船舶操纵水动力导数的数值求解及敏感度分析

[目的]为了兼顾船舶操纵运动预报的成本与精度,基于数值计算方法,结合水动力导数敏感度分析,提出一种船舶操纵运动预报方法.[方法]首先,求解RANS方程,应用流体体积(VOF)法捕捉自由液面,采用动态网格方法对DTMB 5415船型进行约束运动的数值计算,并将回归得到的线性水动力导数与试验值进行对比,验证数值方案的有效性...     

一种三体船快速性的研究方法

选用一种三体船船模,通过理论分析、船模试验及数值模拟,对其快速性进行研究.在快速性试验的基础上,用VB编写的基于混沌算法的系统辨识程序对实验数据进行处理,即通过系统辨识确定快速性数学模型的相关系数,再根据这些系数和部分实验数据预报其他的量,经与实验所得数据对比分析,得到该船型的快速性的有关信息.     

船舶横浪倾覆试验及其数值模拟

本文介绍船模倾覆试验的结果及其数值模拟。试验表明，在横浪情况下船舶因装载造成的横倾角，会大大增加倾覆的危险性。对这一结论进行的数值模拟与实测结果符合良好。     

船用变频启动器试验用电力电子负载研究

针对传统阻感性负载无法满足船舶辅机设备对船用变频启动器启动性能和功率考核的要求,提出一种基于电力电子负载概念模拟电机特性的负载模拟系统。并依据电机本体模型及数学数值计算方法,根据实时仿真技术,将电机动态数学模型转换成可由数字控制器(比如DSP)实时运算的数值运算模型。最后,通过MATLAB/simulink仿真和实验,证明了模拟电机特性的电力电子负载的可行性。     

船模阻力评估模块开发

依托数值水池创新专项,文章借助商业软件STARCCM+方便的可视化界面以及工程应用的经验,探索出了一套船舶阻力计算策略,然后通过策略移植和转化,开发出了基于Open FOAM的船模阻力评估模块。为了达到工业化应用的要求,在开发船模阻力评估模块时不仅力求精确性而且还要兼顾鲁棒性。最后在12艘不同类型单桨商船25个工况点的测试计算中,所有样本点的计算精度都达到了3%以内,船模阻力评估模块的工程实用性得到了验证。     

Mathematical model of single-propeller twin-rudder ship

A mathematical model of a single-propeller twin-rudder ship has been developed from captive and free running model experiments. An open water rudder experiment was carried out to figure out the characteristics of the rudder. Captive experiments in a towing tank were carried out to figure out the performance of a single-propeller twin-rudder system on a large vessel. Interactions between the hull, propeller and twin rudders, including mutual interactions between the twin rudders, were expressed with several coefficients that were calculated from the experimental results at various ship speeds. In the analysis, the unique characteristics of a single-propeller twin-rudder ship, which affects rudder forces, were explained and formulated in the mathematical model. The captive model tests were conducted with zero ship’s yaw rate, so the interaction coefficients, which are influenced by the yaw rate, are determined from free running model experiments. Validation of the mathematical model of a single-propeller twin-rudder system for a blunt body ship is carried out with an independent set of free running experiments, which were not used for determining the interaction coefficients. The validated numerical model is used for carrying out simulations. Based on simulation results, some recommendations have been proposed for installing a single-propeller twin-rudder system.     

内河航道船舶航行操纵平面二维数值模拟初步研究

船舶航行操纵数学模型包括水流数学模型和船舶航行数学模型,其中水流数学模型是船舶航行模拟的基础。基于船舶航行操纵数学模型的基本原理,研究开发了船舶航行操纵平面二维数学模型,其中水流数学模型采用贴体坐标系下的平面二维水流数学模型,采用有限体积法对水流基本控制方程进行了离散,在求解过程中采用了欠松弛技术和逐线迭代法,船舶航行数学模型采用比较流行的"组合型"水动力模型,并采用有限差分法离散求解船舶运动方程。根据实船或船模在静水条件及均匀流条件下的航行试验资料,对所建立的船舶航行操纵数模进行了验证和参数率定,结果表明该船舶数模能够正确模拟船舶的航行操纵性能。     

