This paper presents numerical results based on the ISOPE-2020 comparative study (Sriram, et al., 2020; 2021) on steep focused waves interactions with fixed and moving cylinders. A fully nonlinear threedimensional numerical wave tank based on a high order boundary element method is used. It is parallelized using Message Passing Interface (MPI) and the domain decomposition method to boost the efficiency. The wave elevations and pressures at different positions are calculated and compared with the experimental data provided by the organizers of the comparative study.
Extreme wave conditions can cause great damage to offshore structures (Stansell, 2004) and therefore must be taken into account during the design process. To understand extreme wave loads on structures, such as monopiles, it is essential to reproduce the wave conditions in the laboratory or with numerical simulations. In a wave tank, extreme waves can be modelled using focused waves (Ning, et al., 2009), which are generated based on the linear superposition of many small amplitude components focused at a point. The focal point can be designed so that the highest wave crest collides with the structure.
In order to understand focused wave loads on structures, several numerical methods have been proposed. They usually solve the Navier-Stokes equations using commercial CFD packages (Westphalen, et al., 2012), the volume of fluid method with open source code OpenFOAM (Chen, et al., 2014) and the level set method with open source software REEF3D (Bihs, et al., 2017). It is also possible to study this problem in the framework of potential flow theory with a finite element method (Ma et al., 2001) or a boundary element method (Bai et al., 2007). To benefit from both frameworks, a potential flow solver and a Navier–Stokes/VOF solver can be combined together to lower the computational cost (Paulsen et al., 2014).
To develop a global understanding on the current numerical tools in studying this problem, a comparative study was organized during ISOPE-2020 (Sriram et al., 2020; 2021). A set of experiments were conducted and used for validation. In this study, a fully nonlinear three-dimensional numerical wave tank based on a high order boundary element method is used. The numerical simulations are set-up to mimic as closely as possible the experiments, including the focused wave generation and the distance between the wave maker and the vertical cylinder. To overcome the long length of the wave tank, a domain decomposition method is adopted and the code is fully parallelized to boost the efficiency.
