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远海浮式结构物与供应船旁靠系泊特性研究 总被引：1，自引：0，他引：1
针对远海浮式结构物与供应船进行旁靠作业时,水动力干扰、两船的相对运动、旁靠系缆系统和护舷系统的受力特征等问题开展研究。建立各船的有限元模型,设计出两船旁靠连接缆系统,选取合适的系泊缆和护舷参数。研究表明:浮式结构物和供应船的横荡、纵荡方向存在一定的同步性或跟随性,幅值相差不大,其它方向的运动并不存在明显的同步特征;供应船的各自由度运动幅值均比浮式结构物偏大;旁靠护舷的受力时历出现了明显的低频效应,说明护舷的受力较大程度上受船体低频慢漂运动的影响;浮式结构物对供应船的水动力干扰较大,当浮式结构物在供应船的上风位置时,表现为屏蔽效应,供应船的运动较小;在其背风位置时,运动加剧,出现多次共振、峰值放大现象,供应船对浮式结构物的水动力性能几乎无影响,因此,供应船从浮式结构物的下风口一侧靠泊作业将更有利于船舶的安全性能。这些研究结论可为实际工程操作提供参考。 相似文献
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《中国海洋工程》1998,(1)
A quasi-steady time domain method is developed for the prediction of dynamic behavior of amooring system under the environmental disturbances,such as regular or irregular waves,winds and cur-rents.The mooring forces are obtained in a static sense at each instant.The dynamic feature of the moor-ing cables can be obtained by incorporating the extended 3-D lumped-mass method with the known shipmotion history.Some nonlinear effects,such as the influence of the instantaneous change of the wettedhull surface on the hydrostatic restoring forces and Froude-Krylov forces,are included.Thecomputational results show a satisfactory agreement with the experimental ones. 相似文献
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The coupled hull, mooring and riser analysis techniques in time domain are widely recognized as the unique approach to predict the accurate global motions. However, these complex issues have not been perfectly solved due to a large number of nonlinear factors, e.g. forces nonlinearity, mooring nonlinearity, motion nonlinearity and so on. This paper investigates the coupled effects through the numerical uncoupled model, mooring coupled model and fully coupled model accounting mooring and risers based on a novel deep draft multi-spar which is especially designed for deepwater in 2009. The numerical static-offset, free-decay, wind-action tests are executed, and finally the three hours simulations are conducted under 100-year return period of GOM conditions involving wave, wind and current actions. The damping contributions, response characteristics and mooring line tensions are emphatically studied. 相似文献
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The coupled hull, mooring and riser analysis techniques in time domain are widely recognized as the unique approach to predict the accurate global motions. However, these complex issues have not been perfectly solved due to a large number of nonlinear factors, e.g. forces nonlinearity, mooring nonlinearity, motion nonlinearity and so on. This paper investigates the coupled effects through the numerical uncoupled model, mooring coupled model and fully coupled model accounting mooring and risers based on a novel deep draft multi-spar which is especially designed for deepwater in 2009. The numerical static-offset, free-decay, wind-action tests are executed, and finally three hours simulations are conducted under 100-year return period of GOM conditions involving wave, wind and current actions. The damping contributions, response characteristics and mooring line tensions are emphatically studied. 相似文献
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Extreme value analysis in a multivariate offshore environment 总被引：8，自引：0，他引：8
Floating offshore systems are exposed to a multivariate environment with wind, waves and current all making a significant contribution to the mooring forces. The design of such systems requires an appreciation of the extreme conditions but the concept of the return period value has to be extended to reflect multiple environmental variables. This study examines the practicalities of employing a multivariate point process model in extreme value analyses, using a moored semi-submersible and its responses to the wind and waves as an example. The output from this illustrative bivariate analysis includes both estimates of the 50-year mooring force and also return period contours which indicate the likely combinations of wind and wave which might give rise to the 50-year condition. 相似文献
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Developments in the study of wave forces and construction techniques in deep water by the offshore oil industry have increased the use of marine terminals at deep water locations. A thorough understanding of moored ship dynamics when subjected to waves, wind and current combined with the use of flexible mooring lines would help to design berthing terminals for exposed areas. In this paper, the three dimensional problem of wave interactions with a barge moored to a single point is dealt with, based on the finite element method. The effect of flexibility of the mooring line and the point of mooring on the response of the barge as well as the mooring line tension is investigated. The paper compares the numerical results with model tests carried out on a barge moored to a fixed support under regular and random waves in head sea. The effect of stiffness of the mooring line on the barge response for different mooring points is discussed, which would be useful for the designers. The effect of viscous damping is also considered. The analytical results are in good agreement with the experimental results in both regular and random waves. 相似文献
