Chapter 5 - Gas–Liquid Flows

Abstract

This chapter focusses on the specific modelling approaches and techniques to handle gas–liquid flows. Owing to the complexities of interfaces and resultant discontinuities in fluid properties as well as from physical scaling issues, a statistical, averaged approach is applied in the form of a two-fluid model. Transport equations governing the conservation of mass, momentum and energy are solved for each phase, and exchanges that occur at the interfaces between the two phases are explicitly accounted in which the dynamics of the interaction between the two phases are described through the consideration of constitutive relationships via suitable models of interphase mass, momentum and energy exchanges. Different population balance methods are described to aptly accommodate the phenomena of coalescence and break-up of gas particles. In the context of computational fluid dynamics, the application of population balance models to describe the coalescence and break-up dynamics of these gas particles can be effectively coupled with the two-fluid model to predict the wide range of particle sizes that could exist within the two-phase flow.