title: Oscillation-induced sand ripples in a circular geometry.
abstract: This study deals with the observation of sand ripples in a circular geometry under oscillatory flow. We characterize the observed patterns as a function of the excitation parameters. We report the time evolution of the corrugated front invading the flat bed. These experiments reveal unambiguously, because of the gradient of shear stress, the existence of two separated thresholds: one for grain motion and the other for the appearance of ripples. In addition, we display the phase diagram of this instability as a function of the Froude number and a Reynolds number.
authors.affiliation: Laboratoire J.-A. Dieudonné, Université de Nice-Sophia Antipolis, UMR 6621 CNRS-UNSA, Parc Valrose, 06108 Nice Cedex 02, France. Germain.Rousseaux@unice.fr
authors.forename: Germain
authors.initials: G
authors.lastname: Rousseaux
authors.forename: Joachim
authors.initials: J
authors.lastname: Kruithof
authors.forename: Patrice
authors.initials: P
authors.lastname: Jenffer
authors.forename: José Eduardo
authors.initials: JE
authors.lastname: Wesfreid