Extreme hawser tension assessment for FPSO vessel during offloading operation in Bohai bay

The Floating Production Storage and Offloading Unit (FPSO) is an offshore vessel that produces and stores crude oil prior to tanker transport.Robust prediction of extreme hawser tensions during Floating Production Storage and Offloading (FPSO) operation is an important safety concern. Excessive hawser tension may occur during offloading operations, posing an operational risk. In this paper, AQWA has been used to analyze vessel response due to hydrodynamic wave loads, acting on a specific FPSO vessel under actual sea conditions. Experimental validation of numerical results has been discussed as well.This paper advocates methodology for estimating extreme response statistics, based on simulations (or measurements). The modified ACER (averaged conditional exceedance rate) method is presented in brief detail. Proposed methodology provides an accurate extreme value prediction, utilizing all available data efficiently. In this study the estimated return level values, obtained by ACER method, are compared to the corresponding return level values obtained by Gumbel method. Based on the overall performance of the proposed method, it is concluded that the improved ACER method can provide more robust and accurate prediction of the extreme hawser tension.Data declustering issue has been addressed. Paper highlights ability of ACER method to account for a set of varying sea state probabilities, as required in engineering long term statistical analysis.Described approach may be well used at the vessel design stage, while defining optimal vessel parameters that would minimize potential FPSO hawser tension.     

两船并靠状态下的运动响应数值模拟研究

针对两船并靠工况复杂,各种运动相互间存在耦合的情况,基于三维势流理论和波浪的辐射/衍射理论,应用多体水动力学软件,建立了船体、护舷和缆绳的模型,开展了两船在风、浪、流作用下的运动响应数值模拟。模拟结果可作为并靠方案设计和优化的参考依据,也可为两船并靠状态下的护舷力学性能计算提供支撑。     

干涉对海洋立管涡激振动影响实验研究

文章进行了干涉对海洋立管涡激振动影响的实验研究,实验分为立管前后排列和并肩排列两部分。立管间距为3~10倍直径,模型材料采用有机玻璃,长1.5 m,外径18 mm,壁厚2 mm,边界条件均为铰接,外流速分别从0.3~0.8 m/s,每级增加0.1 m/s。通过在立管表面粘贴应变计获得动态应变数据,分别从立管的横向动态响应、振幅、频率等方面对前后排列、并肩排列立管以及和单独立管的实验数据进行对比研究。结果表明,当有外流通过时,立管会受到其他立管尾流的影响,漩涡脱落引起的振动由于间距及排列方式的不同而显著不同,使得立管的动力特性、动力响应以及漩涡的脱落形式同单个立管相比均有较大的变化。     

基于高雷诺数的并联双圆柱绕流研究

文章采用基于边界瞬时涡量守候的拉格朗日方法(IVCBC),结合并列双圆柱的特点,建立了双圆柱绕流数值计算模型。对高雷诺数下Re=6×10~4,间隙率为T/D=1.1~7的并联圆柱双圆柱二维绕流特性进行了研究。提出了双圆柱间隙中点的速度区别宽窄尾流的新方法。分别讨论了流体力系数随间距增加的特点,脉动流体力的特点,尾流特征以及斯托哈尔数特征。研究发现:区别宽窄尾流的新方法是可靠的;在双圆柱尾流附近有五种尾流模型存在;同时发现了在宽窄尾流的频率,存在一个中间频率。     

两船波浪中并靠补给相对运动模型试验研究

为了设计和实现一种辅助舰船并靠补给的波浪补偿辅助系泊系统,采用接触式测量方法对波浪中并靠两船的相对运动特性进行了模型试验。在4种不同有义波高情况下,对并靠两船在不同的浪向和波浪周期下三个方向的相对运动幅值特性进行试验研究,得出波浪中并靠两船的相对运动特性。     

