title: Thin-film fluid flows over microdecorated surfaces: observation of polygonal hydraulic jumps.
abstract: Liquid films flowing over rough substrates are influenced by asperities whose sizes are comparable to the film thickness. We investigate flows driven by jet impact on a regular array of micron-size posts. We show that the topography modifies the size and the shape of the observed hydraulic jumps: in addition to circular jumps, we obtain a variety of stable polygonal shapes. We rationalize our results by considering a leakage flow through the texture and the free-surface flow above it, coupled by an effective slip boundary condition accounting for the symmetry of the texture. This model is in good agreement with our experiments and allows us to account for the interplay between flow properties and roughness parameters, which has applicability in many other thin-film configurations.
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Emilie
authors.initials: E
authors.lastname: Dressaire
authors.forename: Laurent
authors.initials: L
authors.lastname: Courbin
authors.forename: Jérome
authors.initials: J
authors.lastname: Crest
authors.forename: Howard A
authors.initials: HA
authors.lastname: Stone
mesh_terms: D004129:Dimethylpolysiloxanes / Q000737:chemistry*; D008956:Models, Chemical; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D004129:Dimethylpolysiloxanes; D014867:Water; C013830:baysilon