深水浮式结构物与内孤立波流固耦合作用及载荷响应机理研究

The internal solitary waves (ISWs), have properties of two-way shear profile, significant velocity and acceleration, etc., therefore the ISWs are big threats to deepwater floating structures. In recent years, Offshore oil companies encountered many strong internal waves during its oil&gas exploration and development practice in the South China Sea. The action mechnism of ISWs to floating structures is not clear anyway, ISWs are classified as ocean current in API RP 2SK(3rd edition), ignoring their velocity variance and "wave" characteristics; the offshore floating structures is oscillating under the action of environmental forces, the Fluid-Body Coupling effect is very significant, it is therefore more reasonable to use the relative motion (velocities and accelerations) of ISWs water particle to the floating structures..This project is intended to study the characteristics of inertial force of internal solitary waves, a new method of calculating the internal solitary wave load is proposed considering the fluid-body coupling between the ISWs and the floater, and the developed load calculation method and the floater/riser/mooring coupling model are validated by flume model test and the in-situ measured data. Finally, the engineering phenomenon of "large drift" and vertical "fluttering" in NH8 MODU under actions of strong internal solitary waves is explored scientifically.

内孤立波，具有双向剪切、流速大、范围广等特征，威胁深水浮体的安全，海洋石油开发作业曾多次遭遇强内波袭击。由于内孤立波与浮体的作用机理尚不明确，API RP 2SK(第三版)规范将内波流归类为海流，忽略了其流速变化及惯性力特征；浮体的运动含波频和低频慢漂运动成分，其运动速度和加速度与内孤立波水质点相当，流固耦合作用显著。一方面，内孤立波流速大，加之惯性力作用，致使平台大幅水平漂移；另一方面，内孤立波水质点做周期性垂向运动，会引起大水线面浮式结构物垂向“抖振”。本项目拟研究内孤立波的惯性力特征、内孤立波与浮体的流固耦合作用，提出内孤立波载荷计算新方法；通过模型试验研究手段、利用工程实测数据来验证所发展的载荷计算方法和浮体/立管/系泊耦合运动分析模型，从科学角度探索并解释NH8号钻井平台在遭遇强内孤立波时出现“大幅漂移”和垂向“抖振”等工程现象。

内孤立波，具有双向剪切、流速大、范围广等特征，威胁深水浮体的安全，海洋石油开发作业曾多次遭遇强内波袭击。由于内孤立波与浮体的作用机理尚不明确，API RP 2SK(第三版)规范将内波流归类为海流，忽略了其流速变化及惯性力特征；浮体的运动含波频和低频慢漂运动成分，其运动速度和加速度与内孤立波水质点相当，流固耦合作用显著。一方面，内孤立波流速大，加之惯性力作用，引起平台大幅水平漂移；另一方面，内孤立波水质点做周期性垂向运动，会引起大水线面浮式结构物垂向“抖振”。.本项目研究了内孤立波的惯性力特征、内孤立波与浮体的流固耦合作用，提出了内孤立波载荷计算新方法；验证了所发展的载荷计算方法和浮体/立管/系泊耦合运动分析模型，从科学角度探索并解释NH8号钻井平台在遭遇强内孤立波时出现“大幅漂移”和垂向“抖振”等工程现象。基于弹性梁理论，编写系泊系统静力和动力的分析程序，实现内孤立波与平台、系泊立管系统的耦合分析；通过CFD方法研究内孤立波与浮式平台之间的流固耦合问题，得到浮式平台在内孤立波作用下的运动响应规律；此外，基于逆一阶可靠度IFORM方法，基于南海流花、荔湾等海域风浪流环境参数，建立了深水浮式平台系统的海洋环境参数的联合设计包络图，指导工程设计；基于时域耦合分析程序，建立“起重船-系泊-吊物”耦合分析程序，分析起重船及吊物的运动响应规律；探究波浪二阶慢漂力近似方法对平台运动响应及系泊顶部张力影响。