FSI Analysis of Flow-Induced Vibration in Subsea Jumper Subject to Downstream Slug and Ocean Current

Abstract

This paper presents a multiphysics approach for characterizing flow-induced vibrations in a subsea jumper subject to pressure fluctuation due to downstream slugging and external vortex shedding effects due to ocean current. In this study the associated fluid properties, phase behavior, and slugging dynamics were all characterized at subsea condition using PVTSIM and OLGA programs, respectively; the outcomes were then applied to a two-way fluid-structure interaction analysis (FSI) to quantify the vibration response. To mitigate the resonant phenomenon, detailed modal analysis was also conducted to check the modal shapes and natural frequencies. Therefore, this study integrated the best practices in flow assurance study (OLGA and PVTSim), computational fluid dynamics simulation (CFD), and computational structure analysis (FEA), and provided a complete solution to the fluid-structure interaction involved in a subsea jumper. It is revealed that both the slugging flow and the external ocean current induce vibration response in a subsea jumper. Compared to the vortex-induced vibration due to the external current and the flow-induced vibration due to the internal flow, the pressure fluctuation due to the slug plays a dominant role in generating excessive vibration and fatigue failure of a subsea jumper. Although this study focused on a subsea jumper only, the same approach can be applied to subsea flowline, subsea riser, and other subsea structures.