Long-term approach for assessment of sloshing loads in LNG carrier,Part I: Comparison of Short- and Long-term approaches

To assess the long-term sloshing loads of a liquefied natural gas carrier, Daewoo Shipbuilding and Marine Engineering Co., Ltd., Hyundai Heavy Industry Co., Ltd, Samsung Heavy Industry Co., Ltd. (SHI), Korean Register, and Seoul National University conducted a series of joint industrial experiments using a six-degree-of-freedom irregular sloshing model test. SHI provides a 174 K S-LNGC and its cargo hold information. To consider the numerous test conditions of the long-term approach, the present study focuses on the upper regions of the cargo hold structure, and feasible operating scenarios are assumed. A total of 3870 h at a real scale are simulated based on 387 sailing conditions. Extensive experimental results of sloshing loads are analyzed based on different guidelines suggested by different maritime classification societies. Part I of this study provides an assessment of sloshing loads based on a comparison of short- and long-term approaches distinguished by the guidelines, and the possible reference values are presented. A practical solution for the long-term approach will be discussed in Part II.     

A numerical study of the effects of the longitudinal baffle on nickel ore slurry sloshing in a prismatic cargo hold

The nickel ore slurry sloshing in a rolling partially loaded prismatic cargo hold with a longitudinal baffle is investigated. A numerical model based on the volume of fluid (VOF) method and the non-Newtonian Herschel-Bulkley and Bingham equations is proposed to study the dynamic behavior of nickel ore slurry sloshing. The numerical model is solved by using the finite volume approximations and the dynamic mesh technique is utilized to handle the cargo hold's motion. After taking grid and time step independence study, the numerical results are compared with experimental data. Comparisons show good agreement in the cases investigated. Further, the relationship between the moment amplitude induced on the hold boundary and the excitation frequency is checked numerically. The ratio of baffle height to the initial cargo depth has been changed in the range of 0.0 ≤ h_B/d ≤ 1.2. The variation of the sloshing-induced moment and the deformation of the free surface under different baffle heights have been obtained and discussed. To clearly understand the sloshing behavior of nickel ore slurry, the sloshing of liquid water has also been carried out. Meanwhile, the dynamic viscosity of the nickel ore slurry is monitored. The critical baffle height with regard to the sloshing-induced moment and the elevation difference of the free surface at two sides of the cargo hold has also been presented and discussed.     

Structural behaviour of a high tensile steel deck using trapezoidal stiffeners and dynamics of vehicle–deck interactions

As an early part of a large design and fabrication-oriented project FasdHTS funded by the GROWTH programme of the European Commission, an exotic concept ship was designed in very high tensile steel (EHS690) with the purpose of finding out consequences for design and production. The project has already produced a considerable bank of knowledge for design and shipyard production in this material.This paper presents analysis and discussions on static and dynamic behaviour of a high tensile steel deck designed with trapezoidal stiffeners. First, a finite element model of the deck structure is created. The influence of support condition for the longitudinal girders, and the contact area between the vehicle tyre and panel were analysed. The results from modal analysis of the structure under different load conditions are presented. The different load conditions comprise the unloaded and loaded deck, and the load type, i.e. cargo loads or vehicle loads (car loads or truck loads). From the frequency response analysis under harmonic excitation, it shows how the locations and numbers of cars parked on the deck influence the dynamic response of the structure. Furthermore, by studying the car–deck interaction, it is found that the effects of normal cargo loads are quite different from the vehicle loads due to the spring/damping effects of the vehicles. It is suggested that the carloads have a similar mechanism to that of tuned mass dampers. Finally, two transient analyses of the structure due to excitations transferred from deck supports and lorry braking-induced loading are performed. It is suggested that the deck structure and vehicle design could have more interactions with each other.     

“穷举法”在油船货油舱分舱优化设计中的应用

为实现油船货油舱分舱优化,以一艘大型油船为例,根据MARPOL公约和共同结构规范(HCSR)的要求,在主尺度、船型和货油舱总舱容确定的情况下,以最小静水弯矩为优化目标,基于"穷举法"编制优化货油舱横舱壁位置的应用程序。实际应用结果表明,该程序可运用到油船的分舱优化中,能达到快速、合理地分舱,提高设计效率的目的。     

Numerical simulation of flow around a smooth circular cylinder at very high Reynolds numbers

High Reynolds number flows (Re = 1 × 10⁶, 2 × 10⁶ and 3.6 × 10⁶, based on the free stream velocity and cylinder diameter) covering the supercritical to upper-transition flow regimes around a two-dimensional (2D) smooth circular cylinder, have been investigated numerically using 2D Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations with a standard high Reynolds number k ? ? turbulence model. The objective of the present study is to evaluate whether the model is applicable for engineering design within these flow regimes. The results are compared with published experimental data and numerical results. Although the k ? ? model is known to yield less accurate predictions of flows with strong anisotropic turbulence, satisfactory results for engineering design purposes are obtained for high Reynolds number flows around a smooth circular cylinder in the supercritical and upper-transition flow regimes, i.e. Re > 10⁶. This is based on the comparison with published experimental data and numerical results.     

