Prediction of the maneuverability of a large container ship with twin propellers and twin rudders

The maneuvering characteristics of a large container ship with twin propellers and twin rudders were investigated using the horizontal planar motion mechanism (HPMM) test and computer simulation. A mathematical model for maneuvering motion with four degrees of freedom (DOF) for twin-propeller and twin-rudder systems was developed and included the effects of roll motion. To obtain the roll-coupling hydrodynamic coefficients of a container ship, a four-DOF HPMM system having a roll motion mechanism and a roll moment measurement system was used. At the full load condition, HPMM tests were carried out for two different 12 000-TEU container ship models, one with twin propellers and the other with a single propeller. Using the hydrodynamic coefficients obtained from the tests, computer simulations were carried out. Simulation results for the container ship with twin propellers and twin rudders were compared with the results for the container ship with a single propeller and single rudder.     

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.     

船舶大舵角转向时艏摇与横摇的耦合仿真研究

摘要：为进一步研究船舶在大幅度转向时艏摇和横摇的耦合机制,在非线性船舶运动数学模型的基础上,进行了不同情形下的操纵仿真试验。试验结果显示在大舵角转向时,船舶的艏摇和横摇运动存在较强的耦合作用,横摇幅度和艏摇幅度存在正相关性。指出大幅度的横摇使艏摇出现相位滞后和偏离基准航向的现象;在横摇过大的情况下,大幅度动舵和加速操纵将导致稳性迅速消失和航向打横。     

应用支持向量机的船舶操纵运动响应模型辨识

建模是评估船舶操纵性和可控性的重要前提.基于自由自航船模试验的系统辨识方法是求取船舶操纵运动数学模型中的水动力系数的有效手段之一.文中提出了一种使用支持向量回归估计的船舶操纵运动响应模型辨识方法,该方法通过训练自由自航试验数据样本得到参数回归模型.辨识和仿真结果验证了文中所提出的方法的有效性.     

船舶在波浪中操纵运动仿真

本文研究了双浆双舵船在规则波中的回转运动，首先进行了约束模型试验，得到了操纵运动数学模型中的水动力系数，然后，进行了静水操纵运动数值仿真，并与自航模型试验结果进行了比较。最后，预报船舶在规则波中的回转运动，对一些影响回转运动的因素进行了讨论。     

Broaching prediction of a wave-piercing tumblehome vessel with twin screws and twin rudders

The new intact stability criteria which are under development at the International Maritime Organization (IMO) are required to cover a broaching phenomenon, well known as a great threat to high-speed vessels which can lead to capsizing. Some reports exist which demonstrate that their numerical models can predict a highly nonlinear phenomenon of broaching. However, additional validation studies are needed for unconventional vessels, in addition to conventional ones, to develop direct stability assessment methods for the new intact stability criteria. In this research, we selected as the subject ship a wave-piercing tumblehome vessel with twin screws and twin rudders, a design expected to be one of a new generation of high-speed monohull ships. Firstly, a series of captive model tests were conducted to measure the resistance, the manoeuvring forces, the wave-exciting forces, the heel-induced hydrodynamic forces, and the roll restoring variation for the unconventional tumblehome vessel. Secondly, the existing mathematical model which had been developed for broaching prediction of conventional vessels with a single propeller and a single rudder was extended to unconventional vessels with twin propellers and twin rudders. Finally, comparisons between numerical simulations and the existing free running model experiments were conducted. As a result, it was demonstrated that fair quantitative prediction of broaching is realised when the rudder force variation, the roll restoring variation and the heel-induced hydrodynamic force for large heel angles are taken into account.     

基于LS-SVM的船舶操纵运动在线建模

基于最小二乘支持向量机(LS-SVM)和积分型辨识样本结构开展了船舶操纵运动的在线建模.以整体型Abkow-itz模型为辨识对象,大阪号油轮作为具体研究对象.在操纵运动仿真时,采用40个粘性类水动力导数的Abkowitz模型,但是在参数辨识时,采用了仅具有20个粘性类水动力导数的简化模型.为了对建模方法的有效性进行检验,将辨识得到的水动力导数与其原始值进行了比较,同时也针对辨识模型和原始模型的操纵运动仿真进行了比较.辨识结果表明,使用简化模型进行船舶操纵运动的在线建模是合适的,具有较好的预报效果和较高的精度.     

Comparison of the mariner Schilling rudder and the mariner rudder for VLCCs in strong winds

A simulation model of a very large crude carrier (VLCC) with either a mariner type Schilling rudder or a mariner rudder was developed from captive and free-running model tests. Kijima’s regression formula was used to predict the hydrodynamic hull forces on the VLCC. To simulate full-scale maneuvering at cruising speed, the constant torque operation of the main engine was assumed. Considering the higher normal lift force and maneuverability of the mariner type Schilling rudder as compared to the mariner rudder, the size of mariner type Schilling rudder is kept smaller as compared to mariner rudder. To compare the efficiency of the two types of rudder system, maneuvering simulations at constant engine torque and course-keeping simulations at various gusting wind speeds and encounter angles were carried out. Based on the simulation results, the two rudder types were compared from the viewpoint of maneuvering and fuel efficiency in windy conditions.     

