Experimental Investigation on Dry Granular Flows Driven by Gravity

Abstract:

Flows involving solid particulates are widely present in both industrial applications and geophysical processes. Most of the research published concerns inclined granular flows over bumpy and flat rigid base, while only few of them focus on fully developed steady flows over an erodible bed. This kind of flows are important to understand the dynamics of complex phenomena such as dense snow-avalanches and rock-avalanches, whose rheology is still ambiguous and not well defined.

We report on laboratory investigations regarding uniform flows of identical particles over a loose bed in a rectangular chute. Accurate measurements were carried out through imaging techniques based on the Voronoï diagrams to track each particle composing the flow. Additionally, direct methods were tested to assess the stresses exerted by the flow at the lateral walls.

We present detailed profiles of the mean velocity, solid concentration, and granular temperature for a large set of flow-rates and widths, for which the uniformity and steadiness of the flow are accurately checked. Vertical and transversal structures are highlighted, and the role of the boundary conditions on the uniformity of the flow is emphasized. Concerning the lateral confinement, an increasing role of the instantaneous collisions is observed by enlarging the channel at different flow-rates. Finally a new device intended to measure the shear stresses at the side-walls is discussed.