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Current-induced scour beneath initially elevated subsea pipelines

Lee, JY ORCID: 0000-0001-5884-7077, Hardjanto, FA ORCID: 0000-0002-9489-7474, Cossu, R, Chai, S ORCID: 0000-0001-5186-4456, Leong, ZQ ORCID: 0000-0002-0644-1822 and Forrest, AL ORCID: 0000-0002-7853-9765 2019 , 'Current-induced scour beneath initially elevated subsea pipelines' , Applied Ocean Research, vol. 82 , pp. 309-324 , doi: 10.1016/j.apor.2018.11.011.

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Abstract

When a subsea pipeline is laid on an uneven seabed, certain sections may have an initial elevation with respect to the far-field seabed, eo, and thus potentially affecting the on-bottom stability of the pipeline. This paper focuses on quantifying the effects of the upstream dimensionless seabed shear stress, θ∞, and Reynolds number, Re, on: (1) the maximum dimensionless seabed shear stress beneath the pipe, θmax, to be compared to the critical shear stress in order to determine whether scour would occur and progress towards an equilibrium state; and, (2) the dimensionless equilibrium scour depth beneath the pipe, Seq/D. Using a 2-D Reynolds averaged Navier-Stokes (RANS) approach along with the k-ω Shear Stress Transport (SST) turbulence model, a parametric study involving 243 computational fluid dynamics (CFD) simulations was conducted. The simulation results were used to develop a closed-form equation for the prediction of θmax. Subsequently, experimental measurements of Seq/D have been compiled from published literature, to develop a new closed-form equation for the prediction of Seq/D with a high correlation to the experimental data. In summary, we present two closed-form equations for the prediction of θmax and Seq/D for pipelines with an initial eo/D, which are applicable for both clear-water and live-bed conditions. The effects of θ∞ and Re have been included, albeit Re having a small influence as compared to the other parameters.

Item Type: Article
Authors/Creators:Lee, JY and Hardjanto, FA and Cossu, R and Chai, S and Leong, ZQ and Forrest, AL
Keywords: maximum seabed shear stress, equilibrium scour depth, subsea pipelines, initial pipe elevation
Journal or Publication Title: Applied Ocean Research
Publisher: Elsevier Sci Ltd
ISSN: 0141-1187
DOI / ID Number: 10.1016/j.apor.2018.11.011
Copyright Information:

Copyright 2018 Elsevier Ltd.

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