The optimization of ship weather-routing algorithm based on the composite influence of multi-dynamic elements (II): Optimized routings

The ship routing problem can be known as a multi-objective problem. Since the operation strategy is influenced by ocean environments, e.g. wind, waves or ocean currents, it is therefore weather routed. In this study, the three-dimensional modified isochrone (3DMI) method utilizing the recursive forward technique and floating grid system for the ship tracks is applied to globally search for the optimum route. The proposed method considers two types of routing strategies, i.e. ETA (Estimated Time of Arrival) routing and FUEL (FUEL-saving) routing, with different constraints, such as land boundaries, significant wave heights, engine revolution speeds and roll responses. As a result, it is verified that the robustness of the proposed method appears to be a practical tool by adjusting the safety threshold for the trade-off of ship efficiency and economics.     

基于RMF技术的远洋船舶定量风险评估方法研究

在远洋船舶运输中，设备失效是导致各类事故的一个重要因素。文中引人RMF技术，将其应用到远洋船队的定量风险评估中，以及时查找并消除设备方面的事故隐患。首先找出潜在的风险事件及相关风险因素，然后运用模糊综合评判方法和事故损失综合评估理论对设备风险事件的模糊概率和损失程度后果进行量化，最后依据风险评价结果对需要控制的风险源给出控制措施。实例分析亦表明，运用RMF技术能对远洋船舶的各类设备及属具实施科学的风险管理。     

Nonlinear optimization method of ship floating condition calculation in wave based on vector

Ship floating condition in regular waves is calculated. New equations controlling any ship＇s floating condition are proposed by use of the vector operation. This form is a nonlinear optimization problem which can be solved using the penalty function method with constant coefficients. And the solving process is accelerated by dichotomy. During the solving process, the ship＇s displacement and buoyant centre have been calculated by the integration of the ship surface according to the waterline. The ship surface is described using an accumulative chord length theory in order to determine the displacement, the buoyancy center and the waterline. The draught forming the waterline at each station can be found out by calculating the intersection of the ship surface and the wave surface. The results of an example indicate that this method is exact and efficient. It can calculate the ship floating condition in regular waves as well as simplify the calculation and improve the computational efficiency and the precision of results.     

船体曲面几何表达及水动力性能计算的NURBS方法

采用非均匀有理B样条(NURBS)对船体曲面形状进行几何表达,所生成的网格直接用于后续的有关船体水动力性能计算工作中。对Wigley船型的线性兴波阻力和斜航操纵运动的船体,结合近似的Kutta条件作了相应的数值计算,从与试验结果的比较来看,该方法具有较好的工程精度,对船舶及海洋工程领域中的计算机辅助设计(CAD)与计算流体动力学(CFD)之间的相互集成,具有推动与促进作用。     

不规则波作用下的船舶撞击作用

随着波谱理论研究的发展,各种海工结构及船舶的荷载及其内力分析也日趋应用不规则波的计算方法。目前对于外海码头在波浪作用下的船舶撞击荷载还应用规则波的研究方法,对其应用不规则波分析方法的途径以及在考虑波谱作用后会有怎样的结果等问题目前还较少研究。本文试图对此问题进行初步的分析。     

西北太平洋船舶避风暴分析

本文首先对远望二号船避９７０８号强热带风暴航行的情况作了简要回顾,对当时选择航线、悠入航线、徘徊、加速等一系列措施作了详细分析,还探讨了９７０８号强热带风暴的形成和路径预报问题;最后对远洋避风暴方法作了理论探讨。     

平面移行点源兴波过程影象模拟的初步研究

基于影象模拟在海洋学上应用的初步探讨,对移行点源兴波中的Ｋｅｌｖｉｎ船波这种较为简单的海洋现象,用影象模拟的方法,即结合数值方法,高度真实感图形绘制、计算机动画仿真等技术,把平面移行点源兴波过程用高度真实感的图形显示在荧屏上,并实现运动过程的显示,其间通过计算原始数据、生成图象、实现动画的步骤,解决了数值计算、Ｚ缓冲区数据显示、光线追踪、动画制作等方面的问题,在较低的计算机硬件要求下得到了较好的模     

风浪流联合作用下单点系泊船的受力分析

研究了风浪流联合作用下单点系泊船的受力问题.在应用Newman公式计算波浪漂移力的基础上,结合文献《Fleet Moorings Design Manual》,提出了不同方向的风、浪、流联合作用时,单点系泊船所受到的横向力、纵向力和回转力矩的计算方法.提出了风浪同向时,不同风流夹角组合对应的船舶平衡位置的确定方法.为缆绳、锚的选择以及舵角的控制提供了依据.最后通过算例验证了本方法的适用性和实用性.     

