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Predicting scour beneath subsea pipelines from existing small free span depths under steady currents

Citation

Lee, JY and McInerney, J and Cossu, R and Leong, ZQ and Forrest, AL, Predicting scour beneath subsea pipelines from existing small free span depths under steady currents, Journal of Ocean Engineering and Science pp. 1-52. ISSN 2468-0133 (In Press) [Refereed Article]


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DOI: doi:10.1016/j.joes.2017.03.001

Abstract

An equation was developed to predict current-induced scour beneath subsea pipelines in areas with small span depths, S. Current equations for scour prediction are only applicable to partially buried pipelines. The existence of small span depths (i.e. S/D < 0.3) are of concern because the capacity for scour is higher at smaller span depths. Furthermore, it is impractical to perform rectification works, such as installing grout bags, under a pipeline with a small S/D. Full-scale two-dimensional Computational Fluid Dynamics (CFD) simulations were performed using the Reynolds-averaged Navier–Stokes approach and the Shear Stress Transport k-ω turbulence model. To predict the occurrence of scour, the computed maximum bed shear stress beneath the pipe was converted to the dimensionless Shields parameter, and compared with the critical Shields parameter based on the mean sediment grain size. The numerical setup was verified, and a good agreement was found between model-scale CFD data and experimental data. Field data were obtained to determine the mean grain size, far field current velocity and to measure the span depths along the surveyed pipe length. A trend line equation was fitted to the full-scale CFD data, whereby the maximum Shields parameter beneath the pipe can be calculated based on the undisturbed Shields parameter and S/D.

Item Details

Item Type:Refereed Article
Keywords:sediment scour; subsea pipelines; small span depths; steady currents
Research Division:Engineering
Research Group:Maritime Engineering
Research Field:Maritime Engineering not elsewhere classified
Objective Division:Transport
Objective Group:Other Transport
Objective Field:Pipeline Transport
Author:Lee, JY (Mr Jun Lee)
Author:Cossu, R (Dr Remo Cossu)
Author:Leong, ZQ (Dr Zhi Leong)
Author:Forrest, AL (Dr Alexander Forrest)
ID Code:115606
Year Published:In Press
Deposited By:NC Maritime Engineering and Hydrodynamics
Deposited On:2017-04-01
Last Modified:2017-04-03
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