Numerical simulation of 2D steady granular flows in rotating drum: On surface flows rheology

TL;DR

This study uses Non Smooth Contact Dynamics simulations to analyze the rheology of steady surface granular flows in a rotating drum, identifying the inertial number as key to understanding flow transitions.

Contribution

It introduces the inertial number as a critical parameter for describing flow regimes in 2D granular surface flows in rotating drums.

Findings

Inertial number effectively characterizes flow transition.

Stress tensor components vary with inertial number.

Flow behavior differs between quasi-static and flowing phases.

Abstract

The rheology of 2D steady surface flow of cohesionless cylinders in a rotating drum is investigated through {\em Non Smooth Contact Dynamics} simulations. Profile of volume fraction, translational and angular velocity, rms velocity, strain rate and stress tensor were measured at the midpoint along the length of the surface flowing layer where the flow is generally considered as steady and homogeneous. Analysis of these data and their inter-relations suggest the local inertial number - defined as the ratio between local inertial forces and local confinement forces - to be the relevant dimensionless parameter to describe the transition from the quasi-static part of the packing to the flowing part at the surface of the heap. Variations of the components of the stress tensor as well as the ones of rms velocity as a function of the inertial number are analysed within both the quasi-static and the flowing phases. Their implications are discussed.