3842 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
(blue region) itself is not very well represented by PEPT. As
a Lagrangian measurement technique, adequate tracer cov-
erage is essential for accurate mapping of a region. Perfect
tracer coverage is theoretically achievable only with an infi-
nite experiment duration, which is impractical. To address
this, we run experiments for a sufficiently long duration to
attain reasonable coverage, guided by the Ergodic assump-
tion central to PEPT data analysis theory. However, recent
research by de Klerk et al. (2019) revealed that this assump-
tion may not always hold true, identifying specific regions
in the mill where the PEPT tracer is more likely to be found.
At higher viscosities, a noticeable modification in the
free surface (represented by the black solid line, delineating
the bulk bed from the cataracting region) is evident, char-
acterised by a reduction in the S-shape. Prominent models
describing axial segregation in rotating drum flows heavily
rely on the free surface as a critical boundary condition for
evolving the solution. However, the algorithm for delineat-
ing the free surface encounters challenges at elevated viscos-
ities, prompting consideration of an alternative approach in
future work to address this discrepancy.
The anticipated alteration in the free surface profile
at higher viscosities aligns with expectations. Increased
viscosity is associated with a smoothing effect, mitigating
fluctuations and reducing the likelihood of instabilities,
thereby resulting in a more controlled free surface. In con-
trast, lower viscosities promote a more fluid-like behav-
iour within the granular bed, enhancing the characteristic
S-shape of the free surface. The complex response of the
free surface to varying viscosities provides valuable insights
into the complex interplay between fluid properties and
granular dynamics in rotating drum flows.
Figure 3 indicates the glass bead solids fractions derived
from DEM-SPH coupled simulations. As observed by
Moodley and Govender (2022), the DEM distributions
are typically smoother than the PEPT because of the better
averaging achieved using the ~10,000 particle trajectories
available in the DEM compared to the single particle cover-
age available in the PEPT.
To quantify the error between PEPT and DEM, a bin-
by-bin solids fraction error analysis was undertaken for the
10mm beads at different mill speeds. The profiles generated
by both PEPT and DEM for the 10mm glass beads are
shown in Figure 4. One observes in Figure 4 that, in certain
cases, the cataracting and toe regions have been truncated
due to insufficient tracer coverage. Additionally, the mean
(a) and standard deviation (b) is shown in the diagram itself
denoted by (a ± b). The bed itself has significant portions
of the error of less than 15% for the 10mm beads with
standard deviations of about 10% for each data set. This
Figure 3. DEM glass bead solids fraction results at various speeds and a viscosity of 0.011Pa·s
Figure 4. DEM-PEPT glass bead solids fraction comparison results at various speeds and a viscosity of
0.011Pa·s
(blue region) itself is not very well represented by PEPT. As
a Lagrangian measurement technique, adequate tracer cov-
erage is essential for accurate mapping of a region. Perfect
tracer coverage is theoretically achievable only with an infi-
nite experiment duration, which is impractical. To address
this, we run experiments for a sufficiently long duration to
attain reasonable coverage, guided by the Ergodic assump-
tion central to PEPT data analysis theory. However, recent
research by de Klerk et al. (2019) revealed that this assump-
tion may not always hold true, identifying specific regions
in the mill where the PEPT tracer is more likely to be found.
At higher viscosities, a noticeable modification in the
free surface (represented by the black solid line, delineating
the bulk bed from the cataracting region) is evident, char-
acterised by a reduction in the S-shape. Prominent models
describing axial segregation in rotating drum flows heavily
rely on the free surface as a critical boundary condition for
evolving the solution. However, the algorithm for delineat-
ing the free surface encounters challenges at elevated viscos-
ities, prompting consideration of an alternative approach in
future work to address this discrepancy.
The anticipated alteration in the free surface profile
at higher viscosities aligns with expectations. Increased
viscosity is associated with a smoothing effect, mitigating
fluctuations and reducing the likelihood of instabilities,
thereby resulting in a more controlled free surface. In con-
trast, lower viscosities promote a more fluid-like behav-
iour within the granular bed, enhancing the characteristic
S-shape of the free surface. The complex response of the
free surface to varying viscosities provides valuable insights
into the complex interplay between fluid properties and
granular dynamics in rotating drum flows.
Figure 3 indicates the glass bead solids fractions derived
from DEM-SPH coupled simulations. As observed by
Moodley and Govender (2022), the DEM distributions
are typically smoother than the PEPT because of the better
averaging achieved using the ~10,000 particle trajectories
available in the DEM compared to the single particle cover-
age available in the PEPT.
To quantify the error between PEPT and DEM, a bin-
by-bin solids fraction error analysis was undertaken for the
10mm beads at different mill speeds. The profiles generated
by both PEPT and DEM for the 10mm glass beads are
shown in Figure 4. One observes in Figure 4 that, in certain
cases, the cataracting and toe regions have been truncated
due to insufficient tracer coverage. Additionally, the mean
(a) and standard deviation (b) is shown in the diagram itself
denoted by (a ± b). The bed itself has significant portions
of the error of less than 15% for the 10mm beads with
standard deviations of about 10% for each data set. This
Figure 3. DEM glass bead solids fraction results at various speeds and a viscosity of 0.011Pa·s
Figure 4. DEM-PEPT glass bead solids fraction comparison results at various speeds and a viscosity of
0.011Pa·s
