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Key contribution of
Oceanographic research in
providing an economic solution to
Zeebrugge’s lack of hinterland
connectivity
Paul Moeyaert
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Wave measurement
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Solutions:
• Noorderkanaal
• Dockships
• “extended” estuair regime
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Access to the network of inland
waterways from Zeebrugge:
•
Traditional inlandwater tankers
Provided “good’ weather
•
Coasters
But too high requirements
And high investment/operational costs
Due to lack of reliable knowledge of the
risk-level
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Extended Estuair
• Based on Risk analyses
• Simulation of ships motions and
behaviour as a response to the
10years wave spectra: in the
particular sea area
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Statistical distribution of
occurances of dangerous
situations
• Slamming
• Greenseas
• Rolling
• Bending moment
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Acceptable frequency
• Bending moment : once a life time
• Slamming: once per year
• Green seas : once per life time
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Iterative process of design
If the number of incidents proves to be too
high : 2 possible actions:
•Restrict the allowable weather
conditions
And/or
•Increase strength
Optimum solution
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Relative vertical motion of point : fore, keel exceeding draft fore: number of
exceedings per trajectory as a function of significant wave height in measured
directional wave spectra Bol van Heist, Western Scheldt – Zeebrugge
significant wave height (m)
0
0.5
1
1.5
2
2.5
1.0E+02
number of exceedances per trajectory (-)
1.0E+01
1.0E+00
CARCARRIER - DRAFT 2.5 m
MOTION POINTS 7-9 - SLAMMING
REF LEVEL KEEL
SCHELDT-ZEEBRUGGE-SCHELDT
DIRECTIONAL SPECTRA BOL VAN HEIST 1998
1.0E-01
1.0E-02
1.0E-03
1.0E-04
conditional minimum
1.0E-05
conditional maximum
conditional average
1.0E-06
cumulative average
3
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Significant Wave Height
• Is a far more accurate criterion for
reflecting the risks compared to the
old yardstick : Beaufort Number
• As basis for designing ships
• But also as a criterium for the
captain: whether to make the voyage
or the wait for better circumstances
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Further possible improvements
•
Accuracy of predictions on medium term
•
Directional predictions
•
Distinction between:
Swell
– Caused by remote storms
– Long waves, traveling at known speed
– well predictable
Local waves
– Same predictability like the local wind
– Shortcrested waves
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1.4
side vertical amplitude due to roll / wave amplitude
(m/m)
CARCARRIER
DRAFT 2.50 m
angle of incidence (deg)
1.2
0
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
1
0.8
0.6
180
0.4
0.2
0
0
0.5
1
1.5
wave frequency (rad/s)
2
2.5
3