The physical simulation of wave groups and their variations in a wave flume

The physical simulation method of wave groups in a wave flume is proposed and verified by the exper- iments. The experimental results demonstrate that random waves with desired wave groupiness, which simultaneously includes the wave group height and length, can be generated satisfactorily at the specified position in a wave flume using the proposed method. Furthermore, the transformation properties of the wave groupiness along the fiat-bottomed wave flume are investigated based on the physically simulated waves. Associated proposals with the physical simulation of wave groups are given.     

多向不规则波浪作用下群墩结构上爬高的计算研究

波浪的方向分布对波浪的传播及其与工程结构物的作用都具有明显影响,目前现有的研究大多是基于单向波浪进行的。为了研究方向分布对群墩结构上的爬高影响,基于规则波浪与群墩作用的理论解,结合多向不规则波浪的造波方法,建立了多向不规则波浪与群墩作用的计算模型,同时进行了物理模型试验对模型的有效性进行了验证。系统地对群墩周围及表面上的波浪爬高进行了计算分析,结果表明,方向分布对波浪爬高具有较大的影响,且不同位置处的影响并不相同,在实际的工程设计中如果按照单向波浪计算,可能低估或者高估群墩周围的爬高。     

斜向和多向不规则波在斜坡堤上的平均越浪量的试验研究

通过三维物理模型试验研究了在斜坡堤上斜向和多向不规则波在非破碎条件下的平均越浪量与波浪参数及堤参数的关系.着重考察了波浪以小角度(0°~30°)斜向入射时平均越浪量的变化情况,肯定了多向波的越浪量在这一范围内有所谓“小角度斜向增加”的现象,但否定了单向波也具有这一现象.在考察波浪的方向分布影响时发现波浪斜向入射时多向波的越浪量往往要比单向波的大.比较了已有的相关研究成果,给出了适用于混凝土护面和扭工字块体护面斜坡堤上斜向和多向不规则波的平均越浪量的估算公式.     

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     

Time-domain numerical and segmented ship model experimental analyses of hydroelastic responses of a large container ship in oblique regular waves

Real sea conditions are characterized by multidirectional sea waves. However, the prediction of hull load responses in oblique waves is a difficult problem due to numeral divergence. This paper focuses on the investigation of numerical and experimental methods of load responses of ultra-large vessels in oblique regular waves. A three dimensional nonlinear hydroelastic method is proposed. In order to numerically solve the divergence problem of time-domain motion equations in oblique waves, a proportional, integral and derivative (PID) autopilot model is applied. A tank model measurement methodology is used to conduct experiments for hydroelastic responses of a large container ship in oblique regular waves. To implement the tests, a segmented ship model and oblique wave testing system are designed and assembled. Then a series of tests corresponding to various wave headings are carried out to investigate the vibrational characteristics of the model. Finally, time-domain numerical simulations of the ship are carried out. The numerical analysis results by the presented method show good agreement with experimental results.     

考虑边界波浪方向的缓坡方程自适应求解模型

缓坡方程是描述近岸波浪运动较好的数学模型之一。在发展的自适应有限元求解缓坡方程的基础上,采用迭代求解的方法,确定波浪相对于边界的入射方向,从而对边界条件进行改进,建立了求解缓坡方程的数值计算模型。典型算例表明,考虑波浪相对于边界的入射角度后,模型可以更好地模拟吸收波浪边界,同时对多向波对双突堤的绕射进行了模拟研究,与试验结果比较表明,所建立的数值计算模型能够适用于多向不规则波传播过程的模拟研究。     

斜向和多向不规则波在斜坡堤上的单波越浪量的实验研究

通过三维物理模型实验对斜坡堤上斜向和多向不规则波的单波越浪量进行了研究.实验考察了入射方向为0°~45°的斜向波和方向分布宽度为0°~25°的多向波以及混凝土和扭工字块体两种护面形式.在混凝土护面堤上用Weibull分布函数拟合了单波越浪量的累积频率分布,在影响因素不同的条件下确定了分布函数中的系数和越浪比例,给出了计算单波越浪量的公式,同时对扭工字块体护面堤上大约100个波中最大的单波越浪量进行了估算.     

畸形波传播速度实验和数值模拟研究

畸形波的传播速度是其最重要的特征参数之一。研究畸形波的传播速度有助于深入和全面了解畸形波的生成机理及其演化过程,另外还可以用于畸形波的预报。针对现有关于畸形波传播速度计算方法(高阶Stokes波理论近似估算,Hilbert变换和两固定点的距离除以畸形波的波峰经过两点所用时间)的不准确性和局限性,使用32个测点描述畸形波波峰沿波浪水槽的运动轨迹,再用回归分析法估算波峰运动轨迹与时间的相关关系,从而计算出畸形波的传播速度。基于288组物理模拟畸形波和364组数值模拟畸形波传播速度的计算结果,使用回归分析方法得出了畸形波传播速度的半经验半理论计算公式,同时还分析了畸形波传播速度的强非线性特征。     

多向不规则波浪的确定性模拟

波浪波动时间过程及波列的模拟,对于开展实际波浪对于工程建筑物的作用具有重要的意义。本文采用线性叠加的单叠加模型,建立了多向不规则波浪的确定性模拟方法。基于理论模拟的规则波、单向不规则波和多向不规则波,验证了波浪确定性模拟方法的有效性。定性地对比分析了模拟波列和已知波列的一致性;定量地研究了模拟波浪在空间范围rr/L_s的误差分布情况(rr表示指定位置与给定位置的空间距离,L_s为有效波长)。并且建议,采用本文方法进行波浪确定性模拟时,最佳的浪高仪间距应小于0.12L_s。     

Local properties of sea waves derived from a wave record

It is demonstrated that for linear deep sea waves with small directional scattering the particle motion at the sea surface and energy transmission may be retrieved from a wave record by means of the Hilbert transform. A physical interpretation of the envelope of the two-dimensional deep sea waves as well as a new method for wave group analysis is presented.     

