Granular segregation in dense systems: the role of statistical mechanics   and entropy
  Granular segregation is ubiquitous in industrial, geological or daily-life context, but there is still no unifying theoretical approach. In this review, we examine two examples of granular segregation -- shallow rapid flows and rotating drums -- which suggest that the dynamics of systems at intermediate and high density might be amenable to a statistical mechanics approach. 
Matthias Schr\"oter and Karen E. Daniels
cond-mat.soft