8000kW救助船规则波下的运动与波浪载荷预报

随着数值计算技术的发展,船舶运动与波浪载荷预报精度也在不断提高。介绍了三维势流理论方法在规则波上船舶运动与波浪载荷预报中的应用,以8 000 k W救助船为例,预报了其运动与波浪载荷。通过应用三维势流理论,可以为船舶耐波性评估和结构设计提供依据。     

多功能支持船波浪载荷研究

波浪载荷研究是船舶性能预报和结构安全评估的关键内容。文中利用势流理论直接数值求解多功能支持船遭受的波浪载荷(包括一阶波频力和二阶漂移力),利用统计方法得到波浪载荷的长期预报和短期预报极值,包括波浪总纵弯矩和垂向波浪剪力以用于后续的船舶整体结构安全评估,以及纵向漂移力、横向漂移力和首摇漂移力矩用于船舶的动力定位能力分析中。研究结果表明:求解波浪载荷的势流理论方法精确,能为后续的船舶性能预报和结构安全评估提供可靠的载荷输入。     

基于三维势流理论的耐波性数值预报

准确预报船体运动响应对于砰击等波浪载荷的计算以及合理结构设计具有重要意义。船舶在大幅波浪中的运动呈明显的非线性,而现阶段耐波性预报多采用线性切片方法。三维水动力分析软件 WASIM基于时域势流理论,采用 Rankine面元法预报船舶在波浪中的运动响应,并考虑了多种非线性因素。本文以标模 DTMB5512为对象,采用 WASIM预报其在不同航速下的耐波性,并与基于线性切片理论的计算结果和模型试验结果进行对比。结果表明：利用 WASIM计算得到的船体运动响应比其他方法更接近试验值,合理体现了船舶在风浪中的实际耐波性能。因此,利用 WASIM能够较好地评估船舶在波浪中的非线性耐波特性。     

基于三维势流理论的耐波性数值预报

准确预报船体运动响应对于砰击等波浪载荷的计算以及合理结构设计具有重要意义。船舶在大幅波浪中的运动呈明显的非线性,而现阶段耐波性预报多采用线性切片方法。三维水动力分析软件WASIM基于时域势流理论,采用Rankine面元法预报船舶在波浪中的运动响应,并考虑了多种非线性因素。本文以标模DTMB5512为对象,采用WASIM预报其在不同航速下的耐波性,并与基于线性切片理论的计算结果和模型试验结果进行对比。结果表明:利用WASIM计算得到的船体运动响应比其他方法更接近试验值,合理体现了船舶在风浪中的实际耐波性能。因此,利用WASIM能够较好地评估船舶在波浪中的非线性耐波特性。     

内河船舶波浪载荷研究

利用内河波浪散布图和修订波浪谱对内河系列船舶进行了波浪载荷的计算预报,首次分析了内河船舶波浪载荷的规律和特点,并与俄罗斯内河登记局(RRR)和法国-德国船级社(B-G)的内河规范载荷对应的等效模数要求进行了比较分析。结合实船测试结果表明：波浪载荷变化规律与国外同类规范一致,预报波浪载荷水平与测试结果及国外同类规范要求相当。内河船舶波浪载荷预报应考虑航速和水深的影响,载荷预报结果可以作为制定内河波浪载荷公式的基础。     

内河船舶波浪载荷计算预报及规律

利用内河波浪散布图和修订波浪谱对内河系列船舶进行波浪载荷计算预报,分析内河船舶波浪载荷的规律和特点,与俄罗斯内河登记局(RRR)和法国-德国船级社(B-G)有关内河规范载荷对应的等效模数要求进行比较,并结合实船测试结果进行分析。结果表明:波浪载荷变化规律与国外同类规范一致,预报波浪载荷水平与测试结果及国外同类规范要求相当;内河船舶波浪载荷预报应考虑航速和水深的影响,载荷预报结果可以作为制定内河波浪载荷公式的基础。     

全航速三维线性波浪载荷时域内数值计算研究

高速船舶波浪诱导载荷存在航速效应,波浪诱导船体垂向弯矩随航速增加而增加.针对某集装箱船采用三维时域全航速水动力分析理论预报集装箱船在波浪上的运动性能和剖面载荷,深入分析船体运动性能和剖面载荷的航速效应,得到船体纵荡、横荡,横摇和首摇以及船体扭转波浪弯矩航速效应显著,为船舶结构设计人员在波浪载荷的计算上有一定的参考.     

