Dynamics of density waves in a two dimensional funnel on an inclined plane

We report here experiments on two-dimensional funnel flow of 1 mm diameter glass beads on an inclined plane. We have investigated the properties of th e flow according to the outlet size D of the funnel and the gravity. We hav e identified three different regimes. For small funnel outlet sizes, there is no significant change in flow density: the flow is rather steady and hom ogeneous. For intermediate outlet sizes (20 mm < D < 80 mm), the flow is in termittent, consisting of spatially ordered density waves propagating upwar ds. At bigger outlet sizes, density waves do not exhibit any ordering and t he flow dynamics becomes chaotic. In addition, we find that the flow dynami cs is independent of the funnel opening angle except close to the channel f low configuration. Finally, it is stressed that the interactions between th e beads and the inclined plane play a crucial role in the mechanism of form ation of density waves.