title: Global nature of dilute-to-dense transition of granular flows in a 2D channel.
abstract: The dilute-to-dense transition of granular flow of particle size d(0) is studied experimentally in a two-dimensional channel (width D) with confined exit (width d). Our results show that with fixed d and D there is a maximum inflow rate Q(c) above which the flow changes from dilute to dense and the outflow rate <Q(t)> drops abruptly from Q(c) to a dense rate Q(d). A rescaled critical rate q(c) is found to be a function of a scaling variable lambda only: q(c) approximately F(lambda), where lambda identical with d/d(0) d/D-d. This form of lambda suggests that the dilute-to-dense transition is a global property of the flow, unlike the jamming transition which depends only on d/d(0). Furthermore, the transition is found to occur when the area fraction of particles near the exit exceeds a critical value which is close to 0.65+/-0.03.
authors.affiliation: Institute of Physics, Chinese Academy of Sciences, Beijing 100080. mayhou@aphy.iphy.ac.cn
authors.forename: M
authors.initials: M
authors.lastname: Hou
authors.forename: W
authors.initials: W
authors.lastname: Chen
authors.forename: T
authors.initials: T
authors.lastname: Zhang
authors.forename: K
authors.initials: K
authors.lastname: Lu
authors.forename: C K
authors.initials: CK
authors.lastname: Chan