In this paper, a Reynolds-averaged Navier-Stokes (RANS) equations solver, interFoam of OpenFOAM®, is validated for wave interactions with a dike, including a promenade and vertical wall, on a shallow foreshore. Such a coastal defence system is comprised of both an impermeable dike and a beach in front of it, forming the shallow foreshore depth at the dike toe. This case necessitates the simulation of several processes simultaneously: wave propagation, wave breaking over the beach slope, and wave interactions with the sea dike, consisting of wave overtopping, bore interactions on the promenade, and bore impacts on the dike-mounted vertical wall at the end of the promenade (storm wall or building). The validation is done using rare large-scale experimental data. Model performance and pattern statistics are employed to quantify the ability of the numerical model to reproduce the experimental data. In the evaluation method, a repeated test is used to estimate the experimental uncertainty. The solver interFoam is shown to generally have a very good model performance rating. A detailed analysis of the complex processes preceding the impacts on the vertical wall proves that a correct reproduction of the horizontal impact force and pressures is highly dependent on the accuracy of reproducing the bore interactions.

Short duration bores in the coastal zone are generated by wave breaking in shallow water and mild foreshore conditions. In storm weather situations and for sea level rise scenarios, these bores approach the dike and interact with previously overtopped or reflected bores. Combined laser scanner and video measurements were used to study the complex and turbulent bore interaction processes. Five bore interaction patterns were distinguished as (1) regular bore pattern; (2) collision bore pattern; (3) plunging breaking bore pattern; (4) sequential overtopping bore pattern, and (5) catch-up bore pattern. Video images of the bore running up the wall and motion tracking of the leading edge were used to obtain a time series of the run-up water at the wall. The impact loads of the bore hitting the wall on the promenade were studied based on the signal of a vertical array of 13 pressure sensors installed over the wall height. Three impact types were distinguished and classified as (1) impulsive impact type; (2) dynamic impact type; and (3) quasi-static impact type. The majority of ~2/3 of the total number of impacts were comprised of the quasi-static impact type.