不对称船体结构动态特性研究

针对计算常规船舶结构动态特性的方法不适用于计算左右不对称横剖面船体梁动态特性的问题，本文将船体视为薄壁梁并离散成梁段，推导出迁移矩阵法迭代求解不对称船体结构固有及固有振型的公式系统，计算了左右不对称程度不同的梁结构及不对称船 梁的固有频率及振型。指出不对称梁 有振动为弯扭耦合振动，其固有频率与振动型的对应关系与对称梁不同。     

破损船体极限强度非线性有限元分析

本文基于通用有限元系统,结合船体破损机理和初始缺陷处理方法,建立船体极限强度非线性有限元分析的完整框架.利用对水面舰船和双壳油船极限强度模型试验的比较验证,合理解决非线性有限元分析的关键技术,并对完整和破损船体极限强度进行非线性有限元法分析.然后,在模型试验和非线性有限元分析的基础上提出面向设计的适合破损船体和双向弯曲状态的船体极限强度分析的改进解析方法.     

Dynamics of ships running aground

A comprehensive dynamic model is presented for analysis of the transient loads and responses of the hull girder of ships running aground on relatively plane sand, gravel, or rock sea bottoms. Depending on the seabed soil characteristics and the geometry of the ship bow, the bow will plow into the seabed to some extent. The soil forces are determined by a mathematical model based on a theory for frictional soils in rupture and dynamic equilibrium of the fluid phase in the saturated soil. The hydrodynamic pressure forces acting on the decelerated ship hull are determined by taking into account the effect of shallow water. Hydrodynamic memory effects on the transient hull motions are modeled by application of an impulse response technique. The ship hull is modeled as an elastic beam to determine the structural response in the form of flexural and longitudinal stress waves caused by the transient ground reaction and hydrodynamic forces. A number of numerical analysis results are presented for a VLCC running aground. The results include bow trajectory in the seabed, time variation of the grounding force, and the maximum values of the sectional shear forces and bending moments in the hull girder.     

Effects of the standoff distance on hull structure damage subjected to near-field underwater explosion

The near-field underwater explosion poses a great threaten to marine ships by introducing both local and overall damage on their hull structures. In this paper, a series of near-field underwater explosion experiments were carried out on the mimic steel hull structures to investigate the effects of the standoff distance on their dynamic behavior. Special attention was paid on their deformation process and failure modes. After that, a fluid-solid coupling algorithm was implemented in establishing a finite element (FE) model to simulate dynamic response of the hull structures under a near-field underwater explosion. The numerical results showed a good agreement with the experimental data. A standoff distance threshold was found to result in the maximum structural deformation. The deformation magnitude was monotonically decreased by either increasing or decreasing the standoff distance from the threshold value.     

破损散货船剩余极限强度的评估与分析

船体发生破损后.其剩余有效剖面是非对称的,船体还可能倾斜.根据IACS共同规范(CSR),采用逐步破坏分析法计算船体梁在不同破损情况下的剩余极限强度,同时编制了计算程序.对1艘散货船在完整和不同破损状态下的船体结构安全性进行了系统评估,并得到了一些有意义的结论.     

A practical method for torsional strength assessment of container ship structures

Container ship structures are characterized by large hatch openings. Due to this structural property, they are subject to large diagonal deformations of hatch openings and warping stresses under complex torsional moments in waves. This necessitates torsional strength assessment of hull girder of container ships in their structural design stage. In this paper, a practical method for torsional strength assessment of container ship structures with transparent and consistent background is discussed based on the results from up-to-date analyses. In order to estimate the torsional response characteristics as accurately as possible, three-dimensional Rankine source method, after being validated by tank tests, is employed for estimation of wave loads on a container ship, and FE analyses are conducted on the entire-ship model under the estimated loads. Then, a dominant regular wave condition under which the torsional response of the container ship becomes maximum is specified. Design loads for torsional strength assessment that give torsional response equivalent to the long-term predicted values of torsional response are investigated based on the torsional moments on several container ships under the specified dominant wave condition. An appropriate combination of stress components to estimate the total hull girder stress is also discussed.     

