共查询到18条相似文献，搜索用时 109 毫秒
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通过波浪水槽实验,对海平面变化造成的波浪动力因素改变引起的沙质岸滩形态响应开展机理性研究。实验采用1∶10单一沙质斜坡概化岸滩,利用3种不同实验水深模拟海平面变化,考虑椭圆余弦波、非规则波、规则波和孤立波4种类型波浪作用。实验对波浪在斜坡上的传播变形、破碎、上爬和回落过程的波高及波浪作用后的岸滩地形进行了测量。实验结果表明,椭圆余弦波、规则波和非规则波作用下,平衡岸滩呈现出滩肩形态,孤立波作用下则呈沙坝形态。海平面上升造成波浪动力增强,沙质岸滩平衡剖面形状基本保持不变向岸平移,槽谷、滩肩、沙坝位置以及岸线蚀退距离,均呈现出良好规律性。 相似文献
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通过物理模型实验研究了海岸沙坝剖面和滩肩剖面的形成和演化过程,给出了稳定的沙坝剖面和滩肩剖面的几何特征。实验中考虑了两种初始坡度(1∶20和1∶10)和不同波高的规则波和不规则波,讨论了不同初始坡度海岸上破碎波空间分布特征。结果表明,沙坝产生后存在向岸和离岸两种运动形态,但最终将停留在稳定位置。稳定的沙坝剖面对应不同初始坡度和波浪存在不同的大沙坝和小沙坝分布。沙坝剖面由长时间小波高波浪序列作用后可转化为稳定滩肩剖面,该剖面不依赖于波浪和初始坡度。实验也给出了平衡剖面与理论曲线的对比以及剖面上泥沙粒径的分布。 相似文献
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海滩形态是近岸过程与海岸工程的一个重要研究内容,为探讨人工沙滩平衡剖面的形成及其形态特征和波浪作用下的滩面泥沙运动,从泥沙与波浪运动的相似规律出发,采用天然沙以正态整体模型进行二维沙质海滩的形态试验.试验证明人工沙质海滩在波浪作用一定时间之后,其剖面基本趋于一种平衡状态,沙源的向岸推移和向海下拉的情况也基本稳定.试验显示混合波的冲刷要大于单纯斜向波,单纯斜向波的冲刷大于单纯正向波,因此人工沙质海滩施工时应考虑到不同来波方向对剖面的影响.对比各个系列的整个人工沙质海滩剖面变化情况,可以看出整个沙滩剖面呈冲刷形态:从岸向海方向,在滩肩平台上形成一定的沙源堆积体;在滩肩缘到斜坡中部侵蚀最大,在斜坡下部侵蚀较小且向海呈逐渐减小趋势. 相似文献
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《热带海洋学报》2017,(1)
红树林广泛分布于我国南方沿海地区,可有效减小波浪对岸滩的破坏,研究其在规则波作用下对岸滩变化的影响具有重要意义。基于波浪水槽实验,采用PVC圆管模拟红树林,选取无黏性沙堆砌而成的1/10~1/20组合坡概化岸滩。实验结果表明,在规则波作用下,红树林的存在对岸滩剖面变化产生了较大影响;并分析了规则波波陡、植物分布密度和排列方式对岸滩剖面变化的影响。基于实验数据,建立了在实验条件下的岸滩冲刷坑尺度、淤积沙坝尺度、最大冲刷深度、最大淤积高度与规则波波陡、红树林的分布密度和排列方式之间的关系式,结果呈幂指数函数关系。揭示了岸滩剖面变化与规则波水动力特性、红树林、泥沙颗粒和岸滩坡度之间的联系。引入植物综合系数,预测给定规则波波陡和波长情况下的岸滩冲淤演变特征值,为海岸生物防护工程的建设提供科学依据。 相似文献
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破碎波对近海海岸地形以及海岸建筑物影响强烈,通过物理模型实验对孤立波、规则波作用下破碎带的床面形态以及孔隙水压力进行分析。破碎波冲击海床,破碎处床面上形成沙坝和沙坑,与规则波相比,孤立波破碎时对床面的冲刷更加剧烈,床面形成的沙坝和沙坑尺度更大,且土体内孔隙水压力幅值也较大。同时研究了波面变化对孔隙水压力的影响,发现波面变化历时曲线与孔隙水压力历时曲线相似,与孔隙水压力梯度历时曲线更为相似,说明波面变化更能反映海床内部孔隙水压力梯度的变化。通过探讨波浪与海床之间相互耦合作用,发现破碎带地形变化使得波浪出现不同破碎类型,分析得出卷破波比崩破波作用下孔隙水压力幅值大。 相似文献
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近年来风暴潮等海洋灾害日趋频发,沙质海岸侵蚀问题也愈发突出,沙滩稳定防护显得日益重要。为研究风暴浪作用下沙质岸滩稳定机制问题,设计了一系列的水槽试验,对风暴浪作用下沙质岸滩的稳定机制和演变过程进行了录像观察和研究分析。试验中采用图像处理技术,根据水和岸滩床面的像素值差异,对岸滩整体剖面进行实时动态提取;对比和分析了不同入射波高、波周期、水深、岸滩初始坡度以及波高连续变化下沙质岸滩演变过程。试验结果表明,岸滩稳定与岸滩初始坡度和沙坝的发育直接相关,而波参数主要影响岸滩扰动幅度和沙坝以及前滩侵蚀边界的位置变化。当入射波高连续变化时,沙坝迅速响应并向离岸迁移。岸滩变化幅值与入射波能流存在明显正相关关系,波能流越大对岸滩稳定性的危害越大。而水位升高会增强前滩向岸侵蚀风险。此外,在本试验尺度下,前滩以侵蚀为主。当岸滩初始坡度小于稳定坡度且波陡较小时,即Dean参数Ω''较小时,岸滩才发生明显的前滩淤积,这对于试验尺度下岸滩恢复工况研究至关重要。具体来说,当岸滩整体坡度为1:10且前滩坡度达到1:5~1:2.5时,岸滩稳定性最好,岸滩形态最接近最终平衡剖面,岸滩趋于稳定的时间最短。 相似文献
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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
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了解波浪破碎速度场的分布特性对于波浪破碎物理机制的研究极为重要,同时,对比研究不同类型破碎产生的气液混合区的演化特征有利于波浪白冠覆盖率模型的完善。在实验室水槽,生成了深水临界波、单次崩破波和单次卷破波,采用图像测速技术获取了波浪破碎图像、波面下水体和气液混合区速度场。结果表明,崩破波的水平向速度u和垂直向速度v在波峰前和波峰后的分布极为不对称,其水平向最大速度umax并不位于峰顶,而是在主导波峰前0.7ηm ax处;卷破波的umax出现在波峰峰顶前端极小的区域内,且该区域与周围区域的速度梯度极大。崩破波和卷破波生成的气液混合区发展特征也存在差异：崩破波的umax值大、影响区域长、混合区厚度较小、各区域影响时间短;而卷破波的各项特征参数与崩破波形成对比。 相似文献
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LI Yucheng 《中国海洋工程》2000,14(1):59-67
—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. 相似文献
12.
不同沉积物养护海滩对台风响应的差异性研究 总被引：2，自引：2，他引：0
本文通过对厦门天泉湾人工卵石滩和会展人工沙滩在1614“莫兰蒂”超强台风影响前后的典型剖面监测，结合水文动力要素的观测和数值模拟，计算了台风影响过程的波浪场、总水位，分析了剖面形态和台风过程的剖面平均变化量。结果表明，强潮海岸人工卵石滩与人工沙滩对台风响应的特征明显不同，人工卵石滩横向上大部分卵石向岸输移堆积，滩面侵蚀，滩肩堆积形成更高的风暴滩肩，坡度明显变陡。而人工沙滩则表现为明显的沉积物离岸输运，上部滩面侵蚀，下部滩面淤积，滩面坡度明显变缓，受台风登陆后的强烈向岸风作用，滩肩顶有所夷平，滩肩高度变化很小。海滩滩肩在台风过程中是否侵蚀与台风登陆和影响过程的总水位(天文潮、风暴增水、波浪爬高)密切相关，两个人工海滩的风暴响应模式均为冲蚀；台风影响过程中，波浪能量相对强、滩面坡度相对陡的人工卵石滩比人工沙滩的剖面平均变化量小，对于台风的响应程度小，在强侵蚀高能海岸采用砾石等粗粒径沉积物进行海滩养护是减缓砂质海滩侵蚀的一种有效手段。 相似文献
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Experimental Study on the Bed Shear Stress Under Breaking Waves 总被引：1，自引：0，他引：1
