Characterization and modeling of greenwater overtopping of a sea-level deck

Greenwater overtopping occurs when the deck of a marine structure or ship is submerged by a large non -breaking wave. This overtopping wave develops into a fast-moving mass of water that can damage deck structures. In this work we use laboratory experiments to characterize the kinematics of the greenwater fronts, showing that there are two main classes of flow. One class is an essentially two-dimensional flow with a single wave front traversing the entire deck, while the second type has multiple wave fronts originating from all sides of the platform. We characterize each type with respect to wave conditions and describe the transition between the two types. We then discuss two modeling approaches that can be used to simulate the kinematic of the overtopping fronts. A simple linear model, based on linear wave theory and on the assumption of the overtopping as a dam break, to predict the type and the propagation of the overtopping wave on the deck. The second is a three-dimensional nonlinear numerical hydrodynamics model, based on Smoothed Particle Hydrodynamics method, which reproduces the geometry of the overtopping in the laboratory more accurately. We compare the outputs of these models with laboratory observations and discuss their applicability.