the effect of the particle size distribution on non-newtonian turbulent ...

Chapter 2 Literature Review Page 2.9
slurries as well as those requiring turbulent flow to maintain homogeneity. This study will
concentrate on homogeneous slurries.
2.6.2 Heterogeneous Slurries
By contrast, heterogeneous slurries do not behave as single-phase fluid ie. <strong>the</strong> fluid and solid
phase retain <strong>the</strong>ir separate identities. Hence, <strong>the</strong>se slurries will flow with a non­
axisymmetric concentration <strong>distribution</strong>. The solids phase tends to have larger <strong>particle</strong>s than
homogeneous slurries.
2.7 TIME-INDEPENDENT FLUIDS
2.7.1 Introduction
Bingharn plastic, pseudoplastic and dilatant fluids all fall into this category. However, all
<strong>of</strong><strong>the</strong>se rheological relationships as well as <strong>the</strong> Newtonian and yield dilatant relationships can
be described by <strong>the</strong> yield pseudoplastic model (sometimes referred to in <strong>the</strong> literature as <strong>the</strong>
generalised Bingharn model). The rheological assumption for <strong>the</strong> yield-pseudoplastic model,
as suggested by Herschel & Bulkley (1926), is as follows:
T = T + K [_ dUJ D
Y dr'
where T y is <strong>the</strong> yield stress;
(2.6)
K is <strong>the</strong> fluid consistency index which characterizes <strong>the</strong> "thickness" <strong>of</strong> a fluid and
is similar to <strong>the</strong> viscosity <strong>of</strong> a Newtonian fluid,
n is <strong>the</strong> flow behaviour index and characterizes <strong>the</strong> extent <strong>of</strong>deviation <strong>of</strong>a fluid from
Newtonian behaviour (Metzner,1956).
The above mentioned rheological relationships can be described using <strong>the</strong> yield pseudoplastic
model depending on <strong>the</strong> values <strong>of</strong> T y and n:
(a)
(b)
Bingham plastic
Yield pseudoplastic
{Ty>O and n=l}
{Ty>O and n < 11