高桩-混凝土承台式海上风电塔强振分析

对某个风电场的23座高桩-混凝土承台式海上风电塔进行了1年的强振监测,统计了其在台风、偏航冲击等作用力下的强振特性。监测数据分析发现:机舱对风向偏航时会引起塔筒强烈振动,且此类型强振现象持续时间达几十秒,有时振动加速度可超过10 m/s^2,每个月多达几百次;在某次台风作用下,塔筒的振动加速度接近10 m/s^2;施工船靠船时的碰撞引起塔筒的强振幅值接近15 m/s^2;通过分析风电塔1年运营期间的塔筒固有频率值,发现前3阶固有频率值、阻尼比未发现变化。监测结果表明:高桩-混凝土承台式风电塔在台风、机舱偏航,施工船碰撞时都会产生强烈振动。因此,机舱偏航和施工船碰撞引起风电塔的强振现象过于频繁发生,是风电塔疲劳损伤的重要因素。本文的研究成果可为此类型风电塔设计、运营安全监测及损伤诊断提供参考。     

Computation of Design Load and Motion for Floating Structures Navigating in Waves

—Analytical and numerical investigation is made of the source potential for floating structurewith forward speed in waves.A particular form is selected for numerical applications,where the double in-tegral of the Green function is transformed into the single one and the oscillation characteristics forintegrands in the specific computation domain are treated numerically.A comparison of calculated exam-p1es with published data is given and it shows that the numerical simulation is satisfactory and the accura-cy is adequate to engineering application.     

A mixed continuous and discrete nonlinear constrained algorithm for optimizing ship hull structural design

A nonlinear search algorithm for optimizing constrained design of ship structures is presented. The decision variables can be continuous or discrete and the constraints can be homogeneous or inequality nonlinear functions of those variables. The algorithm does not use gradients; therefore, it can work with non-systematized functions such as tables or another class of design routine. It was tested in the structural design of a Patrol Boat and has proved to be a powerful tool decreasing the time expended in preliminary design when it is done by the conventional spiral approach.     

Application of extended state space to nonlinear ship rolling

It is well known in the field of marine hydrodynamics that the added mass, damping and wave exciting forces are functions of frequency (Newman, 1977. Marine Hydrodynamics. MIT Press, Cambridge). Although most previous studies of nonlinear ship rolling motion have assumed that these forces do not vary with frequency, in this study the frequency dependent added mass and damping coefficients are approximated in the time domain with extended state space variables. Using numerical time simulation (integration), the extended state space model is compared to the constant coefficient model with a constant frequency forcing and the results for two constant value approximations of the added mass and damping are compared to the extended state space model with a multiple component pseudo random forcing.     

船舶噪声对浅海海洋环境噪声空间相关的影响

通过对2001年亚洲海国际声学实验(ASIAEX)得到的海洋环境噪声数据进行处理,计算了噪声场空间相关系数、功率谱密度和垂直指向性,分别研究了受到远距离和近距离船舶辐射噪声影响的海洋环境噪声空间相关性.结果表明:船舶距离较远(10 km)时其辐射噪声会导致500 Hz以下的海洋环境噪声的空间相关性提高,而对500 Hz以上噪声的空间相关性没有影响;船舶距离较近(≤10 km)时,船舶辐射噪声会导致500 Hz以下的海洋环境噪声相关系数振荡变化,噪声空间相关性曲线在噪声信号声程差相差四分之一波长时出现第一个零点,对500 Hz以上的海洋环境噪声则会引起噪声能量升高,噪声的空间相关性也相对提高.基于现有理论,分别讨论了远距离船舶和近距离船舶产生的噪声场声学特性,对两种噪声场的海洋环境噪声空间相关性进行了合理的解释.     

基于无网格MPS方法数值分析方舱破舱进水问题

采用移动粒子半隐式法(moving particle semi-implicit,简称MPS)对自由漂浮二维方舱的破舱瞬时进水过程进行数值模拟。首先,采用基于GPU平台自主开发的MPS软件模拟破舱进水问题,并与其他方法得到的数值模拟结果进行对比验证。然后,对该二维方舱的各种模型进行了数值模拟,其中开孔位于不同位置以表示舷侧不同高度下的损坏。此外,还研究了不同类型的挡板对破舱进水后方舱稳定性的影响。结果表明损坏的孔洞和内部挡板会影响损坏舱段的运动特性,开孔距静水面的距离越大引起舱段的横摇等运动幅度越大,垂直挡板比水平挡板对舱内洪水的影响更大。     

SAR图像船行尾迹检测的Radon变换和形态学图像处理技术

该文提出了一种由Radon变换与形态学图像处理技术检测船行尾迹的算法SWDRM（Ship Wake Detection Algorithm based on Radon transformation and Morphologic image processing technology)，算法特点是：在Radon空间进行处理后，得到逆变图像，通过图像后处理，可得到二值图像，以用于尾迹自动检测，对海洋卫星合成孔径雷达（SEASAT SAR）图像及模拟乘性斑点噪声中舰船尾迹进行了检测，结果表明，SWDRM具有很好的鲁棒性，能够适应不同水平的噪声环境，同时对阈值系数和工作窗口宽度的选择范围都比较大，在一定的噪声水平范围，给定阈值系数后，得到近似于恒虚敬率的检测结果，结合图像后处理，可得到二值图像用于自动尾迹检测。     

Stability Analysis of Bohai Oil-Drilling Ship No. 6 Under Static and Cyclic Loads

- This paper presents a procedure to calculate the safety factor against sliding of a marine gravity structure subjected to a combination of static and cyclic loads. This procedure claculates the stress at the sliding surface by the finite element method (FEM) and takes the dynamic properties of clay into account. With this procedure, the stability of a Bohai oil-drilling ship is analyzed. The calculated safety factor is much smaller than 1, indicating that this oil-drilling ship would fail just as what had happened to it.     

利用小波包分析和混沌特征提取进行船舶辐射噪声分类

基于船舶辐射噪声信号具有非线性、非平稳的特征，提出采用提取船舶辐射噪声信号的非线性混沌特征量和多尺度小波能量特征，并将两者综合作为特征参数输入神经网络分类器进行船舶分类识别。实验结果表明，该方法能较好地区分不同类型的船舶。