Discharge Flow of Spherical Particles from a Cylindrical Bin: Experiment and DEM Simulations

Rafał Kobyłka,Mateusz Stasiak,Józef Horabik,Marek Molenda,Joanna Wiącek,Maciej Bańda,Piotr Parafiniuk

doi:10.3390/pr9111860

Rafał Kobyłka, Mateusz Stasiak + Show 5 more

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https://doi.org/10.3390/pr9111860

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Abstract

A series of the DEM simulations of the outflow of wooden spheres from a flat-bottomed container was reported, considering the maximum diameter to arrest the flow. Numerical simulations of the discharge process were performed, and the micro-mechanics of the discharged particles were described. The effect of the sliding friction coefficient between particles, rolling friction coefficient, and modulus of elasticity of particles on the clogging process was investigated. The results of the simulations of the mass flow rate of spheres have shown a fairly close agreement with the experimental results. The real particles of wood were not perfectly spherical, their properties were anisotropic, and their frictional properties were non-homogenously distributed on the surface. Nevertheless, these deviations from ideal conditions did not produce a considerable discrepancy in the results. No direct relationship between the interparticle friction and the clogging was found; however, a relationship between the stability of the dome formed at flow arrest and the rolling friction was observed. An increase in Young’s modulus of particles by two orders of magnitude did not affect the clogging process, but a slightly higher probability of clogging was found for softer particles.

Highlights

Gravitational flow is a basic phenomenon for numerous technologies important for undisturbed flow, dosing based on the flow rate, consistency of the composition of mixtures in agriculture, as well as the food or pharmaceutical industry
Numerous efforts have been made to predict the mass flow rate of granular materials discharged from the silo
A study on the flow rate of sands and seeds varying in grain size discharged from a silo with various outlet widths conducted by Beverloo et al in 1961 [9] revealed a relationship between the mass flow rate and the mean grain diameter

Summary

Introduction

Gravitational flow is a basic phenomenon for numerous technologies important for undisturbed flow, dosing based on the flow rate, consistency of the composition of mixtures in agriculture, as well as the food or pharmaceutical industry. The study of the hopper discharge of granular materials has an extensive history and still remains an important research area, as the general understanding of the problem is far from being satisfactory. Numerous efforts have been made to predict the mass flow rate of granular materials discharged from the silo. The authors proposed a law predicting the flow rate of grains through an orifice considering its dependence on different parameters. It has been revealed that the flow rate is different for small and large orifices. While the flow rate of grains through large orifices is known to be dependent on its diameter to a 5/2 power law [9], this relation breaks down for small orifices [14,15]. Numerical simulations of flow from a hopper conducted by Danczyk et al [17] showed high sensitivity of flow to contact parameters and the need for detailed local observations of the process for the validation of the computational technique

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