One studying the motion of fluids relative to particulate systems is
soon impressed by the dichotomy which exists between books covering
theoretical and practical aspects. Classical hydrodynamics is largely
concerned with perfect fluids which unfortunately exert no forces on the
particles past which they move. Practical approaches to subjects like
fluidization, sedimentation, and flow through porous media abound in
much useful but uncorrelated empirical information. The present book
represents an attempt to bridge this gap by providing at least the
beginnings of a rational approach to fluid- particle dynamics, based on
first principles. From the pedagogic viewpoint it seems worthwhile to
show that the Navier-Stokes equations, which form the basis of all
systematic texts, can be employed for useful practical applications
beyond the elementary problems of laminar flow in pipes and Stokes law
for the motion of a single particle. Although a suspension may often be
viewed as a continuum for practical purposes, it really consists of a
discrete collection of particles immersed in an essentially continuous
fluid. Consideration of the actual detailed boundary- value problems
posed by this viewpoint may serve to call attention to the limitation of
idealizations which apply to the overall transport properties of a
mixture of fluid and solid particles.