【作者】 李航；

【导师】 徐万海； 刘彬；

【作者基本信息】 天津大学 ， 土木水利， 2023， 硕士

【摘要】 立管束作为海洋工程中生产的关键部件,其碰撞损伤问题是海洋工程中的难点和关键点。针对立管束或柱群干涉的研究已有一定成果,但对于弹性支撑的刚圆柱碰撞响应以及相对应的立管碰撞的研究相对不足。立管碰撞的相关研究仍局限于局部碰撞尚无完整的整体碰撞动力学行为分析。针对上述问题,本文开展了相关研究,主要研究内容与结论如下:(1)分析了立管夹角和立管径厚比对于Hertz模型计算准确性的影响;发现立管夹角越小和径厚比越小,采用Hertz模型计算的误差越大;最终通过在Hertz模型添加与径厚比相关的修正系数对Hertz模型进行修正,使得Hertz模型能够应用于立管碰撞。(2)利用实验分析了不同间距比下并列双圆柱干涉的物理机制发现:并列双圆柱的流体力主要由流体弹性不稳定、漩涡脱落和湍流抖振共同作用,随着约化速度的增加,流体力的主控机理逐渐从流体弹性不稳定转换为漩涡脱落,约化速度较高时伴随着湍流抖振;当间距比1.2<S/D<2.0时,圆柱间偏射对于圆柱的影响较为激烈,对流体力有明显的影响;当间距比S/D<1.2时,圆柱之间会有一定的相互排斥作用,偏射流的影响较小。最后在实验分析所得流体力特性的基础上,拟合了并列双圆柱流体力的经验模型。(3)基于欧拉-伯努利梁理论和立管排布方式建立了并列双立管干涉的模型,通过判断立管之间的距离实现了碰撞搜索定位和碰撞力计算。通过计算分析发现,立管之间的碰撞会触发立管产生更高阶的振型,在轴向产生多点碰撞并在每个撞击点产生多次碰撞,容易造成立管冲击损伤和疲劳损伤。本文的研究工作和成果填补了关于并列立管干涉碰撞的研究空白,提供了一种可供选择计算并列立管干涉碰撞的方法,为工程中立管束的设计提供理论参考和方法借鉴,具有重要的理论价值和工程意义。更多还原

【Abstract】 As a crucial component in marine engineering production,riser systems pose challenges and key issues regarding collision damage.While there have been some achievements in studying riser or column interference,research on the collision response of elastically supported rigid cylinders and the corresponding riser collision remains relatively limited.The existing studies on riser collisions are still confined to local collisions,lacking a comprehensive analysis of the overall collision dynamics.To address the aforementioned issues,this paper conducts relevant research,with the main research contents and conclusions as follows:(1)Analyzing the influence of riser inclination angle and the ratio of diameter to thickness on the accuracy of Hertz model calculations.It is found that smaller inclination angles and smaller diameter-to-thickness ratios result in larger errors when using the Hertz model for calculations.To address this,a modification coefficient related to the diameter-to-thickness ratio is introduced to adjust the Hertz model,enabling its application to riser collisions.(2)Experimental analysis is employed to investigate the physical mechanisms of interference in parallel double cylinders under different spacing ratios.It is discovered that the fluid forces acting on parallel double cylinders are primarily attributed to the combined effects of fluid-elastic instability,vortex shedding,and turbulent buffeting.As the reduced velocity increases,the dominant mechanism transitions from fluid-elastic instability to vortex shedding,accompanied by turbulent buffeting at higher reduced velocities.When the spacing ratio falls within the range of 1.2<S/D<2.0,cylinder deflection significantly affects the fluid forces.When the spacing ratio is S/D<1.2,there is a certain mutual repulsion between the cylinders,resulting in a lesser impact on the fluid forces.Finally,an empirical model for the fluid forces of parallel double cylinders is fitted based on the experimental analysis of fluid force characteristics.(3)A model for the interference of parallel double risers is established based on the Euler-Bernoulli beam theory and riser arrangement.Collision detection and collision force calculation are achieved by evaluating the distances between the risers.Through calculation and analysis,it is found that riser collisions trigger higher-order vibration modes and result in multiple collisions at different axial positions,which can lead to impact damage and fatigue damage to the risers.The research work and findings of this paper fill the research gap in the field of interference and collisions of parallel risers,providing an alternative method for calculating collision in parallel riser interference.It offers theoretical references and methodological insights for the design of riser systems in engineering,demonstrating significant theoretical and engineering significance.更多还原