Study on the maneuverability of a large vessel installed with a mariner type Super VecTwin rudder

The suitability of the Mariner type Super VecTwin rudder (hereinafter, the MSV rudder) for a large vessel is assessed in this article. Several experiments in a maneuvering pond were carried out and their results analyzed and summarized. Free-running tests such as turning, zigzag, and stopping tests were carried out with a 4-m free-running model of a very large crude carrier (VLCC) ship with the MSV rudder and the Mariner rudder. The results were compared to validate the maneuverability of a VLCC-sized a ship installed with the MSV rudder. A mathematical model of an MSV rudder is proposed for maneuvering simulation of a large vessel. To develop a maneuvering simulation for the model ship that was used in the free-running tests, hydrodynamic coefficients were estimated based on Kijima's regression formula. The coefficients of interaction between the hull and rudder (t_R, a_H, x_H) were obtained from a self-propulsion test in a towing tank. The complicated flow around the rudders is simplified to model the flow speed around the rudders. This simplified flow speed is utilized to compare the time histories of the free-running tests with the simulations. The mathematical model of the MSV rudder was further improved using the results of this comparison.     

拖曳水池标模阻力复合航次试验不确定度分析

参考国际拖曳水池会议(ITTC)推荐的规程,对船模拖曳水池的阻力试验进行不确定度分析。根据船模阻力试验的流程,确定试验过程中的误差源;根据不确定度的传递方程,确定误差源对试验结果的影响;基于一艘船模标准模型进行带舵的复合航次重复试验,并根据试验误差源分析得到试验结果的不确定度。在此基础上,提出降低试验不确定度的方法。分析结果表明,在95%置信水平下(k=2),总阻力及其主要水动力系数的不确定度均小于1%,试验结果可作为标模基准校验使用。     

二级深拖系统的回转运动特性

相对于一级深拖系统,二级深拖系统具有良好升沉补偿功能,并且较易对拖体进行定深或定高控制。在实际工作中,母船经常需要根据探测情进行回转机动。为了研究母船回转过程中拖体运动规律和拖缆构形的变化情况,采用凝集质量法建立了二级深拖系统的数学模型,计算分析了母船不同回转参数下拖体运动状态的变化规律,得到了拖缆的瞬态和稳态构形图。仿真结果表明,在360°稳态回转和360°单圈回转条件下,母船回转半径、拖曳速度均对一级拖体和二级拖体的深度变化以及稳态特性有显著影响。母船小半径大速度回转时,两级拖体的回转半径和深度变化较大,应予以特别关注。     

Circular motion tests and uncertainty analysis for ship maneuverability

Circular motion test data and uncertainty analysis results of investigations of the hydrodynamic characteristics of ship maneuvering are presented. The model ships used were a container ship and two tankers, and the measured items were the surge and sway forces, yaw moment, propeller thrust, rudder normal and tangential forces, pitch and roll angles, and heave. The test parameters were the oblique angle and yaw rate for the conditions of a hull with a rudder and propeller in which the rudder angle was set to zero and the propeller speed was set to the model self-propulsion conditions. Carriage data showing the accuracy of the towing conditions in the circular motion test are also presented. It was confirmed that the uncertainties in the hydrodynamic forces such as the surge and sway forces, yaw moment, rudder tangential and normal forces, and propeller thrust were fairly small. The reported uncertainty analysis results of the circular motion test data may be beneficial in validating data quality and in discussing reliability for simulation of ship maneuvering performance.     

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.     

实尺度喷水推进船拖泵工况数值模拟与分析

对于四泵推进的喷水推进船,在巡航工况时中间加速泵通常处于锁轴状态,其拖曳阻力的大小对喷水推进器的选型以及船泵机的最优匹配有着重要影响。然而,拖泵阻力很难通过船模试验的方法获得。为此,该研究在验证均匀和非均匀条件喷水推进器数值模型的准确性基础上,采用数值试验的方法对18节航速下某双泵推进喷水推进船的实尺度"船体+两台喷水推进器"系统带自由液面的流场进行了数值模拟,计算此时喷泵拖曳阻力及其所占船体阻力的百分比。以此喷泵拖曳阻力作为参考,对尺寸与上述喷水推进泵相近的某四泵推进喷水推进船的喷泵进行了选型和设计,并对该船在18节航速下加速泵拖曳阻力的大小进行了计算,进一步验证选型时拖曳阻力取值的合理性。为消除尺度效应的影响采用实尺度模型对"船体+四台喷水推进器"系统带自由液面的非定常流场进行计算,并探索了大尺度条件下船泵系统考虑自由液面和重力影响的非定常计算方法。     

A proposal for propulsion performance prediction of a single-propeller twin-rudder ship

The influence of a rudder’s axial force on the prediction of full-scale powering performance of a ship is investigated in this paper. Axial force characteristics of different rudder types were investigated by open water experiments. Viscous scale effects on the rudder’s axial force were investigated by carrying out open water experiments with different sizes of rudder. Experiments were carried out in the towing tank for a model ship fitted with different rudder systems to investigate the influence of rudder’s axial force on full-scale propulsion performance prediction. Based on the experiment results, a new prediction method is proposed for estimating full-scale power that considers scale effect on rudder’s axial force. Good performance of the proposed prediction method is demonstrated by estimating the engine power of a ship installed with a special high lift twin-rudder system from model experiments and comparing it with the values measured on the ship during full-scale experiments.     

