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

Numerical investigation of breaking wave interaction with vertical wall attached with recurved parapet
using qaleFOAM
Qian Li, Shiqiang Yan, Qingwei Ma, Ningbo Zhang
Department of Civil Engineering, School of Mathematics, Computer Science and Engineering, City, University of London
London, UKABSTRACTThis paper presents a numerical investigation of the interaction between
the breaking waves and vertical wall attached recurved parapet for botha small 1:8 scale and a large 1:1 scale model using a hybrid solver,
qaleFOAM. qaleFOAM applies the domain-decomposition approach inwhich a two-phase incompressible Navier-Stokes (NS) solver InterFoam
couples with the Quasi Lagrangian-Eulerian Finite Element Method(QALE-FEM). The practical performance of qaleFOAM is demonstrated
by comparing its prediction with the experimental data, including thewave elevation and pressure on the vertical wall and recurved parapet.
Good prediction of the breaking wave elevation is achieved, whilst tobetter address the high frequency, highly stochastic impulsive pressure
problem, a compressible qaleFOAM solver should be adopted.

KEY WORDS: Wave-structure interaction (WSI); Breaking wave;
Hybrid method; Recurved parapet; CFD.
INTRODUCTION
Understanding of the loads caused by the large wave heights is important,especially when facing more frequent extreme weather events. Rather
than increasing the sea wall height, it has been proved that the recurved
parapet is more efficient in reducing the wave overtopping bydischarging part of seawater back into the sea. Therefore, investigationof the behavior between the breaking wave and the curved parapet isessential. To address this issue, a wide range of numerical simulations
and model tests have been carried out. The breaking wave impact on a
vertical wall is simulated using a compressible multiphase flow solver
and the results show that the variability of maximum impact pressure on
the wall is very large. The air pocket impact shows a plateau peakadjacent to the impact position, whilst flip through impact exhibits asingle sharp peak at the location where the wave trough strikes the wave
crest (Gao, F., et al, 2015). Molines et al. (2020) studied the influence ofa parapet on wave overtopping of mound breakwaters with crown walls.
The authors noticed a reduction in the dimensionless mean wave
overtopping discharges when a parapet was constructed. Ravindar andSriram (2021) studied the behavior of parapets for a range of breaking
monochromatic waves to understand the influence of the type of2012

breaker–structure interaction on the loading pattern on the overall
structure.
Besides, the modelling of the breaking wave raises new challenges in therobustness and reliability of the numerical models in both the spatial andtemporal scales. Due to the extremely refined mesh and small-time stepthat should be applied to capture the transient phenomenon of wave
impact, one may expect a very high computational cost. To deal with thisissue, one of the feasible solutions is to apply the hybrid model. Recentyears have witnessed developments in hybrid models in modelling WSIs.
They take advantage of the simplified theories for robust modelling oflarge-scale wave propagations within their range of application and theadvantages of the NS models on resolving small-scale viscous/turbulent
effects, vortex shedding and flow separation, fluid compressibility, andaeration. To capture the wave propagation precisely, the computational
cost is dramatically increasing due to the decrease of the spatial andtemporal scale around the free surface. Therefore, a shortercomputational domain or coupling with a simplified solver is desired tomake the simulation numerically affordable, this is especially true whena Reynolds-averaged Navier-stokes (RANS) turbulent model is required.
To address this issue, there are hybrid models combining wave theories
with the NS model using a one-way zonal approach or functional
decomposition method. Both the function-splitting, e.g. the velocitydecomposition (Edmond et al, 2013), space-splitting/domaindecomposition (e.g. Colicchio et al, 2006; Yan and Ma, 2010a;Hildebrandt et al., 2013; Sriram et al. 2014; Fourtakas et al. 2017; Li etal. 2018; Zhang et al. 2020) and time-splitting approaches (e.g. Wang etal, 2018) have been attempted. Systematic reviews on the developmentof the hybrid models can be found in Sriram et al. (2014), Li et al. (2018),
Wang et al. (2018), and Zhang et al (2020). The performance of thehybrid model on improving the computational efficiency has beenreported by a recent CCP-WSI blind test for modelling the interaction
between the focused wave and the floating bodies (Ransley, Yan andBrown et al, 2020). It was concluded that the hybrid methods combining
the FNPT with NS solvers, including the qaleFOAM combining theQALE-FEM with openFOAM (Li et al., 2018; Yan et al 2019; Yan et al.
2020) and a one-way hybrid model combining the FNPT with SPH(Zhang et al 2020), demonstrate a potential improvement in the required
CPU effort when compared to the most robust NS solvers participating
to the test, including one adopting the linear and second-order wave
condition in the OpenFOAM (wave2Foam, Jacobsen et al. 2011).
Therefore, the hybrid model qaleFOAM is applied in this study toinvestigate the performance of the vertical wall attached recurved