Pattern scaling in the axial segregation of granular materials in a rotating tube
Pattern scaling in the axial segregation of granular materials in a rotating tube
Published in Granular Matter, Nov 2005, Page 46, or http://dx.doi.org/10.1007/s10035-005-0208-z
Christopher R. J. Charles, Zeina S. Khan and Stephen W. Morris
Department of Physics,
University of Toronto, 60 St. George St., Toronto, Ontario, Canada M5S 1A7.
Granular mixtures frequently segregate by grain size along the axis of partially-filled, horizontal, rotating tubes. When segregation approaches saturation at the surface, a well-defined pattern of bands with wavelength lambda emerges. The long-term dynamics of the pattern involves a much slower coarsening process. We characterized the initial saturated wavelength lambda as a function of the diameter of the tube D for a filling fraction of 30%, for 1.9 cm < D < 11.5 cm. We also studied the initial growth-rate of the bands as D varies. We find that lambda/D is not constant, but rather increases rapidly for small D. The growth-rate of bands decreases with smaller D and segregation is suppressed completely for sufficiently small D. These relatively simple features are not captured by any of the existing models of axial segregation.
