1
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H. Oumeraci, E-mail: [email protected]ß-Institute for Hydromechanics and Coastal Engineering, Technical University Braunschweig, BraunschweigCoastal Research Centre, University Hannover and Technical University Braunschweig, Hannover
Hydraulic Performance and Stability of Coastal Defence Structures
FZK
2
Rubble Mound Structures and Breakwaters:
Wave-Induced Internal Flow and Hydraulic PerformanceEffect of Core Permeability on Hydraulic Stability and Performance
Hydraulic Performance of an Artificial Reef with Rectangular Shape
Hydraulic Performance of Wave Absorbers
Submerged Wave AbsorbersSurface Piercing Wave Absorbers
Submerged Wave Absorbers as Artificial Reefs for Coastal Protection
Soft Wave Barriers for Coastal Protection
Geotextile Structures for Coastal Protection
OutlineOutline
3
Rubble Mound Structures and Breakwaters
4
Wave-Induced Internal Flow and Hydraulic Performance
• Muttray, M. (2000): Wave motion at and in rubble mound breakwaters-large-scale model and theoretical investigation, PhD-Thesis, TU Braunschweig 282p. (in German)
• Muttray, M., Omeraci, H. (2005): Theoretical and empirical study on wave damping inside a rubble mound breakwater, Coastal Engineering vol. 52 .pp. 709-725.
References:
5
Rubble Mound Breakwater: Model Construction in GWKRubble Mound Breakwater: Model Construction in GWK
PressureTransducers
h = 4,50 mH = 1,00 mT = 6,00 s
Run Up Gauges
6
SWL
1 2 3 4 5
H(x)
1 2 43 5
breakwater corebelow seaward slope nearfield at lee sidenearfield in frontof breakwater
Hi, Hr
H(x)p/ρg(x, z, t)P/ρg(x, z)
R, H(x), η(x) RC, RF, naη(x), Δη/Δx
p/ρg, grad p/ρg
H0, H(x)P/ρg(z), p/ρg(z)
Kt
Kt
ΔE/Ei
on seaward slope
Research Strategy for Rubble Mound BreakwatersResearch Strategy for Rubble Mound Breakwaters
7
Experimental Set-Up for Rubble Mound Breakwater ModelExperimental Set-Up for Rubble Mound Breakwater Model
240 244 248 252 256 260
distance to wave paddle x [m]
1 2 3 4 5 6 7
8 9 10 11 12 13
14 15 16 17 18
19
20
2122
23
24
25
26
27
28
29
30
3132
33
34
272120191817 22 23 24 25 261
2 3
+2.50m+2.90m
+1.50m
SWL
±0.00m+0.60m
2.00m
+4.30m
+3.75m
wave gauges & wave run-up gauges
pressure transducers
sand subsoil
8
Wave-Induced Pore Pressure FieldWave-Induced Pore Pressure Field
247 249 251 253 255 257distance to wave paddle x [m]
-2
-1
0
1
2
elev
atio
n z
[m
]
pressure transducer
η(t)
0.10.20.3
0.3
0.40.4
0.5
0.6 0.70.8 0.9 1.0 1.1
wave parameters:h = 2.49m; T = 5s; Hi = 1.06m
9
Internal Wave-Induced Pressure GradientInternal Wave-Induced Pressure Gradient
Regular Wavesmax. Wave Run-up: t = 0 [s]
Water Depth : d = 4,50 [m]Wave Height : H = 1,00 [m]Wave Period : T = 6,00 [s]
Max. Run-up
10
Wave Energy Dissipation at and in the BreakwaterWave Energy Dissipation at and in the Breakwater
0.05 0.1 0.5 1 5relativ width k0h cotα [-]
0.0001
0.00050.001
0.0050.01
0.050.1
0.51
rela
tiv e
nerg
y de
nsity
E/E
i [-
]
Kt2 regular waves
Kt2 wave spectra
Kt2 + (1 - Kr)
2 regular wavesKt
2 + (1 - Kr)2 wave spectra
0
0.25
0.5
0.75
1
E/E i
[-]
Kt2 regular waves
Kt2 wave spectra
Kt2 + (1 - Kr)
2 regular wavesKt
2 + (1 - Kr)2 wave spectra
(1 - Kr)2(1 - Kr)2ΔE/EiΔE/Ei
Kt2Kt2
1 - (1 - Kr)21 - (1 - Kr)2
(1 - Kr)2(1 - Kr)2
dissipated wave energy in the partial standing wave fielddissipated wave energy in the partial standing wave fieldin front of the breakwaterin front of the breakwater
11
Effect of Core Permeability on Hydraulic Stability and Performance of Rubble
Mound Breakwater
• Oumeraci, H.; Kortenhaus, A.; Werth, (2007): Stability and Hydraulic Performance of a conventional rubble mound breakwater and breakwater with sand in geo containers. Submitted to ASCE Coastal Structure, Conf. Venice.
