Computation of Ship Hydrodynamic Interaction Forces in Restricted Waters using Potential Theory

A computer code based on the double-body potential flow model and the classic source panel method has been developed to study various problems of hydrodynamic interaction between ships and other objects with solid boundaries including the seabed. A peculiarity of the proposed implementation is the application of the so-called ＂moving-patch＂ method for simulating steady boundaries of large extensions. The method is based on an assumption that at any moment just the part of the boundary （＂moving patch＂） which lies close to the interacting ship is significant for the near-field interaction. For a specific case of the fiat bottom, comparative computations were performed to determine optimal dimensions of the patch and of the constituting panels based on the trade-off between acceptable accuracy and reasonable efficiency. The method was applied to estimate the sway force on a ship hull moving obliquely across a dredged channel. The method was validated for a case of ship-to-ship interaction when tank data were available. This study also contains a description of a newly developed spline approximation algorithm necessary for creating consistent discretizations of ship hulls with various degrees of refinement.

Optimization of Bow Shape for a Non Ballast Water Ship

In this research,a commercial CFD code ＂Fluent＂ was applied to optimization of bulbous bow shape for a non ballast water ships（NBS）.The ship was developed at the Laboratory of the authors in Osaka Prefecture University,Japan.At first,accuracy of the CFD code was validated by comparing the CFD results with experimental results at towing tank of Osaka Prefecture University.In the optimizing process,the resistances acting on ships in calm water and in regular head waves were defined as the object function.Following features of bulbous bow shapes were considered as design parameters： volume of bulbous bow,height of its volume center,angle of bow bottom,and length of bulbous bow.When referring to the computed results given by the CFD like resistance,pressure and wave pattern made by ships in calm water and in waves,an optimal bow shape for ships was discovered by comparing the results in the series of bow shapes.In the computation on waves,the ship is in fully captured condition because shorter waves,λ/Lpp 0.6,are assumed.

Added Resistance Acting on Hull of a Non Ballast Water Ship

In this paper, added resistances acting on a hull of non ballast water ship(NBS) in high waves is discussed. The non ballast water ships were developed at the laboratory of the authors at Osaka Prefecture University, Japan. In the present paper, the performances of three kinds of bow shapes developed for the NBS were theoretically and experimentally investigated to find the best one in high waves. In previous papers, an optimum bow shape for the NBS was developed in calm water and in moderated waves. For a 2 m model for experiments and computations, the wave height is 0.02 m. This means that the wave height is 15% of the draft of the ship in full load conditions. In this paper, added resistances in high waves up to 0.07 m for a 2 m model or 53% of the full load draft are investigated. In such high waves linear wave theories which have been used in the design stage of a ship for a long time may not work well anymore, and experiments are the only effective tool to predict the added resistance in high waves. With the computations for waves, the ship is in a fully captured condition because shorter waves, λ/Lpp<0.6, are assumed.

Acoustic multipath structure in direct zone of deep water and bearing estimation of tow ship noise of towed line array

In the towed line array sonar system,the tow ship noise is the main factor that affects the sonar performance.Conventional noise cancelling methods assume that the noise is towards the endfire direction of the array.An acoustic experiment employing a towed line array is conducted in the western Pacific Ocean,and a strange bearing-splitting phenomenon of the tow ship noise is observed in the array.The tow ship noise is split into multiple noise signals whose bearings are distributed between 10°and 90°deviating from the endfire direction.The multiple interferences increase the difficulty in recognizing the target for the sonar operator and noise cancellation.Therefore,making the mechanism clear and putting forward the tow ship noise splitting bearing estimation method are imperative.In this paper,the acoustic multi-path structure of the tow ship in deep water is analyzed.Then it is pointed out that the bearing-splitting phenomenon is caused by the main lobe of direct rays and bottom-reflected rays,as well as several side lobes of direct rays.Meanwhile,the indistinguishability between the elevation angle and the bearing angle due to the axial symmetry of a strict horizontal line array causes the bearing to deviate from the endfire direction.Based on the theory above,a method of estimating bearing of the tow ship noise in deep water is proposed.The theoretical analysis results accord with the experimental results,which helps to identify the target and provide correct initial bearing guidance for noise cancelation methods.

