Hydrodynamic Model for a Dynamical Jammed-to-Flowing Transition in Gravity Driven Granular Media

Granular material on an inclined plane will flow like a fluid if the angle θ the plane makes with the horizontal is large enough. We study chute flow down a plane using a hydrodynamic model previously used to describe granular Couette flow. Our model predicts a jammed-to-flowing transition as θ is increased even though it does not include solid friction, which might seem necessary to stabilize a state without flow. The transition is driven by coupling between mean and fluctuating velocity. In agreement with experiments and simulations, it predicts flow for layers with a thickness H larger than a critical value Hₛₜₒₚ(θ) and absence of flow for H<Hₛₜₒₚ(θ).