Model test investigation of a spar floating wind turbine

Several floating wind turbine designs whose hull designs reflect those used in offshore petroleum industry have emerged as leading candidates for the future development of offshore wind farms. This article presents the research findings from a model basin test program that investigated the dynamic response of a 1:50 scale model OC3 spar floating wind turbine concept designed for a water depth of 200 m. In this study the rotor was allowed to rotate freely with the wind speed and this approach eliminated some of the undesirable effects of controlling wind turbine rotational speed that were observed in earlier studies. The quality of the wind field developed by an array of fans was investigated as to its uniformity and turbulence intensity. Additional calibration tests were performed to characterize various components that included establishing the baseline wind turbine tower frequencies, stiffness of the delta type mooring system and free decay response behaviour. The assembled system was then studied under a sequence of wind and irregular wave scenarios to reveal the nature of the coupled response behaviour. The wind loads were found to have an obvious influence on the surge, heave and pitch behaviour of the spar wind turbine system. It was observed from the experimental measurements that bending moment at the top of the support tower is dominated by the 1P oscillation component and somewhat influenced by the incoming wave. Further it was determined that the axial rotor thrust and tower-top shear force have similar dynamic characteristics both dominated by tower’s first mode of vibration under wind-only condition while dominated by the incident wave field when experiencing wind-wave loading. The tensions measured in the mooring lines resulting from either wave or wind-wave excitations were influenced by the surge/pitch and heave couplings and the wind loads were found to have a clear influence on the dynamic responses of the mooring system.     

方形自升式平台稳性计算

以上海中远船务工程有限公司研发的一型正方形自升式生产平台为依托,依照美国船级社MODU规范的要求,分析了平台的完整稳性、破损稳性和剩余稳性,总结了该类平台稳性分析的方法及过程.对方形自升式平台稳性计算具有一定的参考意义.     

Passive control of jacket–type offshore wind turbine vibrations by single and multiple tuned mass dampers

Vibration control is gaining focuses in the field of offshore wind turbines (OWTs) in recent years as the turbine tower becomes taller and more slender. Although a number of research works have been carried out to control the OWT vibrations, using tuned mass damper (TMD) and multiple tuned mass dampers (MTMDs) to control the jacket–type OWT vibrations is rarely reported, especially for the MTMDs, of which the application in the field of OWTs is still in the initial stage. This study focuses on the performance of TMD and MTMDs in controlling the tower vibrations of the jacket–type OWT subjected to the combined wind, wave and current loads, which are the most common external vibration resources for OWTs. The control effectiveness is numerically investigated and evaluated by the reductions of the standard deviation displacement (σ(d)) and the standard deviation acceleration (σ(a)) of the tower top. After the installation of TMD, σ(d) and σ(a) are reduced by 32% and 29% respectively. Larger TMD mass ratios lead to better control effectiveness, but the improvement becomes less obvious as the mass ratios constantly increase. The control effectiveness of the MTMD system is slightly decreased compared with a single large TMD. However, the robustness of MTMDs is superior since the OWT vibrations can still be controlled effectively even if some TMDs do not function. The control effectiveness of the MTMD system can also be affected by the change in the positions of malfunctioned TMDs.     

Development of interlink wear estimation method for mooring chain of floating structures: Validation and new approach using three-dimensional contact response

Long-term operation of mooring systems is one of the challenging issues of floating structures such as floating offshore wind turbines (FOWTs). For integrity assessment, fatigue and its affecting factors have generated considerable recent research interest as the occurrence of a large number of mooring chain failures at a high rate has been reported. By contrast, only few studies on the effect of nonuniform volume loss of mooring chain links due to wear can be found because of difficulties to estimate wear amounts quantitatively. Considering this issue, in this paper, validation of the quantitative interlink wear estimation method is investigated by applying to a spar-type floating structure. Firstly, the method is presented which consists of the material test, derivation of an interlink wear estimation formula with FE analysis, and calculation of mooring chain response with coupled dynamic analysis using a mass-spring model. To improve insufficient accuracy due to the mass-spring model around a clump weight and the touchdown point, the method is further modified by using a 3-D rigid-body link model. The estimation results and comparison show that the modified method distinguishing between rolling and sliding can calculate the interlink wear amount closer to the chain diameter measurements and more reasonable than the method using the conventional mass-spring model.     

Mussel and Seaweed Cultivation in Offshore Wind Farms: An Opinion Survey

German coastal regions and adjacent offshore waters are claimed for a variety of different, and often overlapping, uses. Conflicts of interest are expected to increase due to the planned construction of offshore wind farms. The development of an integrated approach combining different commercial activities, such as open ocean aquaculture and wind farming, could be a possible solution to overcome these conflicts. To illuminate existing perception and opinions on this multiple-use idea, this study examines the attitudes of representatives of eight different actor groups toward potential offshore wind farm–mariculture integration in the German North Sea. Results from our questionnaire survey show that the respondents’ attitudes toward the suggested multiple-use setting seem to be largely influenced by their general opinion toward offshore wind farms. The Fisheries actor group differs from the other questioned groups in that negative attitudes are overall predominant. This case study points to the need for a credible mechanism that more successfully integrates key actor groups, such as fisheries, into future planning and research issues.     

漓江旅游客船防抗雷雨大风的稳性分析

文章针对漓江旅游客船易受雷雨大风袭击的事故特点,分析了雷雨大风的形成原因,探讨了航向、风向、流向对航行安全的影响,建立了漓江旅游客船防抗雷雨大风的稳性衡准式,并提出了客船防抗雷雨大风的注意事项。     

The Effects of Boating Safety Regulations

This article investigates the effects of boater education programs and an increase in the number of water patrol officers on the prevention of recreational boating accidents. The empirical study, which estimates a reduced-form model similar to those used in the automobile safety literature, analyzes data on boating accidents that occurred in 1994 from 49 states and the District of Columbia. Model simulations, based on empirical estimates from Poisson and negative binomial models, suggest that a uniform law-enforcement policy of one-and-a-half water patrol officers per 1,000 boaters would prevent between 2,229 (negative binomial) and 2,318 (Poisson) accidents in 44 states.     

某轮在文茨皮尔斯港锚地抗大风的几点启示

某轮在文茨皮尔斯港外锚地抗大风历时2天,经过全体船员的努力奋斗,终于保住了船舶和船员的安全,但留给我们的还有许多情况值得思考,以期在今后的抗大风操作中提醒广大船长和船员能做的更好,使船舶更安全。     

自升式平台风载荷的空气动力学干扰研究

风载荷是白升式平台的主要控制载荷,现行规范在计算风载荷时主要采用面积投影法,不考虑空气动力学干扰的影响,结果偏于保守。以自主研发的122m（400ft）自升式平台为例,通过风洞实验得到其各风向角下的干扰因子伊。在此基础上,采用求解RANS方程的方法,结合k—ε湍流模型对风载荷的空气动力学干扰现象进行数值模拟,所得伊值与实验结果吻合良好,揭示了这种干扰现象对自升式平台风载荷的影响。     

港口系泊船舶受风高度取值问题研究

根据现行规范中船型尺寸、排水量、受风面积、形状系数等船舶参数与船舶形状特性的关系,以及船舶照片与船舶本身符合比尺相似这一特点,搜集船舶图片及其相关资料并进行研究分析,得出船舶水面以上高度的计算方法以及相关参数。解决了JTS 144-1—2010《港口工程荷载规范》中未给出船舶水面以上高度取值方法带来的问题。