Bragg scattering of surface gravity waves by an array of submerged breakwaters and a floating dock

Abstract

The scattering of gravity waves by a rigid floating dock in the presence of an array of porous and non-porous breakwaters of different configurations is analysed under the framework of linear potential flow theory. The waves passing the submerged porous structures are assumed to follow Darcy’s law. Two independent physical problems such as the array of porous and non-porous breakwaters, placed (i) underneath the floating dock and (ii) at a finite distance from the floating dock, are examined. The occurrences of Bragg resonant reflection and corresponding bandwidth by each of the structural configurations are accounted for additional advancement of coastal rehabilitation. With the introduction of structural porosity to submerged breakwaters, the fluid force diminishes monotonically due to the wave energy dissipation by the porous structure. The floating dock exhibits a significant impact in reflecting the incident waves of shorter wavelength. The free spacing available between the breakwaters and the floating dock increases the Bragg resonance. The magnitude of the hydrodynamic force experienced by the floating dock is truly maximal on account of triangular periodic breakwaters due to extremely insignificant wave damping as a result of zero-crest width near the submerged end of the breakwaters. The semi-trapezoidal and trapezoidal structures show practically identical benefits of dissipating coefficients due to the slanting interfaces. The scattering coefficients reveal that the array of rectangular breakwaters located at a finite distance from the floating dock are advantageous than that of breakwaters located underneath the dock for dissipating the incident wave energy.