Arrest of the flow of wet granular matter

We study the arrest of three-dimensional flow of wet granular matter subject to a sinusoidal external force and a gravitational field confining the flow in the vertical direction. The minimal strength of the external force that is required to keep the system in motion, i.e. the critical force, is determined by considering the balance of injected and dissipated power. This provides a prediction whose quality is demonstrated by a data collapse for an extensive set of event-driven molecular-dynamics simulations where we varied the system size, particle number, the energy dissipated upon rupturing capillary bridges, and the bridge length at which rupture occurs. The same approach also works for systems that are kept at a fixed density by confining walls. In both cases, this universal method provides the critical force irrespective of the flow profile, and without specifying the hydrodynamic equations.