The working conditions.

The lazy-wave riser is an input and output riser for a flexible development system, which is widely used in all the riser and pipeline systems. Because of the influence of various factors, its configuration description, control and motion which have a strong nonlinear character are complex during the running process of the lazy-wave riser. Reference to the specific structure and environmental parameters of a certain lazy-wave risers system with a 300 thousand tons FPSO, with the basis of the specific process of the flexible riser system at work, the lazy-wave risers were discretized into lumped mass models, combined with AQWA, the simplified dynamic model of the whole system at the depth of 2100m has been established by the large hydrodynamic analysis software OrcaFlex. The dynamic response characteristics of the lazy-wave risers have been given by using time domain coupling method. With and without the consideration of the 2nd wave drift load in the simulation process, the effects of the 2nd wave drift load on the results are obtained. The simulation results reveal the difficulty of simulation convergence caused by a large number of risers and flexible components. The 2nd order wave drift loads have a significant effect on the riser system, resulting in the increasement of the effective tension at each end of each riser. To counteract the magnitude of the FPSO response caused by such loads, the number of mooring lines needed to be increased or combined with dynamic positioning techniques to optimize the design.

缓波立管（lazy-wave riser）是柔性开发系统的输入输出立管，广泛应用于各类立管与管道系统中。由于受多种因素影响，缓波立管在运行过程中，其构型描述、控制与运动均具有较强的非线性特性，运行工况复杂。针对某配套30万吨级浮式生产储卸油装置（FPSO）的缓波立管系统的具体结构与环境参数，结合柔性立管系统的实际工作流程，将缓波立管离散为集中质量模型，结合水动力分析软件AQWA，依托大型水动力分析软件OrcaFlex建立了2100米水深下全系统的简化动力学模型。采用时域耦合方法分析得到了缓波立管的动态响应特性。通过在仿真中分别考虑与不考虑二阶波浪漂移载荷，得到了该载荷对仿真结果的影响规律。仿真结果表明，立管数量较多且包含柔性构件会导致仿真收敛难度增大；二阶波浪漂移载荷对立管系统具有显著影响，会使各立管两端的有效张力升高。为抵消此类载荷引发的FPSO响应幅值，需增加系泊缆绳数量，或结合动力定位技术开展优化设计。