Segregation and mixing are two very interesting phenomena appearing in granular material.
The interplay of different sizes, densities, shapes etc. can lead to a variety of effects.
Research of band formation and segregation in a rotating drum
containing glass beads of two sizes: After mixing two types of glass beads in a rotating drum
a number of bands appear which over time change in shape and thickness. Bands merge
and sometimes complete segregtion occurs. The time of segregation and merging as well as the shape of
the bands depends for example significantly on the speed of rotation. A large number of experiments
is performed to study this behavior. Numerical investigations of the band forming behavior
are carried out. The experiments include optical observation, NMR scans of the
internal bead distribution as well as PIV (particle image velocimetry) measurements
of the particle flow on the surface.
Axial and radial segregation is observed and compared to
existing models. A new model based on a simple random walk behavior is used
to intepret the experimental data.
