Numerical investigation of the stability of armour units in low-crested breakwaters using combined SPH–Polyhedral DEM method

Abstract

Low-crested breakwaters have become more attractive because they do not hinder the beautiful coastal landscape and are more environmentally friendly comparing to traditional breakwaters. The available formulae for design of these types of structures mainly focus on wave transmission, reflection and dissipation aspects. However, stability of the armour blocks are not directly taken into account in the design process. In this study the Lagrangian meshfree method of SPH along with a discrete element method i.e. Polyhedral DEM are used to simulate the interaction between the sea water waves with different characteristics and low-crested breakwaters constructed using cubic armour blocks. SPH is used for computing the wave forces and moments applied to each armour unit subjected to sea wave action under various conditions. The fluid velocity and pressure time series near the armour units are calculated and based on those, the applied forces and moments are determined. Stability analysis for armour units are conducted by employing DEM which can determine whether the armour units can be displaced by wave action, a phenomenon that causes failure of the whole breakwater over time. Based on the results of a large number of numerical simulations, a practical non-dimensional relationship is proposed for calculating the required dimension of the cubic armour units that can be used for preliminary design of low-crested breakwaters. The newly proposed relationship can fill the gap that currently exists in the literature regarding using cubic armour units for this type of marine structures.