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 k t < 0.20) of a wing-type FB, the geometric parameters, including FB width ( W FB ) and draft ( D FB ), as well as wing height ( H wing ), width ( W wing ), and angle ( A wing ), were optimised under the selected extreme wave condition. A Support Vector Regression (SVR)-trained surrogate model was used to predict k t 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 W FB by 15 %, and decreased D FB by 47 %. As A wing and H wing / L w ( L w is wavelength) increased, k t decreased and then increased, with the minimum values occurring when A wing was between 20° and 40° and H wing / L w was between 0.02 and 0.03. Increasing W wing , D FB, or W FB reduced k t . 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, k t of the wing-type FB was less than 0.60. This study offers a useful reference for the design of FBs in offshore environments.