Shape of free-fall arch in quasi-2D silo--颗粒学报PARTICUOLOGY

Wang, Q., Chen, Q., Li, R., Zheng, G., Han, R., & Yang, H. (2021). Shape of free-fall arch in quasi-2D silo. Particuology, 55, 62-69. https://doi.org/10.1016/j.partic.2020.10.001

Shape of free-fall arch in quasi-2D silo

Qi Wang ^{a 1}, Quan Chen ^{a 1}, Ran Li ^b, Gang Zheng ^b, Ren Han ^a, Hui Yang ^a *

a School of Optical-Electrical and Computer Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
b School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China

10.1016/j.partic.2020.10.001

Volume 55, April 2021, Pages 62-69

Received 19 May 2020, Revised 3 September 2020, Accepted 1 October 2020, Available online 29 October 2020, Version of Record 3 February 2021.

E-mail: yanghui@usst.edu.cn

Highlights

• The experimental method could be used to obtain the FFA above the orifice.

• The average FFA after several times is parabolic. The shape of FFA has a certain effect on the flow rate through the orifice.

• The structure of FFA shows instability from flowing state to jamming in the silo.

Abstract

In this study, the optical flow method is used to measure the velocity distribution of a granular flow in a rectangular quasi-two-dimensional silo. Using the velocity gradient, a free-fall arch (FFA) is obtained and its geometric characteristics are calculated. A parabola-shaped FFA structure is discovered above the orifice in the steady flow state. The shape of the FFA affects the flow rate through the orifice. Furthermore, as jamming begins to occur, the geometry of the FFA disappears gradually from both sides and then from the middle; finally, the FFA disappears completely in the state of jamming. As the boundary between finite-stress and stress-free regions, the FFA facilitates further studies regarding the discontinuity of the stress area above the orifice.

Graphical abstract

Keywords

Granular flow; Optical flow method; Velocity field; Free-fall arch; Flow rateJamming

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