CFD simulations of instantaneously released liquefied gas in urban areas: A case study of LPG tank truck accident in Wenling, China

•Investigate the dispersion of instantaneously released LPG by CFD model.•Reconstruction of a realistic accident scenario of LPG release using 3D terrain.•Validation of the CFD model using the damage distribution of an actual accident.•Effect of the instantaneous release source parameters on cloud dispersion.•Large obstacles and terrain conditions strongly affected the dispersion behavior. The accidental release and ignition of flammable liquefied gas can cause catastrophic events, such as flash fires, vapor cloud explosions, and boiling liquid expanding vapor explosion, which severely endanger urban residents and the environment. In the current study, a method for simulating liquefied gas instantaneous release accidents was established to explore the vapor cloud diffusion behavior in urban areas. The rare liquefied petroleum gas instantaneous release accident in Wenling, China is considered as a test case. To this end, an instantaneous release source model that considers the gas phase, liquid pool, and droplets was developed. The CFD model was validated using the damage distribution at the accident site. The simulation results revealed that droplets in the release source, terrains, and large obstacles significantly affected the dispersion behavior and extension distance of the vapor cloud. The evaporation of droplets resulted in a mushroom-shaped cloud. In addition, when the cloud was ignited, the area covered by the LFL was 1.94 and 2.07 times larger in the cases with droplets than those without. The method developed in this study is applicable to developing hazardous chemical transportation and emergency response measures in urban environments to maintain the sustainable cities development.