Numerical investigation of dynamic response of a pipeline-riser system caused by severe slugging flow

Internal two-phase Flow Induced Vibration (FIV) is significantly important to secure the reliability and integrity of the piping systems in processing/engineering systems. To predict the dynamic behavior of a pipeline-riser system caused by Severe Slugging (SS), a fluid-structure interaction model was developed involving SS transient model and theories of plane frame structure. In numerical solutions, Euler's method was used to solve the equations of SS model, and Galerkin's method was adopted to discretize the dynamic equations in space, and Newmark 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 verification experiments were performed to study the characteristics of SS and piping vibrations. The results show that the model predictions are in agreement with the experiment data basically. Detailed analysis of the simulation results reveals that the dynamic response of the pipeline-riser system is closely related to the periodic characteristics of SS. The elastic foundation can suppress the vibration amplitude and the internal force of the declined pipe, while the bending moment can be transferred to the riser, which can induce the intense bending vibration of the riser. The shearing force and bending moment of the declined pipe on the elastic foundation vary in large range when the slug heads and tails are passing through. The results indicated vulnerable spots and components of a pipeline-riser system when SS appear, which are significant to the safety and health of piping systems.