波流耦合作用对圆筒型FPSO运动响应的影响

Influence of Wave-Current Interaction on Motion Response of Cylinder FPSO

采用模型试验的方法研究圆筒型浮式生产储卸油装置(Floating Production Storage and Offloading,FPSO)在不同实验室模拟海流作用下的运动特征,从频域和时域的角度对FPSO运动响应的关键特征进行分析研究。试验以施加等效流力和水池造流两种方式模拟海流。结果表明:满载和压载吃水变化对FPSO运动响应的影响不大;直接施加等效流力除了对六自由度运动平衡位置产生小幅偏移外,对其余运动无明显影响;在波流耦合作用下,即使约化速度小于锁定区间,纵荡幅值仍然显著增大。由于实际环境可能比试验环境恶劣,因此在设计FPSO时应考虑波流耦合作用。在波流耦合作用下,横向运动趋向于分布在更宽的范围内,且振幅更大。波流耦合也会使横摇和横荡的谱峰频率往低频偏移,其低频运动的平均幅值也在波流耦合作用下显著增大,增幅为2倍左右。

The motion responses of cylinder Floating Production Storage and Offloading(FPSO)under different simulated ocean currents in the laboratory are investigated.The key characteristics of the motion responses are analyzed in frequency domain and time domain.The current is modeled by direct applying the equivalent current force and current generated in basin.The results show that:the change in the full loaded and ballast loading condition is of little effect on the motion of FPSO;directly applying the equivalent current force is of barely influence on the form of cumulative distribution of 6 Degree-of-Freedom(DOF)responses,but with slightly changes in the equilibrium position of 6 DOF response;considering wave-current interaction,the surge amplitude increases significantly even if the reduced velocity is less than the lock-in region.Because the real environments can be harsher than the experimental one,the wave-current interaction should be taken into consideration when designing FPSO.With the coupling of current,the transverse motion tends to be distributed in a wider range with larger amplitude.The spectral peak frequency in Low-Frequency(LF)moves to lower frequency for sway and pitch responses under wave-current interaction.And the mean amplitude of LF and Wave-Frequency(WF)of 6 DOF responses are also significantly amplified.