Fine structure of granular banding in two-phase rimming flow

Solid-liquid two-phase flow inside a partially filled horizontally rotating cylinder is investigated. We document the observation of a new, secondary banding pattern developing in the flow when the solid phase comes out of su spension to accumulate as regularly spaced, circumferential bands on the in ner cylinder wall. This secondary pattern, the fine structure, is superpose d on the primary pattern which we previously described [O. A. M. Boote and P. J. Thomas, Phys. Fluids 11, 2020 (1999)]. The fine structure is characte rized by each of the primary bands adopting a compound structure consisting of three individual, narrower secondary bands. New results on the influenc e of the physical properties of the solid phase on transitions between char acteristic flow states are briefly discussed. It is reported that state-tra nsition boundaries in the phase plane and the wavelength of the primary ins tability are insensitive to particle size and shape while there exist influ ences due to the particle density. (C) 2001 American Institute of Physics.