Prediction of Lee-Wake Scouring of Pipelines in Currents

Abstract

A numerical model for the equilibrium profiles of the local scour around pipelines is developed. The numerical model solves the turbulence flow field around the pipeline using a large eddy simulation model in a curvilinear coordinate system with frequent updates of the scoured seabed. The iteration method of determining the equilibrium scour profile is based on the assumption that the equilibrium seabed shear stress is equal to the critical shear stress of the sediment for clear-water scour or the undisturbed seabed shear stress for live-bed scour. Based on this assumption the model predicts the equilibrium scour hole without using any sediment transport formula. The calculation results clearly reveal that the lee wakes behind the pipeline contribute significantly to the local scour hole development, especially to the gentle scour slope observed in experiments. The predicted maximum scour depth and the shape of the scour hole compare favorably with the experimental data published in the literature.