A TRANSIENT 2-FLUID MODEL FOR THE SIMULATION OF SLUG FLOW IN PIPELINES .1. THEORY

A one-dimensional transient two-fluid model is developed to predict tr ansient slug flow in pipelines. To account for the interphase interact ions, new constitutive relations for the drag coefficient and the virt ual mass force for the slug flow regime are derived by applying the co nservation equations to a geometrically simplified slug unit. New coef ficients in the pressure gradient term in the two-fluid momentum conse rvation equations are also obtained to account for the non-uniform dis tribution of the phases and of the pressure drop along a slug unit. Th e new relations yield a more accurate treatment of the hydrodynamics o f slug flow than traditional two-fluid models. Constitutive relations for other Bow regimes can also be incorporated into the model, allowin g the analysis of general transient two-phase flows in pipelines.