References:
12
Twin-Wave Flume at Leichtweiß InstitutTwin-Wave Flume at Leichtweiß Institut
Length ≈ 90m
2m 1m
Depth = 1,25m
WaveWave
(a) General bird view of twin-flume
b) Twin-Wave Paddle (Synchronor independent)
• Regular waves: up to H= 30cm
• Random wave: up to HS= 20cm
• Solitary waves: up to H= 30cm
13
Geo-Core and Conventional Rubble Mound Breakwater Models in Twin-flumeGeo-Core and Conventional Rubble Mound Breakwater Models in Twin-flume
(b) Geo-Core Breakwater model in thefirst flume
(c) Conventional Breakwater model in the2nd. flume
(a) Model Breakwaters in the Twin-flume
14
Permeability Model TestsPermeability Model Tests
3.881 x 10-1Structure made of gravel
2.412 x 10-2
GSC-structure made of geotextile sand
containers placed randomly
Darcy´s permeability coefficient k value
[m/s]DescriptionMode of Placement
15
Stability Number: Geo-Core vs. Traditional BreakwaterStability Number: Geo-Core vs. Traditional Breakwater
0.00
0.20
0.40
0.60
0.80
1.00
-1 1 3 5 7 9Ns
*=NS*sp-1/3
Df=N
od/N
a
= sm
m
Hs local wave steepness
L
Stability Number
( )− −= ⋅ ⋅ ⋅4.51415 1/3
f ,t S m
Traditional Breakwater
D 5.0 10 N s
−= ⋅* 1/3s s mN N s
Dam
age
Df=
Nod
/Na
( )− −
−
= ⋅ ⋅ ⋅5.14355 1/3
f ,G S m
Geo Core Breakwater
D 5.0 10 N s
=⎛ ⎞ρ
−⎜ ⎟ρ⎝ ⎠
ss
sn50
w
HN
1 D
Nod= Number of displaced rock units
Na= Number of rock units in the upper armour layer
16
KD – Value in HUDSON-Formula for Traditional BreakwaterKD – Value in HUDSON-Formula for Traditional Breakwater
Slope
Slope
Slope
Slope
5%
Dam
age
Df[-
]
⎛ ⎞= ⎜ ⎟
⎝ ⎠S
D fm
HK f ,D
L
−
ρ ⋅ ⋅=
⎛ ⎞ρ− α⎜ ⎟ρ⎝ ⎠
3s S
50 3
SD
w
HUDSON Formula:
g HW
K 1 cot
KD= 1.12
= Sp
p
Hs
L
17
KD – Value in HUDSON-Formula for Geo-Core BreakwaterKD – Value in HUDSON-Formula for Geo-Core Breakwater
Slope
Slope
SlopeSlope
Dam
age
Df[-
]
5%
KD= 1.12
⎛ ⎞= ⎜ ⎟
⎝ ⎠S
D fm
HK f ,D
L
−
ρ ⋅ ⋅=
⎛ ⎞ρ− α⎜ ⎟ρ⎝ ⎠
3s S
50 3
SD
w
HUDSON Formula:
g HW
K 1 cot
= Sm
m
Hs
L
18
Stability Number for the Rear SideStability Number for the Rear Side
0.00
0.20
0.40
0.60
0.80
1.00
0.50 0.70 0.90 1.10 1.30 1.50 1.70 1.90 2.10
Rc/Hm o [-]
Dr
( )−= ⋅9.155
f C m0
Both Breakwaters
D 0.3455 R /H
Dam
age
Df[-
]
Freeboard −C m0R /H [ ]
Traditional Breakwater
Geo-Core Breakwater
Total Damage (Geo-Core)
Geo-Core Breakwater
Traditional Breakwater
19
Wave Overtopping PerformanceWave Overtopping Performance
Traditional Breakwater
( )= − ⋅
=
* *
2
Q 0.096exp 3.103 R
R 0.928
Traditional Breakwater
( )= − ⋅
=
* *
2
Q 0.096exp 2.81 R
R 0.967
Geo-Core Breakwater
1,00E-07
1,00E-06
1,00E-05
1,00E-04
1,00E-03
1,00E-02
1,50 1,80 2,10 2,40 2,70 3,00 3,30 3,60 3,90 4,20 4,50 4,80
Geo-Core Breakwater
Q* =
q/(2
g*H
mo^
3)^0
.5
.
R* = Rc/Hm0*1/γ
20
Wave Reflection PerformanceWave Reflection Performance
(Regression according to Oumeraci and Muttray, 2001)
= π0 0k 2 L
21
Wave Transmission PerformanceWave Transmission Performance
Traditional BreakwaterGeo-Core Breakwater
0,00
0,05
0,10
0,15
0,20
0,25
0,30
0,0 0,2 0,4 0,6
Rm = Rc/HS(sm/2π)0.5 [-]
k t [-
] Geo-Core Breakwater−
⎡ ⎤⎛ ⎞= ⋅ ⎢ ⎥⎜ ⎟π⎝ ⎠⎢ ⎥⎣ ⎦=
1.7550.5
C mf
S
2
R sk 0.001
H 2
R 0.756
Traditional Breakwater
−⎡ ⎤⎛ ⎞= ⋅ ⎢ ⎥⎜ ⎟π⎝ ⎠⎢ ⎥⎣ ⎦
=
0.8550.5
C mf
S
2
R sk 0.011
H 2
R 0.890
Tran
smis
sion
Coe
ffic
ient
= Sm
m
Hs
L
22
Hydraulic Performance of an ArtificialReef with Rectangular Shape
