The paper presents the numerical results for the focusing wave interacting with a FPSO-like structure using the FNPT-NS solver. The case configuration is defined by CCP-WSI blind test in ISOPE 2018. The incident waves are uni-directional focusing waves with different spectrum bandwidths and wave heights. The structure is fixed and subjected to different heading. The numerical model used in present work is a hybrid model combining a fully nonlinear potential theory (FNPT) and a Navier-Stokes (NS) theory using a domain- decomposition approach. The Quasi Arbitrary Lagrangian Eulerian method is used to solve the FNPT in a large domain covering the entire wave basin with the same size as the experiments. For the later, the OpenFOAM (interDyMFoam) is utilized to achieve the solution near the structures, where the viscous effect may be important. In addition, the wave generation and the convergence of the hybrid model are discussed in detail.
It is nowadays increasingly recognized that accurate and efficient predictions of the wave load on offshore structures are very important for accessing their survivability in extreme weather conditions. Such assessments can always be performed in laboratory environment or in the numerical wave tanks, where the extreme waves are often modeled by using, e.g., the NewWave theory (Tromans, et al., 1991). In order to perform reliable predictions of the wave loads, classical approaches in frequency domain are employed, such as linear and second order theories, which however are shown to be insufficient when higher-order nonlinear effects are pronounced. Such higher-order nonlinearities are pointed out to play important roles in the interactions between extreme waves and structure (Zang, et al., 2010). To overcome this drawback, approaches in time domain while considering sufficient nonlinearities are developed, e.g., models based on the fully nonlinear potential theory (FNPT) and those based on the general flow theory by Navier-Stokes (NS) and continuity equations. The former assumes the flow to be inviscid and irrotational, which includes a variety of numerical tools, such as the boundary element method (BEM) (Longuet-Higgins & Cokelet, 1976; Grilli, et al. 2001), finite element method (FEM) (Wu & Eatock-Taylor, 2003) and quasi-arbitrary Lagrangian Eulerian finite element method (QALE-FEM) (Yan & Ma, 2007; Ma & Yan, 2009), etc. Meanwhile, the latter can be solved by using mesh-based methods (Chen, et al., 2014; Hildebrandt & Sriram, 2014), or alternatively, meshless smoothed particle hydrodynamics (SPH) (Lind, et al., 2012; Zheng, et al., 2014) and the meshless local Petrov-Galerkin (MLPG_R) method (Ma, 2005; Zhou & Ma, 2010; Sriram & Ma, 2012).
