Inertia and Air Drag in the Brazil Nut Problem
  The rise dynamics of a large spherical particle, in a granular bed under vertical vibrations, is experimentally studied. An inductive device has been designed to track the particle while it climbs through the bed under different conditions. A simple model based in energy considerations is presented to explain our experimental data, drawing important conclusions about the physics of the phenomenon. 
Y. Nahmad-Molinari, G. Canul-Chay and J. C. Ruiz-Suarez