The rapid development of hydrogen energy transportation presents significant leakage risks, especially for high-pressure road transport via tube trailers in confined tunnels, where dispersion is impeded by vehicle blockage (β) but aided by longitudinal ventilation (v). However, the coupled effect of these competing factors on risk remains unquantified, hindering safety optimization. This study employs a transient Computational Fluid Dynamics model to investigate a 20 MPa hydrogen leak, systematically evaluating blockage ratios (β = 0–0.207) and ventilation velocities (v = 0–9 m/s) under a worst-case traffic stagnation scenario. Key findings reveal a clear competition between ventilation-driven dilution and blockage-induced accumulation. The initial leak forms a momentum jet that transitions into a buoyancy-driven flammable cloud. While increased blockage paradoxically enhances local accumulation via turbulence, ventilation proves to be the dominant mitigation factor. Velocities below 4.5 m/s allow for significant flammable gas accumulation, whereas a velocity of 4.5 m/s or greater effectively suppresses hydrogen concentrations below the 4% lower explosive limit, even under severe blockage. By first quantifying this competitive β–v coupling mechanism and developing a model showing ventilation's dominance, this study establishes 4.5 m/s as a critical safety threshold. These results provide a vital quantitative basis for optimizing tunnel ventilation designs and developing robust emergency strategies to significantly reduce hydrogen explosion risks.
Chen et al. (Fri,) studied this question.