A 3D Navier-Stokes solver to investigate Water-On-Deck events within a Domain-Decomposition strategy

The present analysis is a part of a research activity aimed to develop a numerical method reliable and efficient for seakeep-ing problems with water-on-deck occurrence. Highlighting the need for efficient solutions, the Domain-Decomposition (DD) algorithm was chosen. A two-dimensional DD strategy has already been developed and assessed by comparison against experimental data and other numerical results for fluid dynamic problems similar to the one of interest. Its details can be found for instance in Colicchio et al. (2006) and Greco et al. (2007) and have been documented also at previous workshops. A preliminary 3D analysis was obtained combining a weakly-nonlinear potential flow solver for the exter-nal seakeeping problem with an in-deck shallow-water approximation to handle the water-on-deck events (see i.e. Greco et al. 2009). This has the advantage of being very efficient but has limitation in terms of validity because the nonlinearities involved in the water-ship interactions are accounted for only partially. Just to mention, the water run-up is not properly described when high-speed jets are formed and the plunging-wave phase, which usually characterizes the initial stages of the water shipping, is not captured. The present study is an initial step toward a fully 3D more-general DD solver. The focus is on head sea waves and vessel without forward motion, which are of interest for FPSOs ships used as oil platforms. On the basis of previous 2D and 3D physical and numerical studies, surface tension and turbulence effects are neglected. Within the DD, a linear Boundary Element Method (BEM) will be used to describe the seakeeping problem in the whole fluid domain but fo