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.     

Design sea state assessment using genetic algorithm approach

Two major statistical issues can be distinguished in the procedure of wave extreme prediction. The first issue is that predicted extreme values must be based on data collected in a relatively short time. The second issue is extrapolation of the observed data into its extreme region, typically lying well beyond from even the most extreme available observation. The process of extrapolation plays a fundamental role in this area of analysis and therefore it is essential to fit empirically a convenient probability distribution that describes the available data as closely as possible. Determination of extreme values probability distribution parameters by genetic algorithm is applied to improve the methodology of extreme sea state prediction.Illustrative applications of the method are given for a North Atlantic sea environment. The results are presented as crest height maximum values occurring with a given probability or in a design storm that has a specified return period.     

长江口洪水期潮波变形数值模拟研究

由长江口现场水文测验资料分析知,洪水期潮波上溯过程中,潮波变形具有先加剧后趋缓的特点。基于非结构网格FVM方法建立大通至外海的大范围数学模型,复演长江口潮波传播过程,以此为基础,研究长江口洪水期潮波变形特征的形成原因。研究认为:洪水期长江口潮波变形转折点位于潮流界上游;转折点下游潮波变形逐渐加剧是由于高低潮位潮波传播速度差异造成的;转折点上游潮波变形趋缓是由于高潮位重力引起的潮波传播阻力对潮波传播影响大于高低潮位潮波传播速度差异造成的。     

舟山东港新城溃堤洪水演进数值模拟

台风会引起风暴增水和强浪。围填海工程建于软土地基上,海堤易产生不规则沉降,在台风引起的强浪作用下有可能发生溃堤,海水在高水位下大量涌入围区,引发灾难。针对溃坝的急变流特性,基于Delft3D Open Source,采用一种基于经典交错网格的改进型数值方法(其水流扩展流动数值近似算法符合动量守恒,而水流收缩流动数值近似则满足伯努利方程),建立了舟山东港新城溃堤洪水演进模型,并计算了最大可能风暴增水条件下溃堤洪水在东港新城的演进过程。结果表明,围区内的地形形势对洪水的演进及最终分布起了决定性作用,当溃口出现在不同位置时,影响范围和程度不一样。东港南部由于地势较低,且没有大型的吸纳洪水的人工湖,当附近出现50 m宽的溃口时,近乎整个南部区域都会受到海水的影响;而北部由于地势相对较高,影响有限。     

Mooring optimization of floating platforms using a genetic algorithm

This paper presents a new procedure for the optimization of the mooring design of floating platforms, in which an automatic design sequence is also established. Regarding the optimization philosophy, the following aspects are dealt with:

• The optimization of the platform heading and its mooring pattern, taking into account the environmental force spreading;

• optimum line length or line tension for each mooring line, associated to the optimization of the mooring line materials and sizes.

Basically, the main goal of this paper is to introduce a new method, which will provide the quickest way to find the best mooring system, defined here as that which minimizes platform responses.A genetic algorithm (GA) is applied in this contribution, and this paper describes exactly the procedure of developing a GA code directed toward the solution of mooring design optimization problems. In order to prove the efficiency and the vast potential of the proposed algorithm as a design tool, sample moorings are analyzed for different environmental conditions and the final results, including the time required to run them, are presented.     

厦门地区旱涝灾害的分析

本文应用厦门海岛资源综合调查收集到的1952～1990年的气象资料,对厦门干旱、暴雨等灾害性天气的出现规律和分布特征,进行了天气气候分析得出厦门干旱突出,具有机率多、旱期长;暴雨成灾不及干旱频繁,但一旦发生,强度大、灾害严重等结论。     

非线性波传播的新型数值模拟模型及其实验验证

以一种新型的Boussinesq型方程为控制方程组,采用五阶Runge-Kutta-England格式离散时间积分,采用七点差分格式离散空间导数,并通过采用恰当的出流边界条件,从而建立了非线性波传播的新型数值模拟模型.通过对均匀水深水域内波浪传播的数值模拟说明,模型能较好地模拟大水深水域和强非线性波的传播.通过设置不同的入射波参数来进行潜堤地形上波浪传播的物理模型实验,并将数值解与物理模型实验结果进行了比较.     