浮码头与旁靠船舶的运动响应特性研究

本文基于三维势流理论，采用数值分析方法研究了浮码头与散货船旁靠系泊的运动特性。考虑缆绳和护舷的非线性特性，探求了波浪周期对浮体运动、系缆力的影响规律。研究结果表明：考虑间隙内水体运动影响，旁靠散货船在横浪条件下的纵摇和纵荡运动有所增大。浮码头在计算工况下，缆绳受力较大，在某些工况条件下超出了国际系缆力标准的要求，旁靠散货船的缆绳在计算工况下均未超标，满足要求。研究结果为浮码头系泊系统的设计及工程运营提供理论参考。     

大缆材料对旁靠外输系统的动力响应影响分析(英文)

In order to provide a theoretical guide for choosing the material for the hawsers for the FPSO side-by-side offloading system, which is moored by the yoke system, the 3D potential flow theory and full coupled time-domain analysis are presented to study the dynamic response of the offloading system. The Ming Zhu FPSO offloading system in the field BZ25-1 is simulated here; and four different characteristic fiber ropes are used as the material for the hawsers. To acquire an accurate hawser line tension, the polynomial fitting method is used to calculate the nonlinear stiffness of the hawsers. By comparing the hawser lines' tension and the relative motion between the FPSO and the shuttle tanker, a suitable material for the hawser lines is chosen and discussed in this paper. The results indicate that the nonlinear stiffness characteristic of the fiber rope has a small effect on the relative motion of the vessels, but the hawser lines' tension is greatly influenced by the different characteristics of the fiber ropes. The hawser lines' tension with nonlinear stiffness is in accordance with the one with the upper and lower bound linear stiffness, which proves this method of fitting the fiber ropes' nonlinear stiffness is reasonable and reliable.     

PHC刚性管桩基础上的闸首底板内力计算方法

为了合理解决复合桩基上的闸首底板内力简化计算问题,分析复合桩基沉降机理,基于应力与沉降分解法给出桩与桩、桩与土、土与桩和土与土的沉陷系数计算式,结合并列铰接地基梁法建立考虑桩-土-结构共同作用的计算模型。依托高石碑船闸工程实例,通过与查表法的对比验证计算程序的可靠性,研究在不同工况时底板单宽弯矩、沉降、地基反力的变化规律。结果表明,该模型计算的桩土分担比与有限元分析结果接近,计算精度可以满足结构简化分析的需要,能合理反映基桩的根数、以及间距与桩长不规则等因素对底板沉降和内力的影响。运营期相对于完建期而言,地基均处于回弹状态、底板弯矩增量有正负值,可优化调整底板宽缝封闭前边墩浇筑高程、回填土高程,使得运营期出现的正负弯矩接近相等。     

西非海域外输系统中输油管的疲劳分析

外输系统在深水油田开发中得到了广泛应用,而其中输油管的疲劳问题是外输系统设计分析的关键。针对西非深水海域外输系统中的输油管展开疲劳特性分析,基于典型西非海况下外输系统整体时域耦合分析结果,对输油管时域应力曲线采用雨流计数法进行分析,然后根据合适的S-N曲线和Miner线性准则对输油管进行疲劳损伤计算。分析内容包括西非海域不同的环境条件对输油管疲劳的作用,穿梭油轮系泊情况下输油管的疲劳特性并考虑了横向升力对于输油管疲劳损伤的影响等。通过分析得出与输油管疲劳特性相关的环境参数及造成输油管疲劳损伤的主要因素,为输油管的设计与分析提供参照。     

基于AQWA的旁靠油轮水动力相互作用研究

船舶旁靠系统的水动力响应是一个非常复杂的工程问题,系统中每一个结构的动力响应会受到其他结构的耦合影响。针对两旁靠FPSO和LNG运输船组成的旁靠系泊系统,基于三维势流理论,应用多体水动力学软件AQWA,在考虑两船间水动力相互作用的情况下,计算两旁靠船舶所受到的波浪载荷,并与不考虑两船水动力相互作用的计算结果进行对比分析。结果表明,旁靠系泊系统水动力相互作用是不可忽略的。同时也分析了不同旁靠间距对水动力性能的影响,结果发现旁靠间距只在中高频段时对水动力性能的影响较大。研究结果可为旁靠系统系泊方案的设计和研究提供一定的参考。