Active spreading and hydrothermalism in North Fiji Basin (SW Pacific). Results of Japanese French Cruise Kaiyo 87

The aim of the Japanese-French Kaiyo 87 cruise was the study of the spreading axis in the North Fiji Basin (SW Pacific). A Seabeam and geophysical survey allowed us to define the detailed structure of the active NS spreading axis between 16° and 22° S and its relationships with the left lateral motion of the North Fiji Fracture Zone. Between 21° S and 18°10′ S, the spreading axis trends NS. From 18°10 S to 16°40 S the orientation of the spreading axis changes from NS to 015°. North of 16°40′ S the spreading axis trends 160°. These two 015° and 160° branches converge with the left lateral North Fiji fracture zone around 16°40′ S to define an RRFZ triple junction. Water sampling, dredging and photo TV deep towing give new information concerning the hydrothermal activity along the spreading axis. The discovery of hydrothermal deposits associated with living communities confirms this activity.     

涡激振动实验中的流速增大装置研发与性能研究

拖曳水池中进行立管涡激振动实验时,为了保证采样时间长度,难以达到较高的Re数。流速增大装置可以在不提高拖车车速的情况下增大立管外的流速。利用这种流速增大装置还可实现流速分层流场中细长柔性立管涡激振动实验。经过对流速增大装置中的进流段曲线进行优选,发现Witozinsky曲线的总体性能最好。在对流速增大装置进行水池实验和数值模拟后,发现流速增大区域的流速增大倍数接近进流段收缩比,流速增大区域流场比较稳定、均匀,流速增大装置对其外的流场影响很小。此流速增大装置不但可应用于拖曳水池中的立管涡激振动实验,还可以应用于对流速要求较高的水下航行体的水池试验,如鱼雷、水下机器人等。     

Air-floating towing behaviors of multi-bucket foundation platform

Air-floating towing beha viors of multi-bucket foundation plat form （MBFP） are investigated with the 1/20-scale model tests and hydrodynamic so ftware MOSES. MOSES numerical model was val idated by test results, and M OSES prototype model of MBFP can eliminate scale effect of model. The influences of towing factors of to wing speed, water depth, freeboard, and w ave direction on air-floating tow ing stability of MBFP were analyzed by model tests and validated MOSES prototype mod el. It is sho wn that the re duction of towing sp eed can effectively d ecrease the to wing force and surge acceleration to improve towing stability. Water depth is another f actor in towing s tability. Obvious shallow water effect will appear in shallow water with sma ll water depth-draft ratio and it w ill disappear gradually and air-floating towing becomes more stable with the increase of water depth. Accelerations of surge, s way and heave are small and they have modest changes when freeboard increases from 0.5 to 2 m. For MBFP, the freeboard is not suggested to be larger than 2 m in following wave. Wave direction has large influence on the towing stability, the surge acceleration and towing force are sensitive to the va riation of wave direction, the surge acceleration and towing force in following wave （0°） and counter wave （180°） are much larger than that in transverse sea （90°and 270°）.     

水下拖曳系统运动姿态仿真研究

采用凝集参数法建立了水下拖曳系统的三维离散模型,该模型由一系列的质量点和不计重量的弹簧组成.采用数学模型编程对NCEL浮球实验和四个典型拖曳系统进行了仿真计算.计算结果表明此数学模型具有一定的理论意义和工程实用价值.     

Development and deployment of a stable tow body

With the introduction of improved underwater transducers, there is a need for a stable tow body for oceanographic measurements. This paper summarizes the development of a 260 kg, 1.83×1.06×0.81 m tow body. It covers the performance requirements, the tow body design and manufacture as well as its tow trials off of Biloxi, Mississippi aboard the R.V. Tommy Munro.     

立式翼型主体拖曳式水下潜器的设计及操纵性能

针对现有拖曳式水下潜器控制机构复杂、航向与姿态不容易稳定的缺陷,提出和设计了一种具有航向与姿态稳定的多自由度可控制拖曳式水下潜器样机。该样机主要由鱼雷状浮体、固定水平主翼、转角可控制襟翼、立式翼型主体等部分组成,潜器的深度控制通过控制襟翼的偏转来诱导固定水平主翼攻角的改变来实现;潜器的横荡运动操纵以通过控制两个作为转艏控制器的导管螺旋桨的转向与转速、诱导立式翼型主体产生诱导力矩使其产生横向偏转来进行。文中所提出和设计的样机具有运动过程中自我稳定能力强、航向稳定性好、控制机构简单并具有较高实用价值的特点。     

拖曳式剖面探测拖体系统构成及运动控制试验

拖曳式剖面探测拖体是一种能做波浪式轨迹运动的载体,可对海洋进行实时多参数剖面探测.阐述国内首台拖曳式剖面探测拖体的组成、功能及运动轨迹,并对运动轨迹控制进行实船试验研究.结果表明,拖曳式剖面探测拖体具有控制性能优良,实现传感器数据的实时采集.     

波浪式拖管法铺设海底管道力学性能研究

海底管道铺设是海洋油气资源开发的重要环节,传统的拖管法不能很好地适应海洋深度和复杂环境的变化。针对 Acergy公司在Girassol项目中提出的一种波浪式拖管方法,对其应用于2.0 km 长海底管道铺设进行分析。首先,结合深水海洋环境特征,采用集中质量法建立管道拖航数值模型,并介绍管道、拖缆和浮筒力学计算及水动力荷载计算方法;其次,基于非线性有限元OrcaFlex软件对拖管过程建模,以模拟实际项目拖管过程;然后,通过对比相同条件下的单波式和双波式两种拖管方式,探讨管道和拖缆的动态力学性能变化;最后,针对不同浮重比、拖航速度、拖缆长度和悬垂角、海流流速和流向角等因素展开敏感性分析。结果表明：波浪式拖管法可以有效地降低施工时对拖缆的张力需求,但也会因此增加管道局部弯矩和应力响应;相对于单波式拖管,双波式拖管在缓解由于拖航速度等变化而产生的管道局部损伤效应上更有优势,并能较好地适应不同水深环境;复杂的海流工况对拖航时管道的力学性能影响十分显著,施工前应选择合适的铺设窗口期以防止管道产生损伤。     

水平轴潮流能水轮机数值模拟方法对比分析

叶素动量理论和CFD方法是水平轴潮流能水轮机性能分析中运用较为广泛的数值模拟方法,文中结合小尺寸水轮机模型试验,对比分析了叶素动量理论和CFD方法在水轮机性能分析中的准确性和适用性.验证结果表明:叶素动量理论和CFD方法均能对水轮机的性能进行预报,且CFD精度高于动量叶素理论;大尖速比时,动量叶素理论偏离较高,不再适合性能预报;在小尖速比下,建议采用RNGk-ε模型的CFD方法进行分析计算;动量叶素理论适合设计初期设计方案的对比分析,而CFD方法适合对设计结果的验证校核和详细分析.