Abstract
This paper presents a study of run-up/overtopping over a smooth impermeable dike with promenade using 2D and 3D mesh-based and mesh-free numerical models and results from 2D physical modelling for strong energetic incident waves. These waves induce plunging wave breaking and a complex water/air mixture turbulent flow before overtopped the dike, a challenging configuration for numerical models. The analysis is structured in two phases: (i) evaluates the results of 2D numerical and physical models for run-up and overtopping; (ii) compares qualitatively the results of 3D numerical models for overtopping over a dike with promenade between groins located in front of a slope beach. The results indicate that the main differences obtained in run-up and overtopping are due to differences in wave generation and active absorption systems used in physical and numerical models and in turbulent models used by the numerical models. These differences lead to changes on incident wave height and on wave breaking and, consequently, on reflection, run-up and overtopping over the structure. For 3D simulation, even if larger discrepancies were found on overtopping along the dike, mean wave overtopping discharge and water flow height at the crest of the groin head show a similar order of magnitude.
Highlights
Flooding risk in coastal urban fronts protected by very shallow foreshores dikes is mainly dominated by strong wave action and high-water level
Convergence of mean wave overtopping discharge with mesh refinement was not observed and can be explained by: (i) overtopping, and subsequently the water flow on dike, was very sensitive to mesh refinement in both directions and depends on water height and water velocity at the dike crest; and (ii) wave breaking presents a chaotic behaviour with a large variability of water height and flow field before and over the dike
3D versions of DualSPHysics and FLUENT are applied for modelling runup and overtopping in a 1:15 slope beach protected by a smooth impermeable dike with promenade located between two impermeable groins and the results of both models are compared
Summary
Flooding risk in coastal urban fronts protected by very shallow foreshores dikes is mainly dominated by strong wave action and high-water level. The methodology has the following main components: (i) 2D physical model tests for obtaining breaking characteristics and measuring run-up and overtopping on a smooth impermeable dike for scenarios of sea level rise; (ii) verification of performance and accuracy of the three 2D numerical models comparing results with the physical model data; and (iii) 3D modelling, using the RANS-VoF and mesh-free models, of run-up/overtopping in a 1:15 slope beach protected by a smooth impermeable dike located between two impermeable groins This is the first step for numerical modelling of a dike between groins, an important and urgent tool to assist in the perdition of flooding risk at coastal cities protected by structures and in studying alternative solutions to mitigate these risks
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