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In this paper, we propose a numerical simulation procedure of moored ship motions due to initial attack of large-scaled tsunamis and investigate the effects on the motions and mooring loads. The effect of methodology on selection of tsunami wave components and of the drag forces are then considered by using the numerical simulation method, applying to several case studies for LNG-carrier. Large ship motions and excessive mooring loads beyond the safe working loads are induced by the resonant tsunami wave components in the sway and surge motions and drag forces. 相似文献
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This paper presents the research on the external mechanism of collision characters for a SPAR platform. The collision characters of SPAR platform have not attracted so much attention as that of ships in the past, because short of this kind of collision accidents reported. But with the increasing number of SPAR platforms in the world, the possibility of such kind of accident also increases. Therefore, it is necessary to master the character of SPAR collision. Model test technique is employed to study the external mechanism. The collision scenario is a ship colliding with a SPAR platform moored in the site with 1500 meters water depth. The striking ship hits the SPAR platform on the hard tank near water surface in its longitudinal direction. The specifics of the SPAR＇s motions and the tension forces of the mooring lines are collected to summarize the hydrodynamic characters in the collision scenario. It is found that the maximal displacements and the maximal pitch angles of the SPAR platform, and the maximal tension forces of mooring lines are all linearly proportional to the initial velocity of the striking ship basically. Mooring lines play elastic roles in the collision course. 相似文献
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The effects of free-surface waves on the floating structures are of great importance in the offshore industry. Among the six degrees of motions of a surface ship the absence of restoring forces in surge, sway and yaw led to critical situations for moored ships in the recent times. The order of forces in horizontal plane and their exciting frequencies are matters of interest. The resonance with the presence of moored chains led to many accidents in the recent past. The lines in dry conditions may not give good damping and in wet condition they may trigger the system to chaotic motions and jumps. Two different loading conditions of a container ship model are tested with waves in laboratory conditions in two different drafts. The mooring lines are chosen as per scale law and the energy under the response spectrum is determined from the plots. The results give new insights into the movement of a berthed ships subjected to waves. Response of the moored ship to different loading conditions in different water depths are discussed in this paper. The paper gives the order of energy due to first-order and slowly varying movement of a berthed container model in a towing tank. 相似文献
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At present the position keeping of ocean going vessels, offshore service vessels, etc., is performed by mooring systems to resist external forces under severe environments consisting of wave, current and wind. A variety of mooring systems are employed depending on the shape, principal dimensions, etc., of the vessels in addition to the surrounding conditions of the water areas. Ocean going ships are moored to the shore structures through a multiple system of moorings. The determination of the forces in the cables is essential for the design of moorings and the berthing structures. However, the ships engaged for offshore operations are moored by the mooring cables, spread around the ships with the other ends of the moorings anchored to the sea bed. In these cases, the required number and length of cables can be arrived for a given ship of known dimensions and environmental conditions. With the increased overall dimensions of the vessels, it is necessary to conduct a study on enhancing the accuracy in estimating the mooring system performance. Hence, the present work is mainly intended to carry out model tests to investigate the behaviour of moored ships that are subjected to wave and current loadings. These model experiments were conducted in a 30 m × 2 m × 1 m wave-current flume at the Ocean Engineering Centre, Indian Institute of Technology, Madras. 相似文献
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单点系泊船舶在受到风、流等外力作用下通常会产生大幅周期性艏摇运动，称为“鱼尾运动”。剧烈的鱼尾运动可能会导致系泊系统的锚链承受过大的张力从而遭到破坏。为了充分认识单点系泊状态下养殖工船的鱼尾运动，针对一艘十万吨级单链式系泊养殖工船进行了数值分析及模型试验研究。首先，通过风洞模型试验测得养殖工船的风、流载荷系数，以此作为输入对风、流联合作用下养殖工船的动力响应进行了数值模拟分析；同时，开展水池模型试验验证了数值计算结果的准确性和可靠性；最后，通过数值计算研究了不同风速和流速下单链式系泊养殖工船鱼尾运动的特性和规律，为实际工程设计提供一定的参考。 相似文献
