ct530816
TRANSCRIPT
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Vermelding onderdeel organisatie
February 1, 2012
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Chapter 16: Flow developments in closure gaps
ct5308 Breakwaters and Closure Dams
H.J. Verhagen
Faculty of Civil Engineering and Geosciences Section Hydraulic Engineering
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Closing a river channel
• Example connection between Rhine and Meuse
• In case of a level difference of 2 m over 13 km applying Chezy will lead to u = 0.80 m/s
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channel view
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closing a river channel
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effect of closure
Using Chezy and
Backwater-curve
calculations:
90 % blockage gives:
0.40 m/s in AC
0.55 m/s in BC
4.50 m/s in the gap
nearly 100% blockage gives head difference of 2 m
velocity becomes 6 m/s
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two basins on which the calculations are based
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four cases calculated
• horizontal closure of a short basin
• horizontal closure of a long basin
• vertical closure of a short basin
• vertical closure of a long basin
• stepwise reduction of the gap in 5 steps (100%, 50%, 25%, 10% and 3%)
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closure gap dimensions and stages
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identical points
• all discharge coefficients are 1
• all elements of the dam are impermeable
• tide is simple (sinus with constant amplitude of 1.5 m)
• C = 50
• Duflow is used for all computation (for info about Duflow see : www.duflow.nl)
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output presented in the graphs
• water level just outside the the basin near the gap
• water level just inside the basin near the gap
• water level at the end of the basin
• flow velocity in the gap
Note: for short basin water level in the whole basin is identical
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horizontal closure, short basin (16.5)
note printing error in book
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horizontal closure, long basin (16.6)
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vertical closure, short basin (16.7)
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vertical closure, long basin (16.8)
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flow velocities depending on closure methods and gap-size