Theoretical and experimental study of breaking wave on sloping bottoms

This paper studies the continuous evolution of breaking wave for the surface water waves propagating on a sloping beach. A Lagrangian asymptotic solution is derived. According to the solution coupled with the wave breaking criteria and the equations of water particles motion, the wave deformation and the continuous wave breaking processes for the progressive water waves propagating on a sloping bottom can be derived. A series of experiments are also conducted to compare with the theoretical solution. The results show that the present solution can reasonably describe the plunging or spilling wave breaking phenomenon.     

三次黑潮大弯曲形成机制的分析

通过对HYbrid Coordinate Ocean Model(HYCOM)高分辨率海洋环流模式(1/12°)数值模拟结果的分析发现,该模式对1993—2003年的模拟结果出现了3次显著的黑潮大弯曲现象。研究表明,日本以南这3次黑潮大弯曲路径的形成与2种机制有关:沿30°N西传的海洋Rossby波将太平洋145°E附近海面高度正异常信号传到九州岛东南海域是第二次黑潮大弯曲的主要形成机制;而冲绳海槽北部海水的位势涡度负异常则有利于九州岛东南反气旋再循环流海域海面高度正异常,有助于第一次和第三次黑潮大弯曲路径的形成。     

畸形波作用下四立柱张力腿平台动力响应研究

介绍了畸形波生成的方法并对各种线性合成畸形波的效率进行了对比。选用改进的随机波加瞬态波的方法模拟强非线性波———"新年波"的波形。采用微元法对张力腿平台的立柱和浮筒进行离散,编制程序对张力腿平台在强非线性波作用下的耦合动力响应进行了数值模拟,重点比较分析了张力腿平台在随机波及畸形波中所受波浪力、平台动力响应、系泊系统张力特性及浪向角对平台运动的影响。研究表明:在"新年波"作用下,0°浪向时,平台在x和z方向所受波浪力较随机波增长了约1/4,纵荡、垂荡及纵摇响应值分别增加了33%,38%和12%,张力腿张力幅值增加约20%,位于平台四角的张力腿张力有所差异,相邻两根张力腿的张力差别不大,浪向角对平台运动响应、张力腿张力的影响畸形波大于随机波的作用。为今后考虑强非线性波浪影响时张力腿平台的设计提供了借鉴和参考。     

非结构化网格下大范围波生流模拟和应用

波浪破碎引起的沿岸流是近岸海域的关键水动力因素。利用基于缓坡方程得到的光程函数方程和波作用守恒方程建立了考虑绕射效应的大范围波浪传播模型,模型可以考虑流场的影响;将波浪模型计算得到的辐射应力、波浪紊动系数等参数添加到三维水动力模型中,得到大范围近岸波生流的计算模型。模型中流场和波浪可以共用计算网格,且可同步耦合计算;模型基于非结构化网格,可以拟合复杂岸线的变化。模型对波生沿岸流、环流和逆流进行了验证,同时对实际海域的波生流进行了计算,结果表明:该模型对近岸波浪破碎引起的波生流具有很好的精度和适用性,可用于实际工程的计算。     

一种浮摆式波能发电装置摆板运动响应的数值模拟

海况是影响波浪能发电装置运行效率的因素之一。以浮摆式波能发电装置为基础,描述了其中摆板系统的收集原理;并基于AQWA(advanced quantitive wave analysis)水动力学计算软件,仿真计算了三种波况下各摆板的运动响应,发现波向为45°角是摆板系统的最佳运行角度;当波高不超过0.6 m时,摆板的运动状态较易趋于平衡。另外,提出了一种估算摆板采集波能的平均转换效率的方法,并基于相关拟合函数软件,计算了5种较理想波况下摆板采集波能的平均能量转换效率,结果发现,波浪的周期和波高越大,摆板的波能采集效率越低。     

共转换点道集的抽取与转换波时变静校正

纵横波速度比固定时,同一地震道中各时间采样点对应不同的转换点位置,因此,常规的整体抽道方法只能抽取特定深度或特定层位条件下的共转换点道集,它不能保证所有P-SV转换波的反射点位置都在同一水平位置处。提出了一种精确抽取共转换点道集的新方法,运用这种方法抽取的共转换点道集中所有数据对应的转换点在地面的投影都对应于同一位置,因此,该道集是一种真正意义上的共转换点道集,在此基础上提出了一种解决短波长问题的转换波时变静校正方法,实际资料处理取得了好的效果。     

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.     

基于COS-2S模型的ADCP海浪方向谱估计

美国RD公司声学多普勒流速剖面仪(ADCP)使用的波向估计算法是迭代的最大似然算法(IMLM),IMLM可以准确估计出主浪向,但波向估计结果在主浪向以外其他方向上存在由噪声带来的能量分布,使得估计结果变得不准确。设计了基于COS-2S模型的波向估计方法,模型中只含有主波向,算法在准确估计主波向同时有效去除其他方向上噪声带来的能量分布。将一种混合遗传算法(HGA)代替遗传算法(GA)应用到波浪模型的参数求解中,HGA相对GA收敛更快,可有效找出全局最优解。仿真分析和实测数据表明,HGA和IMLM都能准确估计出波浪的主浪向,但HGA可有效去除主浪向以外其他方向上噪声带来的能量分布,HGA比IMLM更加适用于海洋各种噪声存在条件下的测量环境。     

Dynamics of large-truncated mooring systems coupled with a catenary moored semi-submersible

With the floating structures pushing their activities to the ultra-deep water,model tests have presented a challenge due to the limitation of the existing wave basins.Therefore,the concept of truncated mooring system is implemented to replace the full depth mooring system in the model tests,which aims to have the same dynamic responses as the full depth system.The truncated mooring system plays such a significant role that extra attention should be paid to the mooring systems with large truncation factor.Three different types of large truncation factor mooring system are being employed in the simulations,including the homogenously truncated mooring system,non-homogenously truncated mooring system and simplified truncated mooring system.A catenary moored semi-submersible operating at 1000 m water depth is presented.In addition,truncated mooring systems are proposed at the truncated water depth of 200 m.In order to explore the applicability of these truncated mooring systems,numerical simulations of the platform’s surge free decay interacting with three different styles of truncated mooring systems are studied in calm water.Furthermore,the mooring-induced damping of the truncated mooring systems is simulated in the regular wave.Finally,the platform motion responses and mooring line dynamics are simulated in irregular wave.All these simulations are implemented by employing full time domain coupled dynamic analysis,and the results are compared with those of the full depth simulations in the same cases.The results show that the mooring-induced damping plays a significant role in platform motion responses,and all truncated mooring systems are suitable for model tests with appropriate truncated mooring line diameters.However,a large diameter is needed for simplified truncated mooring lines.The suggestions are given to the selection of truncated mooring system for different situations as well as to the truncated mooring design criteria.     

Design of a hydraulic power take-off system for the wave energy device with an inverse pendulum

This paper describes a dual-stroke acting hydraulic power take-off （PTO） system employed in the wave energy converter （WEC） with an inverse pendulum. The hydraulic PTO converts slow irregular reciprocating wave motions to relatively smooth, fast rotation of an electrical generator. The design of the hydraulic PTO system and its control are critical to maximize the generated power. A time domain simulation study and the laboratory experiment of the full-scale beach test are presented. The results of the simulation and laboratory experiments including their comparison at full-scale are also presented, which have validated the rationality of the design and the reliability of some key components of the prototype of the WEC with an inverse pendulum with the dual-stroke acting hydraulic PTO system.