Numerical modelling and validation for a methane leak from a buried pipeline

The release of methane from buried pipelines poses potential risks to humans and the environment. Prediction of the flammable methane-air envelope from a buried leak is important for safety recommendations and the estimation of hazard distances for pipelines. This work describes the development and validation of a computational fluid dynamics model capable of simulating an underground gas pipeline leak. Three-dimensional, unsteady, incompressible flow of methane through a sand layer to the atmosphere was simulated. The sand was considered as a porous medium. A species transport model was used for methane diffusion in sand. The dispersion of a buried methane, leak from a 4 mm and 2 mm diameter leak hole, and pipeline pressure of 300 kPa is presented. Validation of the model against experimental data for the initial stages of the leak is demonstrated. The numerical simulations of the first 60 s of the leak demonstrate a high degree of accuracy in capturing the transient behaviour of methane dispersion when compared with experiment. The model offers insights into the factors influencing the spread and dilution of the flammable cloud, thus serving as a reliable predictive tool for hazard distance estimation. The innovative aspect of this model lies in its unique portrayal of the flammable cloud development that is often overlooked in current modelling approaches. The model can be used to underpin inherently safer design of buried pipelines and devising emergency response procedures to gas leaks.