• Bleck, M. (2003): Hydraulic performance of artificial reef with rectangular shape. PhD-Thesis (in German): www.biblio.tu-bs.de
• Bleck, M; Oumeraci, H. (2002): Hydraulic performance of artificial reefs: global and local description. Proc. ICCE´02
• Bleck, M.; Oumeraci, H. (2004): Analytical model for wave transmission behind artificial reefs. Proc. ICCE´04
References:
23
Wave Transformation at a Reef in Waikiki/Hawaii (Gerritsen, 1981)Wave Transformation at a Reef in Waikiki/Hawaii (Gerritsen, 1981)
Incident Waves
Wave Breaking atReef
Higher Harmonics behindReef
24
Position of the ProblemPosition of the Problem
Reef Structure
S(f)
ffp ffP
Hi
Ti Tt
Ht
Present design: Ct = Ht / Hi (1) and C2t + C2
r + C2d = 1 (2)
However:Shift of wave energy towards higher frequencies behind reef
⇓Equations (1) and (2) not sufficient to describe hydraulic performance
25
Experimental Set-Up in the Wave Flume of LWIExperimental Set-Up in the Wave Flume of LWI
amplifier
Wave makerWave gauges (14)
ADV-probes (3)
Pressure gauges (11)
amplifier
ADV-computer(digital/analog conversion)
digital video camerafor test documentation
(Canon XM 1)
data back-up onCD-Rom
A/D-converter(National Instruments
AT-MIO-64)
main dataacquisition
video data ondigital cassettes
digitalisation ifrequired
test log:visual impression andspecial observation
data back-up onCD-Rom
data analysis
data
CCD-Camera for PIV measurement(TheImaging Source DMP 60 H 13)
Wave absorbing
rubble mound
Glass window
16.00m
1.85m0.15m
3.00m
81.00m
analog signalfordatasynchronisation
Reef
Black Separation Wall
B = 0.5 - 1.0 m
h=0.4-0.6m
Reef
26
Wave Transformation at a ReefWave Transformation at a Reef
0 0,6 1,2 1,8 2,4 3,0 3,6f [Hz]
0
0,002
0,004
0,006
0,008
0,010
0 0,6 1,2 1,8 2,4 3,0 3,6f [Hz]
0
0,002
0,004
0,006
0,008
0,010
Irregular Wave(Hs = 0.12m; Tp = 1.5s)
Regular Wave(Hs = 0.12m; T = 1.5s)
0 0,6 1,2 1,8 2,4 3,0 3,6f [Hz]
0
0,002
0,004
0,006
0,008
0,010
0 0,5 1,0 1,5 2,0 2,5 3,0f [Hz]
0
0,01
0,02
0,03
0,04
0,05
0,06
0 0,5 1,0 1,5 2,0 2,5 3,0f [Hz]
0
0,01
0,02
0,03
0,04
0,05
0,06
0 0,5 1,0 1,5 2,0 2,5 3,0f [Hz]
0
0,01
0,02
0,03
0,04
0,05
0,06
Harfe 2(Nahfeld)
h = 0,50m
B = 1,00m
Harfe 2(Nahfeld)
h = 0,50m
B = 1,00m
Harfe 3 (transmittierte Welle)
h = 0,50m
B = 1,00m
Harfe 2(Nahfeld)
h = 0,50m
B = 1,00m
Harfe 2(Nahfeld)
h = 0,50m
B = 1,00m
Harfe 3 (transmittierte Welle)
h = 0,50m
B = 1,00m
fp = 0,66 Hz
fp = 0,66 Hz
fp = 0,66 Hz
fp,1 = 1,33 Hz
Regular Wave(HS = 0.12; T = 1.5s)
Irregular Wave(HS = 0.12; T = 1.5s)
Tran
smitt
edW
ave
Spec
trum
at 3
Ref
lect
edW
ave
Spec
trum
at 2
Inci
dent
Wav
e Sp
ectr
umat
Gau
geA
rray
2
27
Effect of Relative Submergence Depth dr/Hi on Hydraulic PerformanceEffect of Relative Submergence Depth dr/Hi on Hydraulic Performance
Cr2 + Cd
2 + Ct2 = 1
0 2 4 6 8 10 12Relative Submergence Depth dr/Hi
0
0.2
0.4
0.6
0.8
1En
ergi
e Co
effic
ient
Ct ,
Cr ,
Cd [
-] Transmission Coefficient CtTransmission Coefficient CtReflection Coefficient CrReflection Coefficient CrDissipation Coefficient CdDissipation Coefficient Cd
Ct = 1.0 - 0.83 . exp (-0.72 . dr/Hi)Ct = 1.0 - 0.83 . exp (-0.72 . dr/Hi)σ' = 6.7%σ' = 6.7%
Cd = 0.80 . exp (-0.27 . dr/Hi)Cd = 0.80 . exp (-0.27 . dr/Hi)
Cr = 0.57 . exp (-0.23 . dr/Hi)Cr = 0.57 . exp (-0.23 . dr/Hi)σ' = 26.5%σ' = 26.5%
BB
dfdf
hh
drdr
HiHi HtHt
Ct=1.0-0.83.exp(-0.72. dr/Hi)σ‘=6.7%
