The present paper is focused on the development of an accurate 1D numerical model for pig motion in two-phase flow. The focus will be on the liquid slug that is accumulated in front of the pig, the so-called pig-generated slug. Under the assumption of a stratified flow, we first discuss the academic case of liquid slug accumulation where we neglect the viscosity of the fluids. The size of the liquid slug will then effectively be determined by the speed of the hydrostatic wave which runs ahead of the pig. We also consider the more realistic case which includes the viscosity of the fluid. Finally, we discuss the effect of the presence of a by-pass in the pig on the accumulated liquid slug.


Several efforts have been made in the past to model the trajectory of a pig, which is propelled by the fluids in a pipeline. These efforts often rely on a 1D cross-sectional description of the fluid, while the pig is modelled as a point mass. The reason for this simplified approach is the high aspect ratio of the problem, which leads to an approach in which only considers variations in the direction of the curvilinear coordinate that runs along the pipeline.

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