Coupling effect of vortex-induced vibration and local scour of double tandem pipelines in steady current

Abstract

Submarine pipelines are critical for offshore oil and gas production. However, when these pipelines are located on the seabed, they are susceptible to simultaneous occurrences of local scour and vortex-induced vibration, which impose a significant threat to pipeline safety and integrity. To address this issue, our study investigates the coupling effect of vortex-induced vibration and local scour using Flow-3D. Specifically, we explore the influence of the gap ratio on the vibration and local scour of the pipelines. Our findings reveal that the horizontal gap between the pipelines significantly affects the depth and profile of the scour pits. When the horizontal gap ratio is G/D = 2, pipeline vibrations promote the merging of scour pits. And as the interference effect between the two pipelines weakens with the increase of horizontal gap, the depth difference of scour pits below the fixed and vibrating double pipelines gradually decreases. Moreover, when G/D ≥ 3, the vortices falling off the upstream and downstream pipelines are discharged separately. This results in weak interference between the pipelines and the formation of two independent scour pits.