Cd=0.80.exp(-0.27.dr/Hi)
Cr=0.57.exp(-0.23.dr/Hi)σ‘=26.5%
28
Simplified (dr/Hi)Multiple Regression Analysis
(dr/Hi; Hi/Li; B/Li)
Influencing Parameters on Hydraulic PerformanceInfluencing Parameters on Hydraulic Performance
( )[ ]C d Hr r i= ⋅ − ⋅0 57 0 23, exp ,
σ’Cr = 26,5%
( )[ ]C d Hd r i= ⋅ − ⋅0 80 0 27, exp ,
σ’Cd = 16,4%
Tran
smis
sion
Ref
lect
ion
Dis
sipa
tion
( )[ ]C d Ht r i= − ⋅ − ⋅10 0 83 0 72, , exp ,
σ’Ct = 6,7%
− −⎛ ⎞⎛ ⎞ ⎛ ⎞ ⎛ ⎞⎜ ⎟= + ⋅ ⎜ ⎟ ⎜ ⎟ ⎜ ⎟⎜ ⎟⎝ ⎠ ⎝ ⎠ ⎝ ⎠⎝ ⎠
0,15 0,35 0,7
i rt
i i i
H dBC 0,5 0,5 cos 0,48
L L H
( )σ =t' C 4,6%
⎛ ⎞⎛ ⎞ ⎛ ⎞ ⎛ ⎞⎜ ⎟= + ⋅ ⎜ ⎟ ⎜ ⎟ ⎜ ⎟⎜ ⎟⎝ ⎠ ⎝ ⎠ ⎝ ⎠⎝ ⎠
0,01 0,125 0,2
i rr
i i i
H dBC 0,5 0,5 cos 2,66
L L H
( )σ =r' C 12,3%
−⎛ ⎞⎛ ⎞ ⎛ ⎞ ⎛ ⎞⎜ ⎟= + ⋅ ⎜ ⎟ ⎜ ⎟ ⎜ ⎟⎜ ⎟⎝ ⎠ ⎝ ⎠ ⎝ ⎠⎝ ⎠
0,1 0,14 0,45
i rd
i i i
H dBC 0,5 0,5 cos 1,77
L L H
( )σ =d' C 10,5%
29
Effect of Relative Submergence Depth dr/Hi on Periods of Transmitted WavesEffect of Relative Submergence Depth dr/Hi on Periods of Transmitted Waves
T mm
S(f)dfS(f)fdf
010
1
= = ∫∫
T mm
S(f)f dfS(f)df-10
-1
0
-1
= = ∫∫
C (T )(T )T
01 t
01 i
01= ; C (T )
(T )T-10 t
-10 i
-10=
0 2 4 6 8 10 12Relative Submergence Depth dr/Hi
0
0.2
0.4
0.6
0.8
1
Wav
e Pe
riod
Tran
smiss
ion
C 01,
t, C -
10,t [
-]
CT01 = T01, t / T01, iCT01 = T01, t / T01, iCT-10 = T-10, t / T-10, iCT-10 = T-10, t / T-10, i
CT01, calCT01, calCT-10, calCT-10, cal
BB
dfdf
hh
drdr
HiHiHtHt
CT01 = 1,0 - 0,36 . exp (-0,58 . dr/Hi); σ' = 4,7%CT01 = 1,0 - 0,36 . exp (-0,58 . dr/Hi); σ' = 4,7%
CT-10 = 1,0 - 0,24 . exp (-0,63 . dr/Hi); σ' = 3,0%CT-10 = 1,0 - 0,24 . exp (-0,63 . dr/Hi); σ' = 3,0%CT-10=1.0-0,24.exp(-0.63.dr/Hi); σ‘=3,0%
CT01=1.0-0.36.exp(-0.58.dr/Hi); σ‘=4,7%
CT01=T01,t/T01,iΔ CT-10=T-10,t/T-10,i---- CT01,cal____ CT-10,cal
30
Description of Transmitted Wave Spectrum by Three Spectral Parameters Description of Transmitted Wave Spectrum by Three Spectral Parameters
i0
t0m )(m
)(mC0= ⎟
⎟
⎠
⎞
⎜⎜
⎝
⎛== 2
im
2tm2
)H(
)H(
0
0tC )H/d72.0exp(83.00.1 ir⋅−⋅−=tC
i1
t1m )(m
)(mC =1
( )01TC/
0mC= )H/d58.0exp(36.01)T()T(
iri01
t01 ⋅−⋅−==01TC
i-1
t-1m )(m
)(mC =−1
( )10TC−
⋅=0mC )H/d63.0exp(24.01
)T()T(
iri10
t10 ⋅−⋅−==−
−10-TC
where ;dff)f(S n∫=nm1
0mm
=01T and0
1mm−=-10T
with
with
with
31
Breaking Criterion and Breaker TypesBreaking Criterion and Breaker Types
0 0.03 0.06 0.09 0.12 0.15 0.18dr / Lf
0
0.03
0.06
0.09
0.12
0.15H
i / L
f
non-breakingnon-breakingSpilling breakerSpilling breakerTwo-phase breakerTwo-phase breakerDrop-type breakerDrop-type breaker
(Hi/Lf) = 0,142 . tanh (Mk.2π.dr/Lf)(Hi/Lf) = 0,142 . tanh (Mk.2π.dr/Lf)
(Hi/Lf)two = 1,43 . (dr/Lf)(Hi/Lf)two = 1,43 . (dr/Lf)
Modified MICHE CriterionModified MICHE Criterion
BLECKBLECK
Drop-Type BreakerDrop-Type Breaker Spilling BreakerSpilling Breaker
Non-BreakingNon-Breaking
Two-PhaseTwo-PhaseBreakerBreaker
HiHi
hh
BB
dfdf
drdr
HtHt
Drop-Type Breaker
Non-Breaking
Spilling Breaker
Two-PhaseBreaker
Modified MICHE Criterion)/2tanh(142.0)/( frkfi LdMLH ⋅⋅⋅= π
Bleck 2002)/(43.1)/( frtwofi LdLH ⋅=
Mk= 0.735
dr
32
Cd = 0.4 ÷0.90(Cd ≈ 0.68)
Cd = 0.35 ÷0.85(Cd ≈ 0.54)
Cd = 0.4 ÷0.60(Cd ≈ 0.55)*
Drop- type breakerTwo- Step breakerSpilling breaker
Breaker Types on Reefs: Energy DissipationBreaker Types on Reefs: Energy Dissipation
* Non-Breaking waves:dC 0.33=
= Dd
i
EC E with ED, Ei = dissipated and incident wave energy.
