骑浪/横甩薄弱性衡准和模型试验研究

目前国际海事组织(IMO)正在制定的第二代完整稳性衡准,其中就包括骑浪/横甩薄弱性衡准。文章首先介绍了最新骑浪/横甩薄弱性衡准方法,应用自编的衡准软件进行样船计算,分析了当前衡准的适用性。其次,开展了内倾船型在随浪和尾斜浪中的骑浪/横甩试验,试验中获得了四种与骑浪/横甩相关的运动特性:周期运动、稳定骑浪、横甩和横甩导致的倾覆,而且在某波浪条件下观察到船舶连续发生三次横甩的现象。最后,将内倾船型的骑浪/横甩薄弱性衡准计算结果与试验结果进行对比,验证了衡准方法对于内倾船型的适用性。     

喷水推进船骑浪运动建模及时域仿真

[目的]船舶骑浪/横甩是国际海事组织(IMO)新纳入船舶第二代完整稳性衡准中的5种稳性失效模式之一。针对当前规范仅适用于螺旋桨推进船的局限性,研究喷水推进船骑浪失稳的问题,为后续进一步完善规范奠定基础。[方法]基于喷水推进装置的力学模型和船舶在随浪中的一维纵荡运动方程,建立船舶骑浪运动的数学模型,利用四阶Runge-Kutta法求解模型,实现船舶时域运动仿真。以一艘高速穿浪内倾船型为例,系统性开展时域数值计算,以得出此类型船舶发生骑浪现象时的工况特点。[结果]通过数值仿真,得出了目标船舶在第二代完整稳性衡准要求的波浪工况范围内的预报结果:Fr=0.4时,有80.9%的工况发生骑浪;Fr=0.3时,骑浪发生比例降至59.4%。[结论]研究成果既可为喷水推进船的骑浪/横甩稳性评估提供理论模型和数值分析的手段,也可用于对此类型船舶进行稳性安全评估。     

基于弱非线性耦合数值模型的渔船骑浪横甩界限探究

骑浪横甩是船舶在波浪中失稳模态之一,其具有较强的非线性且多发生于速度较快的小型船舶上,对其发生界限的研究对于船舶设计与安全运营均具有一定实际意义。论文中提出一种考虑船舶操纵性和耐波性运动耦合的六自由度弱非线性统一模型,对一艘ITTC ship A2渔船尾随浪下的骑浪横甩运动进行时域数值模拟。时域模型中,六自由度耐波性运动辐射绕射力采用切片理论计算,并由脉冲响应函数法转化到时域。非线性回复力和入射波力采用瞬时湿表面压力积分方法计算。操纵性运动基于MMG模型,依据统一理论将操纵性与耐波性运动进行耦合计算。文中应用此模型,对不同航速、波高和GM值下渔船在尾随浪中的运动进行时域模拟。通过分析,将结果分类为周期运动、骑浪横甩造成的倾覆、波浪中失稳造成的倾覆等运动模态,并进一步对各模态间发生的界限进行了探究。     

船型参数对骑浪/横甩薄弱性衡准影响研究

骑浪/横甩是IMO船舶第二代完整稳性的五种失效模式之一,是一种基于概率的稳性衡准,制定规范的目的是更有效地保障船舶在实海域中的航行安全,确保不发生稳性失效情况.本研究中,以IMO有关成员国提出的最新版骑浪/横甩薄弱性衡准草案为基础,基于自主开发的骑浪/横甩薄弱性衡准校核软件,针对围网渔船开展了样船计算和比较分析,研究IMO正在制定的骑浪/横甩薄弱性衡准方法对该类船型的适用情况,分析船型参数对骑浪/横甩薄弱性衡准的影响,为我国参与国际法规制定,提出针对骑浪/横甩薄弱性衡准的提案提供技术支撑和依据.     

