Effects of vibration frequency on intruders' position in granular bed

Abstract

In this Letter, we study the motion of multiple intruders in a vertically vibrated granular bed. From molecular dynamics simulations, it is found that the mean vertical position of the intruders, relative to the base of the container, is governed primarily by the vibration frequency for a fixed vibration acceleration. The intruders stay in the upper layer of the granular bed at low frequency, then sink into the granular bed at a certain depth as the frequency increases, but rise up again at high frequency. This implies that the mean position of the intruders in the granular bed can be controlled by decreasing or increasing the vibration frequency. A subsequent theoretical analysis is also conducted to explore the mechanism behind the phenomenon.