The paper presents the contribution to the CCP-WSI Blind Test, in which the responses of wave energy converters subjected to extreme waves are considered, by a hybrid model, qaleFOAM, coupling a two-phase Navier-Stokes (NS) model and the fully nonlinear potential theory (FNPT) using the spatially hierarchical approach. The former governs a limited computational domain (NS domain) around the structures and is solved by the OpenFOAM/InterDyMFoam. The latter covers the rest of the domain (FNPT domain) and is solved by using the quasi Lagrangian-Eulerian finite element method. Two numerical techniques have been developed to tackle the challenges and maximizing the computational efficiency of the qaleFOAM, including a modified solver for the six-degree-of-freedom motions of rigid bodies in the NS model and an improved passive wave absorber imposed at the outlet of the NS domain. With these developments, the accuracy and the computational efficiency of the qaleFOAM are analyzed for the cases considered in the blind test.
A reliable prediction of the responses of the offshore structures in a realistic extreme sea plays a fundamental role in the safe and cost-effective design of such structures. Numerous numerical models and software have been developed based on wide ranges of theoretical models, including the Navier-Stokes (NS) models and the fully nonlinear potential theory (FNPT), which assumes that the flow is incompressible, inviscid, and irrotational.