双椭流线型海底管线抵御滑坡冲击的减灾效果与降阻机制

Effect and mechanism of disaster reduction of pipelines with double-elliptic streamline contour against impact of submarine landslides

近年来,随着海洋能源开发步伐的加快,海底管线铺设的数量不断增加,在服役期内这些管线是否稳定直接影响着海洋油气开采、作业人员生命财产及海洋生态环境的安全。针对海底管线易遭受滑坡破坏的现状,提出一种具有双椭流线型截面的海底管线,基于计算流体动力学(CFD)方法,分析了新型管线在滑坡冲击作用下的减灾效果与降阻机制。研究表明,对于平铺和悬浮式铺设形式,双椭流线型管线可以延缓边界层的分离,降低卡门涡街对管线的振动影响,有效地降低滑移体冲击管线产生的拖曳力和升力,最大可使拖曳力系数降低71.01%,升力系数降低32.14%;并提出双椭流线型管线拖曳力系数和升力系数的计算公式,为海底管线的减灾工程提供了新的思路。

With the rapid development of marine energy extraction, the demand for submarine pipelines has been increasing in recent years. The stability of pipelines during their service period directly affects the safety of the oil and gas exploitation, the workers’ life and the marine ecological environment. In view of the fact that submarine pipelines are vulnerable to the damage from landslides, a novel type of submarine pipeline with a double-elliptic contour is developed. Then, the effect and mechanism of disaster reduction of the pipeline under the impact of landslides are analyzed based on the computational fluid dynamics(CFD) method. The results show that the developed pipeline, no matter in a suspended or laid-on-seafloor status, can delay the separation of velocity boundary layer near the pipeline surface to reduce the influence of Karman Vortex Street. Thus, the drag force and lift force of pipelines imposed by submarine landslides are effectively reduced,with a maximum lessening percentage of 71.01% for drag force coefficients and 32.14% for lift force coefficients. Moreover, the equations for estimating the drag force and lift force coefficients of double-elliptic contour pipeline are recommended, which provides a new reference for the disaster fortification and mitigation engineering on submarine pipelines.