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

2D LES of breaking waves on seawalls with recurved parapets
Andreas T. Asiikkis1, 5, Charalambos Frantzis2, 3, Dimitris Stagonas4, Antonis I. Vakis5, Dimokratis G.E. Grigoriadis1, *1 Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia, Cyprus
2 Electricity Authority of Cyprus, Nicosia, Cyprus

3 Cyprus Marine and Maritime Institute, Larnaca, Cyprus

4 Department of Civil and Environmental Engineering, University of Cyprus, Nicosia, Cyprus

5 Computational Mechanical and Materials Engineering, University of Groningen, Groningen, the Netherlands* Corresponding author

shown to affect the loading conditions at the wall as well. The present
blind test challenge calls for simulations of regular waves breaking on a
vertical seawall equipped with a recurve.

ABSTRACTThe utilization of recurves on vertical seawalls reduces overtopping
without drastic increases in the structures’ freeboard. As part ofISOPE22 blind test challenge, an in-house developed computational
fluid dynamics code is used to simulate the breaking of waves on a
vertical seawall and the interaction of the violent up-rushing flow withthe recurve. The code combines recent advances which speed-up thesolution of Poison’s equation, with an immersed boundary method and a
Large Eddy Simulation model. The comparison of the numerical resultswith the experimental data provided by the organisers shows asatisfactory reproduction of the wave conditions in the flume and a nonnegligible underestimation for the predicted peak pressures. This, with acomputational cost of approximately 2 hours per wave period.

In principle, numerical investigations of wave-structure interaction areassociated with a high computational cost and are challenged by thecomplex nature of the phenomenon. Martin et al. (2021) utilized thenumerical toolbox OpenFOAM to model 2D and 3D impacts of solitary
waves on a vertical wall using the assumptions of both incompressible
and compressible fluids. Using the mesh-less program DualSPHysics
which utilizes a particle-based method, Ma et al. (2021) performed
simulations of the same case as in the experiments of Kisacik et al.
(2012), without considering the presence of air (i.e., single-phase flow)
and using a weakly compressible model for the water. Similarsimulations were performed by González-Cao et al. (2019) who
compared the accuracy of DualSPHysics and IHFOAM which is a meshbased method. Their results indicated that the IHFOAM performed better
compared to DualSPHysics. In addition, they concluded that theaccuracy of capturing the free-surface elevation was higher compared tothe impact forces due to the stochastic nature of wave impacts. Othernumerical studies can be found in (Castellino et al., 2021; Liu et al.,2019)

KEY WORDS: Braking Waves; Seawalls; Wave-StructureInteractions; Computational Fluid Dynamics (CFD); Numerical Wave
Tank (NWT).
INTRODUCTION
During storms the interaction of waves with seawalls often leads to green
water and impulsive overtopping. Recurves placed at the top of theseawall deflect seawards the up-rushing water thereby reducing
overtopping without drastically increasing the freeboard. Following field
failures with recurves being toppled by the wave action, numerical andexperimental investigations on the interaction of such super-structureswith non-breaking (Castellino et al., 2021), and breaking waves(Stagonas et al., 2020), have highlighted the importance of accurately
predicting wave induced loads.

In this paper, a newly developed Numerical Wave Tank (NWT), namely
the LESiT described by Frantzis et al. (2020), is used to reproduce thelarge scale experimental conditions of Stagonas et al. (2020) andcompare numerical predictions of the wave conditions in the flume andwave induced pressures at the structure with the measurements. In theremainder, the numerical methods utilized to solve the full set of theNavier-Stoke equations and the numerical set-up of the experiment areoutlined first. The convergence study is presented before the numericalresults are illustrated and compared with the experimental measurements
provided by the organisers. Soon after, the results and the computationalperformance of the NWT are critically discussed. Finally, theconclusions of the study are drawn, and future work is outlined.

Recent experimental works, e.g. Dong et al. (2021), Ravindar & Sriram(2021a), and Stagonas et al. (2014) among others, highlight a complex
relationship between the super-structure’s design characteristics and thewave induced loads. For example, chamfered parapets and recurves wereshown to experience impulsive loads induced by non-breaking waves,the magnitude of which increases drastically when the waves break at
the wall. For the latter conditions, the shape of the recurve was also2726