Author(s): Weiqiu Chen; Jord Warmink; Marcel Van Gent; Suzanne Hulscher

Linked Author(s): Weiqiu Chen, Jord Warmink, Marcel van Gent

Keywords: Dikes; Berm; Roughness; Waves2Foam

Abstract: Wave overtopping is one of the main causes for dike breaching. The average overtopping discharge is often used to describe the wave overtopping at dikes. However, the average overtopping discharges do not provide information on individual wave overtopping events. The overtopping flow on the crest and landward slope can cause infiltration and erosion at the landward side of dikes, which can finally lead to dike breaching. Therefore, the characterization of overtopping flow related to individual overtopping events on a dike crest provides important information for the safety assessment of a dike. Extreme flow velocities, layer thickness and volumes, which have a low probability of exceedance during a storm event, are usually used to characterize the wave overtopping flow. Some empirical equations are available to estimate the flow velocity and layer thickness. However, these empirical equations were derived based on the experiments performed mainly on the coastal structures that have a smooth straight waterside slope. Berms and roughness elements are widely used at the waterside slope of dikes to reduce the wave overtopping. It remains unclear if these empirical equations are applicable for the structures that have complex configurations. Besides, it is difficult and expensive to measure flow velocity and layer thickness in the physical model tests. Numerical model has become an important complementary tool with experiments to study the interactions between waves and coastal structures. In this study, we focused on the flow velocity and layer thickness related to individual wave overtopping events with a low probability of exceedance. The objective of our study is to investigate the effects of berms and roughness on the extreme flow parameters including flow velocity and layer thickness on the crest using OpenFOAM. The OpenFOAM model was validated by using both small-scale and large-scale experimental data. Based on that, the numerical model was applied to study the effects of berms and roughness elements on the flow parameters by changing the berm width and coverage length of roughness elements at the waterside slope of a dike. The model results show that the berms and roughness elements have a great influence on the flow velocity and layer thickness on the dike crest. A modification of the existing empirical formulas for estimating the flow parameters taking the berms and roughness into account was made based on the numerical results.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022610

Year: 2022