5.1 Introduction
In many practical applications, we need to know the force required to move
a solid object through a surrounding fluid, or conversely, the force that a
moving fluid exerts on a solid as the fluid flows past it. Many processes for
the separations of particles of various sizes, shapes and materials depend on
their behaviour when subjected to the action of a moving fluid. Frequently,
the liquid phase may exhibit complex non-Newtonian behaviour whose characteristics
may be measured using falling-ball viscometry. Furthermore, it is
often necessary to calculate the fluid dynamic drag on solid particles in process
equipment, for example for slurry pipelines, fixed and fluidised beds. Similarly,
in the degassing of polymer melts prior to processing, bubbles rise through
a still mass of molten polymer. Likewise, the movement of oil droplets and
polymer solutions in narrow pores (albeit strongly influenced by capillary
forces) occurs in enhanced oil recovery operations. The settling behaviour of
a particle is also strongly influenced by the presence of other neighbouring
particles as in concentrated suspensions. Furthermore, it is often desirable to
keep the active component uniformly suspended, as in many pharmaceutical
products, paints, detergents, agro-chemicals, emulsions and foams.
Frequently, the particles are in the form of clusters (such as in fixed and
some fluidised beds) and ensembles as in foams, dispersions and emulsions.
However, experience with Newtonian fluids has shown that the hydrodynamics
of systems consisting of single particles, drops and bubbles serves as a useful
starting point for understanding the mechanics of the more complex multiparticle
systems which are not amenable to rigorous analysis. This chapter
aims to provide an overview of the developments in the field of non-Newtonian
fluid–particle systems. In particular, consideration is given to the drag force,
wall effects and settling velocity of single spherical and non-spherical particles,
bubbles and drops in various types of non-Newtonian fluids (particularly based
on power-law and Bingham plastic models). Flow in packed and fluidized beds
and hindered settling are then considered. Detailed accounts and extensive
bibliographies on this subject are available elsewhere [Chhabra, 1986, 1993a,b;
Ghosh et al., 199
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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