Second-order wavemaker theory for multidirectional waves

The present paper develops the complete second-order wavemaker theory for the generation of multidirectional waves in a semi-infinite basin. The theory includes superharmonics and subharmonics and is valid for a rotational as well as a translatory serpent-type wave-board motion. The primary goal is to obtain the second-order motion of the wave paddles required to get a prescribed multidirectional irregular wave field correct to second order, i.e. to suppress spurious free-wave generation. The wavemaker theory is a 3D extension of the full second-order wavemaker theory for wave flumes by Schäffer (1996).     

Active Absorption Wave Maker System for Irregular Waves

1 .IntroductionThephysicalmodeltestisoneofthemainmethodstostudyvariousproblemsassociatedwiththedesignofcoastalstructures .Thecommonlyusedwavemakeristhepiston typewavemaker .Becausethewavemakerishighlyreflective ,akeyproblemisthewavemultiplereflectionsbetweenthewavemakerandthetestedstructuresinthewaveflume .There reflectedwavesfromthewavemakerarespuriouswavesrelativetotheincidentwavestothestructures .Howtopreventthere reflectedwavesfromthewavemakerbecomesacriticalproblemforaccurateexperimental…     

Analysis of Directional Spectra and Reflection Coefficients in Incident and Reflected Wave Field

In this paper, the modified Bayesian method for the analysis of directional wave spectra and reflection coefficients is verified by numerical and physical simulation of waves. The results show that the method can basically separate the incident and reflected directional spectra. In addition, the effect of the type of wave gage arrays, the number of measured wave properties, and the distance between the wave gage array and the reflection line on the resolution of the method are investigated. Some suggestions are proposed for practical application.     

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...     

双边多单元造波机造波性能分析

由若干独立摇板组成的多单元造波机是实验室研究波浪及其与海洋工程结构物相互作用的重要设备。由于单元摇板宽度和波浪周期对斜向波浪模拟方向角的限制、斜向波浪模拟引起的杂波和三维短峰波浪模拟的有效实验区范围等,是影响多单元造波机波浪模拟质量的关键问题。通过对海洋深水池双边多单元造波机性能的分析,获得了波向角与规则波浪周期的关系,避免杂波产生的波浪周期范围和三维短峰波浪有效实验区的范围。分析结果对于海洋深水池高质量模拟波浪并为海洋工程结构物模型试验提供良好的波浪环境条件具有重要意义。     

畸形波数值模拟和定点生成

采用David L等人提出的数值模拟产生畸形波的方法,以Longuet-Hinggins模型为基础,利用一个基本波列和一个瞬态波列线性叠加模拟波面,在很短的波列中得到畸形波,从而使模拟畸形波的效率提高。得到的畸形波畸形程度较高,并且可以控制畸形波出现的时间和地点。用该方法模拟实测畸形波并与其进行对比验证,结果表明模拟产生的畸形波和实测畸形波吻合良好。以此方法为基础,在实验室内物理产生畸形波将更加具有可操作性。     

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。     

波浪反射系数谱的特征分析

应用斜向不规则波反射系数的改进两点法(MTPM),用模型试验研究了混凝土护面堤和块石护面堤波浪反射系数的频率谱和方向谱,结果表明,分析的反射系数随入射波频率的增加、结构坡度的减小和入射角的加大而减小.给出了波浪反射系数频率谱及其随Iribarren数变化的规律,提出了反射系数三维谱的经验公式,由此可定量地描述斜向不规则波的反射系数随无量纲特征参数Iribarren数和入射波角度的变化规律.     

Rogue waves during Typhoon Trami in the East China Sea

As concluded from physical theory and laboratory experiment,it is widely accepted that nonlinearities of sea state play an important role in the formation of rogue waves;however,the sea states and corresponding nonlinearities of real-world rogue wave events remain poorly understood.Three rogue waves were recorded by a directional buoy located in the East China Sea during Typhoon Trami in August 2013.This study used the WAVEWATCHⅢmodel to simulate the sea state conditions pertaining to when and where those rogue waves were observed,based on which a comprehensive and full-scale analysis was performed.From the perspectives of wind and wave fields,wave system tracking,High-Order Spectral method simulation,and some characteristic sea state parameters,we concluded that the rogue waves occurred in sea states dominated by second-order nonlinearities.Moreover,third-order modulational instabilities were suppressed in these events because of the developed or fully developed sea state determined by the typhoon wave system.The method adopted in this study can provide comprehensive and full-scale analysis of rogue waves in the real world.The case studied in this paper is not considered unique,and rules could be found and confirmed in relation to other typhoon sea states through the application of our proposed method.