1. Numerical simulation of wave-induced scour and backfilling beneath submarine pipelines
David R. Fuhrman1, Cuneyt Baykal1, B. Mutlu Sumer1, Niels G. Jacobsen2, Jørgen Fredsøe1
1 Technical University of Denmark
2 Deltares

2. Outline Model description Simulation of wave-induced scour
Simulation of wave-induced backfilling
Conclusions

3. Model description Fully-coupled sediMorph model (OpenFOAM)
Jacobsen & Fredsøe (2014)
Hydrodynamic model
Incompressible Reynolds-Averaged Navier-Stokes (RANS) equations
Two-equation k-w turbulence closure (Wilcox 2006)
Sediment transport model
Engelund-Fredsøe bedload transport method
Turbulent-diffusion equation for suspended sediment concentration
Engelund-Fredsøe reference concentration
Reference level: b=3.5d (similar to Liang & Cheng 2005)

4. Model description (2) Morphological model
Sediment continuity (Exner) equation
Instantaneous bed updating (no smoothing)
Sandslide model of Roulund et al. (2005)

5. Model description (3) Model domain 40D x 10D
Frictionless rigid lid at top boundary
Wave conditions (oscillatory flow) introduced at left boundary

6. Outline Model description Simulation of wave-induced scour
Simulation of wave-induced backfilling
Conclusions

7. Wave-induced scour
Conditions chosen to match selected experimental conditions (Sumer & Fredsøe 1990, Fredsøe et al. 1992)
Pipeline diameter: D = 3 cm, grain diameter d = 0.19 mm
Warm-up period (morphology off) of 10T
KC=UmTw/D
T (s)
Um (m/s)
qmax
5.6
1.10
0.153
0.13 11
1.22
0.240
0.19 15
2.50
0.177
0.10
19.6
3.00
0.196
0.092
21.1
2.64
0.239
0.12
25.3
3.51
0.216
0.094 30
3.50
0.257
0.11

8. Scour (KC = 5.6)

9. Scour (KC = 30)

10. Summary of scour profiles

11. Summary of scour time series

12. Scour (KC = 11)
Features develop matching natural vortex ripple length (Brøker 1985):

13. Summary of scour results
Equilibrium scour:
Time scale:

14. Outline Model description Simulation of wave-induced scour
Simulation of wave-induced backfilling
Conclusions

15. Backfilling (KC = 30 to 5.6)

16. Backfilling time series
to KC = 5.6:
To KC = 15:

17. Backfilling profiles
Backfilling to KC = 5.6:
Scour with KC = 5.6:

18. Backfilling summary
Equilibrium scour:
Time scale:

19. Remarks on practical application
Utilize the time scalings:
Taking the grain size as already full scale, model and full scale morphological times may be related as:
Combining simulated scour/backfilling times give:

20. Outline Model description Simulation of wave-induced scour
Simulation of wave-induced backfilling
Conclusions

21. Conclusions
Fully-coupled RANS model for simulating scour processes beneath submarine pipelines
Hydrodynamics + turbulence description
Sediment transport (bed and suspended load) + Bed morphology
Accurate simulation of pipeline scour depths as well as scour time scales
Model predicts backfilling to profiles governed by new wave climate
Consistent with experimental findings! (Fredsøe et al. 1992)
Results published in:
Fuhrman, D.R., Baykal, C., Sumer, B.M., Jacobsen, N.G. & Fredsøe, J. (2014) Numerical simulation of wave-induced scour and backfilling processes beneat submarine pipelines. Coast. Eng. 94,

22. Animation of tsunami-induced scour ASTARTE EU FP7 project: www
Animation of tsunami-induced scour ASTARTE EU FP7 project:

23. Numerical simulation of wave-induced scour and backfilling beneath submarine pipelines
David R. Fuhrman1, Cuneyt Baykal1, B. Mutlu Sumer1, Niels G. Jacobsen2, Jørgen Fredsøe1
1 Technical University of Denmark
2 Deltares