船舶在恶劣随浪中航行的运动和危险区域

本文介绍了一个用数学模型进行数值实验预报船舶在恶劣随浪中的特性，首先，对船舶在恶劣的随浪和尾斜浪中发生骑波和倾覆的危险状态进行了数值实验研究。其次，对于船舶在恶劣的随浪中发生骑波现象的临界傅汝德数进行了研究，最后，对于作横荡，横摇和首摇耦俣运动时的船舶，计算了方向稳定性的稳定区域和不稳定区域。     

业界

由万科浪骑游艇会举办，深圳市帆船帆板协会协办的首届“浪骑杯”摩托艇精英挑战大赛于8月8日在浪骑附近海域举行。浪骑游艇会会员、深圳帆船帆板协会会员以及深圳民间摩托艇发烧友等近30名水上运动爱好者参加了比赛。     

骑浪横甩薄弱性衡准技术的发展

介绍了骑浪/横甩的物理背景,以及骑浪/横甩第一层和第二层薄弱性衡准发展过程,并分析了骑浪横甩薄弱性衡准计算方法及初步衡准,掌握骑浪横甩薄弱性衡准技术的发展现状,有助于骑浪/横甩相关技术领域的研究,为船舶第二代完整稳性的技术发展奠定基础。     

船舶不规则波中增速骑浪的数值计算及统计分析

船舶在随浪中航行时,受到波浪影响,会产生间歇性的异常高速现象,即"high runs",它反映了一种船速相对于波形高速前冲的危险状态,本文采用"波浪中增速骑浪"指代这一现象.基于统一理论,采用耐波性和操纵性耦合的六自由度弱非线性模型进行求解,对其展开数值计算和统计分析.通过探讨,论证标称航速作为波浪中增速骑浪现象发生判...     

2014“浪骑杯”帆船联赛首场赛讯＆船队风彩

“浪骑杯”首场赛事：小风中，友宝、麦博队齐领航 3月1日，2014“浪骑杯”帆船联赛首场比赛在深圳浪骑游艇会拉开帷幕。15支船队云集于此，虎视眈眈地争夺全年联赛的首场冠军。     

船舶骑浪/横甩薄弱性衡准研究

骑浪/横甩是导致船舶在随浪或尾斜浪中发生倾覆的主要因素之一。为了准确预报船舶是否发生骑浪进而导致横甩,以SLF55/INF.15会议上美国学者提出的船舶骑浪/横甩薄弱性衡准草案和IMO SDC 1/INF 8会议上美国、日本学者联合提出的薄弱性衡准草案为基础,对薄弱性衡准进行分析研究,并编制相应的骑浪/横甩判断程序;以C11船型等样船为例进行样船测试,判断是否发生横甩,并和前人的计算结果相比较,并以此验证该薄弱性衡准草案的通用性和此程序的适用性,为制定第二代完整稳性提供技术支持。     

Prediction methods for the surf-riding threshold and the wave-blocking threshold based on Melnikov’s method

A ship operating in following and/or quartering seas may be susceptible to broaching-to preceded by the surf-riding phenomenon. Therefore, for the safety assessment of fast vessels such as destroyers and patrol craft, the estimation of the surf-riding condition is important. As shown by previous research, there are two boundaries for ship motion in following and quartering seas. These are the surf-riding threshold and wave-blocking threshold. In this study, the theoretical methods to estimate both boundaries are obtained by making use of Melnikov’s method. In order to validate the formulae, free-running model experiments are conducted in the towing tank. Comparisons between the results obtained from calculations and experiments show good agreement. It is concluded that the formulae based on Melnikov’s method could be applicable to the safety assessment of surface ships.     

