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Two types of numerical simulations for the hydrodynamic solution of water entry problems are performed and systematically compared in order to highlight their peculiarities: a viscous Unsteady Reynolds Averaged Navier Stokes (URANS) based on Volume of Fluid (VoF) approach and a meshless Smooth Particle Hydrodynamics (SPH) solver. In both cases open-source software have been chosen. The numerical solutions from the two proposed CFD methods are verified against experimental measurements. The systematic analysis is performed considering a prescribed motion of the wedge aiming to a better understanding of the effect of the model set-up on the prediction of both local and global field variables. Even if a both codes shows a high ability to capture the global physics of the problem, due to the strongly non- linear dynamic of the body-flow interactions involved in impact problems, the local pressure peaks can be hardly predicted if the numerical method is not suitably tuned for the specific problem. Finally the two approaches are performed also for a free falling simulation, comparing the numerical predictions to the available experimental drop tests results.

In the paper a numerical procedure developed in a Matlab® environment is presented, aiming at the definition of the main dimensions of a fleet of ships devoted to the transportation of a bulk cargo. The procedure is meant to provide preliminary indication in the initial phase of feasibility studies. The optimal dimensions are defined through a full factorial analysis. Relevant input data are information about the cargo to be transported (annual quantity, specific gravity, etc.), about the characteristics of the plants needed for cargo handling (weight, dimension, location on board) and about the route. The algorithm is based on a preliminary design modulus which provides solutions in line with requirements and preliminarily checked as regards basic trim and stability requirements. The analysis includes, on the specific geometry considered, an evaluation of the seakeeping performances of the ship in the sea area covering the transportation route. The influence of adverse meteo-marine conditions reflects into an increase in the consumption and in a decrease in the average speed as compared with nominal values (in calm water). The inherent increase in running costs and the need for an incremented net weight nominal capacity to increase the probability of satisfying the specifications in terms of annual actual transportation flow is accounted for. A first set of results is presented, regarding a possible trade of Compressed Natural Gas in the North Sea area.