Experiments and computations of wave-induced oscillations of submerged horizontal plates

Abstract

Wave-induced oscillations of submerged horizontal plates are studied by conducting laboratory experiments and by developing theoretical and computational models. These models include a linear solver based on the Green-function method, a nonlinear model based on Green–Naghdi wave equations, and a model based on computational fluid dynamics. The submerged horizontal plate oscillates in the vertical direction due to oscillatory wave loads. Oscillations of the plate are controlled by the use of a spring-damper system. Laboratory measurements and the models provide quantitative information on (i) how oscillations of submerged plates vary with wave conditions, plate characteristics, and the control system and (ii) how different models using different levels of assumptions predict the wave-induced oscillations. Particular attention is given to energy-production applications of the submerged oscillating plate, and discussion is provided on how the oscillation height and velocity vary with its initial submergence depth, stiffness of the attached spring, and the strength of the viscous damper. It is found that the oscillation varies almost linearly with the wave height, but nonlinearly with the wave period, initial submergence depth of the plate, damping, and the spring stiffness. Overall, it is found that nonlinearity plays an important role in this problem, while the effect of viscosity is negligible.