UNSPECIFIED. (1999) Effects of granular additives on transition boundaries between flow states of rimming flows. PHYSICS OF FLUIDS, 11 (8). pp. 2020-2029. ISSN 1070-6631

Abstract

An experimental study of the rimming flow established inside a partially fluid-filled cylinder rotating around a horizontal axis of rotation is described. For the first time effects of granular additives on transition boundaries between flow states adopted by the fluid for different experimental conditions are studied. For the granule-free fluid and low filling levels we confirm results of previous authors showing that the ratio of viscous stresses and gravitational force remains constant along the transition boundaries considered. For higher filling levels our new data indicate, however, that the gravitational force becomes increasingly more important. For the solid-liquid two-phase flow our data reveal that even small amounts of,granular additives can have a significant effect on a suitable parameter defined to characterize the transition boundaries. Granular additives can lead to the stabilization of states and to the extension of the parameter range over which certain states can be observed. It is shown that the origin of the observed effects appears to be associated with an increased bulk density of the solid-liquid flow. For high granule concentrations a pattern of equally-spaced circumferential granular bands is observed to form on the inner cylinder wall. It is speculated that these bands form as a consequence of the mechanism which has been referred to as shear-induced migration/diffusion in the literature in the past. It appears that the granule-band pattern has not been observed previously for the flow investigated here. (C) 1999 American Institute of Physics. [S1070-6631(99)04508-0].

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