Fluid-structure interaction and blast loading of unconfined hydrogen cloud explosions

This study examines the fluid-structure interaction (FSI) effects of unconfined hydrogen-air cloud explosions on wall barriers with varying width-to-height ratios, drawing on Australia's first large-scale unconfined hydrogen explosion field trials. A one-way coupled Computational Fluid Dynamics and Finite Element Analysis (CFD-FEA) framework is established to assess the influence of pressure clearing and blast wave diffraction under both deflagration and detonation combustion scenarios. The Hudson method is adopted for estimating clearing pressure under hydrogen detonation loading. A new exponential decay model for pressure clearing is developed for deflagration, which is calibrated to the geometric and ambient conditions of the experimental setup. Results indicate that blast wave diffraction significantly affects deflagration loading, reducing structural response during the positive phase and amplifying it during the negative phase. To demonstrate practical relevance, the framework is applied to study wall barrier response at 5 m and 7 m standoff distances against hydrogen blast loads. The validated computational framework provides an effective and practical tool for structural safety assessment in scenarios involving unconfined hydrogen-air cloud deflagrations and detonations.