Categorization of Brazil nut effect and its reverse under less-convective conditions for microgravity geology

• Published in: Monthly notices of the Royal Astronomical Society Vol. 474; no. 4; pp. 4447 - 4459
• Main Authors: Chujo, Toshihiro, Mori, Osamu, Kawaguchi, Junichiro, Yano, Hajime
• Format: Journal Article
• Language: English
• Published: London Oxford University Press 01-03-2018
• Subjects: Acceleration; Classification; Computer simulation; Convection; Friction reduction; Laboratories; Mathematical models; Microgravity; Particulates; Percolation; Planet formation; Vibration; Brazil; methods: analytical; minor planets, asteroids: general; methods: numerical; comets: general; methods: laboratory: atomic
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stx3092

Abstract
Due to its important role in the sorting of particles on microgravity bodies by size, Brazil nut effect (BNE) is a major subject of study for understanding the evolution of planetesimals. Recent studies have revealed that the mechanism for the BNE on microgravity bodies is the percolation of particles or void-filling, rather than granular convection. This study also considers the mechanism for the BNE under ‘less-convective’ conditions and introduces three categories of behaviour for particles that mainly depend on the dimensionless acceleration of vibration Γ (ratio of maximum acceleration to gravitational acceleration), using a simplified analytical model. The conditions for Γ proposed by the model for each category are verified by both numerical simulations and laboratory experiments. ‘Less-convective’ conditions are realized by reducing the friction force between particles and the wall. We found three distinct behaviours of the particles when Γ > 1: the (i) ‘slow BNE’, (ii) ‘fast BNE’, and (iii) ‘fluid motion’ (the reverse BNE may be induced), and the thresholds for Γ correspond well with those proposed by the simple model. We also applied this categorization to low-gravity environments and found that the categorization scales with gravity level. These results imply that laboratory experiments can provide knowledge of granular mobility on the surface of microgravity bodies.