Complex piping systems like subsea rigid jumpers and manifold piping may have several bends and changes in the internal bore diameters that significantly affect the fluid flow profile. Consequently, localized turbulence and slug flow are common problems encountered during operation. This study investigates the vibration of a complex M shaped jumper system in slug flow regime. The slug formation in the M-shaped jumper is predicted using a multiphase CFD model which is first validated on a simplified geometry comprising of a straight section and a 90 degree bend. For this simplified geometry, CFD prediction of slug is compared to experimental data obtained by the state-of-the-art void fraction measurement technology called wire-mesh sensor (WMS). This multiphase CFD model is then implemented in the M-shaped jumper. Two-way FSI analysis is then performed to simulate the interaction between flow forces on the internal jumper wall and the corresponding deformation of the jumper system. Further, spectral analysis is employed to capture the resonant frequencies and vibration modes. Finally this paper discusses how state of the art MEMS based vibration sensors can be integrated with a coupled FEA-CFD model to provide insights into in-service vibration and fatigue damage.
Flow-Induced Vibration (FIV) is the vibration of a piping element caused by hydrodynamic forces imposed by the flow on the element. FIV can bring about serious consequences specifically when the frequency of excitation force and piping element natural frequency are close to each other (resonance). In internal multiphase flow cases, due to the fluctuation of void fraction, phase distributions, structure velocity, pressure, and momentum flux, turning flow elements (e.g. bends, and tees) can experience periodic forces that may result in vibration of the system. This is called internal multiphase flow induced vibration (1) which can be several orders of magnitude higher than vibration in single phase flow (2). In bubble flow, random motion of bubbles can induce turbulence. In slug flow, periodic passages of Taylor bubbles and liquid patches induce momentum fluctuation. In the churn flow regime, periodic liquid structures of different time and length scales can lead to momentum fluctuation.
