WIND EFFECTS ON OVERTOPPING DISCHARGE AT COASTAL DEFENCES

S De Chowdhury,J G Zhou,T Pullen,D Causon,H Winter,A Joly,D Stewart,K Hu,S Manson,M Russell,C Mingham,L Qian,M Wood

doi:10.9753/icce.v36v.papers.40

Abstract

Wind effects on wave overtopping over fully impermeable vertical sea defence is studied in a shallow water flume based on a physical model for the Livermeade defence system. The investigation is mainly focused on impulse type wave interaction with the sea defence, when the overshooting jet is high during overtopping. We are able to identify distinct types of overtopping flows where moderate wind speed is not found to be affecting uniformly in all cases. We try to find explanation of this behaviours by studying the standing waves at the defence and complementary CFD simulations.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/byRz_N9zoXk

Highlights

Many coasts are vulnerable to wind effects at moderate to high wind speeds during normal weather as well as a storm surge
Coastal defences are standard choices to protect the coasts against flooding from wave overtopping and yet still it is not usual to design them based on studies focused on an understanding of wind effects
In this paper we report some preliminary results investigating wind effects on wave overtopping based on physical model tests conducted recently

Summary

INTRODUCTION

Many coasts are vulnerable to wind effects at moderate to high wind speeds during normal weather as well as a storm surge. De Waal et al (1996) and Wolters and van Gent (2007) used paddle wheels rotated at a given speed to transport water spray generated due to the wave impact on the vertical structure These tests suggested a high increase in overtopping rates by wind compared to no wind conditions in some specific types of wave impacts, results could not be quantified fully due to the lack of proper scaling laws. As there is no reliable empirical relations for accessing wind effects on wave overtopping, coastal engineers are left with prescribing a wide margin in the design of a coastal defence-height This appears to be a normal choice for places with high onshore wind speeds in particular, but clearly less economical in practice. We make hypothesis to explain our findings from the physical tests wherever possible and we are able to support that with results from our multiphase CFD simulations

EXPERIMENTS AT HR WALLINGFORD

CONCLUSION