静水航行船舶粘性兴波阻力计算分析(英文)

The prediction of a ship's resistance especially the viscous wave-making resistance is an important issue in CFD applications. In this paper, the resistances of six ships from hull 1 to hull 6 with different hull forms advancing in still water are numerically studied using the solver naoe-FOAM-SJTU, which was developed based on the open source code package OpenFOAM. Different components of the resistances are computed and compared while considering two speed conditions(12 kn and 16 kn). The resistance of hull 3 is the smallest while that of hull 5 is the largest at the same speed. The results show hull 3 is a good reference for the design of similar ships, which can provide some valuable guidelines for hull form optimization.     

Numerical study of viscous wave-making resistance of ship navigation in still water

The prediction of a ship＇s resistance especially the viscous wave-making resistance is an important issue in CFD applications. In this paper, the resistances of six ships from hull 1 to hull 6 with different hull forms advancing in still water are numerically studied using the solver naoe-FOAM-SJTU, which was developed based on the open source code package OpenFOAM. Different components of the resistances are computed and compared while considering two speed conditions （12 kn and 16 kn）. The resistance of hull 3 is the smallest while that of hull 5 is the largest at the same speed. The results show hull 3 is a good reference for the design of similar ships, which can provide some valuable guidelines for hull form optimization.     

水下爆炸气泡载荷作用下船体梁的动态水弹性响应

文章基于势流理论,针对水下爆炸气泡脉动载荷作用下船体梁的动态水弹性鞭状响应及其共振效应进行了研究。阐述了水下爆炸气泡与船体梁之间的流固耦合理论分析,并分别建立了一个考虑气泡迁移,自由面效应和气泡阻力的气泡模型和一个船体梁的弹性响应的计算模型。文中以两条实船作为算例,研究了刚体运动对船体梁弹性振动响应的影响,分析了船体梁在气泡脉动载荷作用下产生的共振破坏的机理。     

高耐波隐身船型设计

具有优良耐波性和隐身性的舰船是当前世界各海军强国舰艇平台技术研究的重要发展趋势。以往舰艇的雷达波隐身设计主要是对上层建筑和舰面设备进行外形隐身设计,对主船体很少进行雷达波隐身设计,主要是因为主船体的隐身设计可能会影响其航行性能。为进一步提高舰船的隐身性和耐波性,本文以几千吨级舰艇为对象,在对船体进行隐身设计的基础上,以深V船型作为设计船体水线以下部分的基础线型,通过对底升角、首部吃水、尾部形状、长宽比和底面的凹凸进行优化,对比在不同情况下的耐波性和阻力,对船舶运动及水动力性能进行分析,提出了一种适用于未来隐身水面舰艇的高耐波性船型。     

Comparative reliability analysis of ships under vector-load processes

This paper deals with reliability analysis of ships under vector-load processes. Failure is expressed by multiple response variables. Different methods can be used to assess failure probability, primary among them are the time-independent and out-crossing (up-crossing) rate methods. This paper describes the procedure for performing reliability analysis of ships under vector-load processes by the out-crossing rate method. Alternative methods based on piecewise linear or continuous modeling of failure surface are explored for calculating the out-crossing rate and compared. The methods are exemplified by calculating the conditional probability of a damaged double hull oil tanker under combined vertical and horizontal bending moments.     

船体腐蚀对船舶强度的影响

基于营运船的船体腐蚀状况,运用船体剖面模数概念,分析了船体腐蚀对船舶强度的影响,提出了一些保证船舶强度的措施,为船舶的保养工作提供参考,以减少船舶安全事故的发生.     

破损船体非对称弯曲极限强度分析及可靠性评估

在船体发生破损后,其剩余有效剖面是非对称的,船体还可能倾斜。本文首先对破损船体非对称弯曲进行了弹性和塑性分析,在此基础上假设了破损船体发生整体破坏时的剖面应力分布,给出了破损船体非对称弯曲极限强度分析方法,并采用了比较精细的方法计算加筋板格的屈曲极限强度。以箱型梁模型和超大型油船为例,将本文的计算结果与试验、ＩＳＵＭ法及解析公式的结果进行了比较。基于破损船体极限强度,结合重要性样本法,对６５,００     

Fatigue damage calculation for oil tanker and container ship structures

The fatigue behaviour of longitudinal stiffeners of oil tankers and container ships, subjected to dynamic loads, is analysed. The following dynamic load components are considered: hull girder vertical wave bending moment, alone and combined with the horizontal wave bending moment, hydrodynamic pressure and inertial forces caused by cargo acceleration.

