Presentation by Ap Van Dongeren, Deltares, The Netherlands, at the Delft3D - User Days (Day 3: Sediment transport and morphology), during Delft Software Days - Edition 2018. Wednesday, 14 November 2018, Delft.

1. 14 November 2018
Implementation and verification
of 2D coastal morphodynamic
module in Delft3D FM
Ap van Dongeren,
Arjen Luijendijk, Johan Reyns,
Arthur van Dam, Björn Röbke,
Marlies van der Lugt and Matthijs Gawehn

2. Motivation
• Delft3D FM Suite is to replace Delft3D 4 Suite as Deltares solver
for hydrodynamics, morphology and water quality
• Large effort in Delft3D FM development so far but 2D morphology
module was not ready for use yet
• Concerted effort to:
• Migrate 2D Delft3D (curvilinear) and XBeach morphodynamic
physics to Delft3D FM
• Parallelize Flow-Sed-Wave for high-performance computing
• Verify performance relative to Delft3D 4 Suite
14 November 2018

3. 2D Morphodynamics included
• Sediment transport formulations in numerous flavors:
• Current driven suspended transport:
Depth averaged advection-diffusion equation
• Bed updating:
Exner equation with morphological acceleration factor
• Avalanching
Avalanching volumes based on exceedance of critical slope
contributing directly to bed load
Flow applicable Flow-Wave applicable
Meyer-Peter-Mueller (1948)
Engelund-Hansen (1967)
Ashida-Michiue (1974)
Wilcock-Crowe (2003)
Wang/Fredsoe
Gaeuman et. al. (2009)
…
Bijker (1971)
Van Rijn (1993)
Soulsby – Van Rijn (1997)
Van Rijn (2007)

4. 2D Morphodynamics included
• Sediment transport formulations in numerous flavors:
• Current driven suspended transport:
Depth averaged advection-diffusion equation
• Bed updating:
Exner equation with morphological acceleration factor
• Avalanching
Avalanching volumes based on exceedance of critical slope
contributing directly to bed load
Flow applicable Flow-Wave applicable
Meyer-Peter-Mueller (1948)
Engelund-Hansen (1967)
Ashida-Michiue (1974)
Wilcock-Crowe (2003)
Wang/Fredsoe
Gaeuman et. al. (2009)
…
Bijker (1971)
Van Rijn (1993)
Soulsby – Van Rijn (1997)
Van Rijn (2007)
Van Thiel – Van Rijn (2008)

5. Verification cases
1. Van Rijn Trench
2. Visser sand dike breaching
3. Tombolo formation behind shore parallel breakwater
4. Tidal inlet evolution
5. Development of tidal channels in estuary

6. 1 Trench migration experiment (Van Rijn, 1985)
Objective:
Calculate evolution of steep-sided trench cut in sand bed of flume
after 15 hours
Simulation setup:

7. 1 Trench migration experiment (Van Rijn, 1985)
Results:
•Good agreement
between Delft3D 4 and
Delft3D FM in 2D model
• But not with
measurements:
• 3D
hydro/morphodynamics
needed here.

8. 2 Sand dike breaching (Visser, 1998)
Hs ~0
Ini waterl evel ~2.75 m+NAP
D50 0.3 mm
Sed. Transport
formulation
vanRijn1993/ Van
Thiel van Rijn
Morfac 1
Field case:
Dune breach ZWIN: Visser (1998)
• Flow driven erosion
• 2-dimensional avalanching

9. 3 Tombolo formation behind breakwater
Tidal amplitude 1.5 m
Hs 2 m
Tp 10 s
Wave dir 270° (normal wave
incidence)
D50 0.2 mm
Sed. Transport
formulation
vanRijn1993/2007
Morphological
time
~3 months
Morfac 25
Morphology around a breakwater

10. 3 Tombolo – ts = 0.75 s; DtUser 30 s
Time step: 0.75 s
Comp. time: ~5.5 h
Sim. time: 95 h
Morfac: 25
Mor. Time: 99 d
Time step: 0.75 s
Comp. time: ~4 h
Sim. time: 95 h
Morfac: 25
Mor. Time: 99 d

11.  Larger time step causes vertical differences near shoreline
 Mass balance issue remaining (working on it!)
3 Tombolo – ts = 5 s; DtUser 30 s
Time step: 5 s
Comp. time: ~1.5 h
Sim. time: 95 h
Morfac: 25
Mor. Time: 99 d
Time step: 5 s
Comp. time: ~35 min
Sim. time: 95 h
Morfac: 25
Mor. Time: 99 d

12. 4 Tidal inlet evolution
11 december 2018
60 km

13. 4 Tidal inlet – Delft3D 4 vs. Delft3D FM (morfac 50)
Comp time = 41 hrs comp time = 35 hrs

14. 11 december 2018
4 Tidal inlet – Impact of DtMax (morfac 50)
 Reasonable results with Delft3D FM, also with a variable time step and a
relatively large DtMax of 30 s
35 hr
18 hr
25 hr
22 hr
(Delft3D 4 = 41h)

15. 4 Tidal inlet – Combined impact (DtMax & morfac)
 High morfac with small DtMax produces similar results as small morfac with
high DtMax in Delft3D FM
-> High morfac with small DtMax is 2x as fast.
Comp time = 35 hrs comp time = 18 hrsComp time = 35 hrs comp time = 82.5 hrs

16. 5 Walsoorden – Model domain
Water level
boundary
Velocity
boundary

17. 5 Walsoorden
Morfac 25
20
Delft3D 4 Delft3D FM
Delft3D4 - Delft3D FM =
 Similar results but vertical
differences
Sim time 83 h

18. 5 Walsoorden
Morfac 50
21
Delft3D 4 Delft3D FM
Delft3D4 – Delft3D FM =
 Delft3D 4 and Delft3D FM
behave similarly with
increasing morfac
Sim time 45 h

19. 5 Walsoorden
Morfac 75
22
Delft3D 4 Delft3D FM
Delft3D4 – Delft3D FM =
 Reasonable match
 Almost linear scaling
Sim time 32 h

20. Parallelization Flow-sed-mor-wave
• Parallelization builds upon the existing D-Flow FM techniques.
• Sediment transport
• Morphological bed updates
• Dredging and dumping.
• Morphological boundary conditions.
• Arbitrary partitioning
• Now parallelized with Flow, Waves in progress

21. Tidal Inlet (D-Flow FM + D-Morphology)
Sequential

22. Tidal Inlet (D-Flow FM + D-Morphology)
Parallel, 3 partitions

23. Automatic partitioning
3 partitions: 11 partitions:
• Automatic partitioning guarantees optimal load balancing of unstructured grid.
• Partitioning can also be adjusted manually.
• Output files are merged automatically

24. Tidal Inlet (D-Flow FM + D-Morphology)
Partition check
31st October 2017 27
3 partitions, configuration a
11 partitions, configuration a3 partitions, configuration c
3 partitions, configuration b

25. Conclusions and remaining issues
• Functionality has been transferred from Delft3D 4 and is available
in Delft3D FM
• Delft3D FM morphological results look very similar to Delft3D 4
results, especially for small time steps
• High morfacs are possible
• Delft3D FM is faster than Delft3D 4, especially for high morfacs
and small time steps
• Ongoing validation and checking, but
• READY FOR APPLICATION