Influence of cross-sectional geometry on the wave attenuation performance of floating breakwaters: an experimental study

Floating breakwaters (FBWs) offer a sustainable alternative for coastal protection against wave-induced erosion. However, the influence of cross-sectional geometry on attenuation performance remains insufficiently quantified. Therefore, this study experimentally investigates the hydrodynamic performance of modular FBWs, focusing on the wave transmission across three distinct profiles: rectangular, triangular, and trapezoidal. These geometries were selected to systematically evaluate the effect of slope angle and wave-surface interaction on wave attenuation. The tested rectangular FBW exhibited a baseline wave attenuation efficiency of 47%, which was systematically improved through geometric modification. Among the three tested inclination angles (α = 30°, 45°, and 60°), the triangular FBW achieved its optimal performance at 30°, reaching an average efficiency of 66%, representing a 19% improvement over the rectangular FBW while requiring 56% less material. The trapezoidal profile demonstrated the highest performance, reaching an average efficiency of 83%. Furthermore, geometric orientation dictates the hydrodynamic mechanism; an upright side-slope configuration outperformed the inverted orientation. In addition, positioning the sloped face on the leeward side enhanced wave attenuation compared to seaward placement. Consequently, a trapezoidal profile with a leeward-oriented slope is recommended for practical implementation because it offers the best balance between hydrodynamic performance, inherent hydrostatic stability, and constructability.