Effect of trench configuration on the scattering and radiation of surface gravity waves by different floating breakwaters

A motion response analysis is conducted to examine the behavior of two distinct floating breakwaters: (i) a breakwater with a slanted front face and (ii) an inverted F-type, in the presence of an array of arbitrary trenches, within the framework of linear water wave theory. This work proposes a numerical and semi-analytical solution based on the boundary element and matching eigenfunction methods. The motions of floating breakwaters are investigated by tracking heave, surge, and pitch responses. This paper describes the construction of a potential floating breakwater design to decrease wave height under varied bathymetric circumstances. The study reveals that the presence of trenches in a periodic structure modifies the effective periodicity, leading to shifts in the harmonic and sub-harmonic peaks of Bragg resonance, as well as potential changes in peak intensity due to scattering and wave localization. Moreover, negative added mass and pronounced peaks in both damping and added mass coefficients were observed when the fluid motion is entrapped and standing waves were generated between the trench and breakwater. Further, the research indicates that the slanted front face floating breakwater with varying lateral inclined angles reduces the structure's substantial wave force and motion responses. However, with its stepped and more complex geometry, the inverted F-type breakwater demonstrates a higher effective added mass and damping coefficient than the slanted front face breakwater due to the intricate water displacement mechanisms caused by the multiple segments and edges.