Model test on the collapse strength of the buffer bow structures

The adoption of double hull system in the side hull of oil tanker has been recognized as an effective countermeasure to prevent a disastrous damage induced by collision accident which might cause cargo oil spill from a struck oil tanker. However, when considering that ocean-going vessels are increasing not only in size but also in speed, a threat of disastrous collision accident should be further mitigated even on the responsibility of striking ships.A series of crush tests using scale models of the buffer bow has been carried out. The test results were compared with those obtained by FEA simulation and a simple analysis. The performance of the buffer bow is discussed focusing on the collapse mechanism and the P–δ characteristics. Then the guidelines for the practical design of buffer bow structure are presented.     

Unsteady numerical simulation of flow around 2-D circular cylinder for high Reynolds numbers

In this paper, 2-D computational analyses were conducted for unsteady high Reynolds number flows around a smooth circular cylinder in the supercritical and upper-transition flow regimes, i.e. 8.21×10⁴<Re<1.54×10⁶. The calculations were performed by means of solving the 2-D Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations with a k-? turbulence model. The calculated results, produced flow structure drag and lift coefficients, as well as Strouhal numbers. The findings were in good agreement with previous published data, which also supplied us with a good understanding of the flow across cylinders of different high Reynolds numbers. Meanwhile, an effective measure was presented to control the lift force on a cylinder, which points the way to decrease the vortex induced vibration of marine structure in future.     

某重件码头固定式桅杆吊墩台的三维协同设计

针对固定式桅杆吊墩台在二维设计过程中专业间协同不充分、图纸表达准确性不够、设计的标准化程度偏低等问题,依托某重件码头工程,采用数字化三维协同设计技术,开展桅杆吊墩台基础的施工图设计阶段的应用研究.通过部署协同工作环境、参数化驱动设计,从多专业协同设计、桩基优化布置、结构计算、预埋件参数化布置、工程量统计及标准出图6个应...     

Inland transportation system planning by life-cycle impact assessment: a case study. 2nd report: single comparison index

A model to estimate and compare the ecological impact and economic feasibility of a land transportation system (trucks) and a marine transportation system (cargo ships) was developed and presented in a previous report.¹ Three different comparison indices—environmental, economic, and customer service—were used to evaluate and compare their ecological impacts and determine their economic superiority. In this article, a single comparison index is proposed and assessed for the two transportation systems. The estimates were made for nine different routes in Japan. A simple mathematical model of the whole methodology is given. The sensitivity of the weighting factors used in the comparison method was analyzed. The social cost saving in monetary terms through a modal shift is also presented. Received: February 15, 2001 / Accepted: September 19, 2001     

空间有限元法在深水散货码头结构设计中的应用

结合营口港鲅鱼圈港区一港池深水散货码头工程结构设计,对建造大型非预应力梁板构件桩基码头,采用空间有限元法对各种计算模型进行分析和探讨,并通过物模验证,取得较为满意的成果,为今后建设此类深水码头工程提出一种新的尝试。     

Optimal handling capacity at a berth

In a recent paper Wanhill [1] described a method for determining the number of berths that should be provided at a port so that the total usage cost would be minimized. However, in many situations a port will provide a single specialized berth to cater for a particular type of cargo; for example, the unloading of iron-ore at a steelworks or the discharge of oil at a general cargo port. The problem then is not one of deciding on the number of berths to be built but rather that of finding the optimal cargo handling capacity for the single berth available. A model is presented in this paper indicating how such a decision may be made, and two examples give approximate lower and upper bounds for the optimal capacity for many practical cases. A second paper will show how a theoretical model often has to be modified in the light of particular circumstances.     

湛江某30 万吨级大型散货码头水工结构优化设计

介绍湛江某30万吨级大型散货码头水工结构设计内容、主要设计条件等基础资料。通过分析湛江某30万吨级大型散货码头结构特点,确定了码头桩基桩型的选型,并提出码头基桩优化布置是优化设计需考虑的关键因素。通过分析比较不同排架间距下码头受力情况,对码头进行优化设计。     

大型油船中剖面结构优化设计的遗传算法

采用遗传算法对大型油船中剖面结构进行了基于DNV规范的优化。以舱段单位长度重量最轻为目标函数,选取了20个设计变量,从DNV规范中提取了32个关于总强度、稳定性等要求作为约束条件,并设计了相应的遗传算法数学模型。算例结果表明单位舱段长度的重量减轻了5.2%,表明该遗传算法在大型油船中剖面的结构优化方面是行之有效的。     