33
Breaker Types on Reefs: Energy DissipationBreaker Types on Reefs: Energy Dissipation
Spilling breaker Two-Step breaker Drop-type breaker
Cd = 0.4 ÷ 0.6(Cd ≈ 0.55)*
Cd = 0.35 ÷ 0.85(Cd ≈ 0.54)
Cd = 0.4 ÷ 0.90(Cd ≈ 0.68)
Reef
Reef
Reef
Reef
Reef
Reef
* Non-Breaking waves:
c c c
return flow return flow
ccc
33.0=dC
34
d) Leeward Upper Vortexc) Seaward Lower Vortex
b) Leeward Lower Vortexa) Seaward Upper Vortex
Vortex LossesVortex Losses
c
current deflection
c
vortexseaward lower
reef induced
seaward uppervortex
cwave inducedorbital velocity
leeward lowervortex
reef induced currentdeflection
leeward uppervortex
c
35
Non-Linear Effects with Wind Waves for B/L = 0.16Non-Linear Effects with Wind Waves for B/L = 0.16
dr = 0.20m
B = 0.50m
water surface elevation [m] water surface elevation [m]spectrum spectrum
0
0,1
-0,1
0
0,1
-0,1
0
0,1
-0,1
0
0,1
-0,1
0
0,1
-0,1
0
0,1
-0,1
0
0,1
-0,1
0
0,1
-0,1
0 3s2s 4s1s 0 3s2s 4s1s
0
0,01
0
0,01
0 1Hz 2Hz0 1Hz 2Hz
0
0,01
0
0,01
0
0,01
0
0,01
0
0,01
0
0,01
16WG 15 14 13 12 11 10 9
Reef
C
t = T + 0.25s t = T + 1.00s
c cHi/Li = 0.04 ⇒ dr/Hi=1.6;
h = 0.50m
B/Li=0.16
36
Non-Linear Effects with Wind Waves for B/L = 0.32Non-Linear Effects with Wind Waves for B/L = 0.32
dr = 0.20m
B = 1.00m
water surface elevation [m] water surface elevation [m]spectrum spectrum
0
0,1
-0,1
0
0,1
-0,1
0
0,1
-0,1
0
0,1
-0,1
0
0,1
-0,1
0
0,1
-0,1
0
0,1
-0,1
0
0,1
-0,1
0 3s2s 4s1s 0 3s2s 4s1s0
0,01
0
0,01
0
0,01
0
0,01
0
0,01
0
0,01
0
0,01
0 1Hz 2Hz0 1Hz 2Hz0
0,01
Reef
C
16WG 15 14 13 12 11 10 9
t = T + 1.00st = T + 0.25s
c cHi/Li = 0.04 ⇒ dr/Hi=1.6;
h = 0.50m
B/Li=0.32
37
Possible Application for Tsunami (Feasibility Study in Progress)Possible Application for Tsunami (Feasibility Study in Progress)
Structure Width B ?
SWL
R ?
hR ?
h ?
Dredged Sand Volume ?
Sea bottom (Sand)
1:n?
1:m?
Reef Parameters
• Location depth h• Structure width B and slope steepness 1:n and 1:m• Reef height hR and submergence depth R• Size (volume, weight) of geotextile containers
Size of Mega-Geotextile -
Containers ?
must be determined as a function of target incident Tsunami wave parameters and target level of tsunami attenuation (transmitted wave parameters). The latter will depend on the nature of the next defence line(s) and the vulnerability of the flood prone area.
38
Example of Mega Geocontainers used for a surfing Reef in AustraliaExample of Mega Geocontainers used for a surfing Reef in Australia
Feasibility for the full range of wave periods (5 - 60 minutes) of tsunamis has first to be first checked.
HWLMWLLWL
Narrowneck Reef- Australia
Sand fill 250m³
Narrowneck Reef-AusraliaMega-Geo-Container(20m×4,80m)
colonised by reef organisms(only after few months)
Sand fill 250m³
Very Large ArtificialReef
1
(1b) Mega-Geo-containers
39
Hydraulic Performance of Wave Absorbers
40
Submerged Wave Absorbers as Artificial Reefs for Coastal Protection
41
Experimental and Theoretical Investigations for Storm Waves
• Oumeraci, H.; Clauss, G.F.; Habel R. Koether, G. (2001): Unterwasserfiltersysteme zur Wellendämpfung. Abschlussbericht zum BMBF-Vorhaben „Unterwasserfiltersysteme zur Wellendämpfung“. Final Research Report, (in German)
• Koether, G. (2002): Hydraulische Wirksamkeit und Wellenbelastung getauchter Eiinzelfilter und Unterwasserfiltersysteme für den Küstenschutz, PhD-Thesis, TU Braunschweig, Leichtweiss-Institut fürWasserbau, (in German)
• Oumeraci, H.; Koether, G. (2004): Innovative Reef for Coastal Protection Part I: Hydraulic Performance, Proc. 2nd joint German-Chinese Symposium on Coastal and Ocean Engineering.
• Oumeraci, H.; Koether, G. (2007): Innovative Reef for Coastal Protection – Part II Wave Loading (in preperation)
References:
42
Submerged Wave Absorbers for Beach ProtectionSubmerged Wave Absorbers for Beach Protection
Damped
Damped
Tsunami
4
orThree-Filter-System
Coastline
„Fun“-Waves
Tourist Activities
20%11%
5%
43
Experimental Set-Up in Large Wave Flume Hannover (GWK)Experimental Set-Up in Large Wave Flume Hannover (GWK)
0m
2m
4m
6m
Filterhöhe dB=3.94mε=0%, 5%, 11%, 20%
NWS h=4.00m
HWS h=5.00m
Pegelharfe 2WellenpegelPegelharfe 1
Einzelfilter
Gauge Array 1 Wave Gauges Gauge Array 26m4m2m0m
0m
2m
4m
6m
Filterhöhe dB=3.94mε=5%
NWS h=4.00m
HWS h=5.00m
ε=11%Zweifiltersystem
6m4m2m0m
50 75 124.1 144.7 165 200 250Abstand zur Wellenklappe [m]
0m
2m
4m
6m
Filterhöhe dB=3.94mε=5%
NWS h=4.00m
HWS h=5.00m
ε=11%ε=20%
Dreifiltersystem
6m4m2m0m
50 75 124 144.7 165 200 250Distance to Wave Generator [m]
Structure Height dB=3.94m
Two -Filter-System
Single Screen
Three - Filter - System
Structure Height dB=3.94m
Structure Height dB=3.94m
10.3 m
10.3 m 10.3 m
HWL
LWL
HWL
LWL
HWL
LWL
⇒ Wave Heights: Hs = 0.5m - 1.5m⇒ Wave Periods: Tp = 3s - 12s
44
Measuring Devices at the WallMeasuring Devices at the Wall
0m ü
.KS
1
m ü
.KS
2m ü
.KS
3
m ü
.KS
4
m ü
.KS
5m ü
.KS
6
m ü
.KS
Einzelfilter ε=5% (dB=3.93m)
1 0.42
2 0.61
3 0.80
4 0.99
5 1.18
6 1.37
7 1.56
8 1.75
9 1.94
10 2.13
11 2.32
12 2.51
13 2.70
14 2.89
15 3.08
16 3.27
17 3.46
18 3.65
19 3.84
DruckaufnehmerKraftaufnehmerUltraschallsonde
2.415
3.365
3.175
Strömungspropeller
1.465
2.415
2.795
3.3653.365
4.000
Single Screen ε = 5%Pressure Transducers (20)Force Transducers (10)ADV (3D) (3)Micro-Propeller Current Meters (4)
ε = 5%
45
Contribution of Each Filter to Total Wave DampingContribution of Each Filter to Total Wave Damping
46
Fluid Fluid Domain 1Domain 1
Fluid Fluid Domain 2Domain 2
BB
AA
Analytical Flow ModelAnalytical Flow Model
h
tB
dB
(h+η)-dB
x
z
SWLη+
η-
HrHi Ht
( ) ( )2 i m m mm 0
a cos z exp x∞
=
φ = φ + μ −μ∑
( ) ( )1 i m m mm 0
a cos z exp x∞
=
φ = φ − μ μ∑
⇒ Velocity Potential
⇒ Matching Conditions at Wall* Upper Zone A (Velocity and Pressure)
1 2φ = φ1 2
x x∂φ ∂φ
=∂ ∂
( )1 22 1i
x x−
∂φ ∂φ= ∝ − φ φ
∂ ∂ S* Lower Zone B (Velocity ∝ Pressure diff.)
