A 3D fully nonlinear potential flow (FNPF) model based on an Eulerian formulation is presented. The model is discretized using high-order prismatic - possibly curvilinear - elements using a spectral element method (SEM) that has support for adaptive unstructured meshes. The paper presents details of the FNPF-SEM development, and a model is illustrated to exhibit exponential convergence for steep stream function waves to serve as validation. The model is then applied to the case of focused waves impacting on a surface-piercing, fixed FPSO-like structure. Good agreement is found between numerical and experimental wave elevations and pressures.


Significant efforts have been made for several decades to develop reliable tools for wave-body interaction based on fully nonlinear potential flow (FNPF) theory: models that can handle real-life geometries of offshore structures and floating bodies. Ma and Yan (2009) discuss the pros and cons of boundary element methods (BEM) and finite element methods (FEM). The review paper of Wang and Wu (2011) provides an overview of the efforts made in FEM-based FNPF solvers. BEM, FEM, and pseudo-spectral-based FNPF solvers have successfully been applied to focused wave groups and extreme waves; see, e.g., Grilli et al. (2010), Ma (2007), and Ducrozet et al. (2007). Handling both the wave propagation problem and the wave-body interaction problem within one model remains a challenging task. Today's state-of-the-art tools are often based on a hybrid modelling approach where two different simulation tools are combined through weak coupling. Typically, an FNPF-based wave propagation model is coupled to a two-phase Reynolds-averaged Navier Stokes model using the volume of fluid approximation (VOF-RANS); e.g., see the work of Duz et al. (2016), or for a smoothed particle hydrodynamics (SPH) model, see, e.g., Verbrugghe et al. (2018).

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