This paper discusses several numerical tools to model scenarios of a hydrogen leak. The first one is a CFD model and the second is HYRAM+, an engineering tool based on publicly available data and models. The CFD model was validated using experimental data and benchmark results of similar models and used to investigate the effect of leak rates and forced ventilation in a 40-foot container. The outcome was compared with HYRAM+ results and differences in layer height and H2 concentration were found, showing that HYRAM+ underestimates both. One of the CFD dispersion results was used as initial situation to simulate the ignition of a Hydrogen layer, resulting in a fast propagation of the flame front and a significant increase in pressure. The results show the applicability of CFD and other numerical tools for the early risk assessment of hydrogen-fuelled ships and, the outcome can be used designing the fuel-cell ventilation systems and performing explosion risk assessments
