Using large-eddy simulation technique for dense particle-fluid flows, the current-induced scour is predicted for both the mono- and bidispersed systems below a horizontal submarine pipeline exposed to unidirectional flow. The simulations are four-way coupled, which implies that both solid-liquid and solid-solid interactions are taken into account. Particles are assumed to behave as viscoelastic solids during interactions with their neighboring particles, and their motion are predicted by a Lagrangian method. The interparticle normal and tangential contact forces between particles are calculated using a generalized Hertzian model. The other forces on a particle that are taken into account include gravitational pressure gradient force accounting for the acceleration of the displaced liquid, the drag force resulting from velocity difference with the surrounding liquid, and the Magnus and Saffman lift forces. The predicted scour profiles for monodispersed system are found to compare favorably with the laboratory observations. For the bidispersed system, a seepage flow underneath the pipe (which is a major factor to cause the onset of scour below the pipeline) is found to be weakened using an appropriate size for the sand bed. This fiffnding highlights the importance of the bed particle size distribution on the onset of scour below the pipelines.

1.
Mao
,
Y.
, 1986, “
The Interaction Between a Pipeline and an Erodible Bed
,” Ph.D. thesis, Technical University of Denmark, Lyngby, Denmark.
2.
Kjeldsen
,
S. P.
,
Gjørsvik
,
O.
,
Bringaker
,
K. G.
, and
Jacobsen
,
J.
, 1973, “
Local Scour Near Offshore Pipelines
,”
Second International Conference on Port and Ocean Engineering. Under Arctic Conditions
, Reykjavik, Iceland, pp.
308
331
.
3.
Sumer
,
B. M.
,
Truelsen
,
C.
,
Sichmann
,
T.
, and
Fredsøe
,
J.
, 2001, “
Onset of Scour Below Pipelines and Self-Burial
,”
Coast. Eng.
,
42
, pp.
313
335
. 0378-3839
4.
Van Beek
,
F. A.
, and
Wind
,
H. G.
, 1990, “
Numerical Modelling of Erosion and Sedimentation Around Offshore Pipelines
,”
Coast. Eng.
,
14
, pp.
107
128
. 0378-3839
5.
Li
,
F.
, and
Cheng
,
L.
, 2001, “
Prediction of Lee-Wake Scouring of Pipelines in Currents
,”
J. Waterway, Port, Coastal, Ocean Eng.
0733-950X,
127
, pp.
106
112
.
6.
Zamankhan
,
P.
, and
Huang
,
J.
, 2007, “
Localized Structures in Vertically Vibrated Granular Materials
,”
ASME Trans. J. Fluids Eng.
0098-2202,
129
, pp.
236
244
.
7.
Zamankhan
,
P.
,
Huang
,
J.
, and
Mousavi
,
S. M.
, 2007, “
Large Eddy Simulations of a Brine-Mixing Tank
,”
ASME J. Offshore Mech. Arct. Eng.
0892-7219,
129
, pp.
176
187
.
8.
Misra
,
A.
, and
Pullin
,
D. I.
, 1997, “
A Vortex-Based Subgrid Model for Large-Eddy Simulation
,”
Phys. Fluids
1070-6631,
9
, pp.
2443
2454
.
9.
Kosovic
,
B.
, 1997, “
Subgrid-Scale Modeling for the Large-Eddy Simulation of High-Reynolds-Number Boundary Layer
,”
J. Fluid Mech.
0022-1120,
336
, pp.
151
182
.
10.
Maxey
,
M. R.
, and
Riley
,
J. J.
, 1983, “
Equation of Motion for a Small Rigid Sphere in a Nonuniform Flow
,”
Phys. Fluids
0031-9171,
26
, pp.
883
889
.
11.
Loth
,
E.
, 2000, “
Numerical Approaches for Motion of Dispersed Particles, Droplets and Bubbles
,”
Prog. Energy Combust. Sci.
0360-1285,
26
, pp.
161
223
.
12.
Shiller
,
L.
, and
Naumann
,
U.
, 1933, “
Uber die grundlegenden Berechungen bei der Schwerkraftaufbereitung
,”
Z. Ver. Dtsch. Ing.
0341-7255,
77
, pp.
318
320
.
13.
Crowe
,
C.
,
Sommerfeld
,
M.
, and
Tsuji
,
Y.
, 1998,
Multiphase Flows With Droplets and Particles
,
CRC
,
Boca Raton, FL
.
14.
Derksen
,
J. J.
, 2003, “
Numerical Simulation of Solids Suspension in a Stirred Tank
,”
AIChE J.
0001-1541,
49
, pp.
2700
2714
.
15.
Zamankhan
,
P.
, and
Bordbar
,
M. H.
, 2006, “
Complex Flow Dynamics in Dense Granular Flows Part I: Experimentation
,”
ASME J. Appl. Mech.
0021-8936,
73
, pp.
648
657
.
16.
Zamankhan
,
P.
, and
Huang
,
J.
, 2007, “
Complex Flow Dynamics in Dense Granular Flows Part II: Simulation
,”
ASME J. Appl. Mech.
0021-8936,
74
, pp.
691
702
.
17.
Zamankhan
,
P.
, 2008, “
Shock Waves in Dense Flows Down a Chute
,”
Shock Waves
0938-1287,
17
, pp.
337
349
.
18.
Johnson
,
K. L.
,
Kendall
,
K.
, and
Roberts
,
A. D.
, 1971, “
Surface Energy and the Contact of Elastic Solid
,”
Proc. R. Soc. London, Ser. A
1364-5021,
324
, pp.
301
313
.
19.
Stone
,
H. L.
, 1968, “
Iterative Solution of Implicit Approximation of Multi-dimensional Partial Differential Equations
,”
SIAM (Soc. Ind. Appl. Math.) J. Numer. Anal.
0036-1429,
5
, pp.
530
538
.
20.
Dormand
,
J. R.
, and
Prince
,
P. J.
, 1980, “
A Family of Embedded Runge–Kutta Formulae
,”
J. Comput. Appl. Math.
0377-0427,
6
, pp.
19
26
.
21.
Sumer
,
B. M.
,
Jensen
,
H. R.
, and
Fredose
,
J.
, 1988, “
Effect of Lee-Wake on Scour Below Pipeline in Current
,”
J. Waterway, Port, Coastal, Ocean Eng.
0733-950X,
114
, pp.
599
614
.
You do not currently have access to this content.