On the CFD modelling of hydrogen dispersion at low-Reynolds number release in closed facility

Hydrogen release inside closed facilities could cause explosions with harmful consequences. Safety assessment should be performed, in order to design prevention and mitigation measures in case of such an accident. A numerical study for helium (as hydrogen surrogate) accumulation inside a closed facility representative of a real-scale garage at low release rate is conducted. Due to the nature of the examined flow several turbulence modelling approaches (RANS and LES type) and the laminar approach are examined with the aim to evaluate their predictive capabilities in flows resulting from low-Reynolds number leaks. Best practice guidelines are followed in the simulations, several sensitivity studies are performed and different grid types are examined. The comparison of computational results with experimental data shows that RANS and LES approaches reproduce well the gas distribution inside the facility, while laminar approach predicts more enhanced stratification at the release phase. Statistical Performance Measures are used to evaluate the models and narrower acceptable ranges are suggested for releases in indoor configurations compared to open environments.