镍矿运输船沉没机理的数值模拟分析

近几年来,多条装运红土镍矿的船舶在南中国海倾覆沉没,引起业界的震惊。红土镍矿是一种非常特殊的矿物质,在运输过程中,如果船舶遭遇风浪,或船舶本身长时间的振动,都会导致该矿石的表面液化。液化后的混合液体具有较强粘性,可以形成自由液面。但由于现存的用于计算船舶自由液面的方法不适合于具有较大粘性的液体,因而无法解释运输该种货物船舶倾覆沉没的原因。所以,该文采用数学建模的方法,对运输红土镍矿的船舶进行了模拟计算。得出的结论是当流体的惯性力大于流体的粘性剪力时,粘性流体对船舶的作用力矩随时间的变化总趋势是逐渐增大。当流体产生的横向惯性力远大于流体的剪切阻力时,流体将会挣脱剪切阻力的束缚,迅速滑向船舶的一侧,使船舶的横稳性迅速消失,最终导致船舶很快倾覆沉没。     

散运红土镍矿风险管控

本文阐述了影响散装货船载运红土镍矿安全的主要因素,分析了舱内红土镍矿液化、位移的过程,以及对船舶安全所带来的影响,并据此提出了散装货船载运红土镍矿时管控安全风险的措施。一、影响散装货船载运红土镍矿安全性的主要因素到目前为止,虽然航运界已对散装货船载运红土镍矿的安全性引起了高度重视,但仍未最终确定促使这些船舶沉没的真正原因。当前,被航运界公认的观点是红土镍矿同其它精粉铁矿一样,     

某散货船载运镍矿稳性分析

针对镍矿在运输过程中易液化,造成船舶发生危险甚至倾覆的问题。文章阐述了镍矿特性及易流态化货物完全液化后自由液面和货物移动对船舶稳性的影响,并通过实船数据计算出货物移动后稳性的变化。货物在液化后会形成横倾力矩,使稳性减小,甚至丧失。     

红土镍矿安全运输经验

文中分析了红土镍矿运输存在的巨大风险,并根据多年运输红土镍矿的成功经验,介绍了公司和船舶化解红土镍矿运输风险应采取的针对性安全措施,对船舶安全运输红土镍矿具有重要意义。     

"镍矿"海运之灾何时消

去年年底,中国航海界经受了近年来少有的安全危机。10月28日,浙江收货人光租一艘"建富星"轮(1970年造)装有4700吨红土镍矿,这艘巴拿马级散货船在琉球群岛南沉没。11月9日,某散货船(1970年造)装有红土镍矿在台湾东部海面沉没。11月10日,N远洋公司M轮从印尼运红土镍矿回张家港卸货,途经冲绳岛南340海里处,倾覆沉没,25名船员,     

货舱内液化矿砂晃荡机理及数值计算研究

装载含水量较高矿砂的船舶在长时间摇摆和振动时,装载的矿砂会出现液化现象,其中的水分会析出,并在矿砂表面形成自由液面.受液化矿砂的粘性流动及表层液面的影响,运输该类货物的船舶易发生倾覆事故.建立了载有液化矿砂的三维货舱数值模型,探讨了货舱晃荡时矿砂液面、壁面载荷以及货舱横摇力矩的变化规律等;结合横摇实验现象对液化矿砂晃动机理和危害性进行了初步验证.结果表明：货舱内粘性矿砂的流动滞后于货舱的横摇运动,因而货舱横摇力矩的变化与货舱运动存在着相位滞后的关系,其最大值发生在货舱处于最大晃动角度后返回到平衡位置的过程中;货舱回摇过程中,倾侧的液化矿砂不能及时回流,会在一侧产生堆积,进而增加船舶倾侧力矩,最终可能会导致船舶倾覆.     

远洋镍矿运输安全分析

为提高镍矿运输的安全性,避免运载镍矿船舶发生沉没事件,对船载镍矿的安全运输技术进行分析。总结实际操作中测定镍矿含水量的方法,判断装运镍矿的自由液面对船舶稳性的影响,提出在监控镍矿装运过程中的注意事项及操作要点,并对镍矿运输船舶的安全运营提出合理建议。     

散运红土镍矿 风险管控

本文阐述了影响散装货船载运红土镍矿安全的主要因素，分析了舱内红土镍矿液化、位移的过程，以及对船舶安全所带来的影响，并据此提出了散装货船载运红土镍矿时管控安全风险的措施。     

试论精选矿粉安全运输

近年来,船舶因装精矿粉而倾覆沉没的恶性事故有所抬头,例如:江苏某公司下属某轮装运精矿粉在汕头沿海倾覆沉没的事故。将精选矿粉海上安全运输问题再一次摆到航运界和船长的面前。     

试论精选矿粉安全运输

近年来，船舶因装精矿粉而倾覆沉没的恶性事故有所抬头，例如：江苏某公司下属某轮装运精矿粉在汕头沿海倾覆沉没的事故。将精选矿粉海上安全运输问题再一次摆到航运界和船长的面前。     

横向规则波作用下的船舶倾覆

运用安全池理论研究了某近海干货船在横向规则波作用下的船舶倾覆问题.用阿当姆斯预估-校正法数值求解时域内单自由度非线性横摇方程.采用三维格林积分方程法计算水动力系数的频域特性.分析了非线性横摇方程中势流阻尼、非线性阻尼以及在横向规则波作用下波高和频率对安全池的影响.     

