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ONE OF THE key issues in the design and construction of any gas pipeline is the
prevention of material fracture. Since the gas is generally transported under high
operating pressures, it must be ensured that the gas pipeline is sufficiently tough to arrest the
propagation of any potential fracture. For several decades, control of gas pipeline fracture
propagation has been under scrutiny due to economic considerations and ecological and safety
hazards related to pressurised pipe failure. The Battelle Two Curve approach has been widely
used to determine the minimum material arrest toughness by comparing the gas
decompression wave velocity with the fracture velocity, both as functions of the local gas
pressure. Sufficient knowledge of the gas decompression behavior following the rupture is
therefore crucial in determining running fracture arrest toughness levels. The decompression
behaviour is influenced by the operating conditions, fluid composition and the material
properties of the pipeline itself. This paper describes a two-dimensional decompression model
developed using the commercial Computational Fluid Dynamics (CFD) software ANSYS Fluent.
The GERG-2008 Equation of State has been implemented into this model to simulate the rapid
decompression of common natural gas mixtures. The evolution of the decompression wave
speed and phase changes under arbitrary initial conditions is reported. Comparison with
experimental results obtained from shock tube tests showed good agreement between
simulation and experiment.