13/06/2018 – P. Rognon – A view on the role of velocity fluctuations in dense granular flows

Séminaire exceptionnel – 13 juin 2017 – 11h salle 250

A view on the role of velocity fluctuations in dense granular flows

Pierre Rognon – Univ. of Sydney

Granular flows in natural and industrial processes often involve countless grains. Continuum models similar to those used in fluid mechanics are then necessary to predict flow paths and impact forces on structures. These models rely on effective parameters such as viscosity and diffusivity. However, these have proven challenging to predict in several instances. The aim of this talk is to show how these parameters can be rationalised by considering the flows internal kinematics. The discussion will be based on results from DEM simulations and experiments performed over the past fifteen years in different groups. The talk will start by establishing how velocity fluctuations are correlated in time and space in dense granular flows. A special attention will be given to the existence of transient clusters of jammed grains that continuously form and break down during shear. The core of the talk will then be dedicated to establishing how these length and time scales can be used to rescale coefficients of self-diffusion, and to explain non-local behaviours at the continuum level.