Theoretical analysis of the two-phase steady-state flow characteristic parameters of a sudden enlargement

The basic parameters of two-phase steady-state flow through a sudden enlargement are defined and developed on the basis of the Eulerian formulations of the physical balance laws. The two dimensionless parameters analysed are the singular pressure variation coefficient and the singular irreversible pressure loss coefficient. They are function of three distinct contributions: the dynamic or kinetic energy terms which depend on the void fraction and phase velocities distributions and the local turbulence intensity, the wall friction and gravity terms. The new general dimensionless equations which are found allow to understand the role of the two-phase how pattern which is taken into account by external closure laws. The theoretical results are applied to the vertical bubbly flow at the subcritical regime in order to analyse the influence of several physical parameters on the two-phase characteristics of the abrupt pipe enlargement. Finally, the proposed model is validated on the basis of experimental data obtained for subcritical air-water bubbly flows through vertical sudden enlargements.