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关于气浮筒群结构的静稳性 总被引：3，自引：1，他引：3
讨论了气浮筒群结构的静稳性问题 ,以三筒组合为算例 ,变化干舷、升沉和绕x轴、y轴的倾角α、β ,给出了静稳性的算法和初步结果。指出存在四个相关的姿态角 ,最后讨论了初始参数干舷的选取 相似文献
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针对圆筒型浮式生产储油平台,对其静稳性曲线做了分析研究,得到了圆筒型FPSO的稳性特点。根据平台实际作业情况,建立了一系列的典型装载工况,分别按照DNV和MARPOL公约稳性衡准的要求,对这些典型工况进行校核,同时得到满足稳性要求的许用重心高度曲线,给平台操作者提供了参考。经过计算,验证了圆筒型FPSO能同时满足DNV和MARPOL公约的稳性要求。最后对影响圆筒型FPSO稳性的主要因素做了分析研究,得到主要影响因素有主船体外形尺寸、装载工况、进水点位置、舱室划分与布置以及风倾力矩等。 相似文献
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船舶随浪运动隐性仿真计算 总被引：3，自引：0，他引：3
本文利用Ｌｉａｐｕｎｏｖ理论，研究了船舶在规划波良运动的稳性；利用摄动理论，求解出船舶运动响应；并讨论了船舶横摇与垂荡运动频率、最大横摇角和波浪要素对稳性曲线ＧＺ的影响，以及流体动压力对稳性曲线的修正，从而给计算船舶在随浪中的稳性提供了一种。方法。 相似文献
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坐底式平台沉浮稳性研究与计算 总被引：3，自引：0，他引：3
坐底式平台的沉浮稳性与它的作业性能密切相关。随着平台作业水深的不断加大,现有平台的沉浮稳性为操作者、设计者及船检部门所重视。文中分析了现有规范对沉浮稳性的衡准,介绍了计算沉浮稳性的程序框图及计算实例。对提高沉浮作业工况的安全性,给出了一些建议,供平台设计和操作者参考。 相似文献
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《中国海洋大学学报(自然科学版)》2021,(11)
基于10 MW级大型风机,采用钢筋混凝土结构,进行了半潜浮式风机平台的概念设计,采用SESAM建立平台的数值模型,对立柱间距、立柱倾角及立柱直径对该半潜平台完整稳性的影响规律进行了重点研究并对平台进行优化,对优化后半潜平台的破舱稳性、综合许用重心高度及固有周期进行了验证。结果表明:以上因素以不同的方式影响平台完整稳性,而增加立柱倾角在钢筋混凝土用量和排水量等方面更具优势,优化后的平台完整稳性、破舱稳性、综合许用重心高度及运动周期均满足设计规范要求。 相似文献
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国内外对移动式平台稳性的研究 总被引：2，自引：0，他引：2
本文对各国的海上移动式平台规范与规则对稳性的要求作了叙述,并进行了对比;收集了若干起和稳性有关的移动式平台重大事故及事故产生原因的有关资料;对国内外研究移动式平台稳性的各种计划介绍了研究内容与主要研究成果。 相似文献
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本文提出了编制计算机程序来进行计算海洋平台导管架在运输、下水、就位中的浮态和稳性。该程序可对导管架在浮运和驳运系统中的浮态、完整稳性、破舱稳性及静水力曲线等进行分析和计算。通过对实例的验算,结果是准确的。该程序已能够为海洋石油开发事业服务。 相似文献
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针对水下系泊监测平台在水流涡激作用下的稳定性问题,考虑了浮体在振动过程中的变形,建立了其流固耦合的非线性动力学方程,利用谐波平衡法进行了非线性特性定性分析,Melnikov方法进行稳定性判据研究及影响因素分析,以系统出现混沌状态为稳定性控制条件,重点研究了系泊缆支撑间距对稳定性的影响,并计算出支撑间距的临界值。结果表明,系统稳定性随支撑间距增加而降低,当支撑间距超过临界值后,稍微增加都可能导致系泊监测平台振动偏离振动轨道而造成局部失稳甚至结构破坏。为保证监测平台的稳定性,应增加支撑数量,且支撑的间距不能超过系统发生失稳的临界值。 相似文献
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针对张力腿结构动力响应特点,提出一套张力腿式浮式风机动力耦合理论模型,编制计算程序,并通过与实验结果的对比,验证理论模型以及程序的适用性。张力腿式系泊系统稳定性好,但张力载荷随平台位移的变化显著;张力腿结构的动态响应与支撑平台和风机系统动态响应存在显著的耦合作用。针对张力腿浮式风机动力耦合特性,采用谱方法对张力腿结构建立耦合动力模型;考虑细长体在波浪中受到的粘性力,通过哈密顿原理推导出张力腿运动控制方程,利用自主开发的计算程序DARwind和数值计算方法求解系统动态响应。最后,将数值计算结果同UMAINE的试验数据进行对比分析,以验证程序的合理性。 相似文献
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This paper studies the chaotic behaviours of a relative rotation nonlinear dynamical system under parametric excitation and its control. The dynamical equation of relative rotation nonlinear dynamical system under parametric excitation is deduced by using the dissipation Lagrange equation. The criterion of existence of chaos under parametric excitation is given by using the Melnikov theory. The chaotic behaviours are detected by numerical simulations including bifurcation diagrams, Poincaré map and maximal Lyapunov exponent. Furthermore, it implements chaotic control using non-feedback method. It obtains the parameter condition of chaotic control by the Melnikov theory. Numerical simulation results show the consistence with the theoretical analysis. The chaotic motions can be controlled to period-motions by adding an excitation term. 相似文献
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表层水温长期预报问题的研究已有多年历史。早期的学者主要用相关分析和水温长期变化的规律来制作月、季或更长期的预报,如Hatanka(1948),Watanabe和Hirao(1955), Kolesnikov(1947,1953)以及Milar(1952)等。六十年代以来,不少学者采用数值计算方法,预报北太平洋及全球范围内的月际温度变异,如Adem(1969,1970),J.Jacobs(1967)和Shigeo Moriyasu (1969,1970)等,他们在数值模式中,考虑了海洋与大气之间的热量交换,洋流与风海流的热量输送及其搅拌作用,以及水平与垂直方向上的涡动扩散;从大范围看,得到了较好的预报效果。Namias(1972)在分析北太平洋海面温度的时空分布及其与海平面气压场的关系时,发现可以根据水温变化的时间持续性和空间相关性及其与海平面气压场的关系,预报月平均水温及相应的海平面气压。以上所述及其他许多研究成果,目前能用于常规预报的,主要仍然是经验方法。本文通过分析黑潮地区表层水温与前期大气环流的相关,选取相关系数高的站点,用阶段回归方法,建立了本海区各月的水温月趋势预报方程。
文中采用的水温资料(1951-1974年)取自日本及美国发表的北太平洋海面水温资料,计算过程中对前后12年资料的系统误差进行了校正,500亳巴高度场资料取自上海中心气象台。黑潮地区的表层水温用20°N,125°E;20°N,130°E;25°N,125°E;25°N,130°E;30°N,130°E;30°N,135°E等六个站的平均资料来代表。 相似文献
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The stability of the motion control system is one of the decisive factors of the control quality for Autonomous Underwater Vehicle (AUV).The divergence of control,which the unstable system may be brought about,is fatal to the operation of AUV.The stability analysis of the PD and S-surface speed controllers based on the Lyapunov' s direct method is proposed in this paper.After decoupling the six degree-of-freedom (DOF) motions of the AUV,the axial dynamic behavior is discussed and the condition is deduced,in which the parameters selection within stability domain can guarantee the system asymptotically stable.The experimental results in a tank and on the sea have successfully verified the algorithm reliability,which can be served as a good reference for analyzing other AUV nonlinear control systems. 相似文献
