Effect of Spoilers on Scour at Submarine Pipelines

Abstract

This paper investigates the effect of a spoiler on local scour around submarine pipelines. Experiments conducted in a unidirectional flow show that the spoiler is capable of increasing both the scour depth beneath (tunnel erosion) and downstream of (lee erosion) the pipeline. The increase is related to the location of the spoiler compared with the direction of the incoming flow. The spoiler attached on top of the pipeline is effective in increasing the blockage to the incoming flow, which deflects a large proportion of the flow downward beneath the pipe, resulting in an increased scour depth. The increase in lee erosion, due to the protrusion of the spoiler above the pipeline, is important in the stimulation of the self-burial potential of the submarine pipeline. Spoilers attached to the lower half of the pipeline effected the formation of a wake zone beneath the pipe, which acts to deflect the flow downward, causing the formation of a deeper tunnel scour hole.