Arjen Luijendijk

PhD at TU Delft / Deltares

Applying Delft3D Flexible Mesh

on the Sand Motor

Lessons learned on how to set up a typical coastal

application

Work in progress

Sand Motor at the Dutch coast mega-nourishment

Area of interest: Sand Motor

Mega-nourishment of 21 mln m3

Scale of intervention:

• 2 km alongshore

• 1 km cross-shore

Sand Motor at the Dutch coast mega-nourishment

July 2011

Sand Motor at the Dutch coast mega-nourishment

March 2013

Sand Motor at the Dutch coast mega-nourishment

March 2013

September 2014

Goal

Operational hydrodynamic predictions for field measurements (6 weeks)

Existing Delft3D 4 model

• Tide

• Waves

• Morphodynamic

Understand the system you are working in

No excuses anymore…

We now have Delft3D Flexible Mesh!

Grid outline and resolution

Resolution:

Deeper water: ~300 m

Sand engine: ~17 m

Boundary conditions:

Offshore: tidal conditions

Fresh river discharges

(operational river models)

Wind

5 vertical layers

~100,000 nodes

Requires 12hrs to run 1 d

Detailed view of mesh

11

november

2014

Add complexity step-by-step

11

november

2014

Start coarse and refine step-by-step

Apply curvi grids where possible

Some first results

Validation - salinities

Figure 1: Measured and modelled salinity at observation station Hoek van Holland. Coloured dots indicate measurements every 10 minutes at 2.5, 4.5 and 9 m depth. Coloured lines indicate model results of the 5 sigma layers. Measurements have the same colour as the closest model layer.

Model warming up: interpolation to restart files

2D 3D – 5lyrs 3D – 15 lyrs

Validation - fronts Boat crew saw front passing by @ 13.24 on 18 Sept

Validation – fronts 13:02

Validation – fronts 13:17

Validation – fronts 13:32

Validation – fronts 13:47

Validation – fronts 14:02

Validation – fronts 14:17

Validation – fronts 14:32

Validation – fronts 14:47

Validation – fronts 15:02

Visualisation

NetCDF enables use of advanced visualization tools (a.o. Paraview)

Remarks

Model is not complete yet regarding:

• vertical layers, large-scale surge levels, wave effects, etc…

Model will be used for decision making on relative contribution to

hydrodynamic characteristics relevant for morphology at Sand Motor

Planning:

• Wave effects included in January 2015 (beta)

• First sediment transport simulations in March 2015 (beta)

Lessons learned

• Understand the system you are working in

• Familiarize yourself with numerical aspects in the D-Flow Flexible

Mesh engine of Delft3D Flexible Mesh

• Start coarse and refine step-by-step

• Warming up: interpolation to restart files for speed-up

• 2D 3D – 5lyrs 3D – 15 lyrs

• Time step implicit

• Check which grid points are limiting (‘Courant-modelling’)

• Saves computational times

• Apply curvi grids where possible

• Explore more advanced data for model evaluation

Questions?

Example of more

advanced data for

model evaluation

Acknowledgements:

Lisanne Braat (UU PhD)

Freek Scheel (Deltares)

Rijkswaterstaat (input data)