Rotating-drum flows span a variety of research areas, ranging from physics of granular matter through hydrodynamics of suspensions to pure liquid coating flows. Recent years have seen an intensified scientific activity associated with this unique geometrical configuration, which has contributed to our understanding of related subjects such as avalanches in granules and segregation in suspensions. The existing literature related to rotating-drum flows is reviewed, highlighting similarities and differences between the various flow realizations. Scaling laws expressing the importance of different mechanisms underlying the observed phenomena have been focused on. An emphasis is placed on pattern formation phenomena. Rotating-drum flows exhibit stationary patterns as well as traveling and oscillating patterns; they exhibit reversible transitions as well as hysteresis. Apart from the predominant cylindrical configuration, this review covers recent work done with tumblers having other geometries, such as the sphere and the Hele-Shaw cell

We report experiments on spatially forced inclined layer convection, where the combined effect of the intrinsic symmetry breaking due to a gravity-induced shear flow and spatially periodic 1D forcing is studied. We observed pattern selection processes resulting in stabilization of spatiotemporal chaos and the emergence of novel two-dimensional states. Phase diagrams depicting the different observed states for typical forcing scenarios are presented. Convection in the weakly nonlinear regime is compared with theory, and a good agreement is found

Non-Brownian particles suspended at low volume concentration in a rotating horizontal cylinder filled with a low-viscosity fluid are observed to segregate into well-defined periodic axial bands. We present an experimental investigation of the dependence of the phenomenon on particle characteristics, tube diameter and length, and fluid viscosity. A theoretical explanation of the phenomenon is suggested, in which the segregation occurs as a result of mutual interaction between the particles and inertial waves excited in the bounded fluid. This leads to the result that macroscopic suspended particles accumulate in alternate nodes of the wave excitation, which is in agreement with the experiments, and leads to two degenerate band patterns for each mode. Under some conditions the observed pattern oscillates between the two possible band configurations. The mechanism underlying the oscillations is unclear. A confirmation of the theoretical approach was obtained by means of a photographic capture of the flow field resulting from the inertial waves.

A nonviscous fluid, completely filling a tube rotating about its horizontal axis, contains a suspension of macroscopic particles. The particles are observed to distribute themselves spontaneously in bands distributed periodically along the axis, with a band separation dependent only on the tube radius and length. In many cases, the bands oscillate periodically between two interleaving patterns. We explain this banding phenomenon as arising from the excitation of inertial standing waves in the rotating fluid.

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