不同方法对南黄海重现波高计算值的影响

采用SWAN波浪模型对江苏南黄海地区1979~2018年共40 a的波况进行模拟及验证,将模拟结果与实测资料进行比对,吻合良好。百年重现波高分布通过基于年极值和月极值的广义极值分布函数(GEV)和超阈值取值方法(POT)的广义帕累托分布模型(GP)计算得出。计算结果表明,不同方法的计算结果在辐射沙洲北部地区差别最大,采用月极值所得重现波高偏小,采用年极值计算的重现波高在辐射沙洲南北外围地区最大,其余地区则以POT方法为大值。在分别采用不同数据长度计算重现波高的试验中得出,取月极值的GEV分布计算结果对时间跨度的改变不敏感,而取年极值受之影响最大,POT方法介于两者之间。     

波斯湾中受随机波作用的某新建离岸导管架平台时域动力分析研究（英文）

API RP2 A WSD is a design code in practice for design of jacket platforms in the Persian Gulf but is based on the Gulf of Mexico environmental condition. So for the sake of using this code for the Persian Gulf, it is better to perform a calibration based on this specific region. Analysis and design of jacket platforms based on API code are performed in a static manner and dynamic analysis is not recommended for such structures. Regarding the fact that the real behavior of the offshore jacket platforms is a dynamic behavior, so in this research, dynamic analysis for an offshore jacket platform in the Persian Gulf under extreme environmental condition is performed using random time domain method. Therefore, a new constructed offshore jacket platform in the Persian Gulf is selected and analyzed. Fifteen, 1-h storm, simulations for the water surface elevation is produced to capture the statistical properties of extreme sea condition. Time series of base shear and overturning moment are derived from both dynamic and static responses. By calculating the maximum dynamic amplification factor(DAF) from each simulation and fitting the collected data to Weibull distribution, the most probable maximum extreme(MPME) value for the DAF is achieved. Results show that a realistic value for DAF for this specific platform is 1.06, which is a notable value and is recommended to take into practice in design of fixed jacket platform in the Persian Gulf.     

基于马尔可夫链的极值波高预测

本文研究了由日最大波高系列估算设计极值波高时，相邻日最大波高间的相关性对极值预测的影响，从日最大波高系列遵从马尔可夫链的假定出发，考虑到国内外经常采用对数一正态分布的韦布尔分布拟合波高长期分布的现实，本文用解析法求解了对数一正态分布情况下的极值预测。同时，对解析法难以求解的非正态随机变量情况（如韦布尔分布），用计算机随机模拟方法求解其极值预测，用上述两种方法对北大西洋和北海有关日最大波高系列的预测     

吉布提LNG厂址波浪极值推算

在吉布提LNG厂址的设计过程中,由于当地可用水文资料缺乏,现场观测活动起步晚、持续时间短(仅1 a),无法满足多年重现期设计波浪要素推算的需求,给后续工作带来了较大的困难。以CCMP风场数据作为驱动,基于波作用量平衡方程建立印度洋大范围波浪数学模型、嵌套的亚丁湾中等范围模型及工程区小范围模型,在现场实测资料的基础上,结合同期的Jason卫星轨道资料对模型进行验证对比,模型验证结果良好。在此基础上,计算了1988—2017年的逐时波浪要素过程,并据此构建出年极值波浪序列,利用P-III型分布函数推算工程区深水处的各重现期波浪极值,结合不同水文条件计算得出工程区的设计波浪要素。     

一种新的路径积分法在船舶横摇概率计算中的应用

基于Gauss-Legendre积分规则提出了一种新的路径积分法来计算随机横浪中船舶非线性横摇运动的概率密度分布,新的路径积分法能够得出精确的瞬态概率密度分布,包括系统响应尾部区域的概率分布,其对系统的可靠性分析是十分重要的.船舶随机横摇运动微分方程考虑到阻尼力与恢复力的非线性.数值模拟了联合概率密度函数随时间的演变,分析了外部激励强度对船舶稳态概率密度分布的影响.数值模拟的结果表明新的路径积分法对研究船舶非线性横摇运动概率密度分布是十分有效的.     

斜坡式防波堤的可靠性分析

对港口工程中常用的可靠度计算方法进行阐述,给出了斜坡堤护面块体稳定性可靠性分析的功能函数,介绍了港口工程中常用的单变量极值分布。以秦皇岛水文观测数据为基础,统计换算斜坡堤护面块体的质量,采用极值分布理论对护面块体的计算质量进行分布拟合,对比得出对数正态分布可以对护面块体质量分布进行较好的适线。从算例计算结果对比中可以发现,Monte Carlo模拟的可靠度指标计算结果比验算点法的计算结果低。两种方法计算的可靠度指标均比规范要求的低。利用Monte Carlo模拟计算结构可靠度,选择合理的模拟次数即可。     

