共查询到20条相似文献,搜索用时 10 毫秒
1.
A nonlinear time-domain procedure is presented which is used to calculate the vertical responses of a container ship advancing
in head waves. The method assumes linear radiation forces represented by time convolution of memory functions, infinite frequency
added masses, and radiation restoring coefficients. The nonlinear hydrostatic restoring and Froude–Krilov forces are computed
exactly over the instantaneous wetted surface of the ship's hull. Forces due to green water on deck are calculated using the
momentum method. Nonlinear effects are identified on different vertical ship responses, namely on the heave and pitch motions,
the vertical accelerations, and the vertical bending moment. These non-linear effects are expressed by the variation of the
transfer function with the wave amplitude, the higher-order harmonics of the time signals, the offset of the time series,
and the asymmetry of the peaks. The numerical results and the quantified nonlinear effects are compared with experimental
results showing an ability to reproduce the main nonlinear effects.
Received: December 17, 2001 / Accepted: January 31, 2002 相似文献
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The theory and procedure established by Wu and Moan in 1996 and 2005 and Wu and Hermundstad in 2002 were applied to a high-speed
transatlantic pentamaran containership. Nonlinear time-domain simulations of ship motions and load effects were carried out
in different sea states. The simulated responses were validated against model tests with satisfactory results. The short-term
probabilities of exceedance were estimated by using different stochastic analysis procedures. The long-term probabilities
of exceedance were obtained based on the short-term results. These served as information about loading in a reliability-based
design approach. The load effects in a semiprobabilistic design were also calculated at an appropriate probability of exceedance
level. 相似文献
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在紧急情况下确保船上人员及时撤离是船舶安全性的最后一个环节,较好的方法是在船舶总体设计阶段进行撤离分析验证。基于《新客船和现有客船撤离分析指南》提出的高级撤离分析方法,对人员撤离仿真的概念、原理、特点作简要介绍,并通过实例说明其在船舶设计中的应用。旨在为船舶设计人员进行撤离分析提供参考,为提升船舶的安全提供建议。 相似文献
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LIU Ya-dong LI Ji-de LI ZhenCollege of Shipbuilding Engineering Harbin Engineering University Harbin China 《船舶与海洋工程学报》2002,1(2):6-11
In this paper a 3-D panoramic simulation system of a ship is described which is developed with the MAXSCRTPT language and VC + + as programming tools on the platform of 3 Dsmax. The strip theory method is applied to the motion prediction of the mono-hull. The time history solutions of heave and pitch are obtained in the condition of head sea to provide the primary data on panoramic simulation. The simulation system has following functions: 1) digital simulation; 2 ) panoramic simulation; 3) environmental set-up; 4) render preview and output. 相似文献
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Makoto Sueyoshi Masashi Kashiwagi Shigeru Naito 《Journal of Marine Science and Technology》2008,13(2):85-94
The moving particle semi-implicit (MPS) method was applied to compute nonlinear motions of a floating body influenced by the
water on deck. To compute the motions of a rigid body, the fluid pressure at the position of each particle on the body surface
was directly integrated in space and the equations of translational and rotational motions were integrated in time to determine
the correct position of the rigid-body surface at each time step of the time-domain calculation. The performance of this method
was validated through a comparison with measured results in an experiment that was newly conducted using a model of a box-shaped
floating body with a small freeboard. Although the overall agreement was good, some discrepancies were observed for a shorter
wave period, especially for the drift motion in sway. The effect of numerical resolution on the results was checked by changing
the number of particles. With a higher number of particles, no obvious improvement was seen in the global body motions, but
the resolution of the local free-surface profile, including the water on deck, was improved. 相似文献
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针对某些国家和地区的航道水深等建港条件受限、大宗散货进口或出运而建设大型码头成本巨大的问题,探讨通过水上过驳系统中转,减少港口建设及营运成本的可行性。结合孟加拉电厂配套煤炭码头的设计过程,探讨如何确定水上过驳装卸工艺系统。采用理论计算和模拟仿真的方式,选择不同的船型组合,合理选择运输船型,并根据乘潮情况确定航道参数。结果表明,采用水上过驳中转系统,可避免大型码头建设及长距离航道的疏浚维护费用,水上过驳成本相对于货物价值影响不大,可作为码头建设一个可行的选择方案。 相似文献
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The paper addresses different uncertainty analysis methods commonly used for uncertainty quantification in Computational Fluid Dynamics (CFD) studies and compares a constant Courant–Friedrichs–Lewy (CFL) number based approach for uncertainty estimation to the ITTC recommended grid and time-independent procedures. Four different uncertainty estimation procedures are presented and discussed. To compare their performance and better understand CFD related uncertainty quantification in wave load simulations on offshore structures, the methods are applied to a case study of the wave loads on a fixed vertical cylinder. The numerical or CFD wave tank is generated using the open-source CFD toolkit OpenFOAM. Uncertainty is assessed for the case study using four different uncertainty estimation procedures for verification and later, validation is attempted by comparing the CFD results with experiments. The study concludes that a constant CFL number based uncertainty study provides more stable results and is better suited for uncertainty estimation in CFD than the ITTC recommended individual grid and time step uncertainty study. 相似文献
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随着现代船舶的巨型化,船舶电力系统集成度越来越高,电力系统的稳定性对船舶航程至关重要。同时,和岸基供电系统不同的是,船舶电力系统动力负载与其发电机组有着非线性耦合关系,所以船舶电力系统属于一类非线性控制系统。本文研究了船舶电力系统的非线性原理及数学模型,分析了系统动力负载的动静态特性以及与发电机组的非线性耦合特性。最后提出了一种利用Hamilton函数方式的并联电力非线性控制系统,并仿真验证了系统的鲁棒性特征。 相似文献
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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 相似文献
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船艇机舱空气流场数值模拟研究 总被引:4,自引:4,他引:0
某船艇机舱温度过高,影响到乘员的健康与动力装置的动力性能.因此,对舱内空气流场研究十分必要.建立了机舱几何模型以及舱内空气流动的数学模型,采用k-ε方程湍流模型对舱内的湍流流动进行描述,对机舱内空气的速度场和温度场进行了三维数值模拟与分析,并对温度场的模拟结果进行了实验验证.验证结果表明,模拟值与测试值最大相对误差为9.2%,其精度能够满足工程需要,该数值模拟方法可用于机舱内空气流动的分析研究. 相似文献
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基于MIKE 21 Mooring Analysis系泊分析软件,模拟研究在不同周期和入射角度的不规则波作用下系泊船舶运动的变化规律。结果表明,系泊船舶运动量随波浪入射角度和波浪周期的变化相互影响。在不同周期波浪作用下的系泊船横移、横摇和升沉运动量均随波浪入射角度的增大而增大,横摇运动的共振效果随着波浪入射角度远离90°方向逐渐减弱,升沉运动量在波浪入射角度靠近90°或0°方向时基本不变。当入射波浪周期较长时,纵移和回转运动量随着波浪入射角度的增大先增大后减小,一般在波浪60°入射时产生峰值。 相似文献
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在非线性波浪载荷作用下计及多种应力组合时船体总纵弯曲累积损伤计算 总被引:2,自引:0,他引:2
在时域内计算计及非线性时的船体总纵弯曲应力,与船体局部弯曲应力迭加后,可得纵向构件中合成应力的时历.对该应力时历进行雨流计数,经统计分析获得应力范围的长期分布,进而算出船体总纵弯曲时纵向构件在多种应力成份组合下的疲劳损伤.为方便此时的计算,本文提出了基于等效规则波概念的简化方法.数例表明按严格方法与按简化方法所得的结果比较接近. 相似文献
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