Numerical Simulation of Two-Phase Slug Flow From Horizontal to Downward Inclined Pipe Using a Hybrid Code Based on Slug Tracking and Two-Fluid Methodologies

The slug flow regime is probably the prevailing pattern in the oil and gas industry, appearing in the nuclear industry as well. As a consequence, several studies have been conducted in order to understand the physics of this flow regime and to obtain a model to predict its properties. This work presents a transient hybrid methodology to simulate the gas-liquid slug regime in pipes with a change of direction from horizontal to downward inclined flow. The simulation initiates with a slug tracking model assuming the pipe to be filled with liquid, and follow the unit cells while they flow through the horizontal section; the information about the unit cells entering the pipe are obtained from experimental data. Near the elbow and beyond, the unit cells are simulated by a simplified two-fluid Lagrangian model, capable of providing flow details with the change of direction, and the dissipation of the slug flow to the stratified regime in a descendent slope. Simulations for a 4.862-m pipe were carried out, with the change of direction from horizontal to −3° and −5°. The results were compared to experimental data, showing that the model can successfully predict the flow behaviour for the given conditions.