基于FY-2遥感数据的台风中心定位

针对台风在形成和消散阶段中心定位准确率较低的问题,本文提出了一种基于云导风的方法,使用的遥感数据来源于FY-2气象卫星的红外通道。该方法首先对红外序列遥感图像进行金字塔分解,然后基于加权的中值滤波光流模型构建云导风场,最后利用密度矩阵计算台风中心。选择2014年真实形成于西北太平洋的台风Rammasun和Halong进行案例分析,结果表明该方法对台风整个生命周期阶段的检测结果均较准确。     

基于图像处理的异重流与系泊结构物作用模型试验研究

异重流广泛存在于江河入海口附近,速度快、破坏力强,给近海工程的施工作业带来不小的难度。为了研究系泊结构物在异重流作用下的运动响应,基于图像处理技术,采用开闸式异重流模型试验方法,将异重流和结构物作为研究对象。利用图像处理技术处理由高速摄像机拍摄的结构物运动图片,从而获得结构物运动的时历曲线。对比讨论了不同密度比的异重流对结构物运动的影响,同一密度比的异重流对处于不同深度结构物运动的影响。研究结果表明：结构物运动受异重流密度的影响较大,结构物的运动幅值随着密度的增大而增大。处于高密度流体非混合层的结构物受到异重流的作用会产生大幅度的顺时针旋转和正x方向偏移;位置较高的方柱受到淡水的主导作用,会产生逆时针旋转和负x方向偏移。位于盐水与淡水剧烈混合区域的方柱并不会产生单一方向的偏移,而是在平衡位置附近波动。     

Experimental study on the hydrodynamic performance of rectangular floating breakwater influenced by reef areas

Abstract

In this paper, series of experimental studies under regular wave actions to investigate the hydrodynamic performance of the rectangular floating breakwater (FB) affected by reefs with different slopes were carried out in a wave flume. The wave transmission coefficients, motion responses and mooring forces can be calculated on the basis of the data obtained from the experiments. A comparative experiment of the only rectangular FB is also conducted. The experimental results reveal that the rectangular FB with different reefs can make more positive effects on wave energy dissipation than that of the only rectangular FB, especially for short-period waves. The characteristics of three degrees of freedom of the rectangular FB affected by reefs are also observed, which can be used to further explain the variation tendency appeared in transmission coefficients. The roll motion of the FB influenced by reefs is intenser than that of the only FB and the changes of slopes have limited effects on the sway motion of the FB. Furthermore, the heave motion of the only rectangular FB is intenser than that of the FB affected by reefs for short-period waves and vice versa for long-period waves.     

Modeling and Motion Simulation for A Flying-Wing Underwater Glider with A Symmetrical Airfoil

The flying-wing underwater glider (UG), shaped as a blended wing body, is a new type of underwater vehicle and still requires further research. The shape layout and the configuration of the internal actuators of the flying-wing UG are different from those of "legacy gliders" which have revolving bodies, and these two factors strongly affect the dynamic performance of the vehicle. Considering these differences, we propose a new configuration of the internal actuators for the flying-wing UG and treat the flying-wing UG as a multi-body system when establishing its dynamic model. In this paper, a detailed dynamic model is presented using the Newton-Euler method for the flying-wing UG. Based on the full dynamic model, the effect of the internal actuators on the steady gliding motion of vehicle is studied theoretically, and the relationship between the state parameters of the steady gliding motion and the controlled variables is obtained by solving a set of equilibrium equations. Finally, the behaviors of two classical motion modes of the glider are analyzed based on the simulation. The simulation results demonstrate that the motion performance of the proposed flying-wing UG is satisfactory.     

波频和慢漂组合作用下钢悬链线立管疲劳损伤研究

为了有效地考虑浮体慢漂运动对钢悬链线立管疲劳损伤的影响,提出了波频和慢漂运动组合作用下钢悬链线立管疲劳损伤简化计算的位置组合叠加法。其核心是:基于浮体慢漂运动概率分布选取若干典型慢漂位置,进行波频运动作用下钢悬链线立管动力响应分析;根据钢悬链线立管运动位置变化特征,截取若干慢漂位置对应的波频应力时程叠加到慢漂应力时程上,得到波频和慢漂运动的组合应力时程;编写基于雨流计数法的MATLAB程序处理立管各节点应力,采用海水环境下Do E.E型S-N曲线和Palmgren-Miner累积损伤准则计算立管各节点疲劳损伤。应用位置组合叠加法对某海域500 m水深的立管进行了疲劳分析,并与全耦合法、权重组合叠加法以及波频和慢漂疲劳损伤简单相加法的结果进行了对比,结果表明该方法具有较高的精度和效率。此外,进行了区域设定系数、波浪高度、波浪周期和土壤表面剪切强度等参数对组合作用下立管疲劳损伤的敏感性分析。     