Qualitative aspects of nonlinear ship motions in following and quartering seas with high forward velocity

By utilizing a four-degrees-of-freedom numerical model with dense grids of control parameters and the sudden-change concept, the qualitative aspects of the nonlinear motions of a fishing vessel complying with the International Maritime Organization's intact stability criteria in following and quartering seas were intensively explored. As a result, capsizing due to broaching, capsizing without broaching, broaching without capsizing, stable surf-riding, and steady periodic motion were identified. The natures of the boundaries of these motions in the control parameter plane were investigated, and the effects of the initial conditions and the nonlinearity of calm-water maneuvering forces are also discussed. Furthermore, comparisons with a model experiment showed that the numerical model used here qualitatively explains capsizing phenomena, but quantitatively overestimates the danger of capsizing. Received: June 11, 2001 / Accepted: October 9, 2001     

Numerical prediction of the surf-riding threshold of a ship in stern quartering waves in the light of bifurcation theory

In order to develop design and operational criteria to be used at the International Maritime Organization (IMO), critical conditions for broaching are explored in the light of bifurcation analysis. Since surf-riding, which is a prerequisite to broaching, can be regarded as a heteroclinic bifurcation, one of global bifurcations, of a surge-sway-yaw-roll model in quartering waves, the relevant bifurcation condition is formulated with a rigorous mathematical background. Then an efficient numerical solution procedure suitable for tracing the surf-riding threshold hypersurface is presented with successful examples. This deals with all state and control variables in parallel, and excludes backward time integration and an orthogonal condition in the iteration process. The bifurcation conditions identified were compared with the results from a direct numerical simulation in the time domain. As a result, it was confirmed that the heteroclinic bifurcation provides a boundary between motions periodically overtaken by waves and nonperiodic motions such as surf-riding and broaching.     

Analytical formulae for predicting the surf-riding threshold for a ship in following seas

Making use of Melnikov’s method, a generalized formula for predicting the surf-riding threshold is developed as an extension to the applications of Kan and Spyrou. A new analytical formula for calculating the surf-riding threshold of a ship in following seas is also proposed in light of nonlinear dynamical system theory. By applying a continuous piecewise linear approximation to the wave-induced surge force, a heteroclinic bifurcation point is obtained analytically with an uncoupled surge equation. Results calculated using these formulae are presented, and they show good agreement with those obtained utilizing numerical bifurcation analysis. Further, it was confirmed that the surf-riding threshold obtained using the proposed formulae agrees reasonably well with that obtained experimentally for an unconventional vessel.     

用谐波小波变换法研究船舶横摇的非线性动力特性

本文探索了一种用小波分析的方法来研究船舶非线性横摇系统的运动.对于非线性非自治系统的响应主要有周期、准周期和混沌几种状态.而在系统参数变化时,又由周期分叉形成了准周期和混沌.因此,需要对周期解做更多的研究.当系统响应是周期的,通过小波变换,可以得到一些不同频率的谐波,这些谐波与谐波平衡法得到的解非常相似,因此也就可以作为系统的近似解.如果系统响应是混沌的,通过小波变换,始终都得不到周期的信号,这一点明显区别于周期运动.也就是说通过小波变换这种方法,可以明显地区别出混沌和周期.     

基于CFD的船舶骑浪状态下的纯稳性损失求解

船舶顺浪航行的纯稳性损失研究已成为国际航海界和国际海事组织(IMO)关注的课题之一。基于计算流体力学(CFD)技术,生成了船舶的骑浪航态,采用系列横摇衰减试验方法,获取到了该航态下某型舰艇的稳性曲线,通过后续计算得到纯稳性损失,并与一般理论计算法得到的结果进行对比,结果验证了该方法的可信度。     

纯稳性丧失和瘫船稳性薄弱性衡准实船验证分析

国际海事组织(IMO)正在制定第二代完整稳性衡准,并计划于2019年开始强制实施.该稳性衡准涵盖了5种稳性失效模式:参数横摇、纯稳性丧失、过度加速度、瘫船稳性和骑浪/横甩.衡准评估由薄弱性衡准和稳性直接评估组成.本文采用实际运营的4艘油船和3艘渔政船对最新草案中纯稳性丧失和瘫船稳性的薄弱性衡准进行了计算,分析了第一层和第二层薄弱性衡准的一致性,为纯稳性丧失和瘫船稳性薄弱性衡准的制定提供参考.