Importance of several nonlinear factors on broaching prediction

In order to realize a more quantitative prediction of broaching and capsizing in following and quartering seas, existing mathematical modelling techniques should be upgraded. Therefore, it is necessary to systematically examine all factors relevant to capsizing in following and quartering seas. To this end, we first attempted to examine the prediction accuracy of wave-induced forces by comparing calculations with captive model experiments. As a result, we found that a wave-induced surge force has a certain nonlinearitiy with respect to wave steepness. The nonlinearity of sway–roll coupling with respect to sway velocity was also found, and our numerical result with these nonlinearities improves the prediction accuracy of the critical ship speed of capsizing in following and quartering seas. The importance of the wave effect on propeller thrust was also examined. We found that this effect is not negligibly small and could improve capsizing predictions in heavy following and quartering seas. Finally, we attempted to investigate the importance of nonlinear heel-induced hydrodynamic forces on numerical predictions of capsizing due to broaching. Here, we propose a new procedure for captive model experiments to obtain hydrodynamic forces with various heel angles up to 90°, and data on heel-induced hydrodynamic forces with respect to heel angle in calm water are provided. We then compare the numerical simulations with the nonlinear heel-induced hydrodynamic forces and without them. These time series comparisons show that the effect of nonlinear heel-induced hydrodynamic forces in calm water is not negligibly small for the case of ship capsizing due to broaching.     

新型气液耦合冲击耗能器的冲击响应特性研究

船舶设备遭受强冲击作用时,能够承受的加速度和相对位移幅值都很小,采用隔振器和限位器均不能满足抗冲击要求,此时需要特殊的耗能元件,吸收大量的冲击能量。基于将传统的隔振抗冲元件和新型耗能装置相结合的思想,设计了一种非线性抗冲击系统,在此基础上建立了气液耦合冲击耗能器的数学模型,并对其各参数(运动传递比和气腔有效横截面积)对抗冲击性能(绝对加速度幅值和相对位移幅值)的影响进行了仿真试验分析。研究表明,与线性隔离系统相比,冲击耗能器能够耗散部分冲击能量,提升系统的抗冲击能力;冲击耗能器的参数影响分析为新型耗能器的设计和开发提供了可行的理论依据。     

Risk zone of wrack hitting marine structure simulated by 2D hydraulic model

The wrack or the ship out of control will drift with flow.One of the most important factors that drive the ship is flow current which moves circularly in tidal area.The wrack from same place always drifts in different ways if the start time is different.So,during the ship drifting period,the drift trace is also determined by both wave and wind forces.The drift direction is limited by water depth which must be deeper than ship draft. These marine structures that can not afford the hit of wrack or will destroy the wrack must be well considered when they are placed near harbor and waterway or other water area with ship running.The risk zone should be consulted according to tide and weather conditions to protect structures and ships in necessary.A method is presented here to simulate the risk zone by 2D numerical hydraulic model with tidal current,wave,wind and water depth considered.This model can be used to built early-warning and protect system for special marine structure.     

Survivability of an ocean patrol vessel – Analysis approach and uncertainty treatment

Military ocean patrol vessels (OPVs) are today an increasingly common type of naval ship. To facilitate the wide range of tasks with small crews, OPVs represent several ship design compromises between, for example, survivability, redundancy and technical endurance, and some of these compromises are new to military ships.The aim of this study is to examine how the design risk control-options in relation to survivability, redundancy and technical endurance can be linked to the operational risk in a patrol and surveillance scenario. The ship operation for a generic OPV, including the actions of the threat, is modelled with a Bayesian network describing the scenario and the dependency among different influences.The scenario is described with expert data collected from subject matter experts. The approach includes an analysis of uncertainty using Monte Carlo analysis and numerical derivative analysis.The results show that it is possible to link the performance of specific ship design features to the operational risk. Being able to propagate the epistemic uncertainties through the model is important to understand how the uncertainty in the input affects the output and the output uncertainty for the studied case is small relative to the input uncertainty. The study shows that linking different ship design features for aspects such as survivability, redundancy and technical endurance to the operational risk gives important information for the ship design decision-making process.     

