Flow and clog in a silo with oscillating exit

Kiwing To and Hsiang-Ting Tai
Phys. Rev. E 96, 032906 – Published 14 September 2017

Abstract

When grains flow out of a silo, flow rate W increases with exit size D. If D is too small, an arch may form and the flow may be blocked at the exit. To recover from clogging, the arch has to be destroyed. Here we construct a two-dimensional silo with movable exit and study the effects of exit oscillation (with amplitude A and frequency f) on flow rate, clogging, and unclogging of grains through the exit. We find that, if exit oscillates, W remains finite even when D (measured in unit of grain diameter) is only slightly larger than one. Surprisingly, while W increases with oscillation strength Γ4π2Af2 as expected at small D, W decreases with Γ when D5 due to induced random motion of the grains at the exit. When D is small and oscillation speed v2πAf is slow, temporary clogging events cause the grains to flow intermittently. In this regime, W depends only on v—a feature consistent to a simple arch breaking mechanism, and the phase boundary of intermittent flow in the Dv plane is consistent to either a power law: Dv7 or an exponential form: DeD/0.55. Furthermore, the flow time statistic is Poissonian whereas the recovery time statistic follows a power-law distribution.

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  • Received 26 May 2017

DOI:https://doi.org/10.1103/PhysRevE.96.032906

©2017 American Physical Society

Physics Subject Headings (PhySH)

  1. Research Areas
Fluid Dynamics

Authors & Affiliations

Kiwing To* and Hsiang-Ting Tai

  • Institute of Physics, Academia Sinica, Taipei 115, Taiwan

  • *ericto@gate.sinica.edu.tw

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Issue

Vol. 96, Iss. 3 — September 2017

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