中长周期波作用下的斜坡堤胸墙波浪力试验研究

在印度洋、大西洋沿岸,海岸工程设计波浪周期多在14 s以上,具有显著的中长周期波特征。通过以往工程项目的试验结果发现中长周期波下,规范计算的斜坡堤胸墙波浪力明显小于试验结果。因此,通过系列物理模型试验研究了中长周期波下的斜坡堤胸墙波浪力。分析斜坡坡度、肩台宽度和波浪条件对胸墙波浪力的影响。通过将试验结果与我国现有规范中的经验公式计算所得结果进行对比,发现规范更适用于胸墙底淹没的情况,而对于肩台出水情况,规范计算结果小于试验结果。由此提出了一种新的波浪力计算方法,计算准确度得到明显提高。     

随机波对水平板冲击作用实验研究

波浪对透空式海上建筑物的冲击作用已经成为此类建筑物安全的重要影响因素。进行了单向随机波对水平板冲击作用水槽实验研究。总共进行了4个方向(0°、15°3、0°、45°),相对入射波波高H1/3/d=0.093 75~0.25,周期Tp=1.0~2.0 s,水平板距离静水面的高度s与入射波高H1/3的比值s/H1/3=0.0~0.5的实验研究。采用小波分析方法去除了由于测压传感器振荡引起的测量数据的振荡和漂移,在此基础上统计分析给出了不同方向水平板下的压力峰值分布情况。采用无因次方法,讨论了无因次冲击力与相对入射波高H1/3/d、相对板宽B/L、相对净空s/H1/3及波向角β的关系。     

变浅作用下浅水海浪谱的计算

深水海浪向近岸传播过程中,由于变浅作用,其波面高度分布,波谱都发生了变化。本文基于非线性系统的输出和输入间亦存在转换关系,通过波面高度分布函数建立了深水正态海浪过程作为输入和浅水偏态海浪过程作为输出之间的非线性转换关系,导出了深、浅水谱间的理论关系。在假定能通量不变的条件下,提出了一种由已知深水谱和波面偏度计算二维海浪变浅作用下的浅水谱的方法,并对其进行了讨论和检验。     

未破碎变浅随机海浪的非线性模式

利用实测和实验室数据分析了未破碎变浅海浪波面高度分布三阶矩(或波面偏度)相对于Hs/d的空间演化,利用本文的经验关系,在二阶近似下,给出了以Hs/d为参量的非线性波面表示模式,并推导了功率谱、二阶谱以及波面高度分布函数等特征量.文中还讨论了波面偏度和峰度的相关关系.     

系泊方柱在畸形波与波群伴生波浪作用下运动响应试验研究

畸形波与波群伴生波浪作用于系泊浮体,和常规随机波浪作用比较,运动响应时频域特征均将发生显著变化。基于物理模型试验,采用小波方法计算伴生波浪和常规随机波浪作用下系泊浮体运动响应的时频域特征变化及波群因子与浮体运动响应时频域特征的定量关系。结果表明:伴生波浪作用下浮体运动响应显著大于常规随机波浪的作用结果,且波群因子G A对浮体运动响应时频域特征有显著影响;伴生波浪作用下浮体纵荡运动的广义能量谱E(t)统计特征值E max(t)、E 1/10(t)、E 1/3(t)、E average(t)均明显大于相同波谱下常规随机波浪的结果,且随着波群因子G A增大显著增大;伴生波浪作用下各运动响应能量集中度δE显著大于常规随机波浪作用结果,且能量集中时域分布范围参数ΔT E以纵荡运动分量最为显著。     

Ⅲ变浅作用下列率谱和频率谱的实验研究

为研究变浅作用下的非线性海浪，本文利用并矢相关谱估计方法，设计并进行了多种强度下，由深水传入近岸浪变浅作用下，列率谱和频率谱随水深和坡度变化的实验比较研究。     

不稳定状态下惯性重力波对台风发生、发展和移动的作用

本文用波动不稳定理论,对台风和热带气旋的发生、发展进行了分析和研究。结果表明,在热带气旋和台风的发生、发展过程中,起主要作用的波动是不稳定状态下的惯性重力波。大气中存在深厚潮湿层和水气凝结加热可促使和加剧波动的不稳定,并有利于波动能量频散减小,因此有利于台风和热带气旋的发生、发展,而且又能使波动移动速度减慢。基本态比容随气压的变化小于绝热分布的情况,也可导致波动不稳定,因此,对台风和热带气旋的发生、发展也可起到一定的作用。     

