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本文对受随机波浪载荷的自升式平台结构非线性随机响应,在时域内作了动态分析。分析中考虑了平台桩腿与海底间的相互作用,用随机模拟的方法产生随机波浪外载荷,并考虑了Morison 力中的非线性,在时域内采用 FFT 法进行了动态响应计算。给出了自升式平台 Dyvi-Gama 在随机波浪载荷作用下的非线性随机响应的极值响应结果,并对所得极值作了若干随机分布分析,指出在所分析的结构响应中考虑非线性因素的情况下,几种分布中,唯有冈贝尔(Gumbel)分布较好地描述了其极值分布特征。 相似文献
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《应用海洋学学报》2015,(2)
水下声探测是外国调查船和水下文物盗捞船进行非法调查和探测的主要技术手段,根据信号的主要声特征,对海洋水下声探测信号进行分类,分为宽带中、低频信号和窄带高频信号.在福建兴化湾海域采集了浅地层剖面仪信号、电火花声源信号、侧扫声纳信号和单频测深信号4种代表性的海洋水下声探测信号,根据声特征分析给出了对应的分类,其中:浅地层剖面仪信号为信号类型确定的中、低频信号;电火花声源信号为宽带脉冲中、低频信号;侧扫声纳信号和单频测深信号为窄带高频信号.通过对4种实测声探测数据的分析研究,给出了对应类型的海洋水下声探测信号的分析、提取方法,其中:信号类型确定的中低信号和窄带高频信号在初步的时、频分析基础上,可通过带通滤波提取;宽带脉冲中、低频信号在初步的时、频分析基础上,可尝试通过小波尺度相关滤波的方法提取.结合已知的水下声探测信号的主要声特征,实现对采集的海洋水下声探测信号的识别. 相似文献
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本文对导管架式固定海洋平台所承受的波浪载荷、结构在波浪载荷下的动力响应与随机响应分析方法进行了论述;编制了基于同一结构描述与特征计算的动力响应分析程序(DYMO)和随机响应分析程序(RANDOM)。文中简要介绍了挪威工学院结构工程研究所应用的结构分析程序 FAROW 中的 DYMO 和 RANDOM 的功能;给出了对设计建造中的高371米的北海某采油平台(STATOIL JACKET)进行响应计算的部分结果;并对两种响应计算结果给出了比较分析。 相似文献
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由于畸形波的物理机制较复杂，有关畸形波-结构物相互作用的理论研究进展缓慢。然而对于较简单的畸形波模型与规则结构体，可以给出畸形波-结构物相互作用的理论解。本文基于畸形波的一种基本模型聚焦模型，采用解析方法研究其对半浸没圆柱体产生的波浪载荷。为保留畸形波的大部分特征，聚焦模型采用高斯包络描述。通过流场分隔给出绕射势，进而给出圆柱所受水平波浪力与波浪弯矩。采用适当方法简化理论公式，并与数值结果进行对比验证。此外，系统分析了聚焦程度、浸没深度与聚焦位置等参数对波浪载荷的影响。 相似文献
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王廷明 《中国海洋大学学报(自然科学版)》2009,39(1)
根据命题逻辑公式的D-随机真度的概念,给出了基于主析取范式中所有极小项的上标向量集合的命题公式D-随机真度的计算公式,讨论了在基本逻辑运算下公式的D-随机真度关系以及逻辑推理的D-随机有效度问题. 相似文献
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本文基于实际金融问题,提出并进一步研究一类不确定模型下的倒向双重随机递归最优控制问题。首先提出在该模型中,代价泛函由sup■定义,其中■是由一组双重倒向随机微分方程的解组成的集合,再利用先验估计、线性化方法、It■公式等方法,推导出该最优控制问题的最大值原理,进而最终给出该问题最优控制的必要条件和充分条件。 相似文献
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针对半潜式平台的立柱群和沉箱群,设计了两套独立的载荷测量系统,利用大型重力式密度分层水槽,在不同来波方向下对孤立波中半潜式平台载荷进行了系列模型试验。研究表明,对平台立柱部分,其内孤立波载荷可以用Morison公式进行计算,基于试验结果建立了Morison公式中其拖曳力系数以及惯性力系数的经验公式;对于半潜式平台的沉箱部分,当来波方向与其中纵剖面不平行时,其水平内孤立波载荷同样可以使用Morison公式进行计算,并建立了Morison公式中其拖曳力系数以及惯性力系数的经验公式;当来波方向与半潜式平台中纵剖面平行时,沉箱群的水平内孤立波载荷可以采用Froude-Krylov公式进行计算;同时,在不同来波方向下沉箱群的垂向载荷同样可以采用Froude-Krylov公式进行计算。 相似文献
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目前,斯托克斯(stokes)五阶重力波理论已广泛应用固定式导管架平台的外载荷估算,波浪速度势大多采用文献[1]给出的公式进行计算。 相似文献
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A fatigue life estimation method for offshore structures under random stress response is studied in this paper. The method of broad band cumulative frequency number is used to determine the effect of band width of stress frequency spectra on fatigue. A formula of correction factor for fatigue under broad band stress spectra is suggested and compared with that given by P. H. Wirsching. 相似文献
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This paper provides a practical method by which the drag force on a vegetation field beneath nonlinear random waves can be estimated. This is achieved by using a simple drag formula together with an empirical drag coefficient given by Mendez et al. (Mendez, F.J., Losada, I.J., Losada, M.A., 1999. Hydrodynamics induced by wind waves in a vegetation field. J. Geophys. Res. 104 (C8), 18383–18396). Effects of nonlinear waves are included by using Stokes second order wave theory where the basic harmonic motion is assumed to be a stationary Gaussian narrow–band random process. An example of calculation is also presented. 相似文献
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In many engineering problems one deals with quantities that must be considered to be of a stochastic or random nature. This is true for the natural environment such as wind, waves, and earthquakes, which are the driving mechanism behind the loadings on a wide variety of land-based and offshore structures. From a design perspective it is important to determine the expected highest value of a stochastic process, and structural fatigue life. The relevant procedures are reasonably well established for processes that have narrow band spectra, but it is much less clear how to deal with non-narrow band cases. In this paper it is shown that the extremes of a Gaussian, non-narrow band process are asymptotically equal to the extremes calculated according to the narrow band formula. Also demonstrated is that fatigue estimates may, with good accuracy, be based on the narrow band formula unless the bandwidth becomes extremely large. These statements are illustrated by examples of a process with (1) a low pass box spectrum, and (2) a Pierson–Moskowitz wave amplitude spectrum. It is also shown that the bandwidth parameter may in some cases be counter-intuitive, as the Pierson–Moskowitz spectrum has a larger bandwidth parameter than the box spectrum, even when both cover the same frequency range. 相似文献
