Breaking wave impacts on seawalls are simulated using a multiphase three-dimensional computational fluid dynamics (CFD) software, neptune_cfd; the focus here is on a particular layout 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 predict 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 seawall. We simulate two experiments involving similar geometries of the seabed and seawall, performed at two different scales (1:8 for case A and 1:1 for case B). After a description of the CFD solver and its numerical methods, the model is applied to the simulation of the two cases involving high-impact pressure peaks at some places on the wall surface. Numerical results are compared with experimental data regarding both free surface elevation and pressure on the wall. In general, a correct agreement between numerical predictions and experiments is obtained for free surface elevation, including the breaking zone. The time history of pressure variations for different positions along the wall during wave impacts is correctly reproduced. Although the measured maximum impact pressure peaks exhibit some variability among successive impacts, the order of magnitude of these maximum pressures 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), because the elevation of the wave impact on the wall happens to be a bit lower in the simulation.
The impact of breaking waves on marine and coastal structures is a question of central interest for many applications, as extremely high-pressure peaks at the wall can occur depending on the characteristics of the breaking wave and 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, intermediate, or finite water depth (e.g., oil and gas platforms; monopiles; or floating structures supporting offshore wind turbines, coastal or harbor breakwaters, vertical quays, and seawalls). Breaking wave impact can also occur in liquified natural gas tanks in some particular sloshing conditions (e.g., Ibrahim, 2020).
