In this study, the Bragg scattering of waves propagating over a series of poro-elastic submerged breakwaters is investigated by theoretical derivation and experimental tests. An analytical solution is developed for waves propagating over a series of poro-elastic submerged structures. Water waves are described using the linear wave theory. The poro-elastic structures are assumed to be homogeneous, isotropic, and can be elastic. Based on the improved poro-elastic medium theory using Biot's theory and the turbulent fricative effect, the governing equations are theoretically developed. Continuity of dynamic pressure and flow flux at the interfacial structures surface are used to solve the problem. The general solutions of the wave motions and poro-elastic submerged structures are also derived. Experiments are also conducted in a wave flume to compare the theoretical results. The comparison shows good agreement between theoretical values and laboratory observations. Using the present analytical solution, effects of elasticity, permeability and the breakwater height of the series of poro-elastic submerged breakwters on Bragg reflection are studied. Calculated results show that the softer poro-elastic structures can induce higher wave reflection and lower transmission.
The use of porosity, surface friction and flexibility characteristics of artificial structures in coastal engineering for harbor and coastal protection has gradually increased, as they can effectively reduce the wave forces acting on, wave reflection and run-up in front of the structure. Instead of impermeable reflective concrete structures, these structures clearly decrease loading and impact on natural environment. Due to the flexibility of soft material, the structural deformation induced from water wave disturbs flow field in the vicinity. Subsequently, the waves can be influenced by the flexibility structure and the characteristics of wave reflection, diffraction, transmission and energy dissipation will be different. Hence, to deal with the Bragg reflection by a series of submerged breakwaters, it is more completed to consider the effects of porous and flexible structures on Bragg scattering of water waves.