决口海堤洪水波传播模拟和分析研究I:方法和验证

选用水槽和港池物理模型方法以及已有的一些物理模型试验成果,结合SWASH模型,对孤立波在海堤斜坡上的爬高和越浪进行验证,确定合适的计算参数;计算和分析几种不同内坡形式的海堤堤顶决口,确定合适的海堤内坡边界条件。研究分析表明,验证后的SWASH模型可以用来进行海侧来波和陆域越堤波浪的联合计算,为决口海堤洪水波传播模拟和分析奠定了基础。     

长江口滞流点洪、枯季移动的数值分析

为研究长江口滞流点位置的季节变化,利用Delft3D-Flow模块建立长江口二维潮流数学模型,通过实测水文资料对模型进行验证。在此基础上,模拟长江口各汊道洪、枯季滞流点移动情况,并从各汊道沿程断面的落潮量、涨潮量和落、涨潮量之比3个方面进行了水动力分析。结果显示:洪季,北支滞流点在八滧港东北方向约1.9 km处;在南支各汊道中,北港滞流点位于鸡骨礁东北方向约10.0 km处,北槽滞流点位于牛皮礁东南方向约3.8 km处,南槽滞流点位于大辑山东北方向约14.1 km处。枯季,除北槽外,其余各汊道均出现两个滞流点,且北支的两个滞流点相距最远,分别在灵甸港西南方向约3.2 km处和六滧港东北方向约3.1 km处;北港滞流点分别在鸡骨礁西北方向约25.8 km和20.2 km处,北槽滞流点在横沙以西约5.3 km处,南槽滞流点分别在中浚西北方向约6.5 km和东北方向约5.5 km处。北支洪、枯季滞流点的移动距离为4.6~53.3 km,北港、南槽洪、枯季滞流点的移动距离分别为22.0~27.7km和34.6~39.2 km,而北槽洪、枯季滞流点的移动距离最大,为57.1km。长江口各汊道滞流点的移动反映了河流径流和海洋潮流的综合作用。     

涨落潮对海湾内新建人造沙滩稳定性的影响

为提高海湾内人造沙滩稳定性,以宁波西沪港北岸人造沙滩为研究对象,结合已有试验段人造沙滩退化过程,分析了沙源流失原因,并以此优化拟建段人造沙滩的位置,再通过波浪-泥沙物理模型试验,研究了不同强度波浪和潮位过程对拟建段人造沙滩稳定性的影响。结果表明：波浪和人造沙滩存在夹角时,沙滩前会存在明显的纵向沿岸输沙;人造沙滩建造后首年,平常浪作用1年对人造沙滩稳定性影响可能会大于单次台风浪对沙滩的作用;常浪作用下涨落潮引起的沙滩前沿水下沙坝发育过程不同,落潮水位过程波浪对沙滩的侵蚀大于涨潮水位过程;人造沙滩前落潮流和波生沿岸流方向一致,会加速沙滩侵蚀,当落潮流作用大于涨潮流,则会进一步导致沙滩严重退化。     

An approach for development of a ship routing algorithm for application in the North Indian Ocean region

This paper presents a general approach for the development of a ship weather routing algorithm for determining optimal route which is taken here as the minimum-time route. The optimization model is based on a form of Dijkstra's algorithm. The developed algorithm is versatile and is capable of considering nearly all realistic practical constraints that a ship faces during her voyage. The ‘weight’ functions and the routes are determined by considering both involuntary and voluntary speed reduction. The algorithm is investigated using various realistic wave data for the North Indian Ocean region obtained from a 3rd generation WAM model. Illustrative examples of minimum-time sea routes on Arabian Sea and Bay-of-Bengal have been determined and presented to demonstrate the capability of the algorithm in handling many practical constraints within its framework.     

厦门嵩屿附近水域洪水期悬浮泥沙活动的特征

本文根据1984～1986年5次水文泥沙观测资料,研究了福建厦门嵩屿附近水域洪水期悬浮泥沙对河口三角洲和厦门西港东渡以南海域的淤积作用。     

江苏省长江干流沿程洪潮设计水位数值模拟研究

长江干流江苏段地处长江下游河口地区,全线位于感潮河段,沿程水位既受上游长江径流、外海潮位、台风的影响,也受到工情变化、支流入汇等影响。长江江苏段现行洪潮设计水位是按《长江流域综合利用规划简要报告》(1990年)中确定的无台风影响水位实施。近年来,由于上游水、沙、工情条件变化,开展上游大通径流、风暴潮、区间入汇等对沿程洪潮水位的影响研究十分必要。建立大通至长江口二维水沙数学模型与外海风暴潮模型,研究不同影响因素作用下长江干流江苏段沿程洪潮设计水位变化。研究成果表明:南京河段水位主要受上游径流影响;江阴以下主要受外海潮汐及风暴潮的影响;南京至江阴段则受上游径流、外海潮汐、风暴潮三者的共同作用影响。外海天文大潮、风暴潮"两碰头"和上游大径流、外海天文大潮与风暴潮"三碰头"引起的沿程增水值呈驼峰分布,最大值分别发生在江阴和天生港附近,最大增幅1.65 m。研究结果已为长江江苏段堤防防洪能力提升工程建设提供技术支撑。     