2.5万载重吨多用途干货船船型优化及节能装置

介绍2.5万DWT肥大型多用途干散货船船型优化及节能装置的船模试验研究.其船体线型优化设计和球艏的优选,在上海船舶运输科学研究所拖曳水池进行.文中给出了船模阻力、自航和尾部伴流场测试的试验结果,分析了船型变化对快速性的影响,同时介绍了尾部加装节能装置前置导管及舵球的节能效果.该船型优秀,快速性指标先进,是经济高效船舶.实船正在建造中.     

水下拖体在回转操纵中的运动仿真模拟

水下拖曳系统为各种内河航道工程,近海港口工程前期的勘探活动提供了一种有效途径,当要求对某个目标进行详细探测时,需要拖船进行回转机动操纵,因此拖体运动轨迹准确位置的预报关系到能否完成对目标的探测。文章采用凝集质量法建立水下缆-体系统模型,编制计算机程序,程序模拟了不同回转半径、不同拖速回转操纵下的拖船与拖体运动轨迹,分析了回转操纵中影响拖体稳态及拖体深度的参数。同时,计算机程序仿真模拟了一个"8"字形拖曳操纵,仿真算例与相关文献进行比较,结果表明此计算机程序具有一定工程实用价值。     

循环水槽隔板设计与水槽倾斜研究

循环水槽同传统拖曳水池相比具有许多优点,因而日益广泛地应用于船型开发和船舶水动力性能研究。在水槽中设置隔板可以模拟海洋中的分层流,但隔板的迟滞作用必然会对循环水槽计测部流场品质造成一定的影响。为了研究这一设想对流场的影响,数值模拟循环水槽在无隔板、整段隔板以及分段隔板情况下的流动情况。对比结果表明,采用分段隔板形式较为理想。另一方面,循环水槽作为一种基础实验设施,对其计测部的水平度有着严格要求,探讨安装中的误差或投入使用后地基沉降引起的水槽倾斜对计测部流动带来的影响。基于VOF模型,模拟水平及各倾角二维条件下循环水槽计测部的流动情况,结果表明,较大倾角时,计测部波面变化较大,且计测部末端有气泡产生,而在微小倾角时,波面变化不明显。     

Comparison of Microbubble and Air Layer Injection with Porous Media for Drag Reduction on a Self-propelled Barge Ship Model

Ship resistance issues are related to fuel economy, speed, and cost efficiency. Air lubrication is a promising technique for lowering hull frictional resistance as it is supposed to modify the energy in the turbulent boundary layer and thereby reduce hull friction. In this paper, the objective is to identify the optimum type of air lubrication using microbubble drag reduction (MBDR) and air layer drag reduction (ALDR) techniques to reduce the resistance of a 56-m Indonesian self-propelled barge (SPB). A model with the following dimensions was constructed: length L?=?2000 mm, breadth B?=?521.60 mm, and draft T?=?52.50 mm. The ship model was towed using standard towing tank experimental parameters. The speed was varied over the Froude number range 0.11–0.31. The air layer flow rate was varied at 80, 85, and 90 standard liters per minute (SLPM) and the microbubble injection coefficient over the range 0.20–0.60. The results show that the ship model using the air layer had the highest drag reduction up to a maximum of 90%. Based on the characteristics of the SPB, which operates at low speed, the optimum air lubrication type to reduce resistance in this instance is ALDR.     

Sea trial of prototype Vertical Weight Stabilizer (VWS) anti-rolling system for small ships

Anti-rolling is an important technique for safety and efficient ship operation. In the era of sailing ships, rolling motions were not so severe compared to those of modern ships running by prime mover without sails, because the sail itself had a damping effect on rolling motion. After propeller driven ships exceeded sailing ships in number and performance, namely, from the end of the nineteenth century, many types of anti-rolling–related techniques were invented and developed, of both passive and active types. Recently (2009, 2010), as sea trials, we carried out proto-type experiments on an anti-rolling system and confirmed its effectiveness. The new concept utilizes the so-called Corioli’s effect, which appears in the rotational coordinate system. Usually, this effect is considered as virtual, but the real effect appears when a mass moves in the radial direction in a rotating coordinate system. In the case of ship rolling, the vertical motion of a mass generates Corioli’s force to finally generate anti-rolling moment. This is the reason the system was named Vertical Weight Stabilizer (VWS). This new system was invented in 1998 by Hirayama, and confirmed by the model experiments in a towing tank. Numerical simulations were carried out by the Sea and Air Control System laboratory of Yokohama National University, but the actual system could not be realized, because we could not find an appropriate actuator. The key technology for the success of the current sea experiment is the powerful, high-speed, compact actuator for the vertical movement of the weight. In this paper, we introduce this new concept by adopting a simple experiment, the control system with new actuator used in an actual sea experiment, and report on the successful results.     

