Numerical simulation of wave interactions with floating offshore renewable energy structures: A comparative study between a Particle-based PIC model and OpenFOAM

Mesh-based Eulerian and particle-based Lagrangian models are common computational fluid dynamics (CFD) tools for simulating wave-structure interactions. While Eulerian models are efficient in terms of computational time, they are limited in their ability to handle large interface discontinuities between two flows and complex structure motion responses. Conversely, Lagrangian models are suitable for such discontinuities and motion responses but can be computationally expensive. However, there is a lack of comprehensive discussion on the (dis)advantages of hybrid Eulerian-Lagrangian models, which have the potential to achieve both numerical efficiency and flexibility through a combined use of mesh and particles. This paper presents a comparative study of a hybrid Eulerian-Lagrangian Particle-In-Cell (PIC) model and the widely-used OpenFOAM model, applied to a variety of complex wave interactions with floating offshore renewable energy structures in both 2D and fully 3D domains. We found that both models demonstrate good performance in simulating complex floating structures. Additionally, it is the first time that the two models have been compared in parallel on the same computing facility, allowing us to directly show their computational efficiency. The PIC model has the advantage of using staggered grids, which enables it to achieve computational efficiency comparable to the pure mesh-based OpenFOAM. The findings of this study provide researchers and practitioners in the field of computational fluid dynamics with a clear understanding of the performance of the hybrid Eulerian-Lagrangian PIC model and OpenFOAM for simulating complex fluid-structure interaction problems.