Numerical simulation of the impact of a plunging breaker on a vertical structure and subsequent overtopping event using a Navier-Stokes VOF model

We study processes that occur during impact of a breaking wave on a vertical wall, and the resulting overtopping event, based on numerical simulations using a multiple-fluid Navier-Stokes VOF model (air-water). The latter allows to track high interface deformations during the breaking and impact. Both impact process and overtopping event are studied as a function of the relative distance of the vertical wall from the breaking point (defined as the location where a vertical tangent appears on the free surface). We study hydrodynamic forces and pressure peaks on the vertical wall, with the temporal and spatial discretizations. Expectedly, a finer discretization leads to a better description of the pressure peak on the wall, which can increase the total force applied to the wall by up to a factor 6. Similarly, we study, overtopping rates as a function of the distance of the breaking point in front of the wall. Some studies indicated that the critical case, yielding maximum volumetric rate, is for a wall placed at the breaking point. In the application studied here, the maximum overtopped volume of water occurs for a distance to breaking equal to 1.69 times the breaking wave height. © 2010 by The International Society of Offshore and Polar Engineers (ISOPE)