and
=
LWILWI
S= Structure Parameter including drag, inertia and vortex losses
47
New Structure Parameter S for Submerged FilterNew Structure Parameter S for Submerged Filter
1(fD+fV) - ifI
S =
Drag ComponentForce Measurement at ∂u1/∂t = 0, u1 ≠ 0,
ModifiedDrag Coeff.
cD*Linearisation fD=fD(CD*)
fI=CI*Modified InertiaCoeff.CI*
Inertia ComponentForce Measurement at u1 = 0, ∂u1/∂t ≠ 0
fv=fv(Cv*)Modified Loss
Coeff.Cv* = Cv(1-ε1/2)and Linearisation
Vortex LossCv by Stiassnie et al. (1984)
Modified MORISON-Equation* *w 1
R D 1 1 I w B
uF C d u u C t d
2 tρ ∂
= ⋅ ⋅ ⋅ + ⋅ ρ ⋅ ⋅ ⋅∂
u1 FR
stB
d
48
0.0 fp=1/5.0 0.4 0.6 0.80
0.1
0.2
0.3
0.4
Calculated Reflected and Transmitted Wave Spectra by ReefCalculated Reflected and Transmitted Wave Spectra by Reef
Ener
gyde
nsity
S(f)
[m2 s
]
Frequency f [Hz]
Si(f)incident
St(f)transmitted
Sr(f)reflected
dB=3.94m B=20.6
h=4m
Hi=1m, Tp=5s
ε2=5%ε1=11%Two-Filter System
Ener
gyde
nsity
(f) [m
2 s]
St(f)transmitted
Sr(f)reflected
Si(f)incident
0.0 fp=1/5.0 0.4 0.6 0.80
0.1
0.2
0.3
0.4
dB=3.94m
h=4m
Hi=1m, Tp=5s
B=20.6
ε3=5%ε1=20% ε2=11%
B1=B2
Three-Filter System
(b) Three filter System
(a) Two filter System
49
Frequency f [Hz]
Ref
lect
ion
Coe
ffici
entC
r(f)
Tp=3.50sHs=0.50mh=4.00mreflected
Waves
IncidentWaves
Cr(f)
S i(f) St(f)
hSr(f) B=10m
11% 5%dB=3.9m
Model Validation for Irregular WavesModel Validation for Irregular Waves
0.0 fp=1/3.5 0.4 0.6 0.80.00
0.25
0.50
0.75
0.00
0.05
0.10
0.15
0.20
0.25Si(f) St(f)
hSr(f) B=10m
11% 5%dB=3.9m
Ener
gyde
nsity
3FSσε*=7%
axy=0.94
Cr (Calculated)
Ct (Calculated)
Cd (Calculated)C
t(M
easu
red)
Cd
(Mea
sure
d)
2FS σε*=17%axy=0.93
2FS σε*=7%axy=0.96
2FS σε*=6%axy=1.03
3FS σε*=26%axy=1.00
3FS σε*=5%axy=1.02
2FS3FS
0.0
0.2
0.4
0.6
0.8
1.0
0.0
0.2
0.4
0.6
0.8
1.0
0 0.2 0.4 0.6 0.8 10.0
0.2
0.4
0.6
0.8
1.0
Measured Calculated
Cr(M
easu
red)
50
Differences between Short and Longer Waves
51
Differences Related to the Involved Processes (1)Differences Related to the Involved Processes (1)
Shorter Period Waves (larger h/L)(representative for storm waves)
Longer Period Waves (smaller h/L)(representative for tsunami)
h
L
h
L
Wave Energy Distribution over the Entire Water column
52
Differences Related to the Involved Processes (2)Differences Related to the Involved Processes (2)
Shorter Period Waves (larger h/L)
Particle Orbitsonly slightly
distorted
Flow field actively involved in wave transmission process
h
Longer Period Waves (smaller h/L)
StronglyDistortedParticleOrbits
Orbital Flow characteristics
53
Differences Related to the Involved Processes (3)Differences Related to the Involved Processes (3)
Shorter Period Waves (larger h/L)
Wave Crest at Wall
Longer Period Waves (smaller h/L)
Wave Crest at Wall
Energy Loss due to Flow Separation and Vorticies at Wall Crest
54
L/2L/4
L
L
Differences Related to the Involved Processes (4)Differences Related to the Involved Processes (4)
L/4
L/2L/4
(Δη) min
B = L/2B = L/2
B(Δη) max
B = L/4B = L/4B
Effect of Phase Shift on the
performance of Submerged
Progressive Filter Systems
55
Hydraulic Performance for Solitary Waves
56
Performance of Submerged impermeable single Wall subject to solitary wavesPerformance of Submerged impermeable single Wall subject to solitary waves
Transmitted wave(cT=0.54)
Reflected wave(cR=0.38)
Incident wave
-4 -3 -2 -1 0 1 2 3-0.2
0.2
0
0.4
0.6
Time relative to wave crest [s]
Surf
ace
elev
atio
nη
[m]
t=188.56s t=215.86s t=204.70s t
