Abstract
The flow characteristics of a gravity-driven dense granular flow in a granular bed with a contracted drainage orifice are studied by using discrete element method and quantitative analysis. Three values of discharging rates, ranging from fast to slow dense flows, are investigated. Time variations and derivatives of mean forces and velocities, as well as their respective correlations, are analyzed to quantitatively depict the characteristics of granular flow as well as flow regime categorization. The auto-correlation functions, as well as their Fourier spectrums, are utilized to characterize the differences between the mechanisms of slow and fast granular flows. Finally, it is suggested that the flow regimes of slow and fast flows can be characterized by the kinetic and kinematic flow properties of particles.
Highlights
Data Availability Statement: All relevant data are within the paper
This work aims to provide the underlying complex mechanisms of slow granular flows as well as some important issues on flow regime characterization, via exploring the intermittency characteristics of a slow granular flow comparing to a fast dense flow
The discrete element method (DEM), which is based on the soft-sphere approach proposed by Cundall and Strack [21], is utilized for the present study to numerically simulate the granular dynamics
Summary
Instead of the hysteretic transition, Fischer et al [16] observed temporal intermittency in the rotating drum with spontaneous erratic switches from discontinous to continous flow regime Such intermittent feature has been found in other types of flows, such as a collection of rigid frictional disks inside a narrow vertical pipe [17], where the intermittent flow is composed of alternating phases of creep motions when the pressure at the bottom of the granular assembly rises nonlinearly with time and sudden slip. More research work is needed to better understand the features of slow particle flow as well as the flow regime characterization Motived by this consideration, this work aims to provide the underlying complex mechanisms of slow granular flows as well as some important issues on flow regime characterization, via exploring the intermittency characteristics of a slow granular flow comparing to a fast dense flow
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