基于重叠网格方法浮筒涡激运动特性数值分析

浮筒被广泛应用在海洋工程中,研究浮筒的涡激运动对于减少其对海洋平台构件的疲劳损坏具有指导意义。传统的动网格方法在处理浮筒转动运动时会因网格变形过大导致计算不收敛,采用了重叠网格方法以解决这一问题。数值试验采用了基于开源工具包Open FOAM自主开发的naoe-FOAM-SJTU求解器。分别进行了自由衰减数值试验和涡激运动数值试验。研究表明,随着折合速度的增加,浮筒的顺流向、横流向、垂荡和艏摇运动频率增加,且顺流向与垂荡频率相近,横流向与艏摇频率相近;其次,根据涡量场分布,表明浮筒前一时刻的泻涡会影响到浮筒之后时刻的周向涡量分布;最后,研究发现自由端对于浮筒尾流场泻涡有着显著影响,为将来探究减少浮筒涡激运动的方法提供指导。     

陆地垂向运动对沿海相对海平面变化的影响

沿岸陆地垂向运动是沿海相对海平面变化的重要组成部分,可以通过GPS直接观测或者联合验潮站和高度计资料进行推算,前者较为精确但目前欠发达国家和地区沿岸数据缺乏,后者资料相对丰富但准确性有待验证。本研究利用全球191个验潮站数据及同步的高度计资料和GPS监测数据,对两种方法得到的陆地垂向运动速率进行了比较,发现对于陆地垂向运动明显的站位,两种方法计算的趋势相同比例为74%;陆地垂向运动速率的空间分布表现为高纬度沿岸陆地抬升和中低纬度不同程度的陆地沉降,这与冰川均衡调整(GIA)模型结果和近期GRACE重力卫星观测较为符合,说明了基于验潮站和高度计联合推算沿岸陆地垂向运动的方法具有较高可行性。将此方法应用于中国沿岸,基于29个长期验潮站数据计算了中国沿海1993—2016年陆地垂向运动速率,发现存在以长江口为分界北升南降的空间特征;南部沿岸陆地沉降会加剧沿海相对海平面上升,给区域经济发展和人民生活带来风险。     

Study on Vortex-Induced Motions of A New Type of Deep Draft Multi-Columns FDPSO

A numerical simulation and an experimental study on vortex-induced motion (VIM) of a new type of deep draft multi-columns floating drilling production, storage and offloading (FDPSO) are presented in this paper. The main dimension, the special variable cross-section column and the cabin arrangement of the octagonal pontoon are introduced based on the result. The numerical simulation is adapted to study the effects of current incidence angles and reduced velocities on this platform''s sway motion response. The 300 m water depth equivalent truncated mooring system is adopted for the model tests. The model tests are carried out to check the reliability of numerical simulation. The results consist of surge, sway and yaw motions, as well as motion trajectories. The maximum sway amplitudes for different types of offshore platform is also studied. The main results show that the peak frequencies of sway motion under different current incidence angles and reduced velocities vary around the natural frequency. The analysis result of flow field indicates that the change of distribution of vortex in vertical presents significant influences on the VIM of platform. The trend of sway amplitude ratio curve of this new type FDPSO differs from the other types of platform. Under 45° current incidence angle, the sway amplitude of this new type of FDPSO is much smaller than those of other types of offshore platform at 4.4 ≤ V_r ≤ 8.9. The typical ‘8’ shape trajectory does not appear in the platform''s motion trajectories.     

基于CFD船舶操纵性预报方法研究

基于CFD技术和重叠网格技术完成了黏性流场中KVLCC2船模的操纵性水动力导数的数值计算。为保证计算的精确性,进行了网格的收敛性分析,给出了合适的网格划分方法;通过数值模拟斜航运动、纯横荡运动和纯艏摇运动计算出的水动力与相应条件下的试验值对比,计算结果与试验值吻合良好,计算出的水动力导数准确度较高。基于MMG分离建模方法建立KVLCC2船模的操纵性数学模型,利用龙格-库塔算法求解微分方程组,对船舶操纵运动进行仿真。回转试验和Z形操舵试验的仿真结果与试验结果对比,其回转直径和轨迹都非常吻合,表明采用的船舶操纵性预报是可行的。     

钢悬链式立管出平面运动刚体模态试验研究

钢悬链式立管为深海浮式生产系统油气输送的首选立管。基于钢悬链式立管刚体摆动模型,通过理论分析和模型试验,研究了钢悬链式立管出平面运动的动力学特性,验证了作者此前提出的钢悬链式立管出平面运动的刚体模态特征。研究表明,在海洋环境荷载作用下,波浪力和涡激升力引起的悬链式立管振动不仅有弯曲变形模态,也存在刚体摆动模态。对于钢悬链式立管,刚体摆动将使触地区产生附加弯矩,从而增大了应力、加速了疲劳损伤。