  Partially saturated granular flows are common in various natural and
industrial processes, such as landslides, mineral handling, and food
processing. We conduct experiments and apply the Discrete Element Method (DEM)
to study granular flows in rotating drums under partially saturated conditions.
We focus on varying the strength of cohesion (surface tension) and rotation
rate within the modes of rolling flow and cascading flow. With an increase in
surface tension, a rolling mode can possess a steeper slope and correspondingly
needs a higher rotation rate to transition to a cascading. The depth of the
flowing region increases with increasing cohesion, while the sensitivity is
reduced for cases of high cohesion. We propose a dimensionless number CE that
captures the combined effects of rotation, gravity and cohesion on the dynamic
angle of repose and flow depth. In addition, we extract statistical information
on the formation of clusters within the flow. We find a power law relation
between the cluster size distribution and its probability, which indicates that
stronger cohesion can promote the formation of larger clusters, and we discuss
how cohesion impact on flows manifested by cluster formation.