Effect of Ship Bow Overhang on Water Shipping for Ship Advancing in Regular Head Waves

This paper presents the results of an experimental investigation dealing with the effect of bow overhang extensions on the quantity of shipping water over the foredeck in case of ships advancing in regular head waves. To perform this investigation, a series of free-running tests was conducted in regular waves using an experimental model of a multipurpose cargo ship to quantify the amount of shipping water. The tests were performed on five bow overhang variants with several combinations of wavelength and ship speed conditions. It was observed that the quantity of shipping water was affected by some parameters such as wavelength, ship speed, and bow shape in terms of an overhang extension. The results show the significant influence of an overhang extension, which is associated with the bow flare shape, on the occurrence of water shipping. These results involve the combined incoming regular waves and model speed.

Eradication of algae in ships’ ballast water by electrolyzing

In order to verify the effectiveness of electrolytic treatment on ships’ ballast water, experiments are carried out by a pilot system in laboratory. The raw seawater and seawater with different concentrations of different algae are simulated as ships’ ballast water. The algae in the raw seawater can be killed if it is treated by electrolysis with an initial residual chlorine concentration of 5 mg/L. If the seawater with one kind of algae (Nitzschia closterum, Dicrateria spp., or Pyramidomonnas sp.105cells/mL) is treated by electrolysis with an initial residual chlorine concentration of 5 mg/L, the alga can be sterilized. If the seawater with one kind of algae (Dunaliella sp., Platymonas or Chlorella spp.) is directly treated by electrolyzing with an initial residual chlorine concentration of 4 mg/L, the instant mortality changes with the concentration of different algae. However, after 72 hours, in all treated samples, there are no live algal cells found.

根据DS理论的船舶风险因素评估分析

针对船舶航行风险评估中存在许多不确定影响因素的问题,提出了在模糊风险评估证据理论基础上建立的风险评估方法。在证据集理论空间中,每一事件均可确认为模糊集合子集且融入了模糊概率理论,从而更全面地描述行业学者的专业经验或证据诠释,由此得出了模糊证据理论质量函数的描述法。最后应用其船舶安全系统,提出了船舶风险因素识别和风险评估详细程序。计算结果证明,此方法可有效避免决策失误,且简单、易行,有较强的推广和应用价值。

实船试航中不同浅水效应修正方法的对比分析

船舶航行时,当水深吃水比小于4或水深傅汝德数大于0.6时,会出现“浅水效应”。在实船测速试验中,需要对浅水效应进行适当修正,才能准确评估船舶的航速。目前常用的船舶浅水效应修正方法有Lackenby方法和Raven方法。本文介绍了这2种方法的基本原理和适用条件,并基于9艘船舶的实船测速试航数据,对这2种方法进行计算和比较,并分析2种方法对实船航速修正结果的影响,可为我国船舶测速试航及航速修正提供参考。

浅水效应下智能技术试验船回转操纵性数值模拟

本文借助STAR-CCM+软件对考虑浅水效应的智能技术试验船回转操纵性进行数值模拟研究。首先对无界流场中智能技术试验船的流体动力性能评估,并且与试验结果对比验证了计算方法的准确性;在此基础上,通过改变智能技术试验船与池底的垂向距离,模拟不同浅水工况下智能技术试验船回转操纵性能。数值模拟结果表明,浅水效应下智能技术试验船侧向力系数显著增大,对应的偏航力矩系数亦有所增加。相关结论可为智能技术试验船浅水航行时安全性能提供指导。

