title: Instantaneous velocity profiles during granular avalanches.
abstract: We perform experimental measurements of the instantaneous velocity profile of the flowing layer during granular avalanches. In the pile depth, the velocity profile follows a pure exponential decrease in contrast with steady flows that are known to exhibit a well developed upper linear part. The velocity profile in the pile width is a plug flow with two exponential boundary layers at the walls. Even though no steady state is observed during the avalanche, these velocity profiles are self-similar and build up almost instantaneously, with time independent characteristic lengths.
authors.affiliation: Laboratoire Fluides, Automatique, Systémes Thermiques (UMR CNRS 7608), Bâtiment 502, Campus Universitaire, 91405 Orsay Cedex, France.
authors.forename: Sylvain Courrech
authors.initials: SC
authors.lastname: du Pont
authors.forename: Raphaël
authors.initials: R
authors.lastname: Fischer
authors.forename: Philippe
authors.initials: P
authors.lastname: Gondret
authors.forename: Bernard
authors.initials: B
authors.lastname: Perrin
authors.forename: Marc
authors.initials: M
authors.lastname: Rabaud