Impact loads on a vertical breakwater

comparison between a sph numerical model and empirical formulations

Abstract

The determination of loads which result from the wave-structure interaction is of upmost importance for structure design. The nature of these loads depends not only on the structure characteristics but also on the incident wave conditions. However, determining loads is not a trivial task, since the involved non-linear phenomena, such as wave breaking or reflection, restrict the application of theoretical formulations in the quantification of these loads, leading to the necessary use of other tools, such as numerical modeling. In this paper, the forces on a vertical breakwater were studied using the numerical model SPHyCE based on the Smoothed Particle Hydrodynamics method. This is a mesh-free method based on a Lagrangian formulation of the Navier- Stokes equations that allows free surface flow modeling. Numerical analyses were performed in order to understand the impact loads evolution, by varying the water depth at the structure toe and the height of the incident wave corresponding to different force regimes. After analyzing the final results it was verified that the type of the force regime, to which the structure was subjected, sometimes was not the expected, due to the non-linear phenomena involved, thus making the study of the impact loads evolution not trivial. The numerical model results were compared with those from empirical formulations and it was found that the results were similar for a regime of quasi-standing wave. However, for the regimes regarding the impact loads there were differences due to the fact that i) the breaking does not occur as expected in the formulations; ii) the numerical model does not include the air particles simulation whose influence on the forces is relevant in cases of wave breaking with entrapped air.