Towards Understanding the Interfacial Structures of Non-developing Slug Flow in Vertical Pipes

Abstract

Non-developing slug two-phase flows in vertical pipes are widely found in various industries. These flows are of a highly complex nature largely due to the deformability of the gaseous phase resulting in unstable interfacial flow structures at different flow regimes. Such complex interfacial structures strongly control the multiphase transport phenomena including energy, mass, and momentum transfer between the phases. Therefore, a clear understanding of the behaviour characteristics of these interfacial structures is critical to the optimum design of multiphase flow systems. This study briefly provides a review on the behaviour of the gas-liquid interfacial structures for the slug flow regime in co-current upward two-phase flows. This review founds that the interfacial structures of gas-liquid interface exhibit different shapes and behaviours in non-developed compared to the fully-developed regions of slug regime. The behaviour of these structures is found to be heavily influenced by gas injector design, pipe diameter, gas and liquid phase properties, and operating flow conditions. The review also showed that the interfacial structures have been widely studied in developed region, while they have remained less understood in the non-developed region. Also, the impact of liquid and gas phases' thermo-fluid properties (density, viscosity, and surface tension) and pipe diameter on the interfacial structures in this flow regime have received the least attention.