approaches a constant value in the inner surf zone, while the standard deviation of the wave period increases as the still water depth decreases. In the outer surf zone, the distribution of the period-averaged turbulent kinetic energy is closely correlated to the initial wave heights, and has a wider variation for narrow-band waves than for broad-band waves. In the inner surf zone, the distribution of the period-averaged turbulent kinetic energy is similar for narrow-band waves and broad-band waves. It is found that the wave elevation and turbulent kinetic energy time histories for the individual waves in a wave group are qualitatively similar to those found in a spilling regular wave. The time-averaged transport of turbulent kinetic energy by the ensemble-averaged velocity and turbulence velocity under the irregular breaking waves are also consistent with the measurements obtained in regular breaking waves. The experimental results indicate that the shape of the incident wave spectrum has a significant effect on the temporal and spatial variability of wave breaking and the distribution of turbulent kinetic energy in the outer surf zone. In the inner surf zone, however, the distribution of turbulent kinetic energy is relatively insensitive to the shape of the incident wave spectrum, and the important parameters are the significant wave height and period of the incident waves, and the beach slope. 相似文献
12.
The random long wave runup on a beach of constant slope is studied in the framework of the rigorous solutions of the nonlinear shallow water theory. These solutions are used for calculation of the statistical characteristics of the vertical displacement of the moving shoreline and its horizontal velocity. It is shown that probability characteristics of the runup heights and extreme values of the shoreline velocity coincide in the linear and nonlinear theory. If the incident wave is represented by a narrow-band Gaussian process, the runup height is described by a Rayleigh distribution. The significant runup height can also be found within the linear theory of long wave shoaling and runup. Wave nonlinearity nearshore does not affect the Gaussian probability distribution of the velocity of the moving shoreline. However the vertical displacement of the moving shoreline becomes non-Gaussian due to the wave nonlinearity. Its statistical moments are calculated analytically. It is shown that the mean water level increases (setup), the skewness is always positive and kurtosis is positive for weak amplitude waves and negative for strongly nonlinear waves. The probability of the wave breaking is also calculated and conditions of validity of the analytical theory are discussed. The spectral and statistical characteristics of the moving shoreline are studied in detail. It is shown that the probability of coastal floods grows with an increase in the nonlinearity. Randomness of the wave field nearshore leads to an increase in the wave spectrum width. 相似文献
13.
基于秘鲁钱凯港的防波堤三维整体模型试验结果,研究了涌浪绕射、透射联合作用对港内波况的影响。分析了不同波向、不同谱峰周期的入射波条件下港内不同功能区的波况分布规律,并对比分析了具有不同周期的入射波对港内不同区域波高的影响,兼顾分析了波向的影响。结果表明,在涌浪作用下,受透射、绕射影响,不同入射波条件下港内比波高分布规律相关性较好,距离口门越近、入射波波长越长,港内比波高越大;入射波周期对港内波况影响的差异和对波向的敏感性因港内不同区域而不同;防波堤阻挡效果好的波向,其入射波对港内的影响较小;对于受防波堤掩护性较好的内侧泊位,应重点关注泊位处的低频波浪对系泊的影响。 相似文献
14.
基于非静压单相流模型NHWAVE建立了高精度二维数值波浪水槽,采用日本2011年实测真实海啸波型系统研究了海啸波在岛礁上传播变形的规律,并且分析了波高、礁坪淹没水深和礁前斜坡坡度等因素对孤立波和真实海啸传播变形的影响。结果表明,相比孤立波,类海啸波的波长明显大于孤立波波长,在测点处引起的水面变化持续时间更长,同等波高情况下真实海啸波型比孤立波能够携带更多的能量,与岛礁的相互作用也更为复杂,在礁坪上形成的淹没水深约为孤立波的两倍。礁前斜坡坡度和礁坪淹没水深均对类海啸波的反射和透射系数有显著影响。随着礁前斜坡坡度的增加,反射系数和透射系数均逐渐增加。随着礁坪淹没水深的增加,反射系数逐渐减小,而透射系数逐渐增大。但是,反射系数和透射系数均随着入射波高的增加而逐渐减小。 相似文献
15.
通过测试一系列不规则波工况研究了防浪建筑物存在下珊瑚礁海岸附近短波、低频长波和增水的变化规律，并对比了防浪建筑物的不同位置情况。分析结果表明：波浪在沿礁传播过程中，短波波高沿礁坪持续衰减，低频长波波高沿礁坪逐渐增大，波浪增水则沿礁坪基本保持不变；海岸附近短波随着防浪建筑物与礁缘距离的变大而减小，低频长波则在防浪建筑物处于礁坪后部时达到最大，防浪建筑物位置的变化对于礁坪波浪增水的影响可以忽略。通过理论分析证明了珊瑚礁地形上低频长波是由于群波破碎造成的破碎点移动而产生的；当特定波况作用于特定位置的防浪建筑物时，低频长波在礁坪上会发生一阶共振效应导致其能量在海岸附近达到最大值。 相似文献
16.
