Keynote lecture. Granular flows

Our understanding of granular flows has progressed considerably over the past two decades. In this talk, I will first review the advances made in the rheology of dense granular media based on the concept of pressure-imposed rheology, discussing the different regimes, from viscous to inertial. I will also illustrate how these rheological descriptions can be used in a two-phase flow approach to model more complex flow configurations, at least in simple small scaled experiments mimicking granular avalanche flows. Can these advances help describe and predict debris flows, is not an easy question, which I will try to discuss by pointing out the limitations and robustness of the rheological models.