风浪流多场耦合作用下海洋立管振动响应研究

发布时间：2018-07-28 06:51

【摘要】：中浅海域海洋环境复杂多变,海洋立管承受风、浪、流的作用,呈现非线性的流固耦合作用。本文利用Fluent软件,通过边界造波法、阻尼消波法和VOF追踪自由表面技术建立风、浪、流多场耦合数值水槽,并在数值水槽中进行海洋立管双向流固耦合数值模拟。主要的研究工作如下：(1)本文构建波浪、波-流耦合、风-浪-流耦合数值环境,通过数值模拟得到压力分布、速度云图、瞬时波浪相云图及波高监测曲线等,与理论计算进行对比验证数值水槽的可靠性。(2)由波浪作用下立管的流固耦合数值模拟研究发现,当立管仅受波浪作用时,在流向上随波浪进行周期性振动,横向振动主要表现为二阶谐力的影响,且随相对水深的增加二阶谐力的影响减弱,并且会在海洋立管周围形成上大下小的漩涡。(3)由波-流耦合作用下立管的流固耦合数值模拟研究发现,立管的流向振动频率为波频,随着相对流速的增加横向振动出现多频现象,横向振动的主频率从2倍波频逐渐变为波频,次频变为2倍波频,且出现的三阶次频,横向振动平衡位置随相对流速增加线性减小,更大的相对流速会使漩涡更早的泄放。(4)由风-浪-流耦合作用下立管的流固耦合数值模拟研究发现,立管在风-浪-流耦合作用时与波-流耦合作用下振动响应大致相同,风场的变化对海洋立管振动影响较小。(5)本文数值模拟得到的立管流向振幅量级为10-3m,横向振幅量级在10-5m到10-4m之间,这可能由于模拟选取的立管刚度较大、长径比较小以及立管所处的约化速度较小等原因共同造成,今后可开展大长径比、柔性管的振动响应模拟,以便于更好的剖析各场贡献度。
[Abstract]:The marine environment of medium and shallow sea area is complex and changeable, and the riser is subjected to the action of wind, wave and current, showing nonlinear fluid-solid coupling effect. In this paper, the coupled numerical flume of wind, wave and flow is established by using the Fluent software, the boundary wave-making method, the damped wave dissipation method and the VOF tracing free surface technique, and the numerical simulation of the two-way fluid-solid coupling of the riser in the numerical tank is carried out. The main research works are as follows: (1) the numerical environment of wave, wave-current coupling, wind-wave-current coupling is constructed. The pressure distribution, velocity cloud diagram, instantaneous wave phase cloud diagram and wave height monitoring curve are obtained by numerical simulation. Compared with the theoretical calculation, the reliability of the numerical flume is verified. (2) the numerical simulation of fluid-solid coupling of risers under the action of waves shows that when the risers are only subjected to wave action, the vertical risers vibrate periodically with the waves in the upward direction. The transverse vibration is mainly affected by the second harmonic force, and the influence of the second harmonic force decreases with the increase of the relative water depth. And it will form a whirlpool around the riser. (3) numerical simulation of fluid-structure coupling of riser under wave-current coupling shows that the flow direction vibration frequency of riser is wave-frequency. With the increase of relative velocity, the transverse vibration appears multi-frequency phenomenon, the main frequency of transverse vibration changes from 2 times to wave frequency, the secondary frequency becomes 2 times, and the third order frequency appears. The equilibrium position of transverse vibration decreases linearly with the increase of relative velocity. (4) the numerical simulation of fluid-solid coupling of risers under wind-wave-current coupling shows that the larger relative velocity will make the vortex release earlier. The vibration response of riser subjected to wind-wave-current coupling is approximately the same as that of wave-current coupling. The variation of wind field has little effect on the vibration of the riser. (5) the magnitude of the vertical tube flow direction amplitude is 10-3 m and the transverse amplitude is 10-5 m to 10-4 m, which may be due to the large stiffness of the riser selected by the simulation. Because of the small length ratio and the small reducing speed of the riser, the large aspect ratio and the vibration response simulation of the flexible tube can be carried out in the future in order to analyze the contribution of each field better.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P756.2

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