A Statistical Analysis of the Fuel Tanks＇ Corrosion Loss over Some Aged Bulk Carriers

This paper deals with modeling corrosion wastage over the fuel tanks＇ structures at the exemplar of ten aged bulk carriers. In this paper, employed method might be treated as a long term one, and it is based on Weibull distribution parameters analysis. The purpose of these analyses is optimal assessing of the average corrosion losses for the bulk carriers＇ fuel tanks areas at different points of time during the whole period of the exploitation, due to uprising the structural stability and safety of bulk carriers in operation. Though, the applied approach, among others, might be of particular importance in determining the amounts （percentage/depths） of time-dependent corrosion losses over different areas of aging bulk carriers＇ fuel tanks during the operational circles, with the ultimate goal of keeping stability and safety of these vital vessels＇ structural components.

Analyzing the Corrosion Wastage over Some of the Bulk Carriers＇ Member Locations

In this paper, well-known and structured Monte Carlo simulation technique has been employed in predicting the amounts of the corrosion wastage over some bulk carriers＇ structural elements in different points of time during their exploitation life. As a base for the realization of the simulations, the appropriate statistical data collected over the group of ten bulk carriers have been used. Both longitudinal and transversal ships＇ hull structural elements have been taken into the consideration. Due to some experts＇ knowledge in this domain, the critical hull zones are identified and certain interventions are done in the pre-processing of the input data to the Monte Carlo simulations, all with the aim of achieving better convergence between simulation results and the experts＇ expectations in this field.

Inspection Plans for Structure Fatigue Deterioration of Bulk Carrier on Active Service

Evolutionary algorithm is applied as an optimization method in this paper. The increment of cumulative failure probability of fatigue, inspection cost, inspection interval and means are adopted as limiting condition, objective function and optimization variable respectively. According to fatigue characteristics of ship structure, the optimization research of inspecting fatigue deteriorating is carried out. The optimal inspection planning of minimal inspection cost is chosen. An example of computation and comparison of inspection plans is given. The results demonstrate that an optimal inspection plan considering security and economics can be chosen by the means in this paper.

Experimental Study of Air Layer Drag Reduction with Bottom Cavity for A Bulk Carrier Ship Model

Air lubrication by means of a bottom cavity is a promising method for ship drag reduction. The characteristics of the bottom cavity are sensitive to the flow field around the ship hull and the effect of drag reduction, especially the depth of the bottom cavity. In this study, a ship model experiment of a bulk carrier is conducted in a towing tank using the method of air layer drag reduction (ALDR) with different bottom cavity depths. The shape of the air layer is observed, and the changes in resistance are measured. The model experiments produce results of approximately 20% for the total drag reduction at the ship design speed for a 25-mm cavity continuously supplied with air at Cq = 0.224 in calm water, and the air layer covers the whole cavity when the air flow rate is suitable. In a regular head wave, the air layer is easily broken and reduces the drag reduction rate in short waves, particularly when λ/Lw1 is close to one;however, it still has a good drag reduction effect in the long waves.

Application of a RaNS and PF-Based Method to Study the Resistance and Motion of a Bulk Carrier

Resistance prediction of ships using computational fluid dynamics has gained popularity over the years because of its high accuracy and low cost. This paper conducts numerical estimations of the ship resistance and motion of a Japan bulk carrier model using SHIP_Motion, a Reynolds-averaged Navier–Stokes (RaNS)-based solver, and HydroSTAR, a commercial potential flow (PF)-based solver. The RaNS solver uses an overset-structured mesh and discretizes the flow field using the finite volume method, while the PF-based solver applies the three-dimensional panel method. In the calm water test, the total drag coefficient, sinkage, and trim were predicted using the RaNS solver following mesh dependency analysis, and the results were compared with the available experimental data. Next, calm water resistance was investigated for a range of Froude numbers. The added resistance in short-wave cases was simulated using both RaNS and PF solvers, and the results were compared. The PF solver showed better agreement with the RaNS solver for predicting motion responses than for predicting added resistance. While the added resistance results could not be directly validated because of the absence of experimental data, considering the previous accuracy of the RaNS solver in added resistance prediction and general added resistance profile of similar hull forms (bulk carriers), the prediction results could be concluded to be reliable.

Development of Energy-Saving Devices for a 20,000DWT River–Sea Bulk Carrier

A reduction of fuel consumption and an increase in efficiency are currently required for river–sea bulk carriers.Pre-swirl and ducted stators are widely used devices in the industry and efficiency gains can be obtained for single-screw and twin-screw vessels.Based on the hydrodynamic characteristics of the 20,000DWT river–sea bulk carrier,in this study,we proposed,designed,and tested a series of pre-swirl energy-saving devices(ESDs).The experimental results demonstrate that the proposed ESDs improved the propulsive efficiency and reduced the delivered power.The results confirm the success of our ESD for the 20,000DWT river–sea bulk carrier.We validated the role of Reynolds-averaged Navier–Stokes(RANS)computational fluid dynamics(CFD)in the twin-skeg river–sea vessel ESD design and found the circumferential arrangement and number of stators to be important factors in the design process.