两坝间河道高含沙水流驱动的下游船闸阀门井水位异常特征分析

葛洲坝船闸充水阀门井与输水廊道进水口水体相连,1993年洪季期间曾发生过阀门井水位异常升高,影响船闸设备设施安全等问题。为分析葛洲坝一号船闸充水阀门井水位异常升高的根本原因,基于Mike三维水沙数值模型,模拟分析了不同流量和含沙量级别下的河道水流和含沙量垂向分布结构特征,进而计算阀门井水位异常升高值与河道水流和含沙量的关系,反演1993年洪季葛洲坝一号船闸两个阀门井出现的水位异常现象。研究结果表明,葛洲坝一号船闸阀门井水位异常超过阈值0.5 m的流量和含沙量条件分别约为(30 000 m^(3)/s, 2.85 kg/m^(3)),(40 000 m^(3)/s, 1.42 kg/m^(3)),(50 000 m^(3)/s, 1.23 kg/m^(3))。受三峡水库及上游梯级水库蓄水拦沙、退耕还林政策等因素的影响,未来葛洲坝船闸出现高含沙水流导致阀门井水位异常升高>0.5 m的可能性极小,但在三峡水库排沙泄洪期间仍应引起重视。研究成果可为葛洲坝一号船闸安全营运和科学管理提供参考依据。

循环水槽船模阻力修正方法

在循环水槽中开展船模阻力测量是船型优劣分析的常规试验之一,因此对循环水槽阻力修正方法进行研究是十分必要的。以集装箱船标模(KCS)为研究对象在循环水槽中开展模型阻力和流场测量试验,根据循环水槽自身流动特性并结合拖曳水池已有的修正方法,分析并总结适用于水槽船模阻力与阻塞效应的修正方法。由总结的修正公式与修正流程可知,循环水槽中2.5~3.5 m尺寸模型试验与大模型试验结果阻力换算偏差在1%左右,设计航速点阻力换算偏差小于1%。结果表明,有必要对循环水槽中阻力进行自由面倾斜度修正,采用Tamura公式进行阻塞效应修正能得到更为精确的阻力试验结果。

船舶轮缘推进器关键技术研究现状和发展趋势

采用电力直驱模式来完成电能与机械能的无传动转化是高端交通动力装备领域的未来战略性技术之一。轮缘推进器(RDT)作为一种高度集成的电力直驱推进,是近年来研究的热点。文章梳理了船舶轮缘推进器的6项关键技术,包括水力部件设计及优化、电机设计及控制、水润滑轴承的设计和性能强化、系统集成与测试、船体匹配及联合控制以及可靠性评估与智能运维;阐述了各项技术的研究现状和趋势,总结了国内外RDT产品和实船应用情况。研究和应用表明,节能、环保、灵活的轮缘推进器是绿色智能船舶电力推进形式的重要选择,高性能轮缘推进器专用化设计、效能提升和状态监测以及智能运维是轮缘推进器未来重要发展趋势。

西部陆海新通道(平陆)运河工程规划设计方案综述

平陆运河是建设西部陆海新通道、加快建设交通强国的标志性工程,工程始于南宁市横州市西津库区平塘江口,终点为北部湾钦州港东航道,按内河Ⅰ级航道标准建设,可通航5000吨级船舶。工程从上游至下游建设马道、企石、青年3个梯级枢纽,各枢纽一次性建成双线5000吨级船闸。项目开发任务以发展航运为主,结合供水、灌溉、防洪、改善水生态环境等,主要建设内容包括航运枢纽、航道、跨河建筑物及道路工程以及配套工程等。平陆运河规划设计始终贯彻系统观、生态文明思想,坚持科技赋能、创新引领,将建设世界上规模最大、启闭速度最快的内河省水船闸。

船舶拥堵水域通行能力预测技术

针对船舶交通流量大、水域繁忙情况下,通行能力预测难度过高的问题,提出船舶拥堵水域通行能力预测技术。利用船舶坐标位置以及航行速度,确定船舶状态,建立船舶航行队列模型。依据船舶领域模型确定船舶航行对应的椭圆形区域,作为船舶拥堵水域的领域。确定船舶领域内,影响航道容量的相关因素。设置船舶密度、船舶航行速度等水域通行能力影响指标,作为长短时记忆网络的输入。长短时记忆网络通过遗忘门、输入门以及输出门3个门控单元,选择保留或遗忘输入的数据,输出船舶拥堵水域通行能力预测结果。实验结果表明,该技术能够有效预测船舶拥堵水域通行能力,提高航道利用率,保障水域交通安全性。

