title: Experimental scaling law for the subcritical transition to turbulence in plane Poiseuille flow.
abstract: We present an experimental study of the transition to turbulence in a plane Poiseuille flow. Using a well-controlled perturbation, we analyze the flow by using extensive particle image velocimetry and flow visualization (using laser-induced fluorescence) measurements, and use the deformation of the mean velocity profile as a criterion to characterize the state of the flow. From a large parametric study, four different states are defined, depending on the values of the Reynolds number and the amplitude of the perturbation. We discuss the role of coherent structures, such as hairpin vortices, in the transition. We find that the minimal amplitude of the perturbation triggering transition scales asymptotically as Re(-1).
authors.affiliation: Laboratoire de Physique et Mécanique des Milieux Hétérogènes, UMR 7636 Centre National de la Recherche Scientifique-École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris, Université Pierre et Marie Curie, Université Paris Diderot, 10 rue Vauquelin, F-75005 Paris, France. gregoire.lemoult@espci.fr
authors.forename: Grégoire
authors.initials: G
authors.lastname: Lemoult
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Aider
authors.forename: José Eduardo
authors.initials: JE
authors.lastname: Wesfreid