Impact of Stepped Structures on Tsunami Wave Propagation and Overtopping Engineering

Abstract

The urgent necessity to fortify coastal regions and safeguard both the natural environment and key coastal infrastructure underscores the significance of structural measures in coastal engineering. Among these, the seawall reigns as the primary fortification method. This study aims to elucidate the impact of a stepped structure on the propagation and overtopping of solitary waves when they encounter an impermeable seawall. The investigation has been conducted using ANSYS Fluent, a widely recognized commercial software. Although previous researchers have extensively used the two-dimensional volume of fluid (VOF) model, based on the Reynolds-Averaged Navier-Stokes (RANS) equations and the k-ε turbulence closure solver, this study fills the gap in the understanding of the stepped structure's effect. It shows a commendable agreement with experimental results, proving its reliability. Simulations were executed with varied configurations of stepped structures (Step width Sw=0.6 m, 1.2 m, 1.8 m, and Step height Sh=0.3 m, 0.6 m, 0.9 m), emulating tsunami waves of constant wave height and water depth over a stepped structure on a 1:20 sloped beach. Initially, the accuracy of the results was substantiated by comparing them with experimental and numerical data of the free surface and the distribution of the pressure field on the seawall. Numerical simulations, incorporating varying wave heights, water depths, and step heights, were performed to scrutinize the evolution of waves and the pressure exerted by waves impacting the seawall.