Experimental investigation on hydrodynamic performance of a helmholtz resonator-based floating breakwater array

Abstract

Addressing the limitations of traditional floating breakwaters in intermediate to long-period wave attenuation, this research experimentally investigated the hydrodynamic performance of a Helmholtz-type floating breakwater (FB) array. Bloch band theory was employed to predict resonant bands. The mechanism of Helmholtz resonance is explained. The influence of geometrical design parameters is also considered. It is found that Helmholtz resonance, unlike Bragg resonance, can occur in a single structure at a lower frequency, making it suitable for attenuating long waves. In addition, the band gaps derived from Bloch Band theory match well with the experimental results, accurately predicting the frequency ranges of Helmholtz resonance. When Helmholtz resonance is activated, the radiated waves produced inside the FB cavity interact with the incoming waves, leading to the dissipation of wave energy. The maximum dissipation coefficient is observed within the frequency range corresponding to Helmholtz resonance. Meanwhile, as the opening width decreases and the draft increases, the Helmholtz resonant frequency shifts toward lower frequencies, and the resonant intensity weakens. Increasing the number of models in the array enhances the resonant strength and improves wave attenuation performance, although the rate of improvement gradually diminishes. Moreover, combining models with the different opening widths and optimizing their arrangement sequence (i.e., placing models with larger openings at the front) can broaden the resonant frequency band and enhance the overall wave attenuation performance.