We formulate a phenomenological model for the segregation of binary mixture
s of granular materials with different roughness in a rotating drum. Our mo
del successfully replicates a range of experimental behaviours, e.g., rapid
radial segregation; slow axial segregation, and nonuniform radial structur
e of axial bands. We present some analytical results and detailed numerical
results for our model. (C) 2001 Elsevier Science B.V. All rights reserved.