DSD-INT 2014 - Symposium Next Generation Hydro Software (NGHS) - Venice Lagoon 3 (estuarine), Giselle Menel Lemos, Technital

Tuesday, November 4, 2014

NEXT GENERATION MODELLING APPLIED TO THE VENICE LAGOON

2nd BATCH PILOT CASE

G.T. Menel Lemos, E. Jeradi

Next Generation Hydro Software Symposium – 2014


Next Generation Modelling applied to the Venice Lagoon

VENICE LAGOON: SENSITIVE ENVIRONMENT

Venice Town

Surface of 550 km2

8% of land

11% of channels

80% of mud flats, tidal

shallows and salt

marshes

Lido Inlet

Malamocco Inlet

Chioggia Inlet


Next Generation Modelling applied to the Venice Lagoon - 1ST BATCH PILOT CASE

TASK 1: Delft3D-FLOW D-Flow FM*: CONVERSION

* D-Flow FM = hydrodynamic simulation engine of Delft3D Flexible Mesh



TASK 2: Delft3D-FLOW D-Flow FM: WATER LEVELS



TASK 2: Delft3D-FLOW D-Flow FM: FLUXES


Next Generation Modelling applied to the Venice Lagoon – 2nd BATCH PILOT CASE

1. Define curvilinear grid for all the main channels

D-Flow FM VENICE MODEL: MESH CREATION


Next Generation Modelling applied to the Venice Lagoon - 2nd BATCH PILOT CASE

1. Define curvilinear grid for all the main channels 2. and sea area (with different resolutions)




1. Define curvilinear grid for all the main channels 2. and sea area (with different resolutions) 3. Define mesh of marshlands (based on samples)





1. Define curvilinear grid for all the main channels 2. and sea area (with different resolutions) 3. Define net of marshlands (based on samples) 4. Define net in the flat areas



D-Flow FM VENICE MODEL: ORTHOGONALITY



~ 170.000 nodes 400.000 links

D-Flow FM VENICE MODEL: COMPLETE MESH



D-Flow FM VENICE LAGOON: NORTHERN PART



NEW D-Flow FM VENICE MODEL: BATHYMETRY



NEW D-Flow FM VENICE MODEL: BATHYMETRY



D-FLOW VENICE MODEL: NORTHERN PART NEW D-Flow FM VENICE LAGOON MODEL: GRID OPTIMIZATION



NEW D-Flow FM VENICE TOWN MODEL: 1D CHANNELS



NEW D-Flow FM VENICE TOWN MODEL: 1D CHANNELS



COMPARISON BETWEEN MODELS AND MEASUREMENTS

Fluxes Water levels



Node velocity







NEW D-Flow FM VENICE MODEL: RESULTS

Salinity



NEW D-Flow FM VENICE TOWN MODEL: RESULTS

Salinity



PERFORMANCE

CPUtime steps / Nr of TimeSteps

TtimeStep D-Flow FM/ TtimeStep Delft3D-FLOW

Run time D-Flow FM/Run time Delft3D-FLOW

Delft3D-FLOW

5 domains D-Flow FM optimized

Timestep (s) 3 auto (CFL)

Simulation period (s) 604800 604800

Nr of timesteps ( ) 201600 223262

CPUtime steps (s) 89890.17** 88787.97

Run time (hh:mm:ss) 22:46:14 25:32:41

TtimeStep 0.44588 0.39769

SpeedFactor TimeStep 0.89190

SpeedFactor Wall Clock 1.12183

**Average cpu time of the 5 domains (not considering ddmodule wait time)



D-Flow FM VENICE MODEL: MESH CREATION ORIGINAL SIN



D-Flow FM VENICE MODEL: MESH CREATION DIFFICULTIES

Connection curvilinear to flat areas (very useful “External triangles to outer quads”)

Flat area –triangulation of samples to net makes… triangles!

Marshlands – a lot of samples so many triangles…

ORTHOGONALITY!!!



DELWAQ

Coupling procedure

Using offline coupling (communication file) and ddbound option to account for dd internal boundaries Pros: • hydro run can have different duration and save only

last cycle to communication file • It is possible to aggregate the grid before coupling it

Cons: • Communication file can be very big • Coupling with ddmodel can be tricky (need manual

modifications of the *.hyd files)

Using online coupling by activating WaqInterval option in the mdu file Pros: • No communication file: creation of WAQ files

(.are, .vol, .flo, etc.) directly • Simple procedure

Cons: • hydro run must have the same duration of

the cycle for WAQ • It is not possible to aggregate the net ** (**for the moment but it will be possible to create the WAQ files on an aggregated grid)

Delft3D-FLOW DD model D-Flow FM



DELWAQ: TEST RUN

Hydrodynamic conditions: • Average tide : semidiurnal +- 35 cm • No wind • Average river flows

WAQ conditions: processes initial sea/river bnd

• Continuity (g/m3) 1 1/1 • Salinity (g/kg) 34 35/0 • Cons. tracer (g/m3) 1 1/0

• Duration: 30 days, • Dispersion: 1 m2/s • Numerical scheme: 15 Iterative solver, backward diff.

1 min timestep 30 s timestep



DELWAQ: FLOCHECK

AFACT BAGGER

Show per time step the multiplication factor Applied to the cross-sectional area of each segment

Show the overall volume change

After the coupling procedure for the Delft3D-FLOW model a utility called “flocheck” has been used. This utility makes a kind of “dredging” to increase the volume and/or lateral surface of isolate segments in order to keep the residence time below the user-defined integration time-step.

1 min timestep 1 m2/s dispersion



DELWAQ: TEST RUN RESULTS – CONSERVATIVE TRACER

Delft3D-FLOW D-Flow FM

Rivers are defined in different way in the two hydro models and so different in the WAQ: • Delft3D-FLOW - as discharges • D-Flow FM - discharges boundaries Same dispersion coefficient: 1 m2/s



DELWAQ: TEST RUN RESULTS - SALINITY

Delft3D-FLOW D-FLOW

Rivers are defined in different way in the two hydro models and so different in the WAQ: • Delft3D-FLOW - as discharges • D-Flow FM- discharges boundaries Same dispersion coefficient: 1 m2/s

D-Flow FM



DELWAQ: TEST RUN RESULTS - CONTINUITY

Delft3D-FLOW D-Flow FM

1 min time step 30 s time step


Next Generation Modelling applied to the Venice Lagoon

COMMENTS

D-Flow FM:

• There was no easy way to de-refine easily the mesh. The existing method involves

making a polygon and merging nodes and than smooth/orthogonalize again. The

procedure is very time consuming in such complex system

• In conclusion the creation of the net should be well planned before starting the work

DELWAQ:

• The online D-Flow FM - DELWAQ coupling procedure constrain to use the same grid for

DELWAQ and Hydro simulations (and the same timestep…)

• It is not possible to use Dido to aggregate the mesh and the flocheck procedure doesn’t

work

• It is not possible to defined an spatial varying initial condition using the D-Flow FM mesh

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we plan the world of tomorrow

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DSD-INT 2014 - Symposium Next Generation Hydro Software (NGHS) - Venice Lagoon 3 (estuarine), Giselle Menel Lemos, Technital