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

Appendix B Conference Paper
where TO = DJip/4L and V=Q/A.
2.3 Rheological Characterization
Rheological characterization involves choosing a rheological model which best fits <strong>the</strong>
data (<strong>the</strong> yield pseudoplastic model is used for this study) and <strong>the</strong>n determining <strong>the</strong>
values <strong>of</strong> T y , K and n for a particular slurry. The viscous flow data in <strong>the</strong> laminar region
is coincident for <strong>the</strong> different tube diameters and <strong>the</strong> rheological constants (Ty, K and
n) were determined using <strong>the</strong> method proposed by Lazarus & Slatter (1988) and Neill
(1988).
2.4 Turbulent Flow
Turbulence is a natural form <strong>of</strong> fluid motion which is characterized by large, random
swirling or eddy motions both parallel and transverse to <strong>the</strong> direction <strong>of</strong> <strong>the</strong> main flow.
Particle paths cross and velocity (both direction and magnitude) and pressure, fluctuate
on a continuous random basis. The flow behaviour becomes extremely complex and full
rigorous analysis becomes impossible (Tennekes & Lumley, 1972).
The turbulent flow <strong>of</strong> <strong>the</strong> non-Newtonian slurries that were tested were modelled using
Slatter's model as well as <strong>the</strong> following models which are already well established in <strong>the</strong>
literature,
- Newtonian approximation
- Dodge and Metzner (1959)
- Torrance (1963)
- Kemblowski & Kolodziejski (1973)
- Wilson & Thomas (1985)
2.4.1 Newtonian Approximation
In order to make use <strong>of</strong>standard Newtonian <strong>the</strong>ory, a value for <strong>the</strong> viscosity <strong>of</strong> <strong>the</strong> fluid
is required. Usually <strong>the</strong> term viscosity is meaningless once a non-Newtonian approach
has been adopted. However, an apparent or secant viscosity (Holland, 1973 and Wilson,
1986) can be defined as
Note that JL' is not a constant for a given fluid and pipe diameter, but must be evaluated
at a given value for TO.
(3)
B.4