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

Two-phase CFD simulation of breaking waves impacting a coastal vertical wall with a recurved parapet
Michel Benoit1,2 , William Benguigui3,4 , Maria Teles1 , Fabien Robaux2 , Christophe Peyrard1,2
1

EDF R&D, Laboratoire National d’Hydraulique et Environnement (LNHE), Chatou, France
Saint-Venant Hydraulics Laboratory (Ecole des Ponts ParisTech, EDF R&D), Chatou, France
3
EDF R&D, Dept. Mécanique des Fluides, Energies et Environnement (MFEE), Chatou, France
4IMSIA, UMR 9219 EDF/CNRS/CEA/ENSTA ParisTech, Palaiseau, France
2ABSTRACTand the shape of the jet impacting the wall, the dynamics of air entrapment, and the shape of the wall (see e.g. Oumeraci et al., 1993). Such impact issues are encountered with offshore structures in deep, intermediateor finite water depth (e.g. O&G platforms, monopiles or floating structures supporting offshore wind turbines, coastal or harbor breakwaters,
vertical quays and seawalls). Breaking wave impact can also occur in
LNG tanks in some particular sloshing conditions (e.g. Ibrahim, 2020).
The prediction of the peak values of these breaking impact pressures ischallenging. Few methods exist based in particular on the analogy withthe slamming effect of a body impacting a free surface at rest (e.g. Ravindar et al., 2019). These breaking waves are usually studied experimentally with model scale tests in wave flumes or basins (e.g. Stagonas etal., 2020; Ravindar and Sriram, 2021). This then raises several issues including taking proper account of scale effects, monitoring the generationof the incident wave(s) to create at model scale the targeted situations,
measuring with accuracy the dynamics of the pressure evolution, in particular the impact peak which is often both high in magnitude and very
short in duration. Specific subsequent signal processing techniques arethen needed to analyze the pressure signal, to separate the quasi-staticpart from the dynamic one induced by the wave impact, etc.
Advanced numerical simulation codes based on Computational Fluid
Dynamics (CFD) approach for solving the Navier-Stokes equations forboth the liquid and the gas phases offer an alternative approach to study
this phenomenon. However, due to the high level of complexity ofthis process and its very transient nature, the accurate modeling of suchbreaking impacts remains challenging.
In this study we aim at evaluating the capabilities and performances of amulti-phase 3D CFD software, named neptune cfd, to simulate the propagation of regular nonlinear waves over variable bathymetry, the depthinduced breaking process and the interaction of these breaking waves
with a vertical wall representing a typical coastal protection. The considered vertical wall is equipped with a recurve in its upper part, a classicalcivil engineering design to reduce wave overtopping. The goal here is
to simulate two recent experimental tests performed in wave flumes witha similar lay-out of the seabed profile and the vertical wall but considering two different scales, namely 1:8 for case A (Ravindar and Sriram,2021) and 1:1 for case B (Stagonas et al., 2014, 2020), and to compare

Breaking wave impacts on coastal protections are simulated using a
multi-phase 3D CFD (Computational Fluid Dynamics) software, named
neptune cfd, focusing on a particular lay-out composed of a plane sloping bottom and a vertical wall with a recurved parapet on top of it. The
goal is to assess the capabilities and performances of the solver to simulate the propagation of regular waves over the variable bathymetry (including shoaling and nonlinear effects), the depth-induced breaking process and the interaction of these breaking waves with the vertical wall.
We simulate two experiments involving similar geometry of the seabedand vertical wall, performed at two different scales (1:8 for case A and
1:1 for case B), as described in Ravindar et al. (2021). After a description of the CFD solver and its numerical methods, the model is applied
to the simulation of the two cases involving extremely high impact pressure peaks at some places of the wall surface. Numerical results arecompared with experimental measurements regarding both free surface
elevation and pressure on the wall. In general, a good agreement of thesimulations with the measurements is obtained for free surface elevation,including the breaking zone. The time history of pressure variations during wave impacts is correctly reproduced. Although the measured maximum impact pressure peaks exhibit some variability among successive
wave impacts, the order of magnitude of these maximum peaks is well
predicted for case A. For case B, however, the maximum impact pressures are somewhat underestimated by the current simulations, requiring
further tests and improvements. This work is a contribution to the benchmark “Comparative Study on Breaking Waves Interactions with Vertical
Wall attached with Recurved Parapet in Small and Large Scale” set up
for the ISOPE’2022 conference.

KEY WORDS: Breaking waves; Wave impact; Free-surface flow;
CFD; Coastal Engineering.

INTRODUCTION
Breaking wave impacts on marine and coastal structures is a question ofcentral interest for many applications as extremely high pressure peaks at
the wall can occur depending on the characteristics of the breaking wave

2004