Vertical gas dispersion from high-pressure pipeline failures: Characterizing hazardous cloud formation in open environments

This paper examines how natural gas disperses vertically when high-pressure pipelines with large openings fail in unconfined environments, providing insight into hazardous gas cloud development and behavior. A comprehensive study was conducted using a full-scale field experiment (1,219 mm diameter, 12 MPa pressure, 100 mm aperture) combined with a validated computational fluid dynamics (CFD) numerical simulation model to systematically analyze the coupling effects of pipeline pressure and ambient wind speed. The results indicate that: (1) Pipeline pressure determines the vertical jet scale, where jet height is positively correlated with pressure; at 12 MPa, the maximum jet height reaches 69.4 m (approximately 2.65 times that at 4 MPa), and the lower explosive limit (LEL) cloud area follows a quadratic polynomial trend.(2) Ambient wind speed significantly alters the diffusion trajectory; at a wind speed of 10 m/s, the LEL gas cloud area expands by 1.69 times compared to calm conditions, while the jet height is suppressed to 29.9 % of the calm wind value.(3) Our developed dynamic prediction model for the hazardous gas-cloud region achieves a determination coefficient of 0.975 and maintaining prediction errors maintained within approximately 12 %. The proposed empirical correlations and dynamic prediction model provide essential quantitative data support for safety-distance design and emergency-response decision-making for high-pressure natural gas pipelines.