The object of present study is to investigate the bed shear stress on a slope under regular breaking waves by a novel instrument named Micro-Electro-Mechanical System (MEMS) flexible hot-film shear stress sensor. The sensors were calibrated before application, and then a wave flume experiment was conducted to study the bed shear stress for the case of regular waves spilling and plunging on a 1:15 smooth PVC slope. The experiment shows that the sensor is feasible for the measurement of the bed shear stress under breaking waves. For regular incident waves, the bed shear stress is mainly periodic in both outside and inside the breaking point. The fluctuations of the bed shear stress increase significantly after waves breaking due to the turbulence and vortexes generated by breaking waves. For plunging breaker, the extreme value of the mean maximum bed shear stress appears after the plunging point, and the more violent the wave breaks, the more dramatic increase of the maximum bed shear stress will occur. For spilling breaker, the increase of the maximum bed shear stress along the slope is gradual compared with the plunging breaker. At last, an empirical equation about the relationship between the maximum bed shear stress and the surf similarity parameter is given, which can be used to estimate the maximum bed shear stress under breaking waves in practice. 相似文献
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The loss of beach sand from berm and dune due to high waves and surge is a universal phenomenon associated with sporadic storm activities. To protect the development in a coastal hazard zone, hard structures or coastal setback have been established in many countries around the world. In this paper, the requirement of a storm beach buffer, being a lesser extent landward comparing with the coastal setback to ensure the safety of infrastructures, is numerically assessed using the SBEACH model for three categories of wave conditions in terms of storm return period, median sand grain size, berm width, and design water level. Two of the key outputs from the numerical calculations, berm retreat and bar formation offshore, are then analysed, as well as beach profile change. After having performed a series of numerical studies on selected large wave tank (LWT) test results with monochromatic waves using SBEACH, we may conclude that: (1) Berm erosion increases and submerged bar develops further offshore as the storm return period increases for beach with a specific sand grain size, or as the sand grain reduces on a beach under the action of identical wave condition; (2) Higher storm waves yield a large bar to form quicker and subsequently cause wave breaking on the bar crest, which can reduce the wave energy and limit the extent of the eroding berm; (3) A larger buffer width is required for a beach comprising small sand grain, in order to effectively absorb storm wave energy; and (4) Empirical relationships can be tentatively proposed to estimate the storm beach buffer width, from the input of wave conditions and sediment grain size. These results would benefit a beach nourishment project for shore protection or design of a recreational beach. 相似文献
15.
M.S. Kirkgz 《Coastal Engineering》1989,13(4)