短峰波中船舶运动与波浪载荷的频域水弹性理论与试验研究

传统的耐波性及波浪载荷理论与试验主要针对船舶在二维长峰波中的运动与载荷响应进行预报,然而实际海浪是三维短峰波。研究表明,基于长峰波的理论计算及水池模型试验所预报的船舶运动与载荷响应与实际情况存在一定的差异,且三维波浪的方向扩散特性是影响船舶运动与载荷响应的重要因素之一。为了研究短峰波中船舶运动与载荷响应特性及其与长峰波中响应的差异性,本文首先基于三维水弹性理论计算船舶在规则波中的频域响应,然后基于二维谱分析法将其扩展至短峰不规则波中船舶运动与载荷响应预报,进而分析短峰波方向扩散函数对于船舶运动与载荷响应的影响,最后基于实际海浪环境下大尺度模型水弹性试验数据验证理论计算结果。     

南海超大型抓斗疏浚船波浪载荷下结构强度评估研究

以一艘200方抓斗式疏浚船为例,阐述船舶波浪载荷长期预报和全船有限元直接计算方法。讨论不同波浪散布函数对船舶波浪载荷计算结果的影响。针对不同海域进行波浪载荷长期预报,通过对比分析得到南海海域波浪载荷水平,提出了南海工作船舶波浪载荷预报建议。在此基础上,对全船进行结构有限元分析,得到不同海域中全船结构应力水平,并对船体局部结构进行了优化,为在南海进行施工作业的疏浚船的设计提供参考。     

船舶波浪与砰击载荷的理性预报方法

本文概要地介绍船舶波浪载荷估算的研究状况，比较详细地介绍了船舶波浪载荷（包括砰击载荷）理性预报方法的基本理论、计算方法，通过两条高速船的算例并与测试结果比较，说明该预报方法具有广泛的应用前景。     

Experimental study of slam-induced stresses in a containership

Experiments for the ship motions and sea loads were carried out on a segmented model of a container ship in ballast condition. Comparisons between the measurements and the theoretical results were carried out for the vertical motions and bending moments. For the evaluation of the primary stresses it is assumed that the total vertical bending moment induced by waves is divided into one component obtained by the linear theory and another one is due to the slamming loads. Several formulations for the determination of the slamming loads are compared with experimental results. The vibratory response of the model is calculated by modelling the hull with rotational springs and rigid links. Linear finite elements with a consistent mass formulation are adopted for the structural model and the response is obtained by modal superimposing and direct integration methods.     

Practical estimation methods of the design loads for primary structural members of tankers

Various design loads used in the strength evaluation of ship structures have been introduced currently by classification societies. As most of these design loads have been determined as the standard loads for the sake of convenience, the relationships between the design loads and the sea states actually encountered by ships seem to be weak. Accordingly, it may be difficult to refer and utilize them as the fundamental design concepts for ship designers or the operational guidelines for ship operators. To overcome these difficulties, the authors have developed practical estimation methods of the design loads having transparent and consistent backgrounds to the actual loads acting on primary structural members of tankers. In this paper, the design sea states that closely resemble the actual sea states which are considered as the most severe for hull structures are firstly proposed. Secondly, the practical estimation methods of the design sea states are proposed by parametric studies using the results of series calculation of representative tankers. Thirdly, the practical estimation methods of design regular waves resulting in the same level of stresses with that induced in irregular waves under the design sea states are proposed. Finally, the practical estimation methods of the design loads such as ship motions, accelerations, hull girder bending moments and hydrodynamic pressures that are induced under design regular waves are proposed.     

基于船舶运动信息的航行海域海浪特性预报

以船舶自身为波浪测量仪,致力于采集方便而又尽可能少的船舶运动信号以提取航行海域实时海浪特性.由于估计中不依赖原始理论计算的传递函数,不需要附带波浪采集装置,而仅利用航行中船舶运动的观测序列完成海浪谱反演,故该海浪测量方法可适应船舶自身运动参数的变化.另一方面,由于反演估计的船舶运动频率响应特性,与事先计算或以其它实验方法得到的船舶运动频率响应特性得以比较,可以深化、修正对许多不易实时测量的海浪激励状态与船舶运动响应关系的认识,并积累船舶工程研究设计所必需的相关海域海浪谱信息.     

有限水深中破损船舶的运动与波浪载荷研究

由于有限水深中船舶搁浅和触礁等严重破损事故频发,为了减少事故的发生,对有限水深中船舶破损后的运动及波浪载荷的研究显得十分必要。文章基于三维势流理论,引入有限水深自由面Green函数,在频域内使用奇点分布法对一艘首部破损进水的散货船在有限水深中的运动与波浪载荷展开了计算,并根据劳氏船级社规范做了短期预报。短期预报结果表明,该散货船破损进水后,船体所受垂向和水平波浪弯矩均比破损前有明显增加,且在较浅水深中变化更为显著。     

基于规范载荷的舰船设计海况等级确定方法

针对军用规范载荷难以给出舰船设计海况等级的问题,本文通过三维时域非线性水弹性理论分析了舰船在典型航速、不同海况下的波浪载荷极值与规范载荷之间的对应关系,进而提出了一种明确舰船设计海况等级的方法。以某型舰船为例,基于该方法确定了该型舰船的设计海况等级。研究成果表明：该方法可有效明确舰船规范载荷对应下的设计海况等级,在一定程度上为舰船的安全使用提供参考。     

