Flow Induced Forces on Multi-Planar Rigid Jumper Systems

Abstract

Rigid subsea jumper systems are typically used as interface between subsea structures and are required to accommodate significant static and dynamic loads. Due to constraints imposed by in-line planar jumpers (e.g. U shaped and M shaped jumpers), the industry is shifting towards the use of multi-planar jumper systems (e.g., Z-shaped jumpers). These multi-planar jumper systems have increased tolerance to end displacements and can be tailored to accommodate cyclic end motions of subsea structures. Multi-planar systems, however, come with unique challenges of their own including the coupling of flexural and torsional responses under vortex induced vibrations (VIV), fluid induced vibration (FIV) and slugging. In particular, the development of hydrodynamic slug flow is a common occurrence in oil and gas pipelines. It is understood to be initiated by instabilities of wave on the gas-liquid interface. It is also understood that slug flows are the source of vibration within pipework when a change of direction occurs e.g. 90° bend at a subsea riser base or top side piping. In standard slug flow vibration analysis, averaged slug frequency and length are used to calculate the force generated. In the case of a multi-planar rigid jumper, several changes of direction occur within a short length of pipe. After each bend the characteristics of the slug flow are modified. It is necessary to accurately capture these changes in order to reproduce the forces generated at critical points along the jumper length. This paper presents a methodology for analyzing slugging induced fatigue that has been developed in an on-going study undertaken by MCS Kenny for design of multi-planar rigid jumper systems. In this methodology, Computational Fluid Dynamics (CFD) is used to accurately simulate the flow within the jumper and provide pressure fluctuations on the internal pipe wall for the vibration analysis. The pressure fluctuations are then incorporated in a Finite Element (FE) model of the jumper system and further used to determine the slugging fatigue damage. CFD (Star-ccm+) and FE (Flexcom, ABAQUS) software programs are used to accurately capture the response of the jumper system. Key conclusions and challenges overcome during the course of this study are presented herein.

Experimental and Numerical Study on the Slug Characteristics and Flow-Induced Vibration of a Subsea Rigid M-Shaped Jumper

“…Jia et al [20] set the length and frequency of the slug by numerical simulation to study the interaction characteristics of the two gas-liquid phases in the jumper interior. Nair et al [21] carried out numerical simulations on the slug in a multi-plane jumper and used a finite element model (FEM) to analyze the fatigue damage of the jumper. Pontaza et al [22] conducted a three-dimensional numerical simulation of the vibration process caused by the slug flow in the jumper, estimated the structural response of the jumper, including the fatigue life, and found that the main frequency of the pipe vibration was related to modes 1-4, and the stress is highest when the gas volume fraction was 55%.…”

Experimental Investigation and Numerical Modeling of Two-Phase Flow Development and Flow-Induced Vibration of a Multi-Plane Subsea Jumper

“…Studies on multi-planar jumpers were rare, and only a few numerical analyses on internal flow characteristics such as slug flow were carried out by Wang, et al [30], Dai, et al [31], Lu, et al [32], and Song, et al [33]. Nair, et al [34] analyzed the vibration fatigue response of a multi-plane jumper structure for an internal Existing studies on the vibration of subsea pipelines mainly focus on in-line planar pipelines and the corresponding vortex-induced vibrations caused by the oscillatory lift force generated by the vortex shedding [17][18][19][20][21][22]. With the development of deepwater oil and gas exploitation technology, the pressure and flow rate in the pipeline gradually increase.…”

“…Studies on multi-planar jumpers were rare, and only a few numerical analyses on internal flow characteristics such as slug flow were carried out by Wang, et al [30], Dai, et al [31], Lu, et al [32], and Song, et al [33]. Nair, et al [34] analyzed the vibration fatigue response of a multi-plane jumper structure for an internal slug. Numerical simulations of the internal flow in the jumper were carried out to obtain the pressure fluctuations on the jumper, which were used to determine the fatigue damage to the slug.…”

Numerical Study on Fluid Structure Interaction of Slug Flow in a Horizontal Pipeline

“…However, in the one way coupling the exerted fluid loads are not altered by the structure's motion or deformation, the effect of the structural load on the fluid domain is negligible. The difference between the two coupling methods is illustrated in Fig 1 . Recently, FSI has been used extensively in various researches [3][4][5][6][7][8] to investigate the phenomenon of slug flow induced vibration and also vortex induced vibration phenomenon was examined by [9][10][11]. This study aims to investigate the effect of slug flow on pipeline structure using fluid structure interaction technique in Star-CCM+ software.…”