At 'macro' scale the unsteady Navier-Stokes equations are solved coupled with the particle equation of motion. Results are presented to demonstrate the effectiveness of the numerical algorithm in handling three dimensional regular and irregular geometries without significant additional computational overhead.

This book contributes to the fundamental understanding of the physical mechanisms that take place in pseudo turbulent particulate flows. In the present work we have considered the sedimentation of large numbers of spherical rigid particles in an initially quiescent flow field. We have performed direct numerical simulations employing an immersed boundary method for the representation of the fluid-solid interface. The results evidence that depending on the particle settling regime (i.e. Galileo number and particle-to-fluid density ratio) the particles may exhibit strong inhomogeneous spatial distribution. It is found that the particles are preferentially located in regions with downward fluid motion. The particles inside clusters experience larger settling velocities than the average. The flow in all flow cases is observed to exhibit characteristic features of pseudo-turbulence. The particle-induced flow field is further found to be highly anisotropic with dominant vertical components. The results indicate that, in the present flow configurations, the collective and mobility effects play significant role for the particle and fluid motion.

Dispersed multiphase flows are frequently found in nature and have diverse geophysical, environmental, industrial, and energy applications. This book targets a beginning graduate student looking to learn about the physical processes that govern these flows, going from the fundamentals to the state of the art, with many exercises included.

This IMA Volume in Mathematics and its Applications PARTICULATE FLOWS: PROCESSING AND RHEOLOGY is based on the proceedings of a very successful one-week workshop with the same title, which was an integral part of the 1995-1996 IMA program on "Mathematical Methods in Materials Science." We would like to thank Donald A. Drew, Daniel D. Joseph, and Stephen L. Passman for their excellent work as organizers of the meeting. We also take this opportunity to thank the National Science Foun dation (NSF), the Army Research Office (ARO) and the Office of Naval Research (ONR), whose financial support made the workshop possible. A vner Friedman Robert Gulliver v PREFACE The workshop on Particulate Flows: Processing and Rheology was held January 8-12, 1996 at the Institute for Mathematics and its Applications on the University of Minnesota Twin Cities campus as part of the 1995- 96 Program on Mathematical Methods in Materials Science. There were about forty participants, and some lively discussions, in spite of the fact that bad weather on the east coast kept some participants from attending, and caused scheduling changes throughout the workshop. Heterogeneous materials can behave strangely, even in simple flow sit uations. For example, a mixture of solid particles in a liquid can exhibit behavior that seems solid-like or fluid-like, and attempting to measure the "viscosity" of such a mixture leads to contradictions and "unrepeatable" experiments. Even so, such materials are commonly used in manufacturing and processing.