Experimental investigation is made on the boundary layers of the transformation zone (i.e. the region between the last symmetrical wave profile depth and the breaking point) of plunging breakers propagating on a smooth beach with 1/12 uniform slope. Using a laser anemometer, the particle velocities are measured at four verticals along the transformation zone for three different steepnesses of waves within the plunging breaker range. The boundary layer flow in the transformation zone is found mostly of turbulent character and vertical distribution of particle velocities does not seem to conform to the classical law of the wall distribution given for steady-flow boundary layers. The results show that free-stream particle velocities, in the boundary layer of the breaker under the crest phase, increase considerably as the wave progresses towards the breaking point. The boundary layer thickness, defined as the velocity-affected region, remains constant throughout the transformation zone but it decreases with increasing deep-water wave steepness for the particular beach slope tested. 相似文献
16.
Franoise Ozanne Andrew J. Chadwick David A. Huntley David J. Simmonds John Lawrence 《Coastal Engineering》2000,41(4)
In this paper, the performance of a 1-D Boussinesq model is evaluated against laboratory data for its ability to predict surf zone velocity moments. Wave evolution over a plane beach and a complex bathymetry both extending into the surf-zone is examined for six cases. For the plane beach, these comprise two cases, a spilling and a plunging cnoidal wave. For the complex bathymetry, these comprise four cases of longer and short wavelengths (spilling and plunging breakers), with regular and irregular periodicity. The model evaluation places emphasis on parameters of the wave field that could be used for the prediction of sediment transport; orbital velocity, undertow, velocity skewness, kurtosis and asymmetry. It is found that, despite an overestimation of the depth-averaged horizontal velocity in the regular waves cases, the predicted higher order velocity moments and undertow are in good agreement with the laboratory data. A bispectral analysis demonstrates that the nonlinear transfers of energy amongst the low order harmonics are well reproduced, but energy exchanges with the higher harmonics are less well predicted. As a result, the model handles velocity moments better in the shorter wave tests than in the long wave cases where triad interactions are stronger. Of the four parameters describing wave breaking, the model behaviour is most sensitive to the critical wave front slope φB, especially with regard to velocity skewness and kurtosis predictions. It is also found that increasing the thickness of the surface roller for the case of plunging breakers improves the model's performance. 相似文献
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《Ocean Engineering》2004,31(11-12):1351-1375
Sorting of sediment on a beach under wave action takes several forms. Stratified layers of finer and coarser sediment, which depend on wave climate, grain size and beach slope are formed. This complex problem can be simplified by defining the cross-shore and longshore sorting according to the angle between the breaking wave and the coast. In the present study, longshore distribution of sediment as well as corresponding beach profiles was measured in a wave basin. Three-dimensional hydraulic model experiments were performed with regular waves. Eighteen sets of experiments performed in longshore sorting mechanism using two different sand beds. The sorting of the bed material and the formation of armour coats along the beach were defined by grain size distributions and dimensionless parameters for sandy beaches.The rate of sediment transport with grain size sorting was measured in a wave basin. A method introduced sorting process was presented in this study. The sediment rate based on sorting mechanism was also discussed with known methods. It has been found that the non-uniformity of the grain size and hence sorting of the beaches play a very important role in the sand transport due to wave motion in a similar way to the case of steady flow in alluvial channels. 相似文献