基于CFD方法的FPSO的波浪荷载和运动响应研究

Research on Wave Loads and Motion Response of FPSO Based on CFD Method

针对浮式生产储油船(Floating production storage and offloading, FPSO)在深水作业时面临的恶劣海况问题,为保证其服役期间的安全性及作业效率,需要准确计算非线性波浪荷载和运动响应。本文应用基于计算流体动力学(Computational fluid dynamics, CFD)的软件STAR-CCM+建立了针对实尺度FPSO模型的数值水池,基于Richardson外推法,针对时间步长和网格尺寸,分析了二者的收敛性和数值不确定度。使用该数值水池模拟了不同波浪工况作用下FPSO的运动响应,计算其受到的二阶波浪力,并与势流结果进行对比。结果发现,随着波陡增大,平均波浪力的CFD结果逐渐大于势流结果,且呈现差异化增大。而波陡大于1/15时,纵摇的CFD结果明显大于势流结果。说明大波陡条件下,黏性效应对平均波浪力和纵摇影响明显,为恶劣海况下预报及修正FPSO的二阶波浪力和运动提供了参考。

Aiming at rough sea conditions faced in deep water operations by offshore structures,like floating production storage and offloading(FPSO),in order to ensure the safety and work efficiency,it is necessary to assess wave loads and corresponding responses accurately.In this paper,the computational fluid dynamics(CFD)software STAR-CCM+is used to established a numerical tank for the prototype FPSO,and the convergence of time step and grid size are validated based on the Richardson extrapolation method.The heave and pitch motions of FPSO are simulated under series of sea states.The CFD results are compared with those from the potential flow theory as well as wave loads.It is found that as the wave steepness increase,the CFD results of mean drift force are gradually larger than potential flow results,and the difference increases.It shows that under the condition of large wave steepness,the viscous effect has a significant impact on the mean drift force and motions,providing a reference for predicting and adjusting the second-order force and motion of FPSO under large wave steepness.