Hydrodynamics-based geometric optimisation and parametric analysis of a wing-type floating breakwater

The wave attenuation performance of floating breakwaters (FBs) is usually limited under long wave conditions. This study investigated wing-type FBs in a two-dimensional wave flume, using the Smoothed Particle Hydrodynamics (SPH) method, which was validated against previous experiments. To minimise the cross-sectional area (Area) while ensuring effective wave attenuation (with transmission coefficient kt < 0.20) of a wing-type FB, the geometric parameters, including FB width (WFB) and draft (DFB), as well as wing height (Hwing), width (Wwing), and angle (Awing), were optimised under the selected extreme wave condition. A Support Vector Regression (SVR)-trained surrogate model was used to predict kt for wing-type FBs, and a genetic algorithm (GA) was applied to identify the optimal solutions. The effects of geometric parameters and wave conditions on the hydrodynamic responses of wing-type FBs were analysed. The results showed that, compared with the initially designed wing-type FB, the optimal solution reduced the Area by 20 %, increased WFB by 15 %, and decreased DFB by 47 %. As Awing and Hwing/Lw (Lw is wavelength) increased, kt decreased and then increased, with the minimum values occurring when Awing was between 20° and 40° and Hwing/Lw was between 0.02 and 0.03. Increasing Wwing, DFB, or WFB reduced kt. For incident wave periods T ≥ 0.9 s, the optimised wing-type FB showed improved wave attenuation compared with the box-type FB; for T < 1.1 s, kt of the wing-type FB was less than 0.60. This study offers a useful reference for the design of FBs in offshore environments.