Pattern formations in particle laden drum flows and Taylor-Couette flows with co-rotating cylinders

In this work, previously undescribed particle patterns are reported for suspensions of initially uniform dispersed non-Brownian particles in completely filled rotating drum flows and in completely filled co-rotating Taylor-Couette (TC) flows under the influence of gravity. Extending previous studies, a thorough phase mapping is performed for the drum flow with a low viscosity working liquid (1 cP) and d(p) approximate to 500 mu m glass beads at a solid volume fraction of Phi = 0:11%. A wide range of cylinder radii is covered (R-o = 7-145 mm), and for the first time, a phase mapping is performed for a co-rotating TC flow for varying radius ratios. A total of 55 different geometrical combinations have been considered within the experiments. For both the drum and the TC flow, a series of clearly distinguishable patterns are observed including three different types of axial band structures as well as azimuthal band structures. The experiments indicate that in the case of the drum flow, the pattern formation strongly depends on the outer cylinder diameter, whereas in the case of the Taylor-Couette flow, the gap height has a strong effect on the pattern formation. In the TC case, it is observed that the wavelength of all band patterns shows a striking dependence on the cylinder radius and the curvature of the system.