title: Scaling behavior in the convection-driven Brazil nut effect.
abstract: The Brazil nut effect is the phenomenon in which a large intruder particle immersed in a vertically shaken bed of smaller particles rises to the top, even when it is much denser. The usual practice while describing these experiments has been to use the dimensionless acceleration Γ = aω(2)/g, where a and ω are, respectively, the amplitude and the angular frequency of vibration and g is the acceleration due to gravity. Considering a vibrated quasi-two-dimensional bed of mustard seeds, we show here that the peak-to-peak velocity of shaking v = aω, rather than Γ, is the relevant parameter in the regime where boundary-driven granular convection is the main driving mechanism. We find that the rise time τ of an intruder is described by the scaling law τ ~ (v-v(c))(-α), where v(c) is identified as the critical vibration velocity for the onset of convective motion of the mustard seeds. This scaling form holds over a wide range of (a,ω), diameter, and density of the intruder.
authors.affiliation: Raman Research Institute, CV Raman Avenue, Sadashivanagar, Bangalore 560080, India. phejmady@rri.res.in
authors.forename: Prakhyat
authors.initials: P
authors.lastname: Hejmady
authors.forename: Ranjini
authors.initials: R
authors.lastname: Bandyopadhyay
authors.forename: Sanjib
authors.initials: S
authors.lastname: Sabhapandit
authors.forename: Abhishek
authors.initials: A
authors.lastname: Dhar
mesh_terms: D003102:Colloids / Q000737:chemistry*; D003198:Computer Simulation; D004058:Diffusion; D006112:Gravitation; D008956:Models, Chemical; D009038:Motion; D010316:Particle Size; D012639:Seeds / Q000737:chemistry*; D014783:Viscosity
chemical_list: D003102:Colloids