Scattering of oblique incident waves by a rigid floating structure in the presence of two surface-piercing thick porous breakwaters: Pattern of reflection, dissipation and wave forces

The present work examines the wave interaction with a rigid floating structure, placed after two distinct porous structures, to mitigate wave-induced forces acting on the floating structure. The physical and mathematical consideration of the wave passing through these thick porous structures is based on the model devised by Sollitt and Cross (1972). Splitting the fluid domain into nine regions, the scattered potential in each region is obtained by setting up a system of equations using the relevant matching conditions across the boundaries. The behavior of the roots of the dispersion relation is analyzed to identify conditions under which the eigenfunction solution may become invalid. The graphs plotted for the reflection coefficient, transmission coefficient, dissipation coefficient, and wave-induced forces acting on the floating structure indicate several findings: (i) if the porosity of the second porous structure is less than that of the first porous structure, then the wave energy loss increases, thereby enhancing the safety of the floating structure through reduction of the forces, (ii) as the value of the friction factor of both breakwaters increases, the reflection coefficient decreases, (iii) by increasing the height and thickness of the breakwaters, more loss of wave energy can be achieved due to the dissipative nature of the porous structures. Consequently, the forces acting on the floating structure decrease, helping in its stability. The findings propose the appropriate values of different parameters for an efficient design of such porous breakwaters, as well as how they need to be located.