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

Appendix B Conference Paper B.Il
through conducting clear water pipeline tests. Mean velocity and wall shear stress were
measured for velocities over <strong>the</strong> test range and roughness was determined using <strong>the</strong>
Colebrook / White (1939) equation.
3.3 Material Used
The solids material used for testing purposes was kaolin clay and sand. Tests were
conducted using kaolin clay and <strong>the</strong>n a mixture <strong>of</strong> kaolin clay and No. 2 Foundry Sand
from Consol at varying concentrations.
- Kaolin Clay
Kaolin clay was obtained from <strong>the</strong> Serina Kaolin (Pty) Ltd which is currently mining a
kaolin deposit at Brakkeklo<strong>of</strong>, Fish Reek, Cape Town, South Africa. The kaolin was
delivered in <strong>the</strong> form <strong>of</strong> pellets and filter cakes. To obtain a homogenous slurry <strong>the</strong>
pellets or filter cake was thoroughly mixed with water using a recirculating pipe after
<strong>the</strong> pump back into <strong>the</strong> hopper before circulating <strong>the</strong> slurry through <strong>the</strong> pipelines.
- Sand
Sand was obtained from Consol in 25kg bags called No. 2 Foundry Sand. The <strong>particle</strong>
<strong>size</strong> <strong>of</strong> <strong>the</strong> sand was between 75 and 350 I'm.
3.3.1 Mixtures <strong>of</strong> Kaolin Clay and Sand
The sand used was found to form a settling slurry with water. In order to obtain a
homogeneous slurry, kaolin clay was used as a suspending agent for <strong>the</strong> sand. Tests
were <strong>the</strong>refore conducted to determine <strong>the</strong> amount <strong>of</strong> kaolin clay needed to suspend <strong>the</strong>
sand. It was found that kaolin clay at a concentration <strong>of</strong>at least Cv = 5% was required.
3.4 Particle Size Distribution
The <strong>particle</strong> <strong>size</strong> <strong>distribution</strong> <strong>of</strong><strong>the</strong> kaolin clay/sand mixture was obtained by combining
<strong>the</strong> PSD <strong>of</strong><strong>the</strong> kaolin clay (determined using a Malvern 2600/3600 Particle Sizer VF.6)
and <strong>the</strong> PSD <strong>of</strong> <strong>the</strong> sand determined through sieving. The dS5 was <strong>the</strong>n obtained from <strong>the</strong>
combined PSD's as shown below in Figure 1.
4. ANALYSIS & RESULTS
The measured variables <strong>of</strong> head loss and velocity were used to plot pseudo-shear
diagrams ie wall shear stress vs pseudo-shear rate. A typical pseudo-shear diagram is
shown in Figure 2 and <strong>the</strong> improvement obtained using <strong>the</strong> new model, is clearly visible,
as opposed to <strong>the</strong> o<strong>the</strong>r <strong>the</strong>oretical models.