Begeleidingscommissie

Schaalmodelproeven voor de impact van golven op een

zeedijk

Activiteit 2 – Vincent GRUWEZ

30 mei 2018 – KUL, Campus Brugge

Storm wall

© Vincent Gruwez (2016)

© René Billiau (2013)

ht

Hm0,o ; Tm-1,0,o

Hofland et al. (2017)

Foreshore slope range Belgian coast: 1/20 – 1/90

Hm0,t ; Tm-1,0,t

© Vincent Gruwez (2017)

© Vincent Gruwez (2017)

Numerical modelling

Experimental modelling

Field measurements

© Vincent Gruwez (2017)

Foreshore slope range Belgian coast: 1/20 – 1/90

2D Experimental modelling – Overview

High spatial resolution

of surface elevationsWave

overtopping

Wave forces

2D Experimental modelling – Model setup

Slope 1/20 – Scale 1:25

Slope 1/50 – Scale 1:25

Slope 1/50 – Scale 1:35

Slope 1/80 – Scale 1:35

RS11

First results (2D) – Wave transformation over the foreshore

First results (2D) – Wave overtopping

Based on Van Gent (1999), recalibrated and extended with equivalent slope concept by Altomare et al. (2016):

First results (2D) – Spectral wave period Tm-1,0 at the dike toe

Hofland et al. (2017):

First results (2D) – Wave impact forces

Load cell at wallLoad cell at window

Numerical modelling

Experimental modelling

Field measurements

3D Experimental modelling – Motivation

Long-crested waves Short-crested waves

3D Experimental modelling – Motivation

Long-crested waves

(2D wave flume)

Short-crested waves

(3D wave basin)

3D Experimental modelling – Motivation

at WTR

Overestimation of energy

at low-frequencies in 2D

modelling

Validated by in-situ

measurements(Ostend, BE)

3D Experimental modelling – Overview

Model setup

Wave

overtopping

Wave forces

Long-crested waves Short-crested waves

First results (3D) – Wave overtopping

43% decrease

Long-crested waves Short-crested waves

First results (3D) – Wave impact forces

F10%=6.9 N/m

F10%=4.3 N/m

•Experimental modelling was conducted to support the development of new (empirical, numerical) tools to aid the design of sea dikes with a very shallow foreshore

•Focus on wave transformation, wave overtopping and wave impact forces

Conclusions

•2D tests (UGent):

‣ HSR tests show a significant increase of long wave energy close to the dike

‣ The foreshore slope value has a clear influence:

The accuracy of the prediction formula for wave overtopping is sensitive to the foreshore slope value for high freeboard values

The prediction formula for Tm-1,0,t will be improved for the case of steeper foreshore slopes (for slopes 1/20 and 1/35)

‣ Illustration of variability of load cell measurements over the width of the flume

Conclusions

•3D tests (FHR):

‣ Short-crested waves cause lower wave height long waves at the sea dike:

Decreased amount of overtopping

Decreased wave impact forces

‣ Short-crestedness important and not to be neglected

Conclusions

Thank you for your attention!