Manoeuvring characteristics of twin-rudder systems: rudder-hull interaction effect on the manoeuvrability of twin-rudder ships

With a recent increase in ship capacity and propulsion performance, a wide-beam ship fitted with a twin-rudder system has been adopted in many cases. However, to improve ship manoeuvring, it is still necessary to have a better understanding of rudder-hull interactions in twin-rudder ships. Captive model tests (oblique towing and circular motion test) as well as free-running tests with a single-propeller twin-rudder ship and a twin-propeller twin-rudder ship are carried out. The effect of drift angle on the rudder forces and some peculiar phenomena concerning rudder normal force for twin-rudder ships are evaluated. A method for estimating the hull-rudder interaction coefficients based on free-running experimental results is proposed.     

Validation of 6-DOF motion simulations for ship turning in regular waves

In this study, a six degrees of freedom (6-DOF) motion simulation method of a ship steering in regular waves is validated. The proposed simulation model is based on the two-time scale concept where the 6-DOF motions are expressed as the sum of the low-frequency maneuvering motions and high-frequency wave-induced motions. Turning simulations of a KCS container ship model with a rudder angle of \(\pm 35^\circ\) in calm water and regular waves are performed and the obtained results are compared with the results of a free-running model test. The model tests were conducted using a ship model of length 3.057 m in a square tank at the National Research Institute of Fisheries Engineering, Japan. The wave conditions were as follows: the wave height was 3.6 m at full-scale, ratio of wavelength to ship length was 1.0, and the ship approached in the head wave direction before it was steered. The present method can simulate both the turning motion and wave-induced motions in regular waves with practical accuracy.

     

Prediction of ship steering capabilities with a fully nonlinear ship motion model. Part 1: Maneuvering in calm water

This paper introduces a new method for the prediction of ship maneuvering capabilities. The new method is added to a nonlinear six-degrees-of-freedom ship motion model named the digital, self-consistent ship experimental laboratory (DiSSEL). Based on the first principles of physics, when the ship is steered, the additional surge and sway forces and the yaw moment from the deflected rudder are computed. The rudder forces and moments are computed using rudder parameters such as the rudder area and the local flow velocity at the rudder, which includes contributions from the ship velocity and the propeller slipstream. The rudder forces and moments are added to the forces and moments on the hull, which are used to predict the motion of the ship in DiSSEL. The resulting motions of the ship influence the inflow into the rudder and thereby influence the force and moment on the rudder at each time step. The roll moment and resulting heel angle on the ship as it maneuvers are also predicted. Calm water turning circle predictions are presented and correlated with model test data for NSWCCD model 5514, a pre-contract DDG-51 hull form. Good correlations are shown for both the turning circle track and the heel angle of the model during the turn. The prediction for a ship maneuvering in incident waves will be presented in Part 2. DiSSEL can be applied for any arbitrary hull geometry. No empirical parameterization is used, except for the influence of the propeller slipstream on the rudder, which is included using a flow acceleration factor.     

Roll-induced bifurcation in ship maneuvering under model uncertainty

In this paper, a mathematical model is developed for the maneuvering motion of a naval ship and bifurcations of its equilibrium are identified in roll-coupled motion. The subject ship is a high-speed surface combatant with twin-propeller twin-rudder system. Captive model tests are conducted for the ship using planar motion mechanism. Maneuvering coefficients are calculated by polynomial curve fitting of the test data. Uncertainty distribution in the coefficients is assumed same as that of the curve fitting errors. Uncertainty in the model coefficients is propagated to full-scale simulation results by the stochastic response surface method (SRSM). This method is computationally efficient as compared to standard Monte Carlo simulation technique. The SRSM uses polynomial chaos expansion of orthogonal to fit any probability distribution. Bifurcation analysis of the mathematical model is performed by varying the vertical center of gravity as the bifurcation parameter. Hopf bifurcation is identified. It is found that the bifurcations occur due to the coupling of roll motion with sway, yaw motion and rudder angle. In the presence of wind, roll angle response in bifurcation diagram is discussed.     

基于减摇鳍辅助回转的船舶操纵性能研究

基于MMG分离式建模思想,考虑作用在船体、螺旋桨、舵、鳍的水动力作用,建立双桨双舵船舶四自由度非线性数学运动模型,对某船模在静水中的回转性能进行仿真分析,将单独舵控制的仿真结果与船模试验结果进行了验证和分析,并对比了单独舵控制和舵、鳍联合控制下的回转性能,结果表明鳍参与控制回转时能明显缓解回转过程中的横倾。     

Broaching prediction in the light of an enhanced mathematical model,with higher-order terms taken into account