一种具有倾斜侧体的三体船阻力试验研究

作为一种高性能船型,三体船受到了研究人员的广泛关注。由于侧体位置对三体船剩余阻力会产生影响,为了研究倾斜侧体对三体船阻力性能的影响,设计了一种新型的倾斜侧体三体船,并在拖曳水池中开展了相应的船模阻力试验。试验中,针对这种新型的斜侧体三体船,采用船模拖曳的试验方法测量了不同装载情况侧体多个倾斜角度下的三体船裸船体阻力。而后,依据傅汝德假定对试验数据进行了计算,分析并讨论侧体倾斜角度对三体船剩余阻力的影响。试验结果表明,选择侧体合适的倾斜角度有利于降低三体船的航行阻力,为此类船型的设计尤其是快速性方面的研究和设计提供参考。     

悬链线法在船舶系柱拖力测试中的应用

由于在实际中没有合适的水流区域及足够大的系缆桩，因此不能够做系柱拖力试验或者环境条件对系柱拖力试验数据准确性影响较大。本文介绍了依据起重铺管船项目系柱拖力测试试验，详介了应用定位锚抛锚方法测试船舶系柱拖力的理论依据、试验步骤和实测结果，并对可能影响试验结果的因素进行了分析，为后续项目试验和研究提供参考。     

海上浮式储油轮狭水道拖航的可行性论证

超大型无动力船舶的拖航是一项高难度的航海作业,尤其是在通航环境复杂的狭水道水域。对于一项难度较大的引航工作,先进行可行性论证,是达到安全引航的必要前提。通过对超大型无动力船舶拖航的实际操纵。总结了拖航的经验,提出了超大型无动力船舶在狭水道拖航操纵作业的相关注意事项。     

拖曳系统运动传递计算

由母船、拖缆和拖体构成的拖曳系统,在拖航作业中,母船受风浪扰动发生升沉和纵摇运动,水面扰动沿缆传递至拖体,影响探测设备性能。文中研究的合理简化的母船波浪运动预报模型、结合已有的拖缆动力学计算模型耦合拖体空间运动模型,构造衔接条件和转换关系式,建立较为完整的水下拖曳系统运动传递模型。编制相应计算程序,计算了二段式拖曳方式对扰动的传递,归纳其扰动传递特性。表明该模型可应用于拖曳运动稳定的设计分析。     

海洋拖曳系统的船/缆/体耦合模型研究

为进一步提高海洋拖曳系统在不同情况下运动响应的预测精度,将拖曳母船、拖缆和拖曳体三者视为一个相互作用的整体,利用其耦合边界条件,将拖缆顶端和底端的张力及其产生的力矩,分别与船舶操纵性运动方程(MMG模型)和拖体六自由度运动方程相结合,利用拖缆的有限差分方程,建立了船/缆/体三者耦合模型,进而采用数值计算方法,对比分析了该模型与常规算法。结果表明,该模型考虑船/缆/体三者的耦合影响,可更加准确全面地反映拖曳母船的速度、旋回半径、横摇角等操纵性特征以及拖曳体的深度、姿态等信息所受到的影响,从而为准确预报海洋拖曳系统的运动响应提供更为直观、科学的理论依据。     

Resistance analysis of unsymmetrical trimaran model with outboard sidehulls configuration

The application of multi-hull ship or trimaran vessel as a mode of transports in both river and sea environments have grown rapidly in recent years.Trimaran vessels are currently of interest for many new high speed ship projects due to the high levels of hydrodynamic efficiency that can be achieved,compared to the mono-hull and catamaran hull forms.The purpose of this study is to identify the possible effects of using an unsymmetrical trimaran ship model with configuration（S/L） 0.1-0.3 and R/L=0.1-0.2.Unsymmetrical trimaran ship model with main dimensions： L=2000mm,B=200 mm and T=45 mm.Experimental methods（towing tank） were performed in the study using speed variations at Froude number 0.1-0.6.The ship model was pulled by an electric motor whose speed could be varied and adjusted.The ship model resistance was measured precisely by using a load cell transducer.The comparison of ship resistance for each configuration with mono-hull was shown on the graph as a function of the total resistance coefficient and Froude number.The test results found that the effective drag reduction could be achieved up to 17% at Fr=0.35 with configuration S/L=0.1.     

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)     

船舶拖航系统六自由度操纵运动仿真

研究拖航作业操纵运动对于提高拖航作业的安全性有重要意义,采用MMG分离式船舶运动数学模型,结合拖缆的悬链线张力计算模型,建立由拖轮、拖缆、被拖轮组成的拖航系统六自由度操纵运动模型,编制仿真程序,通过数值计算,对该系统操纵运动进行仿真模拟。以拖轮和导管架驳船的拖航运动为例,分析拖缆长度、拖航速度对拖航系统操纵运动及拖航航向稳定性的影响,模拟该系统在风、浪、流影响下的操纵运动,运动数据实时解算,为在视景模拟平台上进行作业预演,规避拖航作业风险提供理论指导。