基于拓扑优化的油船货舱结构设计研究

研究油船货舱结构拓扑优化设计和普通构件级结构拓扑优化设计的不同点:如设计变量数目多、约束条件多、计算工况多以及计算工况之间应变能差异等。为使普通计算机也能运行舱段结构拓扑优化计算并得到清晰拓扑构型的结果,有必要对舱段拓扑优化设计的优化对象、单元类型、初始板厚、工具方法、约束条件、体积分数、工况加权权值等主要控制参数进行研究。文中给出工程上适用的舱段拓扑优化基结构建模方法和计算方法,并以某一单纵舱壁型VLCC为例,分别采用SIMP法和BESO法给出舱段主要支撑结构拓扑优化的清晰构型。     

Hydrodynamic optimization of ship hull forms in shallow water

A computational method for improving hull form in shallow water with respect to wave resistance is presented. The method involves coupling ideas from two distinct research fields: numerical ship hydrodynamics and nonlinear programming techniques. The wave resistance is estimated by means of Morinos panel method, which is extended to free surface flow and considers the influence of finite depth on the wave resistance of ships. This is linked to the optimization procedure of the sequential quadratic programming (SQP) technique, and an optimum hull form can be obtained through a series of iterations giving some design constraints. Sinkage is an important factor in shallow water, and this method considers sinkage as a hydrodynamic design constraint. The optimization procedure developed is demonstrated by selecting a Wigley (C _B = 0.444) hull and the Series 60 (C _B = 0.60) hull, and new hull forms are obtained at Froude number 0.316. The Froude number specified corresponds to a lower than critical speed since most of the ships operating in shallow water move below their critical speed. The numerical results of the optimization procedure indicate that the optimized hull forms yields a reduction in wave resistance.     

考虑不确定性因素的路径优化(英文)

A route optimization methodology in the frame of an onboard decision support/guidance system for the ship’s master has been developed and is presented in this paper.The method aims at the minimization of the fuel voyage cost and the risks related to the ship’s seakeeping performance expected to be within acceptable limits of voyage duration.Parts of this methodology were implemented by interfacing alternative probability assessment methods,such as Monte Carlo,first order reliability method(FORM) and second order reliability method(SORM),and a 3-D seakeeping code,including a software tool for the calculation of the added resistance in waves of NTUA-SDL.The entire system was integrated within the probabilistic analysis software PROBAN.Two of the main modules for the calculation of added resistance and the probabilistic assessment for the considered seakeeping hazards with respect to exceedance levels of predefined threshold values are herein elaborated and validation studies proved their efficiency in view of their implementation into an on-board optimization system.     

海口—海安航线客滚船轮机设计

介绍了海口—海安航线客滚船轮机设计的特点。通过调整机舱及辅助设备间布置方案,增加车道,提高了运能。对主推进系统布置中出现的问题提出了解决方法。针对航线特点合理配置应急/停泊发电机组,并介绍了该船消防系统布置特点及居住舱室和车辆舱排水能力计算方法及计算结果。设计中对货舱通风布置方案进行多次调整及优化。     

Influence of different topological variants on optimized structural scantlings of passenger ship

For a multi-deck ships with extensive superstructures (such as passenger and cruise ships, RoPax, mega yachts, etc.) the global structural response can be particularly complex. The influence of the superstructure to the primary strength for those multi-deck ships must be considered from an early design phase. Main global topological parameters (e.g. size of side openings, position and stiffness of longitudinal and transverse bulkheads, etc.) have dominant influence on the shape of hull girder stress distributions over the ship height. The Taguchi concepts and techniques (FFE, orthogonal arrays, ANOVA, etc.) could be used to systematically study influence of multiple topological parameters on the global structural response obtained by FEM analysis. It also enables rational identification of the most dominant parameters and provide designer with the near-optimal level of each topological parameter for the defined design objective. It has been demonstrated how different topological variants can lead to different optimal structural scantlings w. r.t chosen design objectives (mass, VCG, etc.), using simplified full ship 3D FE model of passenger ship as an example. Structural design software MAESTRO and in-house developed framework for the design support system DeMak – OCTOPUS Designer were used as a structural optimization tool. This paper aim to extend the standard scantling optimization by introducing topological aspects as a first STEP in overall optimization procedure.     

关于某离岸式高桩码头引桥桩基承载力的讨论

某在建散货码头,引桥采用桩基础,预制混凝土桩沉至设计标高,贯入度仍有100 mm,现场高应变检测发现桩基实测承载力远小于设计承载力.本文通过分析地质钻孔资料、桩基设计承载力计算、桩基终锤贯入度、高应变检测结果和超静孔隙水压力消散过程,对本项目桩基的承载力进行讨论.本文对类似工程的勘察、设计和施工有借鉴意义.     

公路客货站场建设的模糊排序研究

论述了公路客货运站场建设项目排序的评判指标,运用模糊关联度原理,考虑采用整体投资决策优化模型,分析确定了各项待建项目的关联度,并以南海区的客货运站场规划为例进行了验证,收到了较好的效果。