Bio-inspired wave breakers to reduce swell erosion in the Bay of Biscay using Computational Fluid Dynamics

Abstract

Coastal management is one of the main concerns of coastal countries. Sea level rise caused by climate change can accentuate coastal erosion. One of its principal causes, in France, is swell. Several solutions exist to limit the erosive effects of swell, including wave breakers. Their main issue is that they protect a limited area and they can increase the erosion downstream of the protected structures because of the cut in the longitudinal transport. Therefore, existing wave breakers cannot be a long-term solution to the problem of coastal setback. This paper is a proof of concept on the idea of creating bio-inspired wave breakers that do not increase the erosion downstream but it also shows that all the bio-inspirations are not appropriate. Two types of bio-inspired wave breakers have been modelized on CatiaR2021X®. The first type is inspired by the Torquigener albomaculosus’ nest. The second type is inspired by the mangroves’ shape. Both shapes are known for slowing the seafloor current. The interaction between the wave breakers and the swell in the Bay of Biscay has been simulated with Xflow®2020. The experimental data needed to validate the simulations were provided by the scientific literature. Because the results of the control simulations and of the simulation with existing wave-breaker shapes coincided, the results of the other simulations have been considered as relevant too, even if test bench experiments will be performed later to deepen these results. The simulations’ results have shown that the nest-inspired shapes are increasing the erosion in the non-protected areas. On the contrary, the mangrove-inspired wave breakers could be a possible improvement to slow the coastal setback in the Bay of Biscay. This study aims to give first results about the general interaction between geometrical shapes and swell, independently of the materials of the wave breakers.