Numerical Investigation on Natural Gas Leakage and Diffusion from Buried Pipelines in Soil: Effects of Pipeline Parameters and Leakage Hole Characteristics

Understanding the law of gas diffusion in soil is essential for pipeline risk assessment. A 3D CFD model of natural gas leakage and diffusion from buried pipelines was developed in Ansys Fluent using the Detached Eddy Simulation turbulence model, with soil as an isotropic porous medium. Six parameters—burial depth, pipe diameter, transportation pressure, leak hole diameter, hole shape, and hole orientation—were systematically investigated under an identical numerical framework. First Danger Time (FDT), Farthest Danger Range (FDR), and Ground Danger Range (GDR) were used as unified hazard metrics for quantitative cross-factor comparison. As burial depth increases, FDT and FDR increase monotonically, whereas GDR peaks at 2.0 m. Increasing pipe diameter reduces FDT, FDR, and GDR. Higher pipeline pressure shortens FDT and expands FDR and GDR. Leak hole diameter dominates: increasing from 5 to 200 mm reduces FDT to nearly zero. For equal cross-sectional area, rectangular slits yield the highest mass flow rate and largest danger range, while triangular holes produce the shortest FDT owing to strong corner-induced turbulence. Upward leaks give the shortest FDT but smallest FDR; downward leaks produce the largest FDR; side leaks cause the longest FDT but largest GDR. Factor influence ranking by FDT and FDR change is: leak hole diameter, burial depth, pipeline pressure, hole orientation, pipe diameter, and hole shape. These results provide a quantitative framework for hazard assessment, sensor layout optimization, and emergency-response prioritization in buried natural gas pipelines.