Three hours real-time SPH simulation of sloshing flows inside a LNG ship with realistic severe sea-state forcing

The present work is dedicated to the numerical investigation of three-dimensional sloshing flows inside a ship LNG fuel tank. Long time simulations, involving 3-hours real-time duration with realistic severe sea-state forcing, have been performed using a parallel SPH solver running for several weeks on a dedicated cluster. The adopted SPH method relies on a weakly-compressible approach and a Riemann Solver for the calculation of the particle interactions. The latter increases the stability of the scheme and allows for accurate predictions of the pressure during water impact stages (see also [26]). The intrinsic properties of mass and momenta conservation makes it well adapted for the simulation of such kind of violent free-surface flows for long-time evolution. Single phase model has been adopted with a considerable reduction of the CPU costs (for an in-depth discussion see also [27]). The high values of Reynolds numbers involved requires the implementation of a sub-scale model which was embedded in the SPH scheme following the recent literature (see e.g. [9]). Three different filling height conditions are considered. For all of them energetic sloshing flows are induced with the occurrence of several water impact events. The latter are focused on specific zones of the tank depending on the considered filling height (see also [15]). For some conditions the SPH pressure predictions are compared with the experimental ones provided by Hyundai Heavy Industries (HHI). A critical discussion of these predictions is performed in order to highlight in which cases the numerical solver is able to provide good local loads estimations. Conversely, when the SPH results appear to be not realistic, comments on the causes linked to the disagreements with experiments are given.