Hydrodynamic Coefficients of a Submarine Pipeline Based on Scour Simulation with CFD at High Reynolds Number

Altered flow fields around submarine pipelines cause sediment scour beneath them, and the changing sediment profile is likely to feed back to fluid fields. However, the feedback mechanisms during and after the scour process as well as its impacts on hydrodynamic forcing on the pipeline remain unclear. This work applies two-dimensional fluid–sediment coupled modeling based on computational fluid dynamics (CFD) to study hydrodynamic coefficients of submarine pipelines, vortex shedding, and scour profiles at high Reynolds number. Results indicate that vortex shedding is dominant on the upper side of the pipeline at high flow velocities, while vortices on the underside gradually dissipate due to sediment accumulation downstream of the pipeline. This asymmetric vortex shedding leads to a net downward lifting force on the pipeline, resulting in negative lifting coefficients. Furthermore, scour initiated at high flow velocities can lead to sustained vortex shedding that imposes dynamic loading on the pipeline even under subsequently moderate flow conditions.