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.

A Comparative Study on Generation and Propagation of Nonlinear Waves in Shallow Waters

“…We also use a tank that utilizes the GN equations both at the wavemaker and inside the domain, see [37] for details of the theoretical tank of the GN equations. See [38][39][40][41] for some studies on nonlinear wave dynamics and wave-structure interaction utilizing GN numerical tanks. For internal wave solutions of the GN equations, see, e.g., [42].…”

Scattering of Long Waves by Freely Oscillating Submerged Plates

“…The Level I GN model is best applied to propagation of long waves in shallow water, see e.g. [4], [19] and [22]. For higher level GN equations, the vertical velocity field is prescribed in terms of high-order functions, see e.g.…”

“…at the edges of the plate, the pressure above the plate is equal to that below the plate. See [19] for more details about the jump and matching conditions used in this study.…”

“…At each time step, as the external forces are known, the plate oscillation is determined by use of the fourth-order Runge-Kutta method. See [19] and [31] for more details on the numerical solutions used in this model.…”

“…In this study, we use a nonlinear, dispersive approach to study wave scattering by a submerged, oscillating horizontal plate, namely through the Level I Green-Naghdi (GN) equations. We follow a similar approach recently proposed by [19] to study this problem. The wave scattering is investigated by defining wave reflection and transmission coefficients.…”