Numerical and experimental investigation on ‘C-pile’ breakwaters for wave attenuation

Abstract

The growing threat of wave-induced impacts to coastal sustainability necessitates effective wave attenuation strategies. Breakwaters play a pivotal role in mitigating wave energy, with resonant breakwaters leveraging Bragg and localized resonance mechanisms showing significant promise. This study investigates the wave attenuation performance of a novel C-shaped cylindrical (i.e., C-pile) breakwater through physical experiments and numerical simulations. The reflection coefficient, transmission coefficient, and time histories of water levels were measured through wave flume experiments, with the data used to validate a three-dimensional numerical model constructed in OpenFOAM and predictions from Bloch theory based on linear potential flow. Parametric numerical simulations were systematically conducted to explore the effects of opening width, chamber area, opening angle, and submergence depth on the wave attenuation performance and resonance behavior of individual C-piles. Localized optimization of C-pile arrays was conducted to enhance wave attenuation for specific wave period ranges. Results demonstrate that wave attenuation by C-piles is driven by chamber-wave interactions, where fluctuations in water level and volume within the chamber contribute to wave attenuation. The incident wave frequency and the resonant frequency of the C-pile follow a specific relationship. The latter has a close relationship with the structural dimensions. While parametric adjustments improved attenuation for target wave periods, uniform array modifications did not guarantee consistent performance gains. These findings establish the potential of C-piles as effective alternatives to traditional breakwaters, offering insights into resonance-based attenuation mechanisms and tailored optimization strategies.