Effect of viscosity on the avalanche dynamics and flow transition of wet granular matter (Open Access)--颗粒学报PARTICUOLOGY

Kasper, J. H., Magnanimo, V., de Jong, S. D. M., Beek, A., & Jarray, A. (2021). Effect of viscosity on the avalanche dynamics and flow transition of wet granular matter. Particuology, 59, 64-75. https://doi.org/10.1016/j.partic.2020.12.001

Effect of viscosity on the avalanche dynamics and flow transition of wet granular matter (Open Access)

Jens H. Kasper ^a *, Vanessa Magnanimo ^b, Sjoerd D.M. de Jong ^a, Arjan Beek ^a, Ahmed Jarray ^a *

a Multi-Scale Mechanics (MSM), Thermal and Fluid Engineering, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
b Construction Management and Engineering (CME), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands

10.1016/j.partic.2020.12.001

Volume 59, December 2021, Pages 64-75

Received 30 July 2020, Revised 22 October 2020, Accepted 8 December 2020, Available online 2 January 2021, Version of Record 13 October 2021.

E-mail: j.h.kasper@student.utwente.nl; a.jarray@utwente.nl

Highlights

• A DEM model is employed to investigate the effect of viscosity on wet granular avalanches.

• Simulations are compared to experimental measurements, showing quantitative agreement.

• Increasing the viscous forces decreases the avalanche amplitude and granular temperature.

• Large viscous forces preclude intermittent rigid body motion of the bed, inducing continuous flow.

• The avalanching-continuous flow transition is predicted using a phase diagram.

Abstract

The dynamic behaviour of granular flows is important in geo-mechanics and industrial applications, yet poorly understood. We studied the effects of liquid viscosity and particle size on the dynamics of wet granular material flowing in a slowly rotating drum, in order to detect the transition from the avalanching to the continuous flow regime. A discrete element method (DEM) model, in which contact forces and cohesive forces were considered, was employed to simulate this flow behaviour. The model was validated experimentally, using glass beads in a wooden drum and water–glycerol mixtures to tune the liquid viscosity. The DEM simulations showed comparable results to the experiments in terms of average slope angle and avalanche amplitude. We observed that the avalanche amplitude, flow layer velocity and granular temperature decrease as the liquid viscosity increases. This effect is more pronounced for smaller sized particles. The increase in viscous forces causes the flowing particles to behave as a bulk, pushing the free surface towards a convex shape. In addition, avalanches become less pronounced and the granular flow transitions from the avalanching regime to the continuous regime. The avalanching flow regime is marked by intermittent rigid body movement of the particulate bed and near-zero drops in the granular temperature, while no rigid body movement of the bed occurs in the continuous flow regime. We identified the avalanching-continuous flow transition region as a function of a dimensionless granular Galileo number.

Graphical abstract

Keywords

Granular avalanche; Transition; Cohesion; Viscosity; Rotary drum; DEM

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