The spectral method was selected to calculate the fatigue damage, based on S—N curves and Miner's rule. Following this approach, the fatigue damage may be calculated as a function of a stress parameter Ω_p, which represents the cumulative effect of wave induced loads in the unit of time and incorporates the combined effects of stress level and its occurring frequency.

Simple formulas for Ω_p of oil tankers and container ships are given, obtained from the results of hydrodynamic analyses performed on several ships, in different wave environments.

Several examples show the applicability of the methods to real ship structures. The method, however, still needs to be calibrated because of the simplifying hypotheses introduced in the loading conditions.     

受损船体极限强度分析与可靠性评估

对预报船舶极限强度的解析公式作局部改进，使其更有效地用于评估或预报现代船舶剩余极限强度。将该方法同MVFOSM相结合，对一艘油船进行了完整船体（新建／老龄）与受损结构（搁浅／碰撞）极限总纵强度分析和可靠性评估及预报；某些结论可作为深入研究剩余强度理论或指导实船结构设计的参考。     

大型舰船总纵强度计算方法研究

由于现有国内水面舰船设计规范仅适用于船长160m以下的舰船,为了更好地研究大型舰船的总纵强度,本文对一船长约200m的目标舰按照<中国船级社钢质海船入级与建造规范>(CCS)与基于<舰船通用规范>(GJB)基础上的建议标准以及全船有限元直接计算这三种方法作了计算与比较,得出了一些有益的结论,对大型舰船的总纵强度研究与规范的制定提供了较好的参考.     

大型舰船总振动固有频率近似计算研究

基于我国舰船的设计规律,提出了一种精确计算大型舰船总振动固有频率所需初始数据的虚拟设计方法。以某舰船为原型,设计出177～200 m船长范围内系列虚拟船型主尺度及船体等值梁数据。计算出系列舰船虚拟船型船体的总振动固有频率值,扩展了船体总振动固有频率近似公式中统计系数的统计样本范围,利用扩展的统计样本数据提出了适合估算大型舰船船体总振动固有频率的经验公式。     

水弹性力学在SWATH船体结构振动响应分析中的应用研究

文章以三维水弹性力学理论为基础,对小水线面双体船的船体振动响应特性进行了分析,预报了该船体在航行时受发电机激励下的振动响应,并与实船测量结果进行了对比,结论表明三维水弹性力学方法在船体受机械激励作用下对于船体振动响应的预报是有效的,可应用于工程设计。     

A study of vibration and vibration control of ship structures

This paper examines the vibration characteristics and vibration control of complex ship structures. It is shown that input mobilities of a ship structure at engine supports, due to out-of-plane force or bending moment excitations, are governed by the flexural stiffness of the engine supports. The frequency averaged input mobilities of the ship structure, due to such excitations, can be represented by those of the corresponding infinite beam. The torsional moment input mobility at the engine support can be estimated from the torsional response of the engine bed section under direct excitation. It is found that the inclusion of ship hull and deck plates in the ship structure model has little effect on the frequency-averaged response of the ship structure. This study also shows that vibration propagation in complex ship structures at low frequencies can be attenuated by imposing irregularities to the ring frame locations in ships. Vibration responses of ship structures due to machinery excitations at higher frequencies can be controlled by structural modifications of the local supporting structures such as engine beds in ships.     

计及热辐射及翼翅效应的VLGC温度场计算

运用热力学理论,对设有A型独立液货舱的大型全冷式液化气船（VLGC）的液货、船体结构及海水和空气之间的热传递过程作了研究并对船体结构温度分布作了计算。计算中,除考虑传统的对流和传导之外,还考虑了热辐射以及船体结构加筋板架翼翅效应（fin effect）的影响,提高了计算精度。建立了热传递能量平衡方程,并通过迭代法进行求解,最终得出了船体结构温度场分布。