基于细分曲面的船体曲面造型及静水力参数计算

提出采用细分曲面进行船体曲面造型,结合多边形及多面体的几何特性计算公式进行船舶静水力性能参数计算新方法。推导并整理出两套多边形及由三角单元围成的多面体的几何特性计算公式。根据文中方法对一组数学船型的部分静水力参数进行计算,并将计算结果与精确解进行比较,验证该方法的有效性。同时与传统的辛普生法、Maxsurf软件计算方法作了比较,说明所提出方法的有效性和通用性。     

船舶操纵运动数值模拟在桥梁通航孔布设中的应用研究*

布设于通航水域中的桥墩可能会对桥区河段通航安全产生较大影响,因此对桥位河段的通航情况及通航净空尺度展开分析研究十分必要。目前,桥梁的通航论证研究主要包括水流流速、流向、通航净空高度和和通航净空宽度,而对代表船舶通过设计通航孔时的船舶航行姿态研究甚少。在平面二维水流数学模型基础上,开发建立船舶操纵运动数学模型,通过模拟计算代表船舶通过桥区的航行姿态和航行参数,包括艏向角、舵角、漂角及航速等,结果表明可较好模拟在不同水文组合条件和不同通航孔条件下,船舶通过桥区水域的操控及航行条件。     

Simplified buckling-and-contact-based expansion method for assessment of crashworthiness of double-hulled ship structure

Ship-to-ship collision events can have severe consequences such as loss of life and environmental degradation. For this reason, modern ship designs are required to incorporate a double-hulled structure to prevent inner-hull damage from such events. Using the experimental or numerical method to analyze the crashworthiness of double-hulled ship structures entails much effort, for which reason neither method is easy to adopt at the early design stage. In this paper, an existing simplified method called Ito's method is improved by a new buckling-and-contact-based expansion method. This method can be applied to double-hulled-structure or outer-hull-local-rupture failure mode. The perpendicular bow-to-side collision scenario is assumed for a conservative estimation of damage to a double-hulled structure. The method was verified in the present study by numerical ship collision simulations of several cases. The results for the buckling-and-contact-based expansion method and numerical simulation were similar for a blunt shape of striking body but different for a sharp shape.     

改进的BP神经网络在船舶与海洋工程中的应用研究

人工神经网络作为一个具有高度非线性映射能力的计算模型,在工程中具有广泛的应用前景.在数值预测方面,它不需要预选确定样本的数学模型,仅通过学习样本数据即可以进行预测.文章介绍了BP神经网络,并针对实际应用中收敛速度慢,平台效应等问题对网络进行了改进并优化,详尽地给出了改进的三层BP神经网络数值预测算法.为测试该算法.选用了著名的XOR(异或)问题和和一个高度非线性的0-1矩阵预测问题对其进行了验证.计算结果表明文中算法能给出令人满意的精度.最后结合船舶与海洋工程的两个实际问题,探讨了利用改进的BP神经网络进行数值预测的方法和应该注意的问题,并给出了一些有益的建议.实践表明,文中给出的改进的BP神经网络数值预测算法值得在船舶与海洋工程中加以应用并推广.     

