Attention is focused on a suspension of buoyant particles
(or droplets) in acontinuous fluid. In the presence of a
force field, gravitational or centrifugal, and exposed to
ordinary boundary constraints, a variety of fascinating
flows can be obtained. These motions are essential ingre-
dients in the widely used separation technology, where im-
provedand new designs may be beneficial, but they are also
interesting from a broader, academic point of view. In
these respects, the recent investigations on these flows
patterns, their underlying mechanisms and mathematical
modeling - have accrued to a significant, relevant body of
knowledge. The main objective of this book is to summarize -
in a systematic, coherent and consistent fashion - the
theoretical up to date contributions which seem fundamental
in understanding, simulation and development of the subject.