DYNAMIC RESPONSE OF A MARINE RISER CAUSED BY SEVERE SLUGGING FLOW

A fluid-structure interaction model for a marine riser system on elastic foundation conveying severe slugging flow was developed based on the modified severe slugging transient model and theories of plane frame structure, and solved to simulate the dynamic response of a marine riser system caused by severe slugging flow using numerical methods. The Eulerian method was used to solve the equations of severe slugging flow. Galerkin's method was adopted to discretize the dynamic equations in space and Newmark-β method was employed for time-domain integration of the discretized equations. Variable time-steps were employed for higher computational efficiency and accuracy in the integration process. The comparisons of simulation results with the experimental data show that the mathematical model and numerical methods are reasonable. Detailed analysis of dynamic response, internal force, and reaction force of the hybrid riser reveals that the dynamic response of hybrid riser is closely related to the periodic characteristics of severe slugging flow, and the elastic foundation can suppress the vibration amplitude and the internal force, especially bending stress of the downward pipeline, significantly. The amplitude of high frequency vibration is large and the axial stress and bending stress oscillate acutely. These analyses are significant to guide the design of marine risers.