Download - Simulating Overtopping of seawall defences B.D. Rogers*, M.V. McCabe, P.K. Stansby, D.A. Apsley
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Simulating Overtopping of seawall defences
B.D. Rogers*, M.V. McCabe, P.K. Stansby, D.A. Apsley
*RCUK Research Fellow
School of MACE
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OutlineIntroduction to Overtopping: • The need for numerical models
Numerical Model 1:• Boussinesq-type model• Modification for Seawall
Numerical Model 2: • Smoothed Particle Hydrodynamics (SPH)• Effect of the recurve wall
Results:• Overtopping events and volumes
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Prediction of Wave Overtopping
• Physical Models • Empirical Data
• Numerical Modelling?
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Nonlinear Shallow Water Equations
hpu hp
Boussinesq – type equationsIntermediate depths
NLSW equationsShallow water only
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Shallow Water and Boussinesq Equations with a Vertical Wall
23
1
3
1
0
2
22
3
33
2
32
2
breakpre
breakpost
eb
xBgd
tx
hu
x
dd
x
uh
xxBgd
tx
hudB
x
zgh
x
hgh
x
hu
t
hu
x
hu
t
h
Continuity Equation
Momentum Equation
Boussinesq Terms Dissipation Terms
Fwallu
hwalldx
uhk wallwall2
Force Imposed by a Wall
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0 200 400 600 800 1000 12000
1
2
3
4
5
6
7
Time (s)
Cum
ulat
ive
Vol
ume
(m3
/m)
Wave Overtopping Volumes, Prototype ScaleHm0
= 3.41m, H0 / L0 = 0.04
SWAB Modelwith Force at
Seawall
Laboratory Data
Field Data(from EA)
SWAB Modelwithout Force
at Seawall
Shallow Water And Boussinesq (SWAB) Model Validation
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ExampleOvertopping and Beach Level at Walcott Link to
Movie
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2007 Storm – Overtopping Rates
3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 82.35
2.4
2.45
2.5
2.55
2.6
Hm0 (
m)
3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 81
1.5
2
2.5
3
3.5
Time (hours)
Wa
ter
Le
ve
l (m
aO
D)
3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 80
0.5
1
1.5
Me
an
Ov
ert
op
pin
g R
ate
(l/s
/m)
Hourly Mean Overtopping Rates - SWAB Model vs Neural Network Tool
SWAB ModelNeural Network - No SetupNeural Network + Setup
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Smoothed Particle Hydrodynamics (SPH)
Plunger
Splashup
(Photo courtesy of F. Raichlen)
Overtopping, flooding and inundation
Very complex multi-phase multi-scale
highly nonlinear problems
Breaking waves on beaches
WaterParticles
2h
r Radius of influence
Detailed modelling requires SPH
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The Future: (Multi) Hybrid Chips• Dual-SPHysics (cpu & gpu) – SPEEDUPS of 100 for a Desktop machine =
Supercomputer of 1000’s cores• Crespo et al.
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SPH simulation
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SPH simulation
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SPH simulation
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SPH simulation
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SPH simulation
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SPH simulation
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3m
In SPH, we know that overtopping is dependent on resolution, so with a much finer resolution this could well produce higher values
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Overtopping volumes from SPH Simulations
Results:• With the same bathmetry from the Boussinesq simulations:
overtopping events of 2400 litres/m• With the Recurve wall: overtopping event of 540 litres/m
Comparison with Boussinesq & Eurotop
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Thank you
Acknowledgements:• Maurice McCabe• Nicolas Chini• Peter Stansby
• SeaZone – bathymetry below the low water line• Environment Agency (EA) – beach profile above the low water line