珊瑚礁破碎带附近波浪演化和波生流实验研究 总被引：2，自引：0，他引：2
为了研究珊瑚岸礁破碎带附近波浪演化和波生流特性,通过水槽实验对规则波浪作用下珊瑚岸礁上沿礁分布的水位和流速进行了详细的测量。在典型卷破波条件下,测试了礁冠存在与不存在的两种情况。实验结果表明,多重波浪反射作用引起岸礁上形成不完全驻波,而破碎带附近的浅化作用则产生高次谐波,波浪破碎所耗散的波能主要来源于主频波,礁坪上透射波成分中二次谐波与主频波的能量相当;礁冠的存在引起破碎带宽度减小、礁坪上增水变大以及礁坪上各次谐波变小;礁冠不存在时,岸礁上波生流的沿礁分布与平直海岸相似,而礁冠的存在一定程度上阻碍了礁坪上水体向外海的回流。研究成果将丰富和发展珊瑚礁水动力学理论,并为岛礁工程的建设和维护提供一定的理论参考。 相似文献
17.
低频长波对港湾共振、泥沙输运、波浪爬高与越浪等过程有重要影响。采用非静压模型SWASH模拟了不规则波在浅滩上的传播及破碎过程,重点探讨了滩顶短波破碎程度对低频波能演变的影响。模拟结果显示,当滩顶短波处于临界破碎状态时,低频波能流沿浅滩持续增长,浅滩对低频长波的放大效应（滩后与滩前低频波能流之比）显著;当滩顶短波轻微破碎、破波仅发生在外破波区时,低频波能流的沿滩增长率进一步变大;当滩顶短波剧烈破碎、破波延续到内破波区时,低频波能流沿滩先增长而后转为衰减,滩后放大率较临界破碎时明显减小。研究结果表明,浅滩顶部水深改变了短波破碎程度,进而影响低频长波的演化过程,浅滩上长波总体增长率随滩顶水深的减小呈现先增大后减小的规律,在短波轻微破碎时最大。 相似文献
18.
南沙群岛珊瑚礁动力地貌特征 总被引：1，自引：0，他引：1
南沙群岛受季风、台风和波浪的影响，珊瑚礁体呈ＮＥ－ＳＷ向椭圆形态，西南礁坪宽于东北礁坪。位于不同波能带内的珊瑚礁体发育了与之相适应的动力地貌单元。礁前斜坡高波能带地形陡峭，向风坡礁脊一槽沟系发育。外礁坪消耗大量波能，广泛覆盖生物碎屑，珊瑚生长稀疏。内礁坪宽广平坦，珊瑚生长良好。外礁坪堆积许多大礁块，尤以东北礁坪为甚。在湖低波能带，通常东坡缓于百坡，湖盆一般浪静流缓，为生物碎屑堆积区。 相似文献
19.
The wave runup caused by a vertical cylinder surging in regular waves is studied both experimentally and numerically. The so-called DualSPHysics Smoothed Particle Hydrodynamics (SPH) code is used for the 3-D numerical modelling. A wide range of cylinder sizes and wave conditions is investigated with results comparing favourably between the experimental and SPH model under both fixed and forced-surge conditions. The experimental and SPH results are further used to predict the maximum runup amplification, in particular the ratio of the runup caused by the surging cylinder to that of the fixed, over the phase difference between the incident wave and surge motion. This maximum runup ratio has been analysed for its dependence on factors such as wave steepness, wave scattering and surge amplitude. An empirical equation is proposed for predicting the maximum runup ratio from known incident wave and surge conditions. Comparison with results from linear solvers suggests that the linear solvers under-predict the full nonlinear runup by a factor of 1.3–1.5. 相似文献
20.
Theoretical Analysis of Harbor Resonance in Harbor with An Exponential Bottom Profile 总被引：2，自引：0，他引：2
The general features of oscillations within a rectangular harbor of exponential bottom are investigated analytically. Based on the linear shallow water approximation, analytical solutions for longitudinal oscillations induced by the incident perpendicular wave are obtained by the method of matched asymptotics. The analytic results show that the resonant frequencies are shifted to larger values as the water depth increases and the oscillation amplitudes are enhanced due to the shoaling effect. Owing to the refraction effect, there could be several transverse oscillation modes existing in when the width of the harbor is on the order of the oscillation wavelength. These transverse oscillations are similar to standing edge waves, and there are m node lines in the longshore direction and n node lines running in the offshore direction corresponding to mode (n, m). Furthermore, the transverse eigen frequency is not only related to the width of the harbor, but also to the boundary condition at the backwall and the bottom shape. 相似文献