利用极限质心高度的半潜船装载能力分析

结合某半潜船空载静水力数据和液舱的相关数据提出一种半潜船质心高度计算方法,然后根据半潜船的稳性变化曲线得到其稳性随吃水变化的控制点,通过对比半潜船的质心高度与极限质心高度来确定其装载大型沉箱及异形型沉箱的施工可行性,可进一步形成具有查询、计算功能的数据库为施工人员决策提供参考。     

重现期法进行近岸海区风生海流计算的应用

通过确定不同重现期的风速极值，阐述建立风生海流推算关系及风生海流的特点，给出渤海湾海区风因子的合理取值范围．并描述海流极值的计算方法和计算过程，以解决近岸海区海流极值的计算问题。结合唐山LNG终端站码头区工程海流现场调查及当地历年连续风速数据，确定不同重现期风速极值及风生海流极值，并给出海流极值的结果。该工程采用重现期法进行风生海流计算及海流分析，对于海洋功能开发、灾害预防、港口建设及各种建筑设计具有重要作用。     

海洋平台设计中的风浪参数选取标准

以我国渤海某区1970年至1993年风暴过程的后报资料为基础,提出了泊松二维冈贝尔逻辑分布,并将其用于风暴过程中伴生的风速与波高的联合概率计算,给出了美国石油协会(API)行业标准有关环境条件三种设计标准的具体做法.基于新的统计模式,同时提出了联合概率法设计标准.比较了多种标准所得设计参数的差异,给出了适合工程所在海区的环境荷载参数.计算结果表明,新的统计模式适用于遭受风暴影响的海洋工程结构设计,特别是边际油田的开发建设.     

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.     

规则波作用下斜坡堤越浪量的数值模拟

台风过境产生极端波浪造成斜坡式海堤越浪,现有计算越浪量的经验公式都存在适用性的问题.为探求台风天气下舟山区域斜坡堤越浪量计算公式,基于VOF方法,对Navier-Stokes方程和k-ε方程进行求解,建立速度边界造波和阻尼消波的数值波浪水槽.在水槽中建立斜坡堤模型,通过改变影响越浪量的相关因素,模拟台风浪条件下规则波作...     

基于潮波数值模拟技术的潮位推算及其精度验证

基于潮波数值模拟技术的潮位推算算法可以推算测区内任一区域的潮位,减少临时验潮站,尤其是海上定点验潮站的布设,避免潮位改正模型的误差。文章利用实测潮位资料对基于数值模拟技术的推算潮位进行了验证,取得了较好的结果。     

Discussion on the parameters of design waves

In order to respond the discredit on the design wave standard and to recommend new consideration on design wave parameters, based on the long-term distribution of statistic characteristics of waves and the short-term probability properties of sea state defined by giving the return period, the calculation of the return period, the height, the period, and the oceanic wave parameters of the design wave and the forecasting methods are discussed in this paper. To provide references for the operation reliability of floating structures in the extreme sea state, the method of determining the design wave parameters is resurveyed. A proposal is recommended that the design wave, which can be either significant wave with 500-year of the return period, or the maximum wave with 1/N of exceeding probability, 100-year of the return period, can be applied in the engineering design practice.     

Nonstationary response of floating structures to random waves

Even if ocean waves are treated as a stationary random process, dynamic responses of floating structures to random waves at the transient state are always nonstationary. When nonstationary response statistics is desired, a common technique is to apply Monte Carlo simulations; however, its implementation is costly in computational time. Analytically, this article develops an efficient method for computing nonstationary response statistics, including evolutionary power spectrum and time-varying mean-square values. Assuming a hydrodynamic software has been employed to get various frequency response functions, a prerequisite of the proposed method is to get the elevation-to-motion transfer function formulated in its pole-residue form. The proposed method is applicable to arbitrary wave spectrum and has been based on pole-residue operations implemented in the Laplace domain to obtain closed-form solutions for the response evolutionary power spectrum. Numerical examples choose a single-degree-of-freedom Spar model and a six-degree-of-freedom Floating Production Storage and Offloading model to a Pierson–Moskowitz wave spectrum, and the correctness of the computed mean-square values is verified by Monte Carlo simulations.     

斯里兰卡科伦坡临近海域波浪数值模拟

通过分析斯里兰卡科伦坡港口所处地理位置及气象波浪资料,了解工程海域主要受到季风气候的控制,冬季盛行东北季风,夏季西南季风,热带气旋在经过或影响到斯里兰卡岛时强度较低,风速不是很大,对该区域没有灾害性的影响。文章利用中尺度大气模式MM5模拟历史天气状态,再现1991~2010年20 a的影响工程海域的风场过程。根据得到的风场过程,利用海浪模式SWAN计算科伦坡南港附近海域30 m等深线处各向的波浪要素,并利用卫星观测数据进行结果验证。利用优化后的模型计算了1991~2010年计算方向的波高年极值,P-Ш曲线适线法计算得到不同重现期的外海波要素。     

