Abstract Summary
The analysis of wave-structure interaction in practical coastal and ocean engineering problems requires large-domains and complex geometries. A study using single-physics numerical models can be computationally prohibitive or have limited accuracy. It is the need of the hour to develop models which are accurate, but should also have a reasonable run-time. Hybrid modelling is an approach that can combine the strengths of different models by applying them only within specific regions of the domain. In the context of ocean engineering problems, the potential flow assumption may be sufficient for capturing wave refraction, reflection and diffraction over the majority of the domain. However, an accurate viscous flow model is required in the local sub-domain around fixed and floating structures for simulating the complex fluid-structure interaction. The manuscript presents fluid-fluid coupling between a mesh-based potential flow model named FEBOUSS and a particle-based viscous flow model MLPG_R to develop a hybrid model for simulating wave-structure interaction in 3D. It combines the computational efficiency of FEBOUSS with the accuracy of MLPG_R to reduce computation time, allow subjecting structures to realistic waves and enable the use of particle-based methods for real-domain problems. FEBOUSS is an in-house finite element model for depth-integration potential flow equations. It is a weakly non-linear 2D free-surface model capable of simulating 3D flows under a wave and is hence computationally efficient. It is proven for simulating wave refraction, diffraction and reflection over large domains with complex bathymetries in shallow and intermediate water depths. MLPG_R is the in-house particle-based model for solving the Navier-Stokes equations in a 3D domain. It solves the pressure Poisson equation in weak form using a Petrov-Galerkin approach resulting in smooth and accurate calculation of pressure. Particle-based methods allow a freely moving free-surface and hence are ideal for capturing the interaction of waves with fixed, floating or moving structures, but have a considerable computational cost. This work presents the application of weak coupling between the two models. FEBOUSS will be used for wave generation and propagation in the realistic large domain of a harbour. A small 3D MLPG_R domain will be generated in the vicinity of a coastal structure within this harbour, to expose the structure to realistic wave conditions from FEBOUSS. This work is a demonstration of this hybrid approach, which can simulate realistic wave loadings with reasonable accuracy and at a moderate computational cost. The techniques developed in this work can be applied to fluid-fluid coupling with other high-fidelity hydro-elastic models for studying the response of flexible wave-energy converters and floating solar farms when exposed to directional wave-spectrums in near-shore conditions.