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This study describes an automatic berthing system with mooring lines. It is designed to be berthed by using mooring device on the upper deck of a ship. It is to berth once maintaining parallel with the quay by controlling both forward and aft breast lines. Berthing method is used through length adjustment of mooring lines connected between ship and quay by controlling the angular velocity and the torque of hydraulic motor in mooring device. The study is conducted under three changing conditions of draft, such as even-keel, rise of the gravity center and trim to stern. Variables affecting berthing stability are determined based on the control performance of each condition. Bond graphs method is used to model the system. Controller is designed as PID control method of reference-model algorithm. The control program is composed of synchronous control system based on the equations derived with the numerical analysis. The tank test is conducted to verify the usefulness of the control program. 相似文献
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It is well known in the field of marine hydrodynamics that the added mass, damping and wave exciting forces are functions of frequency (Newman, 1977. Marine Hydrodynamics. MIT Press, Cambridge). Although most previous studies of nonlinear ship rolling motion have assumed that these forces do not vary with frequency, in this study the frequency dependent added mass and damping coefficients are approximated in the time domain with extended state space variables. Using numerical time simulation (integration), the extended state space model is compared to the constant coefficient model with a constant frequency forcing and the results for two constant value approximations of the added mass and damping are compared to the extended state space model with a multiple component pseudo random forcing. 相似文献
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《Ocean Engineering》1999,26(3):227-240
It is well known in the field of marine hydrodynamics that the added mass, damping and wave exciting forces are functions of frequency (Newman, 1977. Marine Hydrodynamics. MIT Press, Cambridge). Although most previous studies of nonlinear ship rolling motion have assumed that these forces do not vary with frequency, in this study the frequency dependent added mass and damping coefficients are approximated in the time domain with extended state space variables. Using numerical time simulation (integration), the extended state space model is compared to the constant coefficient model with a constant frequency forcing and the results for two constant value approximations of the added mass and damping are compared to the extended state space model with a multiple component pseudo random forcing. 相似文献
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Study on the uncertainty of the available time under ship fire based on Monte Carlo sampling method 总被引：1，自引：0，他引：1
Available safety egress time under ship fire(SFAT) is critical to ship fire safety assessment,design and emergency rescue.Although it is available to determine SFAT by using fire models such as the two-zone fire model CFAST and the field model FDS,none of these models can address the uncertainties involved in the input parameters.To solve this problem,current study presents a framework of uncertainty analysis for SFAT.Firstly,a deterministic model estimating SFAT is built.The uncertainties of the input parameters are regarded as random variables with the given probability distribution functions.Subsequently,the deterministic SFAT model is employed to couple with a Monte Carlo sampling method to investigate the uncertainties of the SFAT.The Spearman’s rank-order correlation coefficient(SRCC) is used to examine the sensitivity of each input uncertainty parameter on SFAT.To illustrate the proposed approach in detail,a case study is performed.Based on the proposed approach,probability density function and cumulative density function of SFAT are obtained.Furthermore,sensitivity analysis with regard to SFAT is also conducted.The results give a high-negative correlation of SFAT and the fire growth coefficient whereas the effect of other parameters is so weak that they can be neglected. 相似文献
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The motion response prediction of offshore structures may be carried out using time domain or frequency domain models or model tests. The frequency domain analysis uses the simplified, linearised form of the motion equations and it is very economical. The time domain analysis, unlike frequency domain models, is adequate to deal with non-linearities such as viscous damping and mooring forces, but it requires sophisticated solution techniques and it is expensive to employ. For moored semisubmersibles time domain techniques must be employed since there are strong nonlinearities in the system due to mooring line stiffness and damping and viscous drag forces. In the first part of this paper a time domain model to predict the dynamic response of a semi-submersibles are developed and the effect of thrusters and mooring line damping are incorporated into the time domain model. In the second part time domain simulations are carried out to find the total extreme motions and mooring forces. 相似文献