Research on Numerical Simulation of Gas Migration Patterns during Gas Leaks in Underground Utility Tunnels

Abstract

This study aims to investigate the gas migration behavior during a gas leakage incident in the underground pipe gallery's gas chamber. A geometric model incorporating supports was developed using Fluent numerical simulation software, allowing for an examination of how key factors such as leakage velocity and ventilation conditions influence gas diffusion. The findings indicate that the movement of gas within the pipe gallery begins to stabilize approximately 10 seconds after a leakage event occurs. Under natural conditions, ring vortices form on both sides of the gas gallery; conversely, under ventilated conditions, a counterclockwise vortex develops above the gas pipe. The area of methane accumulation varies with different ventilation scenarios during a leak. In natural conditions, methane primarily establishes a stable circulation pattern on the right side of the pipe gallery, while some is entrained by airflow on its left side and remains trapped; under ventilated conditions, methane accumulates in a circulation zone at the lower right corner of the pipe gallery and adjacent to support structures where it cannot be expelled. As leakage velocity increases, under natural circumstances, the volume fraction of methane rises from 11.17% to 23.38%, reflecting an increase of 12.21%. In contrast, under ventilated conditions, this fraction grows from 1.81% to 3.01%, marking an increase of 1.20%.