【作者】 王建凯；

【导师】 王言英；

【作者基本信息】 大连理工大学 ， 船舶与海洋结构物设计制造， 2008， 硕士

【摘要】 当前船舶底部砰击荷载的理论模型是二维楔形或三维锥体以恒定的速度进入初始静止水面，采用边界元方法求解。由于边界元求解方法受限于研究领域，且程序的通用性差，因而不能广泛地应用于工程领域。本文提出了一种适用于浮式生产储油船(FPSO)的底部砰击荷载的计算方法。这种方法包含三部分内容：采用三维频域边界元法计算FPSO在波浪上的频域运动响应；采用时频转换法得到FPSO船体剖面与波面的垂向相对运动的时间历程，和确定砰击发生的时刻和砰击时船体入水的速度；采用计算流体力学方法(CFD)建立二维入水模型，直接剖面计算压力分布和垂向力。数值计算结果表明，FPSO在压载斜浪入射状态下，相对运动的幅值和出水后的入水的速度幅值最大，最易发生砰击。砰击最大压力和发生砰击的船剖面的几何形状有很大的关系。其中底部平底半宽对砰击压力系数有重要的影响，特别对于类似于FPSO的大平底肥大型工程船影响尤为显著。本文以无因次化平底半宽为自变量得到估算砰击压力系数的回归公式，以供工程设计应用。此方法可简便快速地用于预报FPSO在其工作海域下不同工况下的底部砰击载荷，具有工程上可接受的精度，其结果可为后续结构强度校核提供设计参数。更多还原

【Abstract】 The Boundary Element Method (BEM) is a popular method used to solve the bottom slamming caused by the entering of the two-dimensional wedge or three-dimensional cone into the initial still water with a constant velocity. Because of the limited research field and bad generosity of program, this method can not be applied in practical engineering widely.In this paper, a process which is easy to estimate the slamming load is proposed. The process has three steps. Firstly, the 3D BEM is applied to calculate the motions of the FPSO in frequency domain. Secondly the frequency-time transformation method is used to obtain the relative motions in time domain and get slamming occurrence time and its entry-water velocity. Finally, the two dimensional model established with the method of CFD(computational fluid dynamics) to directly calculate the distribution of the load and the vertical force on the FPSO section.The numerical results show that the FPSO which have the largest relative motions and relative velocity amplitudes, will more likely lead to occur slamming on the condition of blast loads and the incident wave angle of 135 degree. The max slamming loads is greatly related to the shape of the ship section. the half-breadth of the flat bottom is one of the most important factors for slamming loads coefficients, especially for full-formed ship of FPSO shape with large flat bottom. In this paper, a regression formula to estimate the slamming load coefficient is obtained, with the independent variable of the half breadth of the flat bottom, which is conveniently applied in the engineering practice.The method in this paper can be easily applied to estimate the slamming load magnitude with acceptable precision, and the results can be used for strength analysis of bottom frame.更多还原