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

Chapter 5
Table 5.1.
Discussion Page 5.5
Table 5.1: Number Concentration <strong>of</strong> Large Particles in Viscous Sub-layer
Test % Large No. Particles
Particles per m 2
KW 22 163
K 20 20 296
.
RFlO 4 24
RF 20 5 36
RF 30 6 57
S 10 47 336
S 20 55 463
S 30 62 540
From Table 5.1 it can be seen that <strong>the</strong> highest number <strong>of</strong><strong>particle</strong>s per square meter was 540.
This indicates that if <strong>the</strong> <strong>particle</strong>s were evenly spaced that approximately one large <strong>particle</strong>
would be found every 5cm. This is fairly low for one would expect for a <strong>particle</strong> roughness
<strong>effect</strong> for <strong>the</strong>re to be at least one large <strong>particle</strong> per millimetre (Slatter, 1996) and yet even
with a low number concentration <strong>the</strong>re is evidence <strong>of</strong> a <strong>particle</strong> roughness <strong>effect</strong>. In fact,
Slatter (1994) detected a <strong>particle</strong> roughness <strong>effect</strong> even when testing slurries with a
volumetric concentration as low as 2 %. It would <strong>the</strong>refore appear from tests conducted by
Slatter (1994) and test conducted for this <strong>the</strong>sis tllat <strong>the</strong> large <strong>particle</strong>s have a dominant <strong>effect</strong>
on tUrbulence even when <strong>the</strong> number concentration is extremely. This would indicate that
:he Particle roughness <strong>effect</strong> is due to <strong>the</strong> mere fact that <strong>particle</strong>s are present in <strong>the</strong> slurry per
,e but it is strange that a small number produce <strong>the</strong> same <strong>effect</strong> as a large number.