斜向不规则波对直墙作用的实验研究

通过长峰不规则波和方向波谱对直墙作用的实验研究 ,分别给出了每延米斜向不规则波波浪力与正向力之比 ,方向波谱波浪力与斜向长峰不规则波波浪力之间的关系 ,通过与规则波实验结果的比较给出了斜向规则波与不规则波波浪力之间的相对关系 ;并对斜向不规则波的反射系数与正向波时的变化作出了分析     

水重力波统一变分原理导出的风生斜剖面波浪

考虑到目前应用的规则波具有对称于垂直坐标轴的波剖面,这与实际的风生海浪有较大差别,在应用水重力波统一变分原理导出线性波、弧立波、五阶斯托克斯波和流函数波的基础上,本文应用水重力波统一变分原理导出风生斜剖面波浪。其特点是波剖面在风压的作用下,不对称于垂直坐标轴,而是呈向前倾斜的形状。     

长周期波浪激发矩形港池多模态共振研究

长和宽接近的矩形港池存在横向、纵向及横纵向混合共振模态。采用基于混合有限元的椭圆型缓坡方程数值模型模拟不同波浪入射角的低频波浪激发矩形港池的多模态共振,并分析不同平面布置形式的矩形港池模态响应特性。结果表明,斜向波浪会激发港池的横向共振模态,其放大因子受入射角度影响较大,而纵向共振模态的放大因子受入射角度影响较小。口门宽度对港池的共振模态个数与放大因子均有影响,具体为:随着口门宽度增加,各阶模态放大因子减小。口门位置对纯横向以及纯纵向共振的振荡模式有显著影响,而对横向纵向混合模态影响较小。各阶模态放大因子的大小和波节线与波腹线与口门的相对位置密切相关。     

Infragravity Waves Produced by Wave Groups on Beaches

The generation of low frequency waves by a single or double wave groups incident upon two plane beaches with the slope of 1/40 and 1/100 is investigated experimentally and numerically. A new type of wave maker signal is used to generate the groups, allowing the bound long wave (set-down) to be included in the group. The experiments show that the low frequency wave is generated during breaking and propagation to the shoreline of the wave group. This process of generation and propagation of low frequency waves is simulated numerically by solving the short-wave averaged mass and momentum conservation equations. The computed and measured results are in good agreement. The mechanism of generation of low frequency waves in the surf zone is examined and discussed.     

长重力波运动与近岸过程研究综述

简要介绍了长重力波的概念和作用,概述了近岸长重力波的运动形式、类型、分布和波能变化,分析了近岸长重力波与泥沙运动、海岸侵蚀、近岸环流系统、海滩碎波带地貌形态和潮汐等的关系,提出了进一步研究的几点建议。     

Resonance Induced by Edge Waves in Hua-Lien Harbor

This article first reviews previous numerical studies on the resonance problem of Hua-Lien Harbor. All the research leads to the conclusion that resonance can be stimulated by 2-D infragravity waves. However, a literature survey suggests that outside the harbor these plane infragravity waves are too small to excite violent water-body movement inside. On the other hand, 3-D infragravity waves trapped along the coastline, also known as edge waves, are more likely to exist outside the harbor and their effect needs to be thoroughly discussed. Based on previous measurements, the response of Hua-Lien Harbor is best simulated using edge waves of 160 and 140 second periods and their resonance mechanisms are analyzed. The former case has a longitudinal resonant mode and hence the amplitude in the inner harbor is large. The latter case has a transverse mode in the outer basin and hence only berths in the outer basin are influenced. These features are both consistent with field measurement. Therefore, it is very likely that edge waves are responsible for the resonance of Hua-Lien Harbor. Finally, based on observation after the construction of the present offshore breakwaters, a theory is proposed to explain the trapping of incident edge waves, and a measure to further reduce the resonance is discussed.     

