A model for stationary cohesive granular flows on inclines is proposed based on the assumption of an ideal Coulomb material supplemented with a linear $\mu \left(I\right)$ dependence. For assessing the reliability of the model, discrete numerical simulations are carried out in two dimensions, varying both contact adhesion and flow slope on a large range of values. Focusing both on the surface velocity and on the thickness of the surface plug flow, a systematic comparison between discrete simulations data and analytical predictions derived from the model allows for testing the latter. In particular, the ideal Coulomb material hypothesis, including the independence of friction and cohesion, is corroborated, together with the applicability of the linear approximation of the $\mu \left(I\right)$ flow law. Confronting model and discrete simulations discloses a linear relation between macroscopic cohesion stress and local contact adhesion, in agreement with Rumpf's prediction. The bottom velocity is shown to obey a Navier-Robin condition with a slipping length poorly dependent on adhesion properties. In addition, the analysis of the surface topography shows how increasing contact adhesion leads to a more craggy surface line. In the context of a simplified flow configuration, the present work brings clarification on the intricate roles of contact adhesion and flow dynamics on the cohesive behavior of granular flows. It allows for testing the relatively simple theoretical framework and hypothesis used to derive analytical solutions, thus showing that many salient features of cohesive flows are captured by basic ingredients. Based on relatively accessible quantities in laboratory measurements, it may also shed an interesting light on experimental work.

Close

PrevNext

View figure in article

• Granular flows
• Rheology