Local scour around two subsea pipelines in an oscillatory flow

In offshore engineering, wave generated flows are generally modelled as oscillatory flows when flow around small scale cylindrical structures are considered. The understanding of local scour around subsea pipelines under waves is important to ensure the stability of pipelines. In this study, local scour around two identical pipelines in a tandem arrangement in an oscillatory flow is investigated numerically. The flow around the pipelines is simulated by the Reynolds-averaged Navier-Stokes (RANS) equations and the local scour is predicted by solving the conservation equation of the sediment mass. The numerical model is firstly validated against experimental data. Then, the effects of the gap between the two pipelines and the KC number on the scour depth below the pipelines are examined over a wide parameter space.