Shoaling Surface Gravity Waves Cause a Force and a Torque on the Bottom

Freely propagating surface gravity waves are observed to slow down and to stop at a beach when the bottom has a relatively gentle upward slope toward the shore and the frequency range of the waves covers the most energetic wind waves (sea and swell). Essentially no wave reflection can be seen and the measured reflected energy is very small compared to that transmitted shoreward. One consequence of this is that the flux of the wave’s linear momentum decreases in the direction of wave propagation, which is equivalent to a time rate of change of the momentum. It takes a force to cause the time rate of change of the momentum. Therefore, the bottom exerts a force on the waves in order to decrease the momentum flux. By Newton’s third law (action equals reaction) the waves then impart an equal but opposite force to the bottom. In shallow (but finite) water depths the wave force per unit bottom area is calculated, for normal angle of incidence to the beach, to be directly proportional to the square of the wave amplitude and to the bottom slope and inversely proportional to the mean depth; it is independent of the wave frequency. Constants of proportionality are: 1/4, the fluid density and the acceleration of gravity. Swell attenuation near coasts and some characteristics of sand movement in the near-shore region are not inconsistent with the algebraic structure of the wave force formula. Since the force has a depth variation which is significantly faster than that of the dimensions of the particle orbits in the vertical direction, the bottom induces a torque on the fluid particles that decreases the angular momentum flux of the waves. By an extension of Newton’s third law, the waves also exert an equal but opposite torque on the bottom. And because the bottom force on the waves exists over a horizontal distance, it does work on the waves and decreases their energy flux. Thus, theoretically, the fluxes of energy, angular and linear momentum are not conserved for shoaling surface gravity waves. Mass flux, associated with the Stokes drift, is assumed to be conserved, and the wave frequency is constant for a steady medium.     

A Three-Point Method for Separating Incident and Reflected Waves over A Sloping Bed

This study presents a three-point method for separating incident and reflected waves to explain normally incident waves' propagating over a sloping bed. Linear wave shoaling is used to determine changes in wave amplitude and phase in response to variations of bathymetry. The wave reflection coefficient and incident amplitude are estimated from wave heights measured at three fixed wave gauges with unequal spacing. Sensitivity analysis demonstrates that the proposed method can predict the reflection and amplitude of waves over a sloping bed more accurately than the two-point method.     

An Experimental Study on A Trapezoidal Pendulum Wave Energy Converter in Regular Waves

Experimental studies were conducted on a trapezoidal pendulum wave energy converter in regular waves. To obtain the incident wave height, the analytical method (AM) was used to separate the incident and reflected waves propagating in a wave flume by analysing wave records measured at two locations. The response amplitude operator (RAO), primary conversion efficiency and the total conversion efficiency of the wave energy converter were studied; furthermore, the power take-off damping coefficients corresponding to the load resistances in the experiment were also obtained. The findings demonstrate that the natural period for a pendulum wave energy converter is relatively large. A lower load resistance gives rise to a larger damping coefficient. The model shows relatively higher wave energy conversion efficiency in the range of 1.0?1.2 s for the incident wave period. The maximum primary conversion efficiency achieved was 55.5%, and the maximum overall conversion efficiency was 39.4%.     

内波场中水平桩柱波阻的实验研究

分析水平阻力与内波波要素的关系,采用实验室实验的方法,研究了水平桩柱与内波的相互作用,焦点是研究内波波要素与波阻之间的关系。实验中的密度分层采用典型跃层型剖面,而内波是由自行研制的造波机生成。实验结果表明,当内波的频率不变时,水平桩柱所受到的阻力随着内波的振幅增加而增加,它的量值与分层有关。对于强跃层的密度分布,当桩柱处在跃层中时,受到的水平波阻较小,而在跃层之外则受到较大的水平波阻。     

Experimental Study on Mean Overtopping of Sloping Seawall Under Oblique Irregular Waves

In this paper, domestic and abroad research progresses and related calculation formulae of the mean overtopping discharge are summarized. Through integral physical model experiments, the relation between the wave direction and the overtopping discharge on the top of the sloping dike is focused on and put into analysis and discussion; and a modified formula for mean overtopping discharges under oblique irregular waves is proposed. The study shows that the mean overtopping discharge generally goes down as the relative wave obliquity β increases for a fixed measurement point and the mean overtopping discharge generally increases as the wave steepness H/L decreases (the cycle increases) for a fixed relative wave obliquity.     

Hyperbolic Mild Slope Equations with Inclusion of Amplitude Dispersion Effect: Random Waves

New hyperbolic mild slope equations for random waves are developed with the inclusion of amplitude dispersion. The frequency perturbation around the peak frequency of random waves is adopted to extend the equations for regular waves to random waves. The nonlinear effect of amplitude dispersion is incorporated approximately into the model by only considering the nonlinear effect on the carrier waves of random waves, which is done by introducing a representative wave amplitude for the carrier waves. The computation time is greatly saved by the introduction of the representative wave amplitude. The extension of the present model to breaking waves is also considered in order to apply the new equations to surf zone. The model is validated for random waves propagate over a shoal and in surf zone against measurements.