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NUMERICAL SIMULATION OF WAVE-INDUCED SCOUR AND BACKFILLING BENEATH SUBMARINE PIPELINES David R. Fuhrman 1, Cuneyt Baykal 1, B. Mutlu Sumer 1, Niels G.

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Presentation on theme: "NUMERICAL SIMULATION OF WAVE-INDUCED SCOUR AND BACKFILLING BENEATH SUBMARINE PIPELINES David R. Fuhrman 1, Cuneyt Baykal 1, B. Mutlu Sumer 1, Niels G."— Presentation transcript:

1 NUMERICAL SIMULATION OF WAVE-INDUCED SCOUR AND BACKFILLING BENEATH SUBMARINE PIPELINES David R. Fuhrman 1, Cuneyt Baykal 1, B. Mutlu Sumer 1, Niels G. Jacobsen 2, Jørgen Fredsøe 1 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 -  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=U m T w /DT (s)U m (m/s)  max

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 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:

23 NUMERICAL SIMULATION OF WAVE-INDUCED SCOUR AND BACKFILLING BENEATH SUBMARINE PIPELINES David R. Fuhrman 1, Cuneyt Baykal 1, B. Mutlu Sumer 1, Niels G. Jacobsen 2, Jørgen Fredsøe 1 1 Technical University of Denmark 2 Deltares


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