A new approach to the local time stepping problem for scalar transport

A new scalar transport method is proposed to reduce computational time when a large number of scalars are transported in coupled hydrodynamic-ecosystem models. The new Local Mass Transport (LMT) method confines subtime transport computations to regions where the local Courant–Freidrichs–Lewy (CFL) number exceeds a given numerical stability criteria for a global (large) time step, but the method does not require either contiguous regions or special boundary algorithms between regions as used in previous Local Time Stepping (LTS) approaches. The new method uses conservative transport of mass rather than dissolved concentration. This approach allows different faces of a single grid cell to use different subtime steps. The new LMT method is further extended to include background filtering (LMTB) so that scalars below a pre-defined background concentration are ignored in transport calculations. This new approach can further reduce computational time where large regions are at or below an irrelevant background concentration. Both LMT and LMTB methods can be more computationally efficient than global subtime stepping.     

工程影响下长江口涨潮槽演变特征研究--以北港六滧涨潮槽为例

崇明岛南岸发育有六滧涨潮槽,研究其演变过程对于崇明世界级生态岛港口建设、通航安全和岸滩稳定具有重要意义。为此,在长江口北港中上段2000、2004、2008、2012和2018年海图水深数据的基础上,分别于2018年7月利用SeaBat 7125、2019年7月利用M80无人艇搭载的SeaBat T50-P多波束测深系统以及ADCP对六滧涨潮槽开展了水下地形和流速的测量工作,分析工程影响下六滧涨潮槽的演变特征。结果表明:六滧涨潮槽淤浅,外侧沙脊冲刷剧烈,槽内落潮优势明显。其原因为流域来沙减少、以青草沙水库为主体工程的南北港分流口整治及长江大桥的修建导致了北港中上段主槽冲刷、主流北移。同时,六滧涨潮槽局部水动力条件增强,槽内的丁坝坝头局部冲刷加剧,并且奚家港东侧岸滩出现侵蚀,需引起重视。     

钦州湾丰水期和枯水期浮游动物群落特征

在2011年丰水期(7月)和2012年枯水期(3月),分别对钦州湾的内湾和外湾开展了浮游动物调查,研究了枯水期和丰水期钦州湾浮游动物的种类组成、数量分布和季节变化特征。丰水期和枯水期浮游动物种类数量分别为27种和44种,以优势度指数Y0.02确定的优势种丰水期和枯水期分别为3种和4种。丰水期浮游动物丰度为4.0~133.6ind/m3,平均丰度为50.9ind/m3;枯水期浮游动物丰度为1.2~1 725.0ind/m3,平均丰度为272.2ind/m3。丰水期浮游动物(包含鱼卵仔鱼)生物量为1.7~179.2mg/m3,平均生物量为44.0mg/m3;枯水期浮游动物(包含鱼卵仔鱼)生物量为3.1~3 530.0mg/m3,平均生物量为474.9mg/m3。无论是浮游动物的种类数量、丰度和生物量,均显示出内湾低于外湾的空间分布特征,以及枯水期高于丰水期的变化特征。钦州湾浮游动物的这种季节变化和空间分布特征主要是与浮游植物生物量、贝类养殖、环境的稳定度以及人为干扰等有着密切的关系。     

Use of a new clone of Artemia parthenogenetica (OP1) to increase genetic variation

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福建省前汛期旱涝年前冬季500hPa高度场特征及其与东亚冬季风的关系

通过对1961～2001年福建前汛期降水与东亚前冬季冬季风强弱与副高强度间的相关性等统计分析表明：前冬季冬季风强（弱）年，前汛期西太平洋副高偏弱（强），福建降水偏多（少），此外，本文利用ECMWF再分析资料，对比分析了旱涝年份前冬季500hPa环流形势差异．其结果显示：旱（涝）年前冬季，东亚大槽偏弱（强），冬季风减弱（增强），副热带高压偏强（弱）。     

基于遗传算法的缓波型立管多目标集成优化

缓波型立管由于设计参数较多且优化目标之间相互影响,设计结果具有很大的不确定性。随着代理模型和智能优化算法的发展,针对缓波型立管的优化可以提出更好的解决方案。以提高力学性能和经济效益为优化目标,采用基于Kriging插值模型和NSGA-II算法的多目标优化策略,对考虑顶部浮体影响的深水缓波型立管进行动力响应分析,并开展线型—截面双目标优化集成设计和线型—浮筒三目标优化集成设计。将处于不同几何尺度的设计变量进行集成,旨在各目标存在相互竞争的情况下,与截面、浮筒设计形成有效互动以提高线型设计的总体性能。结果表明,Pareto最优解集可提供多个选择方案,以满足工程实际需要。将所选最优方案与初始设计进行对比,并以疲劳性能和成本估算作为优化的校核指标,取得了理想的优化效果。