Numerical Simulation of Biological Impact Caused by Direct Injection of Carbon Dioxide in the Ocean

The direct injection of CO₂ in the deep ocean is a promising way to mitigate global warming. One of the uncertainties in this method, however, is its impact on marine organisms in the near field before CO₂ is diluted widely in the ocean. Since field experiments cost enormously, computational simulations are expected to show detailed information on the dilution process near injection points and its impact on marine organisms. In general, the LC50 concept is widely applied for testing the acute impact of a toxic agent on organisms. As a biological impact model we therefore consider mortality, which reflects recent laboratory experiments on zooplankton at various concentrations of CO₂. Here we regard the sigmoid-transformed mortality as a linear function of time in the logarithmic scale, and not just of the concentration of CO₂ in the logarithmic scale. This model was installed in a computational simulation code for the reconstruction of small-scale ocean turbulence. The results suggest that the biological effect is not significant when the ship speed is 4 knots and CO₂ is injected at 0.1 ton/sec in the form of a spray through 100 nozzles provided vertically on a pipe at 10 m intervals. It is therefore considered that the moving-ship method is effective for direct CO₂ injection. This revised version was published online in July 2006 with corrections to the Cover Date.     

The status of geological dredging techniques

Scientific sea-floor dredging is currently used in marine geology primarily by the hard-rock community interested in the recovery of basement rock samples from the unsedimented deep ocean floor. The technique has generally been eclipsed by ocean drilling for recovery of sedimentary rocks, because of perceived uncertainties in the location of sampling and in the representativeness of recovered material. This contribution reviews dredging equipment currently in use by marine geological institutions and refers to pinger attachments that allow precise information on the behaviour of the dredge to be telemetered back to the ship. We argue that improvements in ship navigation and transponder navigation at the seafloor, when used in conjunction with surface and/or deeply towed sidescan and swathemapping surveys, now allow for considerably less uncertainty on the location of dredge sampling. Refined sorting criteria for dredge hauls are now also available. Recent comparisons of regional sample recovery by ocean drilling and by dredge sampling indicate that the dredge hauls can usefully supplement the drilling data in the construction of sedimentary and tectonic histories of seafloor areas.     

基于随机情景模拟的船舶溢油危害后果量化评价——以台湾海峡北部水域为例

为克服典型情景模拟法的缺陷,综合考虑船舶溢油发生的随机性、海洋水动力和风场的不确定性以及环境资源的敏感性,提出基于随机情景模拟的船舶溢油危害后果定量评价方法。通过随机情景模拟和网格化统计得到敏感区的溢油污染概率和最快到达时间,结合环境敏感指数和溢油量等参数计算综合溢油危害指数,并将其作为溢油危害后果定量评价指标。结果表明:台湾海峡北部水域不同季节发生船舶溢油的危害后果大小依次为夏季(27.8)秋季(25.5)春季(21.1)冬季(16.2),夏季溢油事故对牛山岛保护区的污染概率和危害后果相对最大(P=60%,Ck=41.2),达到较高级别;其他季节东甲列岛保护区的溢油污染概率和危害指数均为最高。随机情景模拟能够弥补事故情景,为评价船舶溢油危害后果风险提供一种新方法。     

A Geometrically Exact Formulation for Three-Dimensional Numerical Simulation of the Umbilical Cable in A Deep-Sea ROV System

This paper proposes a geometrically exact formulation for three-dimensional static and dynamic analyses of the umbilical cable in a deep-sea remotely operated vehicle (ROV) system. The presented formulation takes account of the geometric nonlinearities of large displacement, effects of axial load and bending stiffness for modeling of slack cables. The resulting nonlinear second-order governing equations are discretized spatially by the finite element method and solved temporally by the generalized- implicit time integration algorithm, which is adapted to the case of varying coefficient matrices. The ability to consider three-dimensional union action of ocean current and ship heave motion upon the umbilical cable is the key feature of this analysis. The presented formulation is firstly validated, and then three numerical examples for the umbilical cable in a deep-sea ROV system are demonstrated and discussed, including the steady configurations only under the action of depth-dependent ocean current, the dynamic responses in the case of the only ship heave motion, and in the case of the combined action of the ship heave motion and ocean current.     