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This paper provides a practical method for estimating the drag force on a vegetation field in shoaling conditions beneath non-breaking and breaking random waves. This is achieved by using a simple drag formula based on two empirical drag coefficients given by Méndez et al. (1999) and Méndez and Losada (2004), respectively, in conjunction with a stochastic approach. Here the waves are assumed to be a stationary narrow-band random process and propagating in shallow waters. The effects of shoaling and breaking waves are included by adopting the Méndez et al. (2004) wave height distribution. Results are presented and discussed for different slopes, and an example of calculation is also provided to demonstrate the application of the method. 相似文献
16.
Yu Xiaodong Yan Shuwang Sun Wanhe
Postgraduate Student Tianjin University Tianjin Professor Tianjin University Tianjin Senior Engineer Tianjin Port Engineering Institute Tianjin 《中国海洋工程》1997,(2)
At pesent,it is very popular to estimate pile bearing capacity by use of empirical formula andphysical indexes of soil provided in the design codes for civil construction in China.This paper attempts toapply mechanical indexes of soil and semi-empirical formulas,which are based on soil mechanical theoriesand were summarized and presented by Meyerhof in 1976,to calculate the axial pile bearing capacity.Lo-ading test results of 24 single piles in Tianjin area have been collected and compared with the proposed cal-ulation approach. 相似文献
17.
Sun Jingshi Zhu Yiming
Research Professor Tianjin Research Institute of Water Transport Engineering Tianjin
Associate Professor Dalian Aquatic Product Institute Dalian 《中国海洋工程》1995,(1)
Through hydraulic model experiment and site investigation, this paper has derived a calculation formula of dry-laid stone armour layer thickness of rubble mound breakwaters for fishery harbours. The influences of the friction force between stone blocks and the variations of wave length or period and water depth are considered in the formula. The calculated results of several existing structures are in good agreement with field data. This formula is more practical than those ever published both at home and abroad, and has been adoptted by the technical standards of aquatic projects published by the Ministry of Agriculture of China. It is applicable for the calculation of dry-laid stone armour layer of breakwater for small- or medium-size harbours. 相似文献
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孤立桩柱上不规则波浪力的计算 总被引：4，自引：5，他引：4
随着海洋石油,海上航运等事业的发展,海洋工程迅速增多。这些建筑物的设计外荷载常以波浪力为主,因此,正确确定波浪力对海洋工程具有重大意义,很早就引起人们的注意和研究。自然界的海浪汹涌澎湃,变化多端,是一随机过程,它对建筑物的作用也比较复杂。近十几年,由于海工建筑物向深海发展和大型结构的采用,其低阶自震频率很可能落入海浪显著部分的频率范围,此时结构物对不规则波的动力反响对结构应力分析等具有重大影响,促使对不规则波浪力的研究有较大进展。 相似文献
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Owing to the Benjamin-Feir instability,the Stokes wave train experiences a modulation-demodulation process,and presents a recurrence characteristics.Stiassnie and Shemer researched the unstable evolution process and provided a theoretical formulation for the recurrence period in 1985 on the basis of the nonlinear cubic Schr dinger equation(NLS).However,NLS has limitations on the narrow band and the weak nonlinearity.The recurrence period is re-investigated in this paper by using a highly efficient High Order Spectral(HOS) method,which can be applied for the direct phaseresolved simulation of the nonlinear wave train evolution.It is found that the Stiassnie and Shemer’s formula should be modified in the cases with most unstable initial conditions,which is important for such topics as the generation mechanisms of freak waves.A new recurrence period formula is presented and some new evolution characteristics of the Stokes wave train are also discussed in details. 相似文献
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任意曲线边界条件下缓变水深水域波浪传播的数值模拟 总被引：3，自引：0，他引：3
缓坡方程被广泛地应用于描述波浪的传播变形计算,目前一般采用矩形网格求解.将计算域剖分为任意四边形网格,以格林公式为基础,在变量沿单元边界线性变化的假定下,对双曲型的波能守恒方程、波数矢无旋性方程进行离散,同时通过等参单元变换推求节点偏导数值以离散椭圆型光程函数方程,从而建立了任意曲线边界条件下缓变水深水域波浪传播的数值模拟模型.将模型应用于平行直线型等深线地形,并将计算域剖分为不规则四边形网格,对不同入射角、底坡、波高等多种组合情况比较了数值解与解析解,结果表明两者一致.应用于复杂边界的实例,数值模拟结果与物模实验值基本吻合. 相似文献