Numerical modelling has the potential to probe the complexity of the interacting physics of rubble mound armour systems. Through forward modelling of armour unit packs, stochastic variables such as unit displacement and maximum contact force per unit during an external oscillatory disturbance can be predicted. The combined finite-discrete element method (FEMDEM) is a multi-body method ideally suited to model the behaviour of the armour layer system and the stresses generated within complex shape units. In this paper we highlight the latest developments made with the application of FEMDEM technology to breakwater modelling including realistic rock underlayer and concrete unit layer topologies, maximum contact force distributions, internal unit stresses, fracture and unit breakages. Finally, fully coupled wave and multi-body armour unit motion with internal dynamic stress generation is illustrated.

FEMDEM modelling which combines the multi-body particle interaction and motion modelling (i.e. Discrete Element Model, DEM) with the ability to model internal deformation of arbitrary shape (Finite Element Model, FEM) has been applied to breakwater models. There are two versions of a FEMDEM solver developed; Y3D-D is for deformable materials and is required for dynamic and static stress analysis and Y3D-R is the rigid version often used to numerically construct the armour unit packs. This paper also reports the placement protocols: POSITIT. FEMDEM modelling deals with solids interactions and is one modelling component that is to be coupled to other modelling technologies e.g. CFD, interface tracking, wave models, porous media etc. so that the key fluid-solid interactions can be modelled in a full scale virtual breakwater alongside work on scaled hydraulic laboratory models and prototype structures. The latest developments of two-way coupled interactions of waves with coastal structures are also described in this paper.

The aim of the present study is to provide a rigorous analysis of the water wave modelling capabilities of the advanced multipurpose CFD code Fluidity. This code has been developed at Imperial College London over a large number of years and benefits from an open source GNU license. In contrast to similar studies adopting closed-source in-house or commercial solutions, the results presented herein may be verified by any computer literate reader. The investigation focuses on the simulation of gravity water waves; their detailed understanding being fundamental to the design of many offshore (marine) solutions, including the emerging fields of wave energy conversion and floating offshore wind applications. Both small amplitude (linear hydrodynamics) and finite amplitude (nonlinear hydrodynamics) regular waves are simulated in a 2D Numerical Wave Tank (NWT). First, and assessment of the NWT's capabilities in accurately modelling wave propagation and wave energy conservation of linear waves is undertaken. Subsequently, the simulated wave field is directly compared with results obtained from linear wavemaker theory. For the purpose of the nonlinear wave investigation, two wave generation techniques are adopted, and comparisons with a high-order potential flow theory are made. The overall agreement between the simulation results and theory was found to be very good.