55.91m 162.42m
hs=3.93m h=4.00mε=0%
η η
Wave gauge Wave gauge
Incidentwave
Reflectedwave Transmitted
wave
[m]6
4
2
0
57
Performance of Two-Filter-Reef System for Solitary WavesPerformance of Two-Filter-Reef System for Solitary Waves
Transmitted wave(cT=0. 40)
Reflected wave(cR=0.28)
Incident wave
-4 -3 -2 -1 0 1 2 3-0.2
0.2
0
0.4
Time relative to wave crest [s]
Surf
ace
elev
atio
nη
[m]
0.6
t=188.05s t=213.76s t=208.07s t
52.23m 182.40m
hs=3.94m h=4.00mTwo-Filtersystem
η η
11% 5% Wave gauge
Incidentwave
Reflectedwave Transmitted
wave
[m]6
4
2
0
Submerged two-Filter System subject to a solitary wave
58
Performance of Three-Filter-Reef System for Solitary WavesPerformance of Three-Filter-Reef System for Solitary Waves
Transmitted wave(cT=0. 33)
Reflected wave(cR=0.18)
Incident wave
-4 -3 -2 -1 0 1 2 3-0.2
0.2
0
0.4
Time relative to wave crest [s]
Surf
ace
elev
atio
nη
[m]
0.6
t=188.024s t=210.63s t=208.19s t
52.23m 182.40m
hs=3.94m h=4.00m
η η
20% 11% 5% Wave gauge
Incidentwave
Reflectedwave Transmitted
wave
[m]6
4
2
0
Submerged three-Filter System subject to a solitary wave
59
Surface Piercing Wave Absorbers as Seawalls and Breakwaters
60
Wave Damping at One Chamber System (OCS)Wave Damping at One Chamber System (OCS)
wave dampingby friction
wave damping bydestructive interference
total wave damping
relative chamberwidth B/L [-]
20%
60%
40%
80%
100%
0%0 0.1 0.2 0.3 0.4 0.5
Ei
Er
impermeableback wall
wave chamber
perforated frontwall
B
Reflected Wave Energy
Incident WaveEnergy
Wave Damping relative to incident wave Energy Ei
61
Front Wall of Wave Absorber in GWKFront Wall of Wave Absorber in GWK
62
Breaking Wave on Wave Absorber in GWKBreaking Wave on Wave Absorber in GWK
63
Waves Absorbers Under Freak Wave Loading (Video)Waves Absorbers Under Freak Wave Loading (Video)
64
Reflection Coefficient of OCS and MCSReflection Coefficient of OCS and MCS
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
relative chamber width B/L
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Refle
ctio
n Co
effic
ient
Cr
1
OCS 1 (B=4.8m)
23
6789
11121314
15
16
1
OCS 2 (B=7.8m)
6781112
131516
1233
6789
11121314
15
162
678
111213
16
1
MCS 1 (B1=2.8m)
236789
11121314
1516
2
MCS 2 (B1=7.3m)
678
12
16123
678911
1213141516 2
67881112
13
1
impermeable wall
11
Traditional Jarlan(OCS)
New Concept (MCS)
20% 0%
3.25m
4.00m
4.75m
h1h2
h3
6m
B
26.5% 20% 11% 0%
3.25m
4.00m
4.75m
h2
6m
B=15m
h3h1 B1
65
Resultant Horizontal Wave Forces on OCS and MCSResultant Horizontal Wave Forces on OCS and MCS
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7relative chamber width B/L
0
0.25
0.5
0.75
1
1.25F+ to
tal /
F+ 0
%
OCS1 (B=4.8m)
123
467
8911121314
151617
OCS2 (B=7.8m)
13
68
111315
17
1
23
4
6789
11121314
15
16171
368
1113
15
MCS1 (B1=2.8m)
134
6789
1112
1314
151617
MCS2 (B1=7.3m)
1
3
6
8
11
131517
1234
6789
11121314
1516
17
1
3
6
810
1113
15
20% 0%
3.25m
4.00m
4.75m
h1h2
h3
6m
B
Traditional Jarlan(OCS)
New Concept (MCS)
F+total = Total horizontal shoreward wave force on overall CS
F+0% = Horizontal wave force on vertical impermeable wall
under same incident wave conditions
26.5% 20% 11% 0%
3.25m
4.00m
4.75m
h2
6m
B=15m
h3h1 B1
66
Overall Load on One and Multi Chamber SystemOverall Load on One and Multi Chamber System
Overall Load on One and Multi Chamber Systems
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150FFtot = (d/B)2/3 . (Hi/Ld)-1 [-]
0
3
6
9
12
15
F tot
,0 =
Fto
t/(ρ.
