title: Collective behavior during the exit of a wetting liquid through a network of channels.
abstract: The exit of a wetting fluid from a thin microchannel into a sudden expansion is studied experimentally. In the case of the exit from a single channel, the advancing interface converges to a parabolic shape after an initial transient, in accordance with the lubrication limit analysis of a spreading drop. The experiments are then repeated for the exit from two parallel channels. At early times, the two exiting drops behave independently and display the same evolution as a single exiting droplet, while at late times we recover a single parabolic profile. The transition between the early and late states is due to the merging of the two drops, which is associated with a sudden increase in the flow rate. This is the signature of a collective effect which acts to redistribute the fluid spatially. Finally, the experiment is generalized to the case of seven parallel channels where a cascade of two-by-two mergings is observed, indicating that local interactions dominate the dynamics which lead to the global state of the system.
authors.affiliation: LadHyX and Department of Mechanics, Ecole Polytechnique, CNRS UMR 7646, 91128-F Palaiseau Cedex, France. baroud@ladhyx.polytechnique.fr
authors.forename: Charles N
authors.initials: CN
authors.lastname: Baroud
authors.forename: Xin C
authors.initials: XC
authors.lastname: Wang
authors.forename: Jean-Baptiste
authors.initials: JB
authors.lastname: Masson
mesh_terms: D057927:Hydrophobic and Hydrophilic Interactions; D008153:Lubrication; D044085:Microfluidics / Q000379:methods*; D008954:Models, Biological; D012996:Solutions / Q000737:chemistry*; D013499:Surface Properties; D014867:Water / Q000737:chemistry*; D017155:Wettability
chemical_list: D012996:Solutions; D014867:Water