Prediction of Maximum Scour Depth at Submarine Pipelines

TLDR

Existing scour depth estimation methods are limited, and the undisturbed bed shear stress equals the critical shear stress for sediment entrainment. The study reviews local scour literature and proposes an empirical function linking gap flow through the scour hole to scour depth under given flow conditions. The authors derived this empirical function from experimental data, relating the amount of gap flow to scour depth for specified flow conditions. The function predicts maximum scour depth, indicating that equilibrium scour occurs on a plane bed under unidirectional flow with no sediment transport away, and the predictions agree well with experimental results.

Abstract

This paper examines and reviews published results relating to local scour around submarine pipelines. It highlights the limitations of existing methods for estimating scour depth at the pipeline. Based on experimental results, the study proposes an empirical function relating the amount of gap flow through the scour hole for given flow conditions. With the aid of this function, it is possible to predict the maximum Scour depth at submarine pipelines for given flow and geometric boundary conditions. Published results suggest that the maximum equilibrium scour depth occurs when the pipeline is just lying on a plane bed and subjected to a pure unidirectional current. The undisturbed bed shear stress is equal to the critical shear stress for sediment entrainment. This condition implies that there is no general sediment transport away from the pipeline. The predicted maximum scour depth using the iterative method proposed in this study compares well with experimental results.