A general double layer-averaged model for water–air two-phase pipe flows

Abstract

Water–air pipe flow, a common phenomenon in various engineering areas, usually demonstrates complex flow patterns in response to diverse pipe configurations and operation schemes. However, most existing numerical models for water–air pipe flows only target at one or two flow patterns, demanding a pre-estimated flow pattern and unable to resolve pattern transitions that frequently occur in water–air pipe flows. The present study aims to develop a general double layer-averaged model (DLTP) for water–air pipe flows. The present DLTP model explicitly resolves the pressure, velocity and volume fractions for both phases, vertical water–air distribution, and air configuration. As benchmarked against five distinctly patterned experiments on water–air two-phase pipe flows, the present model demonstrates encouraging performance and exhibits a higher computing accuracy as compared with existing models. Notably, flow transitions are well captured by the present model in a field-scale piston-flow case. Additionally, two experiments on single-phase water flow and airflow are computed as special cases, which demonstrates the ability of the present model to well resolve single-phase pipe flows. The present study facilitates a promising framework for the unified modelling of distinctly-patterned water–air pipe flows, in support of effective pipe design and management.