基于“船载舱养”模式国内养殖工船的大气和水污染排放控制研究

基于“船载舱养”的养殖工船模式构建理念,结合10万吨级大型养殖工船建造项目,阐述目前法规、国标对养殖工船防止大气污染和防止水污染的控制措施,并对养殖工船设计、建造和营运给出建议。

极浅水域船舶航行阻力及下沉量数值计算方法

针对舰船在极浅水域中的航行阻力及航行安全预报问题,提出了静力平衡方程与叠模定常流计算相结合的数值计算方法。经分析比较可知,该方法只需进行一次姿态调整,姿态收敛偏差即可小于5%。水动力计算结果与水池模型试验结果对比表明:当深度/吃水比(h/T_(m))为1.18时,阻力预报相对偏差为3%左右、下沉量绝对偏差小于2 mm,触底航速预报相对偏差小于5%。该方法可有效避免计算过程中姿态波动导致解算失败的问题,具有良好的计算稳定性和收敛性,且计算精度较高,可为浅水航行船舶航行性能数值计算提供借鉴和参考。

纤维素膜在船舶排油污水分离系统中的应用

船舶在运输中会排放很多含油污水,对含油污水的处理具有重要的意义。纤维素膜具有多孔结构、亲水性和疏水性的特点,是一种较为常见的油水分离方法,本文提出一种基于纤维素膜技术的船舶排油污水分离系统,分析纤维素膜油水分离的原理和常见的改性方法,研究一种改性羧甲基化纤维素膜的制备方法,并对制备的改性纤维素膜性能进行分析。本文提出的船舶排油污水分离系统具有较好的油水分离效率和较高的膜通量,具有一定的应用价值。

船闸止水材料性能劣化规律试验研究

平陆运河河口船闸受咸水入侵及船闸闸室频繁灌泄水作用,形成了受紫外光照强、氯盐侵蚀及高频干湿交替共同影响的特殊腐蚀环境。然而,船闸止水材料在这一特殊服役环境下的性能劣化规律不甚明了。为此,文章开展了针对船闸止水材料在纯紫外老化环境、紫外老化与咸水高频干湿交替环境下的加速劣化试验,研究了四类橡胶止水带(包括:普通、OMEGA、GB、超高性能止水带)材料硬度、拉伸强度、断裂伸长率以及极限弹性模量随时间的劣化规律。结果表明:纯紫外老化环境下,四类橡胶止水带材料的硬度、极限弹性模量随劣化时间呈增大趋势,拉伸强度呈先增后减的变化趋势,断裂伸长率则单调减小;紫外老化与咸水高频干湿交替环境下,四类橡胶止水带材料的硬度、拉伸强度、断裂伸长率均随劣化时间呈减小趋势,极限弹性模量则单调增加。研究成果可为平陆运河河口船闸结构缝止水材料的优选类型提供重要参考依据。

水下钻孔爆破技术新发展

水下钻孔爆破虽然经过了几十年的工程实践和理论研究,但成果散乱且不系统,有些资料还相互矛盾,落后的施工工艺及装备还在使用,难以使水下钻孔爆破设计与施工实现正规化、现代化和智能化。通过查阅近二十年的文献资料、现场调研和工程实践等,对水下钻孔爆破的理论、装备、技术与工艺和有害效应控制等最新成果进行梳理与总结,展现水下钻孔爆破最新发展成果。为实际工程项目爆破方案与参数设计、施工工艺与装备选择、有害效应控制与防护措施等提供理论及技术支撑,从而解决水下钻孔爆破中遇到的疑难问题,达到优质安全高效之目的。

基于5G通信的船舶洗舱水监测系统开发

针对化学品船舶洗舱无法实时监测洗舱效果的问题,设计了基于5G通信的船舶洗舱水监测系统。系统由数据控制采集系统、5G数据传输系统和数据监测处理系统组成,数据控制采集系统通过传感器对船舶洗舱水中多参数进行实时采集,基于STM32芯片将采集的数据传输至5G数据传输系统,数据经5G数据传输系统处理后发送至数据监测处理系统,数据监测处理系统通过监测平台将数据显示。该系统通过对船舶洗舱水中多参数的实时监测,有效检测船舶洗舱效果,降低了洗舱和验舱成本以及检舱不合格的风险。