 We have attempted to develop a more consistent mathematical model for capsizing associated with surf-riding in following and quartering waves by taking most of the second-order terms of the waves into account. The wave effects on the hull maneuvring coefficients were estimated, together with the hydrodynamic lift due to wave fluid velocity, and the change in added mass due to relative wave elevations. The wave effects on the hydrodynamic derivatives with respect to rudder angles were estimated by using the Mathematical Modelling Group (MMG) model. Then captive ship model experiments were conducted, and these showed reasonably good agreements between the experiments and the calculations for the wave effects on the hull and the rudder maneuvring forces. It was also found that the wave effects on restoring moments are much smaller than the Froude–Krylov prediction, and the minimum restoring arm appears on a wave downslope but not on a wave crest amidship. Thus, an experimental formula of the lift force due to the heel angle of the ship is provided for numerical modelling. Numerical simulations were then carried out with these second-order terms of waves, and the results were compared with the results of free-running model experiments. An improved prediction accuracy for ship motions in following and quartering seas was demonstrated. Although the boundaries of the ship motion modes were also obtained with both the original model and the present one, the second-order terms for waves are not so crucial for predicting the capsizing boundaries themselves. Received: June 20, 2002 / Accepted: October 10, 2002 Acknowledgments. This research was supported by a Grant-in-Aid for Scientific Research of the Ministry of Education, Culture, Sports, Science and Technology of Japan (No. 13555270). The authors thank Prof. N. Rakhmanin of the Krylov Ship Research Institute for providing the Russian literature, as well as Mr. H. Murata of NHK (Japan Broadcasting Corporation) for translating it into Japanese. Address correspondence to: N. Umeda (e-mail: umeda@naoe.eng.osaka-u.ac.jp)     

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。     

一型小水线面双体船的水动力性能与结构设计

简要介绍了中国船舶重工集团公司(CSIS)建立和发展的一种小水线面双体船(SWATH)优化设计工程技术系统.主要包括SWATH船型的概念设计、主尺度与线型优化、有效功率预报、纵向运动稳定性校验及稳定鳍设计、耐波性预报、结构载荷评估、波浪中的船体结构动、静响应分析等有关设计、预报与评估的系统方法.并以一型1500吨级小水线面双体型海洋调查船设计和评估为例对有关设计方法进行了说明和验证,在该船设计中,采用线性和非线性三维水弹性理论来预报载荷与评估在波浪中航行船体的结构安全性,同时在中国船舶科学研究中心(CSSRC)的拖曳水池与耐波性水池中进行了阻力与自航、耐波性与操纵性、波浪载荷等船模拖曳及自航试验.文中还给出了该船有关优化设计及模型试验结果.     

Fatigue damage prediction of ship rudders under vortex-induced vibration using orthonormal modal FSI analysis

Recently, the fatigue failure of ship rudders owing to vortex-induced vibration has increased as commercial ships become faster and larger. However, previous methods are inappropriate for fatigue failure prevention owing to the lack of fluid–structure interaction considerations. This study aims to develop a fatigue damage prediction method that can be applied at the design stage to prevent fatigue failure of ship rudders under vortex-induced vibration. The developed prediction method employed the fluid–structure interaction (FSI) method to properly consider the fluid–structure interaction and implemented orthonormal mode shapes to reflect the complex geometry and boundary conditions of the ship rudders. For validation, vortex-induced vibration of the hydrofoil model was obtained using the developed method, and the prediction results matched well with the experimental results. Then, the fatigue damage of the ship rudder model under vortex-induced vibration was predicted using the developed method, and their characteristics are discussed. The stress distribution obtained using the developed method matched well with the geometrical characteristics of the ship rudders. The potential for fatigue failure due to the resonance of vortex-induced vibration was expected by comparing the stress distributions for various flow velocities to the S–N curves provided by the DNV classification.     

基于LQR限宽水域中KVLCC2操纵运动控制研究

在航道宽度受限制的水域中,船舶会受到岸壁效应的影响,横向力与首摇力矩将发生变化,这会对船舶的航行安全产生不利的影响.鉴于此问题,本文应用现代控制理论最优控制LQR方法,对在限制水域中航行的超大型油轮KVLCC2的操纵运动进行控制研究.为便于LQR控制器的设计,采用线性状态空间形式的操纵运动方程,基于数值模拟获取的相应线性水动力系数,计算出使目标函数值最小的增益矩阵K,从而得到满足最优控制规律的时域舵角变化,实现对不同宽度水域中船舶运动的最优控制,并与极点配置控制法作比较,验证LQR控制器的优越性.结果表明,当船岸距离d/L≥1.2时,船舶基本不受岸壁效应的影响,控制幅度极小;当岸壁距离d/L=0.25时,摆舵角度将超过6°,同时船舶前进速度也将下降,下降幅度将超过前进速度的10%,岸壁效应明显.     

船舶操纵回转特性的多目标优化设计应用

定常回转直径作为衡量船舶操纵性的一个指标受到人们的普遍重视。为提高船舶的回转性能,基于船舶四自由度的操纵性方程,分析船舶回转直径和回转横倾,讨论影响回转性能的舵型因素,并将其作为优化设计变量,利用Isight优化设计平台,采用遗传算法进行舵型参数的优化设计。通过选取某高速船作为优化对象,利用该方法进行舵型优化后,回转直径及回转横倾都减小。表明借助Isight的优化功能可以实现船舶操纵性能的优化。