基于IVCBC涡方法和动刚度矩阵的深海立管的三维计算模型

Three dimensional computing model of deep sea riser based on IVCBC vortex method and dynamic stiffness matrix

文章针对深海立管长细比非常大的结构特征,视立管为质量集中的多自由度索模型系统。通过有限体积法将该模型系统离散为多个有限体单元,首次提出基于应变能计算立管动态刚度矩阵的算法,并采用IVCBC涡方法计算有限体的外载荷,构建了一种三维数值研究深海立管涡激振动的新方法。应用该数值计算方法探索了立管耦合前后的振型、尾流模型、流体力以及泄涡频率的特征。发现了立管涡激振动的涡泄频率不再满足Strouhal数的规律和多频"锁定"现象导致立管出现多种高阶模态振动共存的特征,该研究为立管的设计制造提供了重要的指导意义。

Being aimed at the structural characteristic of the large slenderness ratio of the deep sea riser, this paper considers the riser as a multi-degree-of-freedom cable model system with concentrated mass. The model system is discretized into several finite volume elements by finite volume method. The algorithm for calculating dynamic stiffness matrix of riser by strain energy is proposed for the first time, and the external load of finite volume elements are calculated by IVCBC vortex method. A new 3D numerical method is presented for studying the vortex-induced vibration of deep-sea riser. This numerical method is used to study the characteristics of vibration patterns, wake models, fluid forces and vortex frequencies under the coupling of riser. It was found that the riser shedding frequencies were not satisfied with the rule of Strouhal number,and the phenomenon of multi-frequency ‘locking＇ led to the coexistence of multiple high-order modes of vibration in the riser. This study provides an important guidance for the design and manufacture of riser.