Numerical study of local scour of subsea pipelines in combined steady and oscillatory flow

Submarine pipelines have played a significant role in coastal engineering, marine engineering, and offshore engineering to transport offshore oil and gas to shore. Over the past decades, identifying the cause of pipeline failure has been a top interest of many researchers. Local scour is reported to be one of the main causes that threaten the safety of subsea pipelines. A great number of experimental and numerical studies have been performed to investigate local scour around subsea pipelines. Oscillatory and steady flows are commonly used to model flow near the sea floor induced by the motion of waves and currents, respectively. However, the studies of local scour around combined steady and oscillatory flow are limited. In this study, local scour around subsea pipelines under combined steady and oscillatory flow is investigated using numerical method. The numerical model comprises RANS flow model, k-ω turbulence model, sediment transport model and seabed evolution model. The effects of the combined flow ratio of the steady to oscillatory flow velocities on the scour are quantified and discussed.