Computations of Multiphase Flows

Computational studies of multiphase flows go back to the very beginning of Computational Fluid Dynamics. It is, however, only during the last decade that direct numerical simulations of multiphase flow have emerged as a major research tool. It is now possible, for example, to simulate the motion of several hundred bubbles and particles in simple flows and to obtain meaningful averaged-quantities that can be compared with experimental results. Much of this progress has been made possible by methods based on the 'one-fluid' formulation of the governing equations, in addition to rapidly increasing computational power. Here, we review computations of multiphase flows with particular emphasis on finite Reynolds number flows and methods using the 'one-fluid' approach. After an overview of the mathematical formulation and the various 'one-fluid' methods, the state-of-the-art is reviewed for three problems: Dispersed bubbly flows, microstructure formation during solidification, and boiling. For the first example numerical methods have reached the maturity where they can be used in scientific studies. For the second and third examples, major numerical development is still taking place. However, progress is rapidly being made and it is realistic to expect large-scale simulations of these problems to become routine within a few years.