The large eddy simulation (LES) model developed at the University of Ulster has been applied tosimulate releases of 5.11 m3 liquefied hydrogen (LH2) in open atmosphere and gaseous hydrogen(GH2) in 20-m3 closed vessel. The simulations of a spill of liquefied hydrogen confirmed theadvantage of LES application to reproduce experimentally observed eddy structure of hydrogen-aircloud. The inclination angle of simulated cloud is close to experimentally reported 300. The processesof two phase hydrogen release and heat transfer were simplified by inflow of gaseous hydrogen withtemperature 20 K equal to boiling point. It is shown that difference in inflow conditions, geometry andgrid resolution affects simulation results. It is suggested that phenomenon of air condensation-evaporation in the cloud in temperature range 20-90 K should be accounted for in future. Thesimulations reproduced well experimental data on GH2 release and transport in 20-m3 vessel during250 min including a phenomenon of hydrogen concentration growth at the bottom of the vessel.Higher experimental hydrogen concentration at the bottom is assumed to be due to non-uniformity oftemperature of vessel walls generating additional convection. The comparison of convective anddiffusion terms in Navie-Stokes equations has revealed that a value of convective term is more thanorder of magnitude prevail over a value of turbulent diffusion term. It is assumed that the hydrogentransport to the bottom of the vessel is driven by the remaining chaotic flow velocities superimposedon stratified hydrogen concentration field. Further experiments and simulations with higher accuracyhave to be performed to confirm this phenomenon. It has been demonstrated that hydrogen-air mixturebecame stratified in about 1 min after release was completed. However, one-dimensional models areseen not capable to reproduce slow transport of hydrogen during long period of time characteristic forscenarios such as leakage in a garage.