Water waves scattering by cylindrical dual porous floating breakwaters connected with a rectangular porous box and floating over an undulated seabed

In this paper, the water waves scattering by a new type of floating porous breakwater is investigated numerically under the assumption of two-dimensional linearized wave-structure interaction theory. The proposed breakwater consists of dual porous cylinders connected with a rectangular porous box and placed over an undulated bottom. The reflection, transmission, and dissipation coefficients, and the wave forces acting on the breakwater system are analyzed for a broad range of structural and wave parameters. Further, the occurrence of Bragg resonance due to sinusoidal and doubly periodic sinusoidal bottom topographies are analyzed. It is observed that the Bragg resonance occurs around the primary Bragg value irrespective of the variations in structural porosities of the seaside cylinder and the rectangular box in case of sinusoidally varying bed profile. Further, the Bragg resonance occurs around the primary and secondary Bragg values in the case of the doubly periodic sinusoidally varying bottom topography. Moreover, the Bragg resonances are strongest around the primary Bragg value and diminish at higher orders with an increase in the porosity of the seaside porous cylinder. In addition, more than $$75\%$$ 75 % of the incoming wave energy can be dissipated with suitable combinations of incident wavenumbers and structural porosities.