wave modelling and field measurements in a complex estuary presentation… · 1 wave modelling and...
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Wave modelling and field measurements in a complex estuary
P. Oosterlo, G.Ph. van Vledder, B. Hofland, J.W. van der Meer, N. Geleynse, M.
Reneerkens, G.J. Steendam, M. Veendorp
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Area of interest: Eems-Dollard estuary
North Sea
Eems-Dollard estuary
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• Combining extensive field measurements and numerical modelling
• Reducing uncertainties in design conditions and improving safety
assessment modelling systems
Field measurements Eems-Dollard
12-year long project
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Field measurements Eems-DollardOnshore wave measurements
• Measuring wave run-up and overtopping
• Innovative wave overtopping tanks
• Innovative laser scanner system
Storm 8-1-2019
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Field measurements Eems-DollardOnshore wave measurements
• Innovative laser scanner system
• First validation tests with wave run-up simulator
Wave run-up Wave overtopping
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Focus & Approach
• Focus on evolution of waves as they propagate into the
estuary
• Previous research:
• Possible fundamental limitations in linear refraction approach in
phase-averaged models in areas with steep slopes
• Diffraction, wave tunnelling, nonlinear effects may play a role
• Approach:
• From simple to complex, gradual build-up in model complexity
• Gain insight into which processes play a role
• Comparison phase-averaged (SWAN) vs. phase-resolving model
(SWASH)
• When available, comparison and validation with measurements
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SWAN versus SWASH
SWAN SWASH
Model type Phase-averaged Phase-resolving
Equations Wave action balance NLSW equations
Propagation x x
Diffraction (x) x
Reflection x x
Transmission x x
Wave growth by wind x
Dissipation x x
Nonlinear interactions x x
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SWAN & SWASH models
• SWASH:
• Non-hydrostatic mode
• 2 vertical layers
• Weakly reflecting b.c.’s & sponge layers
• Dike schematised with exception
values
• Increase in applied Hs necessary
• Calculations on Dutch national
supercomputer Cartesius
• Several issues encountered → Fixed in
newest SWASH version (6.01)
• Choice of spectral estimation method
important
• SWAN:
• Stationary mode
• (Initially) 20 m grid cell size
• 3 versions of the 3rd-generation
physics:
• Van der Westhuijsen et al.
(2007)
• Komen et al. (1984)
• Rogers et al. (2012) (ST6)
• Variations in:
• Grid cell size
• No. directional bins
• Diffraction approximation
• Stop criterion
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1. Semi-infinite breakwater case
• Focus on wave propagation, excluding other physical processes
• d = 18.5 m, H = 3 m, T = 6 s, θ = 270°
Monochromatic, unidirectional waves
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1. Semi-infinite breakwater case
• Relative wave height compared to Sommerfeld (1896) solution
Monochromatic, unidirectional waves
SWASH SWAN SWAN + diffraction approximation
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2. Semi-infinite breakwater case
• Focus on wave propagation, excluding other physical processes
• d = 18.5 m, Hs = 3 m, Tp = 6 s, θ = 270°, dspr = 25°
Irregular, directional waves
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2. Semi-infinite breakwater case
• Relative wave height compared to Goda et al. (1978) solution
Irregular, directional waves
SWASH SWAN SWAN + diffraction approximation
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2. Semi-infinite breakwater case
• Comparison 2D wave spectra SWASH & SWAN
Irregular, directional waves
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3. Storm conditions case
• d = 18.5 m, Hs = 3.4 m, Tp = 6 s, θ = 279°, dspr = 30°
• Partial reflection by porous grid cells
Focus on wave propagation effects only
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3. Storm conditions case
Focus on wave propagation effects only
• Comparison 2D wave spectra SWASH & SWAN
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4. Storm conditions case
• All physical processes except wind growth turned on
Focus on all physics, except wind
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4. Storm conditions case
• Comparison 2D wave spectra SWASH & SWAN
Focus on all physics, except wind
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Conclusions
• 12-year long extensive field measurements in, and numerical
modelling of the estuary
• Phase-averaged models cannot cope with diffraction and
unidirectional waves
• Performance for directionally spread waves is much better
• All physics, no wind: HF peak missing in SWAN, SWAN gives larger
Hs, smaller Dspr
• Current case: only quadruplets and whitecapping of influence
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Ongoing and future work
• Field measurements and further studies ongoing for at least 10
more years
• Continuation of measurements and analyses of oblique wave run-up
and overtopping
• Next steps in wave modelling of the area:
• Tests with XNL quadruplets (see also H2, Van Vledder)
• Influence of wind
• Adding shallow area and slope to model
• Adding channel to model
• Modelling with actual bathymetry
• Comparison and validation with measurements whenever available
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Thank you
Animations by Ricardo Alanis & Patrick Oosterlohttps://www.artstation.com/patomico