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This work deals with parametric resonance which poses a great danger especially for container ships sailing in following or head seas. Important parameters that are effective in roll resonance are pointed out. For this purpose, a containership is taken as an example to analyze its stability in longitudinal waves based on the method worked out by American Bureau of Shipping (ABS). Unfavorable sailing conditions such as heading and speed, which directly depend on the environmental conditions, have been determined for this particular ship. These conditions may be reported to the master to guide him to keep his ship out of parametric resonance zones. Numerical details of the procedure have been worked out and provided as well. 相似文献
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Application of the extended Melnikov's method for single-degree-of-freedom vessel roll motion 总被引：2，自引：0，他引：2
Traditionally, when using Melnikov's method to analyze ship motions, the damping terms are treated as small. This is typically true for roll motion but not always true for other and/or multiple degrees of freedom. In order to apply Melnikov's method to other and/or multiple-degree-of-freedom motions, the small damping assumption must be addressed. In this paper, the extended Melnikov method is used to analyze ship motion without the constraint of small linear damping. Two roll motion models are analyzed here. One is a simple roll model with nonlinear damping and cubic restoring moment. The other is the model with biased restoring moment. Numerical simulations are investigated for both models. The effectiveness and accuracy of this method is demonstrated. 相似文献
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Influence of non-linearities on the limits of stability of ships rolling in head seas 总被引：3，自引：0，他引：3
The present paper describes an investigation on parametric resonance in head seas in which a new third-order coupled mathematical model is considered. The restored modes of heave, roll and pitch are contemplated. The discussion is illustrated for the case of a transom stern fishing vessel at different speeds. It is pointed out that numerical simulations employing the new model are successfully compared to experimental results previously obtained for the vessel.Considering that analyticity is an important tool when handling complex stability issues, some theoretical dynamic characteristics of the equations are discussed. By means of the analysis of the coupled linear variational equation derived from an extended third-order model, the appearance of super-harmonics and increased rigidity proportional to wave amplitude squared due to third-order terms is demonstrated.In the present paper, an important tool is explored, that is the analysis of the limits of stability obtained from the new model. Limits of stability are a well-known and practical way of looking into the problem of parametric resonance. New limits of stability are derived and compared to the more conventional Strut diagram. Dynamic characteristics associated with the new limits of stability are discussed. The influence of different parameters is investigated, including vessel speed, damping and tuning. Consistent and revealing results are obtained through the analysis of the new limits of stability for different speeds and damping. 相似文献
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Considering the actual seaway condition, stability and capsizing of nonlinear ship rolling system in stochastic beam seas is of significant importance for voyage safety. Safe zone are defined in the phase space plan of the unperturbed Hamilton system to qualitatively distinguish ship motions as capsize and noncapsize. Capsize events are defined by solutions passing out of the safe zone. The probability of such an occurrence is studied by virtue of the random Melnikov function and the concept of phase space flux. In this paper, besides conventional wave excitation, the effect of wind load is also taken into account. The introduction of wind load will lead to asymmetry, in other words, it transforms the symmetric heteroclinic orbits into asymmetric homoclinic orbits. For asymmetric dynamical system, the orbital analytic solutions and its power spectrum are not readily available, and the technique of discrete time Fourier transformation (DTFT) is used. In the end, as verification of theoretical critical significant wave height, capsizing probability contour diagram is generated by means of numerical simulation. The contour diagram shows that these analytical methods provide reliable and predictive results about the likelihood of a vessel capsizing in a given seaway condition. 相似文献