Cargo ship aft panel stresses prediction by deconvolution

This article introduces novel extreme value prediction method that can be used for a variety of offshore engineering applications. First, to demonstrate the novel method, fictitious data from a non-linear Duffing oscillator and measured wave heights were used as examples. The second incident included a container ship that experienced significant deck panel strains while traveling across the Atlantic Ocean in bad weather. The main concern for cargo ship transportation is potential loss of container owing to violent movements. It is challenging to model such a situation because waves and ship motions are both non-stationary and complicatedly nonlinear. Extreme motions greatly increase the role of nonlinearities, activating effects of second and higher order.Furthermore, due to the scaling and the choice of sea state, laboratory testing may also be called into doubt. Therefore, data collected from actual ships during difficult weather voyages offers a special perspective on the statistics of ship motions.This paper aims to highlight an alternative method of extrapolation that is based on intrinsic properties of the data set itself and does not assume any extrapolation functional class. Extreme value predictions typically originate from certain statistical distribution functional classes to fit the data and then extrapolate. Engineering design can make use of the unique extrapolation method that has been proposed. The proposed method's forecast accuracy has been verified in comparison to the Averaged Conditional Exceedance Rate (ACER) extrapolation method.     

Modified environmental contour method for predicting long-term extreme responses of bottom-fixed offshore wind turbines

Predicting extreme responses is very important in designing a bottom-fixed offshore wind turbines. The commonly used method that account for the variability of the response and the environmental conditions is the full long-term analysis (FLTA), which is accurate but time consuming. It is a direct integration of all the probability distribution of short-term extremes and the environmental conditions. Since the long-term extreme responses are usually governed by very few important environmental conditions, the long-term analysis can be greatly simplified if such conditions are identified. For offshore structures, one simplified method is the environmental contour method (ECM), which uses the short-term extreme probability distribution of important environmental conditions selected on the contour surface with the relevant return periods. However, because of the inherent difference of offshore wind turbines and ordinary offshore structures, especially their non-monotonic behavior of the responses under wind loads, ECM cannot be directly applied because the environmental condition it selects is not close to the actual most important one.The paper presents a modified environmental contour method (MECM) for bottom-fixed offshore wind turbine applications. It can identify the most important environmental condition that governs the long-term extreme. The method is tested on the NREL 5 MW wind turbine supported by a simplified jacket-type support structure. Compared to the results of FLTA, MECM yields accurate results and is shown to be an efficient and reliable method for the prediction of the extreme responses of bottom-fixed offshore wind turbines.     

大开口型船舶波浪诱导载荷研究

通过对某５万ｔ级大开口型船舶的各种波浪诱导载荷长期预报，详细讨论了不同波浪散布图、装载工况、航速、水动力计算理论和短峰波对波浪诱导载荷长期预报极值的影响，指出了一些值得注意的问题，以期对类似船型的液体波浪诱导载荷预报提供有用的参考。     

Study on real-time estimation of the ship motion cross spectra

 Time-varying coefficient vector autoregressive (T-VVAR) modeling with instantaneous responses is applied to spectrum analysis based on the nonstationary motion data of ships. Because of the ship's maneuvers, changes such as course and speed, the ship motions in waves are regarded as a nonstationary random process, although the seaway can be considered as a stationary stochastic process. The T-VVAR model is transformed into a state space model, and the time-varying coefficients can be evaluated by using the Kalman filter algorithm. Using the estimated time-varying coefficients, the instantaneous cross spectra of the ship motions can be calculated at every moment. In order to examine the reliability of the proposed procedure, on-board tests were carried out. Under stationary conditions, at a constant speed and course, the proposed method shows good agreement with stationary vector autoregressive (SVAR) modeling analysis. Moreover, it is confirmed that the proposed method can estimate the instantaneous cross spectra of the ship motions even under nonstationary conditions, showing that this is a powerful tool for on-line analysis of the nonstationary motion data of ships. Received: August 2, 2002 / Accepted: November 28, 2002 Acknowledgments. The authors thank the captain and crew of the training ship Shioji Maru, Tokyo University of Mercantile Marine. Address correspondence to: T. Iseki (iseki@ipc.tosho-u.ac.jp) Updated from the Japanese original, which won the 2002 SNAJ prize (J Soc Nav Archit Jpn 2001;190:161–168)     

回转体-螺旋桨组合体之推力减额的一个数值预测方法

作者把计算回转体绕流的Landweber方法推广到带有运转螺旋桨时回转体绕流问题的计算,导出了附加螺旋桨影响后的物面速度分布的第一类Fredh-olm积分方程。对该方程的迭代求解则用新的加速迭代公式替代常用的Land-weber迭代公式。通过对带与不带运转螺旋桨时回转体上压力差的积分可以得到推力减额。两条模型(分别在风洞、水池的试验)的数值例子表明:本方法的迭代速度要比Landweber迭代公式快,而计算得的推力减额和表面压差分布与试验结果的一致性很好,优于Huaug用Hess-Smith方法算得的结果。