Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Laboratory study on breaking wave impact on a vertical wall with recurved parapets in small and large
scale
Rajendran Ravindar1, Venkatachalam Sriram1, Stefan Schimmels2 and Dimitris Stagonas3
1

Department of Ocean Engineering, Indian Institute of Technology, Madras, Chennai, India.
2Forschungzentrum Kuste (FZK), Hannover, Germany3Department of Civil and Environmental Engineering, University of Cyprus, Nicosia, Cyprus

hundreds of researchers. Impact pressure is a short-range impulsive
pressure act when a wave hits on the structure. Impact pressures are tentimes higher than non-impact forces, and their impact duration is lessthan 1/100th of the characteristic wave period (Zhou et al., 1991). Impact
pressures are highly stochastic and difficult to understand and interpret(Cuomo et al., 2010a). Localised impact occurs over a small portion of
the entire system, causing major changes in position (Chan, 1994).

ABSTRACTIn this paper, a set of experiments on the breaking wave impact on thevertical wall attached with recurve parapets is being carried out. Thispaper discusses the experimental setup and test cases released for thecomparative study in the ISOPE 2022. The paper discusses thecomprehensive details of the experimental setup, details of model,instrumentation and Data Acquisition (DAQ) and wave characteristics
of small-scale and large-scale experiments. Different test cases withvarying wave height and wave periods are investigated to put forth theeffect of the curvature of recurved parapets and the results are reported
in this paper.

The pressure-time history of a single wave effect on a vertical wall isdepicted in Fig. 1. It comprises a large-amplitude short-duration peak, an
oscillatory pressure, and a steadily varying lesser pressure. The impact
pressure is now generally referred to as the initial pressure peak portionof this trace, which is due to the initial impact on the structure. Then,because of entrapped air oscillations, the oscillatory pressure decays overtime. Finally, the quasi-static pressure is the pressure that lasts thelongest and continues until a wave crest is reflected off the wall.

KEY WORDS: Recurved parapet; wave impact; dynamic pressure;vertical wall; scale effects; large scale.

INTRODUCTION
As global warming worsens, existing vertical walls struggle to withstandthe effect of overtopping, increasing the risk on the leeward side. One
alternative solution followed by coastal engineers is to attach a recurve
on top of the existing vertical wall or build a monolithic recurve wall.
Recurved parapets are an overhang structure facing the seaward side
attached to the new/existing vertical seawall to overcome higher wave
heights during extreme events and the rise in sea level. The efficiency ofthis part is that it takes up-rushing seawater or higher steepness waves tocurl around the structures and deflects back into the seaward side insteadof overtopping. It is required to develop tools for assessing the reliability
and survivability of these structures in the presence of extreme loads,
such as those applied by breaking waves.
Fig. 1: A typical pressure-time history for a single wave impact on avertical wall.

The critical parameters for the design of coastal structures are wave
impact pressure and force. The current research looks at how parapets
affect the vertical wall's hydrodynamic characteristics and wave loading
patterns. The study involves the determination of the performance ofvertical walls attached with different recurved parapets.

Bagnold's (1939) study laid the groundwork for much subsequent
research on wave impacts on coastal structures. Impact pressures varied
substantially even under the identical wave conditions, while thepressure impulse (defined as the integration of pressure over time) wasmuch more repeatable. Bagnold highlighted the importance of entrained

The study of the impact pressure is a vast topic carried out by more than1991