Stability assessment for intact ships in the light of model experiments

A systematic method for assessing intact ship stability with a free-running model in a seakeeping and maneuvering basin is proposed in this paper. Model experiments were carried out in extremely steep regular waves for a model drifting, running in head seas, and quartering seas. This method was applied to two purse seiners, and efficiently identified thresholds in metacentric heights for capsizing of these ships. These capsizing thresholds are compared with requirements of the IMO Code on Intact Stability. This series of model experiments also confirms that capsizing at the threshold occurs only in quartering seas, and shows that capsizing is caused by broaching, loss of stability on a wave crest, or bow diving. Received for publication on Jan. 20, 1999; accepted on July 6, 1999     

自卸砂船稳性分析及其倾覆后应急施救方案

自卸砂船船体结构具有一定特殊性,在稳性方面富余量较小.而运输过程中超载现象普遍且程度较严重,使该种船舶在航行过程中相对而言更容易发生倾覆沉没,对人命和财产造成极大损害.以一起事故为实例,对该类船舶的稳性进行分析;并结合船舶分舱和船舶静力学原理,提出了自卸砂船倾覆翻扣事故发生之后的应急救人措施建议方案.     

随机横浪中船舶倾覆过程模拟与安全域计算

研讨了随机海浪中船舶非线性随机横摇运动倾覆过程和安全域问题.考虑非线性阻尼、非线性复原力矩和随机波浪,建立了随机横浪中船舶运动的随机非线性微分方程.考虑两参数海浪谱和不同的有义波高,计算随机波浪力矩,采用简谐加速度数值计算方法求解随机微分方程,进行了随机倾覆过程的数值模拟.考虑船舶运动的瞬时状态,发展了胞映射方法计算随机非线性横摇运动安全域的方法,并编制了计算机程序.模拟了一条渔船不同有义波高作用下横摇倾覆过程,考虑不同的初始条件及随机波浪参数,在初始值平面上采用胞映射法构造了渔船航行的安全域.波高较小时,安全域是一个连续的区域;随着有义波高增大,安全域面积减小并且不再连续,倾覆域和安全域相互包围.计算结果表明,船舶运动的瞬时状态对安全域具有重要影响,而且随机海浪中安全域具有随机特性.     

Effect of freeboard and metacentric height on capsizing probability of purse seiners in irregular beam seas

The probability of capsize of purse seiners in irregular beam seas and the effect of freeboard height and metacentric height on trapped water on the deck was investigated. The aim was to quantify a safety level that can be achieved by direct stability assessment for this type of fishing vessel. The amount of trapped water on deck was numerically estimated using a hydraulic flow assumption. The long-term capsizing probabilities were estimated using a piecewise linear approach together with wave statistics from major Japanese fishing areas. The estimated safety level of capsizing probability was compared with that obtained by the IMO weather criterion and by the water-on-deck criterion of the IMO Torremolinos Convention. Numerical results for four typical Japanese purse seiners indicated that the effect of freeboard, on the amount of trapped water on deck, is more important than that of the metacentric height. Besides the metacentric height and the freeboard, it was shown that the danger of capsizing is a function of the rise of floor. The safety level obtained by the capsizing probability approach is generally higher than that based on the IMO weather criterion. However, the water-on-deck criterion provides a higher safety level than the capsizing probability approach for ships with a low rise of floor.     

Importance of several nonlinear factors on broaching prediction

In order to realize a more quantitative prediction of broaching and capsizing in following and quartering seas, existing mathematical modelling techniques should be upgraded. Therefore, it is necessary to systematically examine all factors relevant to capsizing in following and quartering seas. To this end, we first attempted to examine the prediction accuracy of wave-induced forces by comparing calculations with captive model experiments. As a result, we found that a wave-induced surge force has a certain nonlinearitiy with respect to wave steepness. The nonlinearity of sway–roll coupling with respect to sway velocity was also found, and our numerical result with these nonlinearities improves the prediction accuracy of the critical ship speed of capsizing in following and quartering seas. The importance of the wave effect on propeller thrust was also examined. We found that this effect is not negligibly small and could improve capsizing predictions in heavy following and quartering seas. Finally, we attempted to investigate the importance of nonlinear heel-induced hydrodynamic forces on numerical predictions of capsizing due to broaching. Here, we propose a new procedure for captive model experiments to obtain hydrodynamic forces with various heel angles up to 90°, and data on heel-induced hydrodynamic forces with respect to heel angle in calm water are provided. We then compare the numerical simulations with the nonlinear heel-induced hydrodynamic forces and without them. These time series comparisons show that the effect of nonlinear heel-induced hydrodynamic forces in calm water is not negligibly small for the case of ship capsizing due to broaching.     

关于山区水域船舶风灾事故的防范

山区水域气候多变且易发突风，对内河小型船舶安全构成严重的威胁。笔者通过对几起船舶风灾事故成因进行分析，就如何提高船舶抗突风能力，增加船舶倾覆不沉能力提出了见解。     

Qualitative aspects of nonlinear ship motions in following and quartering seas with high forward velocity

By utilizing a four-degrees-of-freedom numerical model with dense grids of control parameters and the sudden-change concept, the qualitative aspects of the nonlinear motions of a fishing vessel complying with the International Maritime Organization's intact stability criteria in following and quartering seas were intensively explored. As a result, capsizing due to broaching, capsizing without broaching, broaching without capsizing, stable surf-riding, and steady periodic motion were identified. The natures of the boundaries of these motions in the control parameter plane were investigated, and the effects of the initial conditions and the nonlinearity of calm-water maneuvering forces are also discussed. Furthermore, comparisons with a model experiment showed that the numerical model used here qualitatively explains capsizing phenomena, but quantitatively overestimates the danger of capsizing. Received: June 11, 2001 / Accepted: October 9, 2001