title: Dynamical evolution of sand ripples under water.
abstract: We have performed an experimental study on the evolution of sand ripples formed under the action of an oscillatory flow. An annular sand-water cell was used in order to investigate a wide range of parameters. The sand ripples follow an irreversible condensation mechanism from small to large wavelength until a final state is reached. The wavelength and the shape of these stable sand patterns are mainly governed by the fluid displacement and the static angle of the granular media. A strong hysteresis affects the evolution of steep ripples. When the acceleration of the sand bed reaches a critical value, the final pattern is modified by the superficial fluidization of the sand layer.
authors.affiliation: Laboratoire de Météorologie Dynamique, ENS, 24 Rue Lhomond, 75231 Paris, France.
authors.forename: A
authors.initials: A
authors.lastname: Stegner
authors.forename: J E
authors.initials: JE
authors.lastname: Wesfreid