Abstract
SYNOPSIS A mechanistic description of axial segregation in rotating drum flows remains an open question. Consequently, optimal mixing of grinding balls and rocks for efficient breakage, maximum production of fines, and slurry transport is seldom achieved. Experimental and numerical studies of granular mixtures in rotating drums identify alternating axial bands that eventually coarsen in the long-term limit. Most models of axial segregation are limited to binary mixtures and cannot always predict the logarithmic coarsening effects observed experimentally. A key missing factor is a robust description of the axial free surface profile that is valid across a wide range of flow regimes. We present a practical model of the axial free surface profile by linking it to readily-derived geometric features of the cross-sectional S-shaped free surface profile. A parametric study shows good agreement with experimental measurements reported in the literature and heuristically valid trends. Keywords: rotating drum, granular flow, axial profile, comminution, mixing, segregation.
Highlights
Over the past few decades, rotating drums have attracted considerable research effort by both the engineering and physics communities
The prototypical configuration of rotating drums is often favoured for its ability to display a wide range of granular flow phenomena such as avalanching, chaotic mixing, and segregation (Seiden and Thomas, 2011; Pignatel et al, 2012)
Rotating drum flows exhibit both azimuthal and axial flows with their interplay leading to complex multidirectional flow fields that resist a coherent theoretical description
Summary
Affiliation: 1 Department of Chemical Engineering, University of KwaZulu-Natal, South Africa. A mechanistic description of axial segregation in rotating drum flows remains an open question. Experimental and numerical studies of granular mixtures in rotating drums identify alternating axial bands that eventually coarsen in the long-term limit. Most models of axial segregation are limited to binary mixtures and cannot always predict the logarithmic coarsening effects observed experimentally. A key missing factor is a robust description of the axial free surface profile that is valid across a wide range of flow regimes. A parametric study shows good agreement with experimental measurements reported in the literature and heuristically valid trends. Granular flow, axial profile, comminution, mixing, segregation. 2021 The geometric axial surface profiles of granular flows in rotating drums.
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