Pilot application of Delft3D Flexible Mesh

1. 13-7-2015
Challenge the future
Delft
University of
Technology
Pilot application of Delft3D Flexible Mesh
Assisting a field campaign at the Sand Motor
Arjen Luijendijk, Lisanne Braat, Niek Waagmeester, Freek Scheel,
Matthieu de Schipper, Marcel Stive

2. 2
Sand Motor (ZM) at the Dutch coast
Area of interest: Sand Motor
Mega-nourishment of 21 mln m3
Scale of intervention:
• 2 km alongshore
• 1 km cross-shore
Large signal-to-noise ratio

3. 3
Aerial photograph 3D view of measured bed levels
Sand Motor – Morphological evolution

4. 4
Motivation – Field campaign MegaPEX
Multi-disciplinary field measurements for 6 weeks – Sept14
Goal: Operational hydrodynamic
predictions for field measurements
Dye experiment

5. 5
Coastal processes around the ZM
Hydrodynamics
• Tidal currents
• Wind- and wave driven
• Fresh river outflow
Waves
• From SW and NW
Sediments
• Sandy shores
• Cohesive sediments from river
Rotterdam
Delft
World Forum
Curvilinear - Zeedelta model
No 3D operational model available
covering both river mouth and ZM

6. 6
Computational mesh
Boundary conditions
• Tidal conditions
• Fresh river discharges
• Wind
Resolution
• Deeper water: ~300 m
• Sand engine: ~17 m
Numerics
• ~100,000 nodes
• 5 layers à 15 layers

7. 7
Delft3D - Flexible Mesh
Benefits using Flexible Mesh compared to Curvilinear
• Optimal resolution where needed
• Optimisation of #grid cells (~50% of curvi grid)
• Variable time step
• Parallelization
• Finite volume
• Implicit time integration
• Both BMI compliant – communication with other software
• Both are Open Source

8. 8
Model results – Surface salinities
Validation on remote observations

9. 9
Model validation - fronts
• X-Band Radar images
A good qualitative match was found and
hence model results were used thereafter

10. 10
Findings
• ZM is influenced by hydrodynamics on multiple scales
• System understanding on multiple scales is a prerequisite when conducting
local measurements
• Flexible Mesh allows modeling this interaction on multiple scales
• Validation is taking place with MegaPEX data; first results very promising
• Large added value compared to Delft3D-curvilinear
• Flexible resolution, # of grid cells, parallel

11. 11
Outlook
• Waves (unstructured SWAN) and morphology are being added
• beta version in September
• First step towards seamless modelling for coastal morphology
• Forcing-dependent processes
• Forcing-dependent level of
process representation
• Optimised predictions enables
ensemble runs
Seamless modelling

12. 12
Meirelles: session 3D
De Vries: session 15a
Model combines multi-disciplinary research
Valuable tool in STW-NatureCoast
Transports on
lower shoreface
Sediment
grading
Tidal
characteristics
Aeolian
transports
Hydrology
Cohesive
sediments
Radermacher: session 8F
Hydrodynamics
Benthos

13. 13
Questions / suggestions?
Acknowledgements:
• Lisanne Braat (UU PhD)
• Niek Waagmeester (MSc)
• Freek Scheel (Deltares)
• Rijkswaterstaat (data)
• STW – NatureCoast
• NEMO