In-Line and Cross-Flow Coupling Vibration Response Characteristics of a Marine Viscoelastic Riser Subjected to Two-Phase Internal Flow

Xueping Chang,Wenwu Yang,Jinming Fan,Yinghui Li,Reza Kolahchi

doi:10.1155/2021/7866802

Xueping Chang, Wenwu Yang + Show 3 more

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https://doi.org/10.1155/2021/7866802

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Abstract

This paper studies the in-line and cross-flow coupling vibration response characteristics of a marine viscoelastic riser subjected to two-phase internal flow and affected by the combined effects of several parameters including the volume fraction of gas phase, sea water flow velocity, viscoelastic coefficient of the marine riser, axial tension amplitude, and the in-line and cross-flow coupling effect taking into account both the geometric and hydrodynamic nonlinearities. On the base of extended Hamilton’s principle for open systems, the dynamic equations of the marine viscoelastic riser subjected to the axial tension and gas-liquid-structure interaction are established. Two distributed and coupled van der Pol wake oscillators are utilized to model the fluctuating lift and drag coefficients, respectively. The finite element method is adopted to directly solve the highly coupled nonlinear fluid-structure interaction equations. Model validations are firstly performed through comparisons with the published experimental data and numerical simulation results, and the characteristic curves of the in-line and cross-flow vibration pattern, the in-line and cross-flow displacement trajectories, the in-line and cross-flow space-time response of displacement, and the in-line and cross-flow space-time response of stress versus different parameters are obtained, respectively. The results show that the volume fraction of gas phase, sea water flow velocity, viscoelastic coefficient of marine riser, axial tension amplitude, the in-line and cross-flow coupling effect, and multiphase internal flow velocity have significant influences on the dynamic response characteristics of the marine viscoelastic riser. Furthermore, the maximum displacements and stresses of the marine viscoelastic riser can be increased or decreased depending on the internal flow velocity, and the critical internal flow velocities result in the increase of mode order for different cross-flow velocities. It is also demonstrated that appropriate viscoelastic coefficients are very important to effectively suppress the maximum displacements and stresses.

Highlights

Marine risers are indispensable equipment in offshore oil and gas exploitation, which connects the production platform on the surface and the subsea wellhead and provides key transmission channels transporting the drilling fluid or oil and gas. e marine risers are in a complex ocean environment and subjected to the combined actions of multiphase internal flow, its own gravity, the top tension, and a variety of external currents, such as uniform flow and shear flow, which lead to the complex force and make the marine riser have a variety of dynamic problems [1, 2]. erefore, the marine riser is the weakest and damaged component in the offshore drilling platform system
As an important form of fluid-structure interaction response, the vortex-induced vibration (VIV) of the marine riser affects the fatigue life of the structure and, sometimes, directly causes the destruction of the structure due to the large-amplitude oscillation generated by its frequencylocked resonance, which leads to the occurrence of major accidents in offshore oil and gas exploitation [3,4,5]
By simplifying the threedimensional vibration of the marine riser into a plane model, Srinil [10] studied the dynamic response of the initial plane bending and the response mechanism of vertical pipe under linear shear flow in plane based on the nonlinear theory

Summary

Introduction

Marine risers are indispensable equipment in offshore oil and gas exploitation, which connects the production platform on the surface and the subsea wellhead and provides key transmission channels transporting the drilling fluid or oil and gas. e marine risers are in a complex ocean environment and subjected to the combined actions of multiphase internal flow, its own gravity, the top tension, and a variety of external currents, such as uniform flow and shear flow, which lead to the complex force and make the marine riser have a variety of dynamic problems [1, 2]. erefore, the marine riser is the weakest and damaged component in the offshore drilling platform system. Based on the generalized integral transformation method, Ma et al [41] adopted the Timoshenko beam theory to establish the transverse vibration model of a marine riser transporting two-phase internal flow and studied the influence of different size parameters of the riser and two-phase flow characteristics parameters on the response of the riser. There have been various investigations on the dynamic behaviors of the marine riser in the literature, almost no attention has been paid to the in-line and cross-flow coupling vibration response characteristics of a marine viscoelastic riser subjected to two-phase internal flow and the combined effects of the volume fraction of gas phase, sea water flow velocity, viscoelastic coefficient of the marine riser, axial tension amplitude, and the in-line and cross-flow coupling effect taking into account both the geometric and hydrodynamic nonlinearities on vibration response characteristics. Some numerical results on the in-line and cross-flow dynamic behaviors and response characteristics of the marine viscoelastic riser varied with different parameters of the volume fraction of gas phase, sea water flow velocity, viscoelastic coefficient of the marine riser, and axial tension amplitude are displayed in detail

Dynamic Model

Hydrodynamic Forces

Numerical Results and Discussion