The interaction of surface gravity waves with horizontal pitching plate for actively control waves is investigated based on the linearized theory of water waves. The three-dimensional (3D) problem is formulated for the submerged plate pitching about its middle point and the other plate is considered to be floating above the submerged plate. The submerged plate's thickness is considered negligible in comparison with the water depth and wavelength of the incident wave. The study is carried out using the matched eigenfunction expansion method and the analytical solution is developed for the interaction of the surface gravity waves with horizontal submerged structure. The performance is analyzed for both impermeable and porous submerged pitching plate. The numerical results for the reflection coefficient, transmission coefficient, and free-surface deflection are computed and analyzed. The study is carried to find the optimal value of the length and depth of the submerged plate at which the dissipation of the incident wave energy is observed. The reduction the wave transformation due to the pitching of the plate with the change in angle of incidence is also analyzed. The present study will be helpful in the analysis of proper functioning of submerged pitching plate to control wave motion for the protection of offshore structures.

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