Modelling of annular flow through pipes and T-junctions

This paper describes a computational model for the prediction of isothermal annular two-phase flow in vertical and horizontal intersecting pipes and presents the results of its application to predict phase separation in a horizontal T-junction. The method is based on computational fluid dynamics techniques (CFD) to compute the dispersed core flow simultaneously with the flow of the liquid film along the walls. The core is represented as a dispersed two-phase mixture in which the droplets are tracked using a Lagrangian technique; the wall liquid film is modelled as a thin boundary layer. Full account is made of the interaction between the wall-film and the droplet flow in the core through mass and momentum transfer mechanisms. The method has already been validated against experimental data for fully developed annular flow in vertical and horizontal pipes; there, the predicted film thickness was found to be in satisfactory agreement with data obtained from the literature. The method is now applied to the phenomenon of phase separation occurring in T-junctions where it is found that the predictions for phase split agree quite well with measurements from an independent experiment for a range of phase split ratios. The predictions for wall-film thickness also exhibit similar trends to the data but do not quite match the locations where wall-film thickness peaks occur. (C) 2003 Elsevier Ltd. All rights reserved.