Time-varying mechanism of fluid-structure interaction vibration effects and dynamic characteristics of the cross-over pipeline when the medium flows

Abstract

The time-varying mechanism of fluid-structure interaction (FSI) vibration effects and dynamic characteristics of the cross-over pipeline with the flowing of the crude and natural gas mixture two-phase medium were revealed in this study. An active fluid finite element method (FEM) model was built for the medium that exhibited a volume ratio 1:1 and flowed through the pipeline under a velocity of 2 m/s. The standard turbulence κ-ε model was modified by incorporating the flow velocity and pressure fluctuation changes with the floating of the medium. The pipeline's FSI vibration effects and the pipeline-crossing system's dynamic characteristics were determined and then analyzed. As indicated by the research results, the medium was affected by frictional damping at the pipeline wall and energy transfer losses at the phase interface, such that irregular flow regimes were generated (i.e., slug flow and wavy flow). The flow velocity was further reduced in the 280 s, and the intervals between pressure fluctuations gradually increased. The FSI vibration effects in the middle section of the cross-over pipeline were significant, with a peak displacement response reaching 45.7538 mm while the medium flow. Notable differences and complex changes were identified in the acceleration response among the monitoring sections of the first and second spanning sections. The dynamic properties of the pipeline-crossing system changed significantly with time. The natural frequencies of the 1st to 7th modes decreased with time.In contrast, the natural frequencies of the 8th to 12th modes tended to decline with complex time-varying characteristics more notably. The methods in the respective direction exhibited time-varying characteristics. Specifically, their relative proportions of the effective mass ratio varied with time. As the research concludes, The research concludes that the flowing mechanical behavior can be more accurately expressed by modifying the standard κ-ε turbulence model using the medium's velocity changes and pressure fluctuation curves. This study can lay a theoretical foundation for gaining insights into the time-varying mechanism of the FSI vibration effects and dynamic characteristics in the cross-over pipeline.