Structural Reliability of Broadside of a Bulk Carrier

The ultimate bending moment and maximal shear stress of a bulk carrier with two structural forms （single hull and double hull/ are calculated separately by using the combined moment which is determined by stochastic process. Then the assessment of reliability is carried out. The results indicate that by introducing the double-hull structure, the shear stress of side can be decreased to half of that of the primary structure（ 50.7% i. but the effect on longitudinal strength is not obvious. Finally, the effects of different double-side skin widths on ultimate bending moment and the maximal shear stress are investigated, followed by proposals of the selection of the double-side skin width.

The Stress Combination Method for the Fatigue Assessment of the Hatch Corner of a Bulk Carrier Based on Equivalent Waves

The stress combination method for the fatigue assessment of the hatch comer of a bulk carrier was investigated based on equivalent waves. The principles of the equivalent waves of ship structures were given, including the determination of the dominant load parameter, heading, frequency, and amplitude of the equivalent regular waves. The dominant load parameters of the hatch comer of a bulk carrier were identified by the structural stress response analysis, and then a series of equivalent regular waves were defined based on these parameters. A combination method of the structural stress ranges under the different equivalent waves was developed for the fatigue analysis. The combination factors were obtained by least square regression analysis with the stress ranges derived from spectral fatigue analysis as the target value. The proposed method was applied to the hatch comer of another bulk carrier as an example. This shows that the results from the equivalent wave approach agree well with those from the spectral fatigue analysis. The workload is reduced substantially. This method can be referenced in the fatigue assessment of the hatch comer of a bulk carrier.

A Comprehensive Analysis of the Stability and Powering Performances of a Hard Sail-Assisted Bulk Carrier

The wind-assisted propulsion system is becoming one of the most popular and efficient ways to reduce both fuel consumption and carbon dioxide emission from the ships.In this study,several analyses have been carried out on a model of bulk carrier fitted with five rigid sails with a 180°rotating mechanism for maximum usage of wind power and a telescopic reefing mechanism for folding it during berthing.The stability of the ship has been verified through the calculations of initial stability,static stability,and dynamic stability through the fulfillment of the weather criterion using MAXSURF software.The structural analysis of the sail was carried out in ANSYS static structural module.Several flow simulations were carried out in ANSYS fluent module to predict the thrusts produced by the sails at different apparent wind angles,which would in turn reduce the thrust required from the propeller.In this way,the brake horse powers required for different sail arrangements were analyzed to find out a guideline for this wind propulsion system to generate better powering performances.To consider drift and yaw effect on propulsion system,an MMG mathematical model–based simulation was carried out for different drift angles of motion of the ship considering hard sail–based wind loads.Through these analyses,it has been found out that the hard sail–based wind-assisted propulsion system in some cases have produced a reduction of more than 30%brake power in straight ahead motion and around 20%reduction in case of drifting ships compared to the model having no sails.

散货船第二代完整稳性的薄弱性衡准计算分析

考虑到国际海事组织海上安全委员会发布的第二代完整稳性衡准暂行指南的影响,针对散货船的第二代完整稳性评估,以一型散货船为例,进行第二代完整稳性的薄弱性衡准计算分析,介绍NAPA软件的计算评估流程,对比分析计算结果,总结出不满足稳性衡准的工况。

散货船顶边舱横隔板的拓扑优化设计

针对散货船顶边舱横隔板的设计主要靠母型船和工程师经验进行,以横隔板重量最轻为目标,参照原始设计的应力结果进行基于应力约束的拓扑优化。基于原始设计方案,去除顶边舱横隔板上的开孔面板、防倾肘板和屈曲筋,对结构进行细化后获得响应工况的应力作为拓扑优化的应力约束。分别对单个横隔板进行拓扑优化和对货舱内所有横隔板进行拓扑优化。基于拓扑优化结果,设计新的横隔板开孔方式并进行详细设计,并基于三舱段有限元计算对优化设计进行粗网格和细化分析校核。优化后的构型相对原始设计能获得更轻便的重量和更小的应力结果。本文的研究可以为散货船的拓扑优化、顶边舱横隔板的设计提供参考。

某散货船典型舷侧分段制作工艺

本文对某散货船典型舷侧分段制作工艺流程进行全面介绍,阐述分段划分、脚手架、扫砂等主要工艺流程,及分段DAP、焊接、精度、预密性等主要工艺方法,总结其分段制作工艺。