g.H
i2 ) [-]
Ftot,0 = 12 . tanh1.1(0.009 . FFtot)
1
OCS 1 (B=4.8m)
2
34
6
7
89
11
12
1314
15
16
17
3
OCS 2 (B=7.8m)
6
8
11
13
15
1712
345
6
78
9
11
1213
14
15
16
171
35
6
8
10
1
MCS 1 (B1=2.8m)
2345
6
78910
11
121314
15
16
17
1
MCS 2 (B1=7.3m)
3
6
810
11
13
15
171
2345
6
7
8910
11
12
1314
15
16
171
35
6
810
11
15
1713
15
17regression coefficientr = 0.97standard deviations = 0.18
OCS and MCSmonochr. waveT = 4.5-12sH = 0.5-1.5md = 3.25-4.75m
T \ H 0.50 0.75 1.00 1.25 1.50 [m] 4.5 s 1 2 3 4 5 6.0 s 6 7 8 9 10 8.0 s 11 12 13 14 -12.0 s 15 16 17 - -
description of wave parameters
Ftot Ftot
Ftot
d
BP=20% 0%
Ftot Ftot Ftot Ftot
Ftot
B1
P=26.5% 20% 11% 0%
d
(Oumeraci et al, 2001)
67
Soft Wave Barriers for Coastal Protection
• Oumeraci, H.; Schüttrumpf, H.; Kortenhaus, A.; Kudella, M.; Möller, J.; Muttray, M. (2002): Large-Scale Model Tests for the Rehabilitation and Extension of the Coastal Protection of the North Beach Area in Norderney. Res. Report no. 853, LWI, TU Braunschweig, (in German)
References:
68
Wave Damping Structures in NorderneyWave Damping Structures in Norderney
Design (Computer Model)
69
Wave Damping Measures Norderney Island (North Sea)Wave Damping Measures Norderney Island (North Sea)
GWK Model Innovative Structure in GWK
Innovative Structure: Prototype (1) Innovative Structure: Prototype (2)
70
Open Sea Wall on Island Norderney, North Sea (Video)Open Sea Wall on Island Norderney, North Sea (Video)
71
Application to TsunamiApplication to Tsunami
Objective: ⇒ To progressively weaken tsunami power without completely blocking inundation, but with additional benefit of broadly blocking floating debris.
Application: ⇒ As multi-purpose structures everywhere where planting of coastal forests is not feasible
⇒ Especially appropriate for touristic and urbanized coastal areas where man-made protective structures should be fitted aesthetically into the local marine landscape.
a) Design (Computer Animation) b) Built in Norderney (North Sea)
72
Geotextile Structures for Coastal Protection
73
Dünenverstärkung
GWK Model
Dune Reinforcement and Coastal Protection with InnovativeGeotextileDune Reinforcement and Coastal Protection with InnovativeGeotextile
[Picture: Sylt Picture 2000]
Prototype (Island Sylt)
74
Geotextile Sand Container for Beach ReinforcementGeotextile Sand Container for Beach Reinforcement
75
Geotextile Sand Containers for Coastal Protection and Dune Reinforcement: Experimental Set-Up in GWKGeotextile Sand Containers for Coastal Protection and Dune Reinforcement: Experimental Set-Up in GWK
Sand core
Geotextile
1:n =
1:1
Foreshore (1:m = 1:25)Pressure Transducer (10bar) Pressure Transducer (5bar)
Sand Containerfor Scourtprotection
Hs
1576
54
32
1
1211
109
13 14
8
d= 1,75m1,30m
Location WP 22
plan View
Wel
lena
ngrif
fsric
htun
g
Sand Container lagen Presssure TransducerWave
direction
Pressure Transducer10bar
Pressure Transducer5bar
Wave direction
T-Profile
Installed Pressure Transducer(Frotn view and seaside Dlope)
76
Geotextile Sand Containers: Tests in GWK (Video)Geotextile Sand Containers: Tests in GWK (Video)
77
SWLSWL3,30m3,30m
SWLSWL3,75m3,75m
SandcoreSandcore1:11:1
1:251:25
RcRc
RcRc
0 4 8 12 16 20ξ0(HS)
0.0
0.5
1.0
1.5
2.0
2.5
3.0N
S(H
S)
No motion (150 liter Bags)No motion (150 liter Bags)Motion of slope elements (150 liter Bags)Motion of slope elements (150 liter Bags)Motion of crest elements (150 liter Bags)Motion of crest elements (150 liter Bags)
0 0.2 0.4 0.6 0.8 1 1.2Rc/Hs
0.80
0.90
1.00
NS(
HS) Effect of Freebord (crest elements)
ξ0ξ0tan αtan α
(Hs/L0)1/2(Hs/L0)1/2==
NsNs ==HsHs
(ρE/ρw-1) D(ρE/ρw-1) D D = l.sinαD = l.sinα
Lower Limit for motion of crest elements (Ns≈0,79)Lower Limit for motion of crest elements (Ns≈0,79)
NsNs ==2,752,75
√ξ√ξSlope elementsSlope elements
Ns = 0,79 + 0,09 . (Rc/Hs)Ns = 0,79 + 0,09 . (Rc/Hs) Crest elementsCrest elements
Crest ElementsCrest Elements
SlopeSlopeElementsElements
Hydraulic Stability Formulae for Geotextile Sand ContainersHydraulic Stability Formulae for Geotextile Sand Containers
Improved Stability formulae by accounting for Deformation of GSC see PhD-Thesis of J. Recio (2007)
78
Geotextile Sand Containers: Example ApplicationsGeotextile Sand Containers: Example Applications
5000 5000 SandcontainerSandcontainer
HarlehHarlehöörnrn -- Island Wangerooge 2002 Island Wangerooge 2002 (North (North SeaSea))
((0,05 m0,05 m33))
2000 Sand Container2000 Sand ContainerGloweGlowe -- Island RIsland Rüügen 2002 (gen 2002 (BalticBaltic SeaSea))
(1,50 m(1,50 m33))
(North Sea) 216 Sand Container(North Sea) 216 Sand ContainerArtificialArtificial ReefReef Kampen /Sylt Kampen /Sylt
(10 m(10 m33))
Narrowneck Reef- Australia
Sand fill250m³
Narrowneck Reef-AusraliaMega-Geo-Container(20m×4,80m)
colonised by reef organisms(only after few months)
Sand fill250m³
79
Thank you for your attention!