Discharge of spherical grains from silos with oscillating orifice

Kiwing To^1*, Chien-Hung Yi²

¹Institute of Physics, Academia Sinica, Taipei, Taiwan
²Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan

* Presenter:Kiwing To, email:ericto@gate.sinica.edu.tw

We study the discharge process of mono-disperse plastic beads from a silo with an orifice that is driven to oscillate sinusoidally with amplitude a and frequency f in the horizontal direction. We find that the discharge rate W follows the Beverloo Law: W ∝ (D-D_o)^2.5 that relates W to the orifice diameter D. Surprisingly, the effect of the orifice oscillation to W depends on D. When D is smaller than five times the diameter of the bead d, W increases with the speed of the oscillation v=2πaf. On the other hand, when D ≥ 5d, W decreases with v at large v. These observations will be discussed in terms of the grains dynamics close to the orifice.

Keywords: granular flow, oscillating orifice, silo discharge