散货船风载荷计算方法分析及对比研究

为了更准确地进行船舶风载荷预报,采用数值模拟方法,以某散货船为研究对象,用计算流体力学仿真软件,对某散货船不同风向角下的绕流特性进行仿真计算,得到船舶在不同风向角下风载荷分布及船舶周围流场特性分布,流体动力学(computational fluid dynamics,CFD)计算方法与中国船级社(China Classification Society,CCS)规范计算方法、挪威船级社(Det Norske Veritas,DNV)规范计算方法所得计算结果进行比较分析得出,风载荷计算方法的差异会引起风载荷计算结果的显著变化,规范方法在横风向等遮蔽作用较弱的情况较准确,而对于遮蔽效应强及流场环境复杂的情况则采用CFD方法更加灵活。研究结果可为相似船型风载荷预报提供参考,保证船舶的安全设计与运营。

大型散货船快速性预报的数值模拟研究

为了服务于以低碳排放为主要目标的船型研发和设计,基于计算流体力学(CFD)数值方法,对21万吨大型散货船开展快速性分析。船舶快速性分析包含船体阻力、螺旋桨敞水和船桨自航数值模拟,将数值结果与水池试验进行比较,结果表明:数值模拟的阻力预报误差在1%以内,船桨自航推进效率误差在3%以内,散货船的快速性数值预报精度达到工程应用水平。散货船快速性数值模拟方法可为后续散货船及其他主流船型的研发和设计提供有力支撑。

大型甲醇双燃料散货船设计研究

为了满足日益严苛的碳排放环保要求,该文以21万t常规燃料散货船为基础,开展以甲醇燃料作为船舶推进动力的关键技术研究,包括甲醇燃料储存舱的布置、甲醇燃料注入和供给系统的设计、甲醇燃料应用的安全和消防要求等,从而开发出某型21万t甲醇双燃料散货船。该船型满足国际海事组织MSC.1/Circ.1621导则和IGF Code规范要求,采用全宽式尾部甲板,2个甲醇燃料舱布置在船舶尾部机舱棚两侧,既不影响货物装卸,也不减少货舱容量。在甲醇燃料模式下,该船消除了颗粒物和硫氧化物的排放,氮氧化物排放满足IMO Tier III标准,船舶能效设计指数可满足第3阶段要求。

基于阻力和伴流不均匀度的21万吨散货船线型优化

[目的]基于船体绕流场计算分析,以阻力和伴流不均匀度为优化目标,对21万吨散货船线型进行优化设计。[方法]首先,借助计算流体动力学(CFD)工具对初始线型进行数值评估并计算船体绕流场,得到波形、压力分布、速度分布等流场特征。其次,根据CFD计算结果,构建优化策略,形成改型方案,并对改型方案进行CFD计算,评估阻力和伴流不均匀度优化效果。最后,开展优化后船型快速性模型试验,验证优化效果。[结果]CFD计算结果表明,改型相较于原型,有效功率降低了2.46%,伴流不均匀度降低了8.48%。模型试验结果表明,改型相较于原型,螺旋桨收到功率降低了3.49%。[结论]研究显示,所提出的优化方法可以获得阻力性能优良、伴流场均匀性好的船体线型,具有较强的工程适用性。

散货船改装运砂船工程实例研究

根据改装船舶相关参数的计算,提出将散货船改造为运砂船的方案和装运砂过程中的关键技术要点,成功将散货船改造成运砂船并投入使用,提高了项目的运砂能力,且相关改造经验可为后续类似项目提供借鉴。

某海损散货船艏整体修复方案

世界贸易离不开海洋运输,货船作为主流载体,穿梭在全球各个港口之间。受海洋环境多种复杂因素影响,船舶在营运中常常遭遇不同程度的海损,其中包括较严重的撞击、搁浅、倾覆事故等。然而受海损的船舶按要求修复后仍可继续使用。本文对某巴拿马型散货船“AMC NAVIGATOR”艏部严重海损后整体修复施工方案做了简要介绍。

氨燃料散货船总体设计关键技术

从温室气体减排的目标需求出发,对氨燃料在散货船上的应用进行研究和探讨。从船舶总体设计的角度,通过大量研究案例的展示和比较分析,从舱容、续航力、燃料舱布置、舱型选择以及上层建筑、尾部甲板、燃料准备间、透气桅、加注站等相关系统的布置设计等方面对散货船的氨燃料升级设计做了广泛深入的研究和探讨;进一步对氨燃料引发的安全性问题、风险评估以及对船舶总体性能的影响等开展讨论,并有针对性地提出了应对措施和建议。展示的研究案例和总体设计思路可以对散货船的氨燃料升级设计提供一定的启发和参考。

88000 DWT散货船结构设计优化

随着船东对载货量要求的提高以及船厂建造成本的不断增加,散货船的设计需不断进行优化升级。文章以88 000 DWT散货船为例,通过合理的结构布置和优化,使船舶在满足规范的前提下重量更轻,同时平衡了结构减重和构件数减少的矛盾,实现船舶建造综合成本的下降。文章所提出的优化思路和方法可给后续散货船设计提供参考。