Numerical Model for Local Scour under Offshore Pipelines
Publication: Journal of Hydraulic Engineering
Volume 125, Issue 4
Abstract
A numerical model, based on potential-flow theory is proposed for simulating the equilibrium scour hole formed by unidirectional flow underneath offshore pipelines. The model employs a finite-difference method to solve the Laplace equation in terms of velocity potential in a curvilinear coordinate system. A boundary adjustment technique based on the Newton-Raphson method is used to calculate the free boundary formed by the eroded seabed by means of the equilibrium of all forces acting on a sediment particle on a sloping bed. Because the solution of flow field and adjustment of the seabed topography are carried out in an iterative manner, the model takes into account the interactions between the flow, pipe, and the seabed. The comparison of the present model with empirical formulas on the prediction of the maximum scour depth indicates that the present model is useful for approximate estimation of scour depth at a pipeline on the seabed for the case of clear-water scour.
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References
1.
Allen, J. R. L. ( 1982). “Simple models for the shape and symmetry of tidal sand waves: 1. Statically stable equilibrium forms.” Marine Geology, 48, 31–49.
2.
Bijker, E. W., and Leeuwestein, W. ( 1984). “Interaction between pipelines and the seabed under the influence of waves and currents.” Seabed Mech., Proc., Symp. IUTAM/IUGG. Int. Union of Theoretical Appl. Mech./Int. Union of Geology and Geophys., Graham and Trotman, London, 235–242.
3.
Chao, J. L., and Hennessy, P. V. ( 1972). “Local scour under ocean outfall pipe-lines.” J. Water Pollution Control Fed., 44(7), 1443–1447.
4.
Chiew, Y. M. (1990). “Mechanics of local scour around submarine pipelines.”J. Hydr. Engrg., ASCE, 116(4), 515–529.
5.
Chiew, Y. M. (1991). “Prediction of maximum scour depth at submarine pipelines.”J. Hydr. Engrg., ASCE, 117(4), 452–466.
6.
Chiew, Y. M., and Parker, G. (1994). “Incipient sediment motion on non-horizontal slopes.”J. Hydr. Res., Delft, The Netherlands, 32(5).
7.
Crank, J. ( 1984). “Free and moving boundary problems.” Oxford Science Publications, Oxford.
8.
Dyer, K. R. ( 1986). Coastal and estuarine sediment dynamics . Wiley, Chichester, England, 118–119.
9.
Fredsøe, J., and Deigaard, R. ( 1992). “Mechanics of coastal sediment transport.”World Scientific, River Edge, N.J.
10.
Fredsøe, J., and Hansen, A. E. ( 1984). “Lift forces on pipelines in steady flow.” DCAMM Rep. 295, Technical University of Denmark, Denmark.
11.
Hansen, E. A., Fredsøe, J., and Ye, M. ( 1986). “Two-dimensional scour below pipelines.” Proc., 5th Int. Symp. on Offshore Mech. and Arctic Engrg., ASME, Tokyo, 670–678.
12.
Ibrahim, A., and Nalluri, C. ( 1986). “Scour prediction around marine pipelines.” Proc., 5th Int. Symp. on Offshore Mech. and Arctic Engrg., ASME, Tokyo, 679–684.
13.
Kjeldsen, S. P., Gjørsvik, O., Bringaker, K. G., and Jacobsen, J. ( 1973). “Local scour near offshore pipelines.” Proc., 2nd Int. Conf. on Port and Oc. Engrg. under Arctic Conditions, University of Iceland, Iceland, 308–331.
14.
Kovacs, A., and Parker, G. ( 1994). “A new vectorial bedload formulation and its application to the time evolution of straight river channels.” J. Fluid Mech., Cambridge, England, 267, 153–183.
15.
Leeuwestein, W., Bijker, E. A., Peerbolte, E. B., and Wind, H. G. ( 1985). “The natural selfburial of submarine pipelines.” Proc., 4th Int. Conf. on Behaviour of Offshore Structure (BOSS), Elsevier Science, New York, 717–728.
16.
Mao, Y. ( 1986). “The interaction between a pipeline and an erodible bed.” Series Paper, Institute of Hydrodynamics and Hydraulic Engineering, Technical University of Denmark, Denmark.
17.
Meyer-Peter, E., and Müller, R. ( 1948). “Formula for bed load transport.” Proc., 2nd Int. Assoc. Hyd. Res., 3, 39–46.
18.
Streeter, V. L. ( 1971). Fluid Mechanics . 5th Edition. McGraw Hill, New York.
19.
Sumer, B. M., and Fredsøe, J. (1988a). “Interaction between vibrating pipe and erodible bed.”J. Wtrwy., Port, Coast., and Oc. Engrg., ASCE, 114(5), 599–614.
20.
Sumer, B. M., Jensen, H. R., Mao, Y., and Fredsøe, J. (1988b). “Effect of lee-wave on scour below pipelines in current.”J. Wtrwy., Port, Coast., and Oc. Engrg., ASCE, 114(1), 81–92.
21.
Thompson, J. F., Thames, F. C., and Mastin, C. W. ( 1974). “Automatic numerical generation of body-fitted curvilinear coordinate system for field containing any number of arbitrary two-dimensional bodies.” J. Computational Physics, 15, 299–319.
22.
Whitehouse, R. J. S., and Hardisty, J. ( 1988). “Experimental assessment of two theories for the effect of bed slope on the threshold of bedload transport.” Marine Geology, 79, 135–139.
Information & Authors
Information
Published In
Journal of Hydraulic Engineering
Volume 125 • Issue 4 • April 1999
Pages: 400 - 406
History
Received: Jan 13, 1998
Published online: Apr 1, 1999
Published in print: Apr 1999
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