波浪引起破损船的垂向运动和弯矩（英文）

The wave-induced vertical ship motions and bending moments of a double hull-oil tanker in realistic flooding conditions are studied. The scenarios investigated are represented by water ingress into the starboard ballast tanks for collision damage cases and both starboard and portside ballast tanks for grounding situations. Seakeeping computations are performed for eight damage scenarios and for the intact condition, each corresponding to different changes in displacement, trim, and heel. For each of the damage conditions, transfer functions of vertical motions and loads are calculated using a potential linear 3 D panel hydrodynamic code in the frequency domain that includes effect of the motion of the water in flooded tanks. A MATLAB code is developed to facilitate automated hydrodynamic simulation of many damage scenarios. Verification of seakeeping results is performed by comparing transfer functions with results of the previous study. Wave-induced vertical responses of damaged ship are then compared to those of intact ship using two spectral-based methods originating from uncertainty analysis of wave loads, which are convenient tools to assess consequences of damage on short-term ship responses. Generally, observed trend is that vertical wave-induced responses of damaged ship converge toward those of intact ship with increasing wave period. Fairly small differences between responses of asymmetrically damaged ship with respect to the symmetrical incoming wave directions are found. The results of the study are an efficient method for seakeeping assessment of damaged oil tankers and the framework for evaluating consequences of damage scenarios, heading angles, and sea conditions on seakeeping responses of damaged ships.The results can be used to decide if the intact ship model can be used instead of the damaged one for the emergency response procedure or for the risk assessment studies when modeling and computational time represent important limitations.     

3-D computational method of wave loads on turret moored FPSO tankers

A three-dimensional method of calculating wave loads of turret moored FPSO (Floating Production Storage and Offloading) tankers is presented. The linearized restoring forces acting on the ship hull by the mooring system are calculated according to the catenary theory, which are expressed as the function of linear stiffness coefficients and the displacements of the upper ends of mooring chains. The hydrodynamic coefficients of the ship are calculated by the three-dimensional potential flow theory of the linear hydrodynamic problem for ships with a low forward speed. The equations of ship motions are established with the effect of the restoring forces from the mooring system included as linear stiffness coefficients. The equations of motions are solved in frequency domain, and the responses of wave-induced motions and loads on the ship can be obtained. A computer program based on this method has been developed, and some calculation examples are illustrated. Analysis results show that the method can give satisfying prediction of wave loads.     

航行船舶在波浪中响应长期监测技术

船舶在运营中遭遇恶劣海况时结构可能会发生破坏,从而对船舶在海上航行的安全性产生严重影响.对航行船舶结构安全性的实时监测与评估是船舶设计研究人员非常关注的问题,它对船体结构的研究、设计和标准制定以及航行操作都有重要的意义.对研发成功的一套航行船舶在波浪中响应的长期监测系统(LOTEMS)及其在实船航行中的长期应用情况进行介绍和分析.该系统能对船体结构的总纵强度和局部强度、船舶6个自由度的运动模态以及船舶的加速度进行实时的跟踪测量和分析,可为船舶结构安全状态提供必要的警示信息,以便为船舶操作人员航行决策提供辅助依据.     

SWATH船运动中断分析和减横摇控制器设计

针对SWATH船实航时产生的水平筛动问题,研究由横荡、横摇和艏摇的耦合运动产生的船舶运动中断(MII),提出设计SWATH船稳定鳍减横摇控制器,减小MII。通过理论分析MII产生原因和SWATH船稳定鳍工作时产生减摇作用的力和力矩特性,验证利用稳定鳍减小SWATH船横摇运动,抑制MII的可行性。在保证SWATH船升沉和纵摇运动的基础上,设计稳定鳍减横摇控制器,减小SWATH船横摇。仿真结果表明,控制器使SWATH具有良好的纵向运动性能,有效减小了横摇运动,抑制MII。     

Extensive study on the design loads used for strength assessment of tanker and bulk carrier structures

ClassNK has undertaken wide-ranging basic research covering many aspects related to the safety of ship structures, including design loads, structural analysis, strength assessment of buckling, collapse, and fatigue, and rational corrosion margins to develop new design standards which have transparency and consistency. Among the wide-ranging basic research, this article summarizes the results of extensive work on the design loads used for strength assessments of tanker and bulk carrier structures. The main aim of the research was to develop practical estimation methods of design loads with rational technical backgrounds relating to the actual loads acting on the primary structural members of tankers and bulk carriers. During this study, we proposed the following methodology. Design sea states that closely resemble the actual sea states which are considered to be the most severe for hull structures. Find practical estimation methods for the design sea states by parametric studies using the results of series calculations on representative tankers and bulk carriers. Find practical estimation methods for design regular waves which will result in the same level of stresses as those induced in irregular waves under the design sea states. We also briefly introduced some practical estimation methods for the design loads, such as ship motions, accelerations, hull-girder bending moments, and hydrodynamic pressures that are induced under design regular waves. The findings in this study have been summarized and implemented in the new design standards for tanker and bulk carrier structures.Updated from the Japanese original which won the 2003 SNAJ prize (J Soc Nav Archit Jpn 2002; 191:195–207; 2002; 191:208–220; and 2002; 192:723–733)