Hydrodynamic Performance of an Array of Stratified Pile Rock Breakwaters Placed on Elevated Seabed

The present study outlines the hydrodynamic performance of stratified pile-rock breakwaters (SPRBs) in series using the analytical calculation under the framework of linearized potential flow theory. The rubble mounds are separated into two porous layers (surface and bottom layers) and tightly packed within the space available between the seaside and leeside vertical piles. The SPRB is installed on the elevated bed, and it is considered as a bottom rigid layer. The newly proposed breakwater is titled as stratified pile-rock breakwater and vertical piles are suggested to minimize the unwanted displacements of rubble mounds from frequent failures due to the incident wave stroke. The analytical model is developed based on the method of matched eigenfunction expansions (MMEEs) along with suitable boundary conditions to assess the hydrodynamic performance of the SPRB. The study results are compared with the literature based on experimental and analytical methods for specific conditions. The wave reflection, transmission, and energy damping by a series of SPRBs are reported for changes in incident wave properties and breakwater physical properties. The effect of layer porosity, angle of contact, free spacing, and number of breakwaters on the hydrodynamic coefficients is reported. The study suggested that a pair of SPRBs having 80% and 40% porosities for surface and bottom layers, with clear spacing, varied within 1 ≤ w/h₁ ≤ 2, and the angle of contact varied within 30 deg ≤ θ ≤ 45 deg to achieve a 90% wave-damping when the relative wavenumber is k₁₀h₁ = 1.