A novel numerical model for simulating dynamic pipeline fracture propagation in CO2 considering complex decompression behavior

The pressure wave inside a supercritical/dense CO₂ pipeline that fractures displays typical staged decompression characteristics due to the CO₂ leaking inside the pipeline. It is necessary to consider the effects of CO₂ decompression behavior. Given the high computational cost of fluid-structure interaction (FSI) methods, this paper proposes an efficient and robust decoupled approach for solving CO₂ fracture propagation. This method uses shock tube models, decompression wave models, and empirical formulas for pipe flap decompression to describe the complete decompression behavior of CO₂ in the pipe during the pipe fracture process. Different forms of decompression pressure loads are applied to the crack tip and the areas in front of and behind it to simulate the CO₂ decompression response during the fracture process. Based on the Cohesive Zone Model (CZM), a full-length model and a short pipe section rupture model were built, taking into account the interaction between the pipe and the soil during the rupture process using the SPH method. According to the study, the model's predicted maximum speed and average speed had relative errors of 8.6 % and 12.6 %, respectively. Among them, the full-length model can predict the fracture speed of each pipe section more conservatively, and when the crack propagates to the production pipe, it shows a clear tendency to arrest. The initiation and transition pipes' fracture velocities can be described by the short pipe section model, but it has limited predictive power for fracture arrest.