Numerical investigation of hydrodynamic characteristics and local scour mechanism around submarine pipelines under joint effect of solitary waves and currents

Abstract Submarine pipelines, as an important tool for oil and gas transportation, have been distributed in offshore oil and gas fields worldwide. Under extreme waves, a large number of submarine pipelines have been damaged in the past decades. In order to investigate the effect of extreme marine environments on the pipelines, the joint effect of solitary waves and background currents on the pipelines is numerically studied in this paper by using a numerical wave tank developed with a free surface tracking approach and the immersed boundary method. The sediment transport module including packed and suspended sediment is incorporated with the flow module. In order to ensure the calculation accuracy of this model, three verification cases related to the wave propagation profile, the hydrodynamic force on the cylinder and the scour hole profile are simulated and the numerical results match the experimental and analytical results well. Given the combined wave exerts on the different pipelines, the environmental variables consider the background current velocity and wave height, and the pipeline arrangement includes the different diameters and the suspended pipeline and tandem pipeline. It is noted that the hydrodynamic characteristics, the forces and the local scour around the pipeline are closely related to the background current and the diameter and layout of the pipeline. It is anticipated that the findings in this paper will enhance our understanding of the damage mechanism of submarine pipeline by waves and may also be useful in future design practices for pipelines.