Numerical Model for Wave-Induced Scour below a Submarine Pipeline
Publication: Journal of Waterway, Port, Coastal, and Ocean Engineering
Volume 131, Issue 5
Abstract
A vertical two-dimensional numerical model for local scour beneath an offshore pipeline exposed to waves is developed in this study. Waves are modeled as sinusoidally oscillatory flows, and the phase-resolved velocity field around the pipeline is simulated by solving the Reynolds-averaged Navier-Stokes equations with a turbulence closure. Both suspended and bed loads of sediment transport are considered in the model. A special technique for coupling the solution of the flow field to the scour calculation is developed to accommodate different timescales of the flow and morphological changes. The seabed morphology calculation is based on the period-averaged sediment transport rate with a morphological time step that is chosen by designating a maximum allowable bed deformation in each update. Numerical tests indicate that this technique significantly reduces the computational costs and is of acceptable accuracy. A sand-slide method is employed after each bed update to smooth out small bed irregularities. The model is applied to simulate three cases of wave-induced scour below a pipeline where laboratory measurements were published in the literature. The predicted scour-hole profiles compare favorably with the laboratory observations.
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Acknowledgments
The authors would like to acknowledge the support from Australia Research Council through ARC Discovery Projects Program Grant No. DP0210660.
References
Brørs, B. (1999). “Numerical modeling of flow and scour at pipelines.” J. Hydraul. Eng., 125(5), 511–523.
Cevik, E., and Yüksel, Y. (1999). “Scour under submarine pipelines in waves in shoaling conditions.” J. Waterw., Port, Coastal, Ocean Eng., 125(1), 9–19.
Chao, J. L., and Hennessy, P. V. (1972). “Local scour under ocean outfall pipe-lines.” J. Water Pollut. Control Fed., 44(7), 1443–1447.
Chiew, Y.-M. (1991). “Prediction of maximum scour depth at submarine pipelines.” J. Hydraul. Eng., 117(4), 452–466.
Fredsøe, J., and Sumer, B. M. (1997). “Scour at the round head of a rubble-mound breakwater.” Coastal Eng., 29, 231–262.
Fredsøe, J., Sumer, B. M., Laursen, T. S., and Pedersen, C. (1993). “Experimental investigations of wave boundary layers with a sudden change in roughness.” J. Fluid Mech., 252, 117–145.
Hansen, E. A., Fredsøe, J., and Mao, Y. (1986). “Two-dimensional scour below pipelines.” Proc., Fifth Int. Symp. on Offshore Mech. and Arctic Engineering, Vol. 1, ASME, New York, 670–678.
Jensen, J. H., and Fredsøe, J. (2001). “Sediment transport and backfilling of trenches in oscillatory flow.” J. Waterw., Port, Coastal, Ocean Eng., 127(5), 272–281.
Leeuwestein, W., and Wind, H. G. (1984). “The computation of bed shear in a numerical model.” Proc., 19th Int. Conf. on Coastal Engineering, ASCE, Houston, 1685–1702.
Lei, C., Cheng, L., and Kavanagh, K. (1999). “A finite difference solution of the shear flow over a circular cylinder.” Ocean Eng., 27(3), 271–290.
Li, F., and Cheng, L. (1999). “Numerical model for local scour under offshore pipelines.” J. Hydraul. Eng., 125(4), 400–406.
Li, F., and Cheng, L. (2001). “Prediction of lee-wake scouring of pipelines in currents.” J. Waterw., Port, Coastal, Ocean Eng., 127(2), 106–112.
Liang, D., and Cheng, L. (2005). “Numerical modeling of scour below a pipeline in currents.” Coastal Eng., 52(1), 25–42.
Liang, D., Cheng, L., and Li, F. (2005). “Numerical modeling of scour below a pipeline in currents. II: Scour simulation.” Coastal Eng., 52(1), 43–62.
Menter, F. R. (1993). “Zonal two equation turbulence models for aerodynamic flows.” Proc., AIAA 24th Fluid Dynamics Conf., Reston, Va., 1–21.
Sumer, B. M., and Fredsøe, J. (1990). “Scour below pipelines in waves.” J. Waterw., Port, Coastal, Ocean Eng., 116(3), 307–323.
Sumer, B. M., and Fredsøe, J. (2000). “Experimental study of 2D scour and its protection at a rubble-mound breakwater.” Coastal Eng., 40(1), 59–87.
Sumer, B. M., and Fredsøe, J. (2001). “Wave scour around a large vertical circular cylinder.” J. Waterw., Port, Coastal, Ocean Eng., 127(3), 125–134.
Sumer, B. M., Jensen, B. L., and Fredsøe, J. (1991). “Effect of a plane boundary on oscillatory flow around a circular cylinder.” J. Fluid Mech., 225, 271–300.
Sumer, B. M., Jensen, H. R., Mao, Y., and Fredsøe, J. (1988). “Effect of lee-wake on scour below pipelines in current.” J. Waterw., Port, Coastal, Ocean Eng., 114(5), 599–614.
Sumer, B. M., Laursen, T. S., and Fredsøe, J. (1993). “Wave boundary layers in a convergent tunnel.” Coastal Eng., 20, 317–342.
van Beek, F. A., and Wind, H. G. (1990). “Numerical modelling of erosion and sedimentation around pipelines.” Coastal Eng., 14, 107–128.
van Rijn, L. C. (1986). “Mathematical modeling of suspended sediment in nonuniform flows.” J. Hydraul. Eng., 112(6), 433–455.
van Rijn, L. C. (1987). “Mathematical modeling of morphological processes in the case of suspended sediment transport.” Delft Hydr. Communication No. 382.
Wilcox, D. C. (1994). “Simulation of transition with a two-equation turbulence model.” AIAA J., 32(2), 247–255.
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© 2005 ASCE.
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Received: Jun 7, 2004
Accepted: Feb 24, 2005
Published online: Sep 1, 2005
Published in print: Sep 2005
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