内河航道船舶航行操纵平面二维数值模拟在复杂流态下的应用

基于平面二维水流数学模型和船舶航行操纵数学模型的基本原理,开发了适合内河航道的曲线拟合坐标系下的船舶航行操纵平面二维数学模型,其中水流数学模型采用贴体坐标系下的平面二维水流数学模型,船舶航行操纵数学模型采用比较流行的"组合型"水动力模型。在实船和船模在静水条件及均匀流条件下的航行试验验证的基础上,通过复杂流态河段船舶航行操纵数值模拟的研究,表明该船舶数模基本能够模拟船舶在复杂流态下的航行操纵情况。     

Numerical study of ice-induced loads on ship hulls

A numerical model is introduced in this paper to investigate both global and local ice loads on ship hulls. This model is partly based on empirical data, by which the observed phenomena of continuous icebreaking can be well reproduced. In the simulation of a full-scale icebreaking trial, the interdependence between the ice load and the ship’s motion is considered, and the three degree-of-freedom rigid body equations of surge, sway and yaw are solved by numerical integration. The variations in the level ice thickness and in the strength properties of ice can also be taken into account. The simulated ice loads on ship hulls are discussed through two case studies, in which the ship’s performance, the statistics of ice-induced frame loads, and the spatial distribution of ice loads around the hull are analyzed and compared with field measurements. As far as we know the present paper is the first to integrate all the features above. It is hoped that further studies on this numerical model can supplement the field and laboratory measurements in establishing a design basis for the ice-going ships especially for ships navigating in the first-year ice.     

舰船自动智能避碰数学模型及其仿真研究

为了提高舰船航行的安全和效率,达到最佳操船效果,需要建立舰船自动智能避碰数字模型.当前模型在分析舰船避碰风险度的基础上,通过人工智能、进化计算和软计算等方法实现舰船自动智能避碰,存在避碰识别准确率较低的问题.本文提出一种新的舰船自动智能避碰数学模型,首先对舰船会遇态势进行判断;然后建立预测舰船碰撞风险判断模型,预测本舰船实施自动智能避碰方案后的复航时机是否已到,以及本舰船立即复航是否能够让清目标舰船或其他所有目标舰船;最后依据舰船碰撞风险判断结果,以当前舰船潜在碰撞风险为例,建立舰船自动智能避碰数学模型.仿真结果证明,所提模型能够实现舰船自动智能避碰.     

Modeling nonlinear roll damping with a self-consistent,strongly nonlinear ship motion model

Appropriate modeling of roll damping is one of the key issues in accurately predicting ship roll motion. The difficulties in modeling roll damping arise from the nonlinear nature of the phenomena. In this study, we report a new effort in modeling the bilge keel roll damping effect based on the blocking mechanisms of an object in the potential flow. This effect can be implemented as a component of appropriate ship motion models. We used our digital, self-consistent, ship experimental laboratory (DiSSEL) ship motion model to test its effectiveness in predicting ship roll motion. Our numerical experiment demonstrated clearly that the implementation of this roll damping component improves significantly the accuracy of numerical model results (the results were compared with ship experiment data from the Naval Surface Warfare Center, Carderock Division, Maneuvering and Seakeeping Facility).     

碰撞/搁浅事故中船体强桁材结构损伤机理解析预报方法研究

随着航运业的快速发展,海上航行的船舶越来越多.尽管人们做了许多努力避免海上意外事故的发生,但海难事故依然不可避免.为了降低上述事故造成的损失,需要在设计阶段快速并准确地预报船舶的结构耐撞性.本文以强桁材结构为研究对象,通过开展准静态冲压试验及相应的数值仿真,分析强桁材结构在面内冲压载荷作用下的变形机理,并基于试验与仿真所得到的结构变形特点,提出强桁材面内受压时的变形模式.以此为基础,运用塑性力学理论,推导出结构变形能、瞬时结构变形抗力及平均结构变形抗力的解析预报公式,并将计算结果与试验结果进行比较验证.研究得到的结构面内受压变形能和抗力解析计算公式,可以快速评估事故载荷下结构的响应情况,包括结构变形阻力及能量耗散,具有使用方便,计算速度快,计算结果相对可靠的优点,对船体耐撞结构设计及抗撞性能评估具有一定的指导意义.