方形FPSO系泊系统动力分析

海洋结构物系泊系统设计和分析对其安全操作至关重要,以往的研究大多集中于深水平台。将对浅水中作业的方形FPSO系泊系统动力特性展开研究,分析对比浅水中钢链和聚酯缆两种系泊系统的动力特性和浮体位移,并根据API规范校核自存工况下系缆强度并验证浮体在浅水中是否会触底,之后根据结果确定合理的系泊系统设计方案。分析方法基于三维势流理论和浮体运动的耦合时域模拟,浮体水动力分析中考虑浅水效应,计算了二阶波浪的二次传递函数矩阵,系缆张力分析基于有限元理论。结果表明聚酯缆系泊系统更适用于浅水区域作业的FPSO。     

用时域法求解二维二阶非线性水波的绕射问题

本文用二阶理论在时期围内研究非线性水波的绕射问题。一、二阶问题分别满足各自的自由表面条件和物面条件。用一阶Ａｄａｍｓ格式并配合时步处理来计算自由表面上的波高和速度势，而流场内的速度势通过求解有限元方法得到。采用人工阻尼区来吸收反射波，对水平半圆柱在水面的绕射问题进行了计算，得到了自由表面波高时间历程和圆柱所受到的波浪力，计算结果和有关文献进行了比较，其符合程度是令人满意的。     

往复式泥浆脉冲发生器转子水力转矩

往复式泥浆脉冲发生器是随钻测量（MWD）、随钻测井（LWD）系统的重要组成部分,其转子的水力特性研究对于节约钻井系统能源消耗、提高信号质量、丰富调制方式具有重要意义。由于转子附近机构复杂,湍流现象明显,给研究带来较大困难。利用稳态水力转矩、瞬态水力转矩的相关理论,对发生器中转子水力转矩进行理论分析,利用CFD数值仿真和水力转矩原理实验结果进行验证。研究结果表明,转子在往复式运动中水力转矩基本沿同一方向分布,在10 Hz摆动频率下水力转矩与转子转角密切相关,而与转子角速度及角加速度关系较小,最大水力转矩出现在接近闭合位置。通过加装机械辅助装置,脉冲发生器对电机功率和转矩的需求得到了大幅度的降低。     

Finite element analysis of second order wave radiation by a group of cylinders in the time domain

A finite element based numerical method is employed to analyze the wave radiation by multiple or a group of cylinders in the time domain. The nonlinear free surface and body surface boundary conditions are satisfied based on the perturbation method up to the second order. The first- and second-order velocity potential problems at each time step are solved through a Finite Element Method (FEM). The matrix equation of the FEM is solved through iteration and the initial solution is obtained from the result at the previous time step. The three-dimensional (3-D) mesh required is generated based on a two-dimensional (2-D) hybrid mesh on a horizontal plane and its extension in the vertical direction. The hybrid mesh is generated by combining an unstructured grid away from cylinders and two structured grids near the cylinder and the artificial boundary. The fluid velocity on the free surface and the cylinder surface are calculated by using a differential method. Results for various configurations including the cases of two cylinders and four cylinders and a group of eighteen cylinders are obtained to show the joint influences of cylinders on the first- and second-order waves and forces, including the effects of spacing ratios and wave frequency on the second order waves and the mean force, in particular.