OVERTOPPING REDUCTION FOR HARBOR QUAYS UNDER VERY OBLIQUE WAVES ATTACK

Transcription

1 flanders^ OVERTOPPING REDUCTION FOR HARBOR QUAYS UNDER VERY OBLIQUE WAVES ATTACK Sebastian DAN, Corrado ALTOMARE, Tomohiro SUZUKI, Tim SPIESSCHAERT, Mare WILLEMS, Toon VERWAEST Flanders Hydraulics Research, Antwerp, Belgium

2 landers Content 1. Introduction 2. Research question 3. Method 4. Results 5. Conclusions

3 flanders^ Introduction Belgian harbors - weak links for extreme storms Oostende Blankenberge

4 HYDRAUL CS RESEARCH Introduction Mobility Public Overtopping estimation in literature (EurOtop Manual) Reduction factor for wave obliqueness: Vertical dikes - non-impulsive waves : = 0.04 exp 2.G Jïp \ , y ß = ß, for 0 < ß < 45' Yß = 0.72, for ß > 45 Rc Hm0 hs a = crest freeboard = wave height at the toe of the structure = water depth at the toe of the structure = slope angle of foreshore foreshore slope 1:m - impulsive conditions: just for ß = 15, 30,60 Sloping dikes: Yß= ß for 0 < ß < 80 ß = wave angle relative to the normal, in degrees

5 landers ^ Research questions ctépartmmt 1. Overtopping reducing due to wave obliqueness 2. Influence of a storm return wall

6 tendere Method Physical model - structure with 16 overtopping boxes

7 flanders^ Method Structure Overtopping boxes Guiding wans Quay structure Conditions Storm return wall Physical model Scale Slope Wave type Significant wave height 1:50 1:2.5 Long crested, irregular Peak period 1.5 to 3.0 m 6 to 12 s Prototype values Freeboard crest Storm return wall (Rc) Position Height 0, 0.75, 1.0, 1.75, 2.0, 2.75 m 0, 5, 25 and 50 m 1.0 or 2.0 m

8 flanders^ Method Instruments 17 wave gauges: -1 close to wave paddle -1 0 split in 2 arrays for wave direction - 7 in front of the structure 4 automatic water level gauges -1 for water level in basin - 3 for water level in three overtopping boxes 16 manual water level gauges -1 for each overtopping boxes Automatic gauge

9 I M *. * Method Wave analysis 3D Variance Spectrum WaveLab 3.39 (Aalborg University, 2011) Wave parameters 2 wave arrays - total waves

10 flanders^ Sloping dyke Results Vertical wall No storm return wall Storm return wall 1m height 5m prototype Storm return wall 1m height 25 m prototype

11 i # h y d r a u i. es r f s e a r o h Results Vertical wall Prototype values Storm return watt Position

12 I M *. * K e s u l t s dec overtopping discharge per box (prototype scale) 80 degrees! Vertical walls Strong variability of the CO overtopping discharge 1 along the structure X distance total wave height (prototype scale) 80 degrees... following the same trend as the wave height distribution I

13 Results Mob/V/tyo/id C jmparisun CLASH v : \V _ (ws _ the edgtl Vertical walls Smaller values for the measured overtopping than for the calculated one O C A R h < 45 c - A s i : = 1-: \Y p -Í I h :*nfi firmln :l h it Rc/Hi T(SEO=1-O.OOB2p(forp<=45) icr Measured vs predicted q O W L data 80 degrees wall on the edge W L data 80 degrees with berm C -A S I C ' 15 C. A R h = 45 \V _ p = 33 E. 'I t o p predictior Calculated q [l/s/m ] 2 1QJ 101 Rc% 0)*H T(í w l =D.3 (P=80) ypeo=1-q.00b2p (fur p<=45) C _ A S h i c 45 C ^A S i - =.io W _ p = 33 h :*««p firm iii iiiii 1 D n 10 io' Measured q [l/s/m ] ' >VWH Experiment overtopping (WL) vs. similar cases from Clash database

14 I M *. * Results Measured vs predicted Q - Vertical walls Influence of the storm return wall position and height G É EurOtop prediction i - ÿgte A 0 25m 50 m * Positive A «\ e ; s :iv e A c KM Measured vs predicted Q - G S

15 flanders^ Conclusions r > 1. The EurOtop formula overestimates the overtopping discharge for very oblique waves. 2. The reduction factor calculated using the FHR data is approximately Yß.\NL = 0.3 for 80 wave angle and vertical walls. Significant difference respect to EurOtop Manual which suggest a coefficient Yß = The high obliqueness combined with long berms (comparable with the wave length) leads to very low or no overtopping discharge. 4. The berm length has a stronger influence on the overtopping reduction than the wall height. 5. Reduction for sloping dikes was also observed, larger than the one proposed by EurOtop, but not significant as for the vertical wall. 6. Supplementary investigations on the overtopping reduction: - control 0 and 45 to check the compatibility with the previous experiments; - intermediary 60 to 70 to define reduction coefficients for the rest of oblique wave directions.