Kostarisk joint research laboratory has received government funding managed by the French National Research Agency under the France 2030 Investment Plan (ref. ANR-16-IDEX-0002).
Numerical study of extreme wave impacts on temporary flood-fighting structuresPhD – Mohamed Rozki
Dates: 2021 – 2024.
Host: SIAME.
Direction: S. Abadie, D. Morichon.
Link to manuscript : https://theses.fr/2024PAUU3083
Summary – The rise in sea level due to global warming is likely to intensify the 1 impact of storm events. To counter this trend, protective walls, located at the top of the beach, whether fixed or mobile, are commonly used to reduce the impact forces of waves on downstream infrastructure. However, their design is complex and currently relies on empirical formulas. This is due to a lack of understanding of the physical processes governing the interaction between wave-generated flows and structures positioned at the top of the beach.
This thesis aims to improve the understanding of these processes. In the first part of this work, we study the forces generated by broken waves on temporary defense barrier. The objective is to determine the characteristics of the flows impacting these structures under real conditions. The second part, which forms the core of this study, focuses on a detailed analysis of impact forces at the scale of individual waves. This numerical study uses two Reynolds-Averaged Navier-Stokes (RANS) models to simulate the impact of a surge generated by a dam break on a vertical wall.
The simulations show that the impact force has two peaks. The first corresponds to the impulsive phase of the impact, a well-documented phenomenon. The second peak occurs during the closure of an air cavity. Our study demonstrates that this closure is responsible for the occurrence of this force peak.
Finally, we examine the dependence of the second force peak on different parameters, such as the upstream reservoir filling, or a finite obstacle height allowing some overtopping. We find that the piston effect, due to the trapping of an air cavity, occurs in the majority of the studied cases.
