A Discrete Particle Model for Bubble-Slug Two-Phase Flows

Abstract

Most two-phase flow models are based on the fully averaged two-fluid concept. This paper describes a new discrete particle model that is intermediate between the numerically intractable local instant description and the fully averaged two-fluid model, thereby providing a more detailed but still tractable description of dynamical two-phase flow phenomena. The new model uses a Lagrangian description for a single dispersed bubble phase and a one-dimensional Eulerian description for a single continuous liquid phase. In contrast to many other particle simulation models, the present model includes compressible phases and large bubbles whose size may be comparable to the computational cell size. The discrete Lagrangian description of the dispersed phase allows the particles to have a distribution of sizes, shapes, etc., thereby capturing the important statistical aspects of dispersed two-phase flow. In contrast to the two-fluid models, the discrete particle model allows the use of more mechanistic models for dispersed phase coalescence and breakup, wakes, etc., thereby allowing the dynamic prediction of flow regime evolution and transitions without the use of flow regime maps inherent in two-fluid models. Numerical simulations for two test problems are presented. Agreement with experimental data is generally satisfactory. Extensions of the model to heat transfer and to two discrete and two continuous phases will be described elsewhere.