A Geometrically Exact Formulation for Three-Dimensional Numerical Simulation of the Umbilical Cable in A Deep-Sea ROV System

This paper proposes a geometrically exact formulation for three-dimensional static and dynamic analyses of the umbilical cable in a deep-sea remotely operated vehicle(ROV) system. The presented formulation takes account of the geometric nonlinearities of large displacement, effects of axial load and bending stiffness for modeling of slack cables. The resulting nonlinear second-order governing equations are discretized spatially by the finite element method and solved temporally by the generalized-a implicit time integration algorithm, which is adapted to the case of varying coefficient matrices. The ability to consider three-dimensional union action of ocean current and ship heave motion upon the umbilical cable is the key feature of this analysis. The presented formulation is firstly validated, and then three numerical examples for the umbilical cable in a deep-sea ROV system are demonstrated and discussed, including the steady configurations only under the action of depth-dependent ocean current, the dynamic responses in the case of the only ship heave motion, and in the case of the combined action of the ship heave motion and ocean current.     

Weather routing for offshore transportation using genetic algorithm

Conventional weather routing is defined as determining the optimum route for a merchant ship such that distance or duration of the voyage and fuel consumption are minimized. If the purpose of a voyage is offshore transfer, the term “optimum” includes aspects of operational safety such as towing tension and six-degree motion response of tow. This paper presents the development of a weather routing method for determining the optimal route, which is defined here as the route with minimum average towing tension with a restricted time of arrival and significant motion response. A genetic algorithm is applied to solve optimization problems. Optimized routes of this research have an advantage in towing tension and satisfy motion constraints. The result of this study can contribute to safe and effective planning for offshore transport.     

海洋工程模型运动测量装置的研制

本文介绍由磁通门数字罗盘和改进的航空垂直陀螺仪构成的海洋工程模型运动测量装置。装置简单实用，性能稳定可靠，试用表明它能满足海洋工程模型在风浪流作用下有关运动的测量要求。     

浮式生产储油船振动噪声混合数值预报

建立了可覆盖全频域的浮式生产储油船(FPSO,floating production storage and offloading)工作环境下振动噪声混合数值预报技术流程。将声学计算基本理论方法(有限元/边界元方法与统计能量法)应用于宽频带多噪声源的海洋工程船舶设计中,为设计能保证人员正常进行生产、生活噪声环境下的FPSO提供指导,满足国内船舶设计部门对该技术的迫切需要。文中采用声学边界元求解了FPSO上层建筑低中频域振动噪声,采用统计能量分析方法求解了高频域振动噪声,通过两种方法接力运用和不同模型间的顺利转换,实现了FPSO声学问题全频域分析。并讨论了各类方法的适用范围。     

Vertical synthetic aperture sonar for ocean acoustic tomography

This paper presents the result of a first attempt to achieve a vertical synthetic aperture in the ocean for SOFAR multipath identification. The experiment was conducted during the deployment of a tomographic array in the Mediterranean Sea. Drifting the hydrophone up or down from a ship while listening to the transmitted signal created a powerful synthetic aperture at 400 Hz. Wide-band phase-coded signals, typically used in ocean tomography, were found suitable for this application. The displacement length was 100 m and the hydrophone velocity 1 m/s. The obtained resolution of 1° enabled all the rays in the tested middle range configuration to be resolved and identified. Most of them could not have been resolved with a static hydrophone. Several Doppler processing methods are presented. The narrowband approximation leading to fast algorithms is discussed. Phase time series of individual paths obtained with an array-like wave separation method show that the phase coherence of the different multipaths is nearly perfect. An angle/velocity calibration method and a first rough inversion are finally presented     

浅水中浮体在波浪作用下运动的三维时域计算模型

港口中系泊船在波浪作用下运动问题的本质是浅水波浪与浮体的相互作用。与深水情况不同,浅水问题应当考虑水底、水域边界的影响及浅水波浪自身的特性,单一模型很难实现该模拟过程。为此,建立了Boussinesq方程计算入射波和Laplace方程计算散射波的全时域组合计算模型。有限元法求解的Boussinesq方程能使入射波充分考虑到水底、水域边界的影响和浅水波浪的特性;散射波被线性化,采用边界元法求解,并以浮体运动时的物面条件为入射波和散射波求解的匹配条件。该方法为完全的时域方法,计算网格不随时间变动,计算过程较为方便。通过与实验及其他数值方法的结果进行比较,验证了本模型对非线性波面、浮体的运动都有比较理想的计算结果,显示了本模型对非线性问题具有较好的计算能力。     

Homotopy Method for Inverse Design of the Bulbous Bow of A Container Ship

The homotopy method is utilized in the present inverse hull design problem to minimize the wave-making coefficient of a 1300 TEU container ship with a bulbous bow. Moreover, in order to improve the computational efficiency of the algorithm, a properly smooth function is employed to update the homotopy parameter during iteration. Numerical results show that the homotopy method has been successfully applied in the inverse design of the ship hull. This method has an advantage of high performance on convergence and it is credible and valuable for engineering practice.