Mechanism for Surface Waves in Vibrated Granular Material

TL;DR

This study uses molecular dynamics simulations to analyze how surface waves form in vertically vibrated granular materials, revealing the key role of particle collisions and horizontal movements.

Contribution

It uncovers the detailed processes of horizontal particle movements and their correlation with surface profiles, advancing understanding of wave formation in vibrated granular media.

Findings

Horizontal particle movements increase sharply during collisions.

Post-collision horizontal velocities are correlated with the surface profile.

Two distinct processes govern particle movements leading to surface waves.

Abstract

We use molecular dynamics simulations to study the formation of surface waves in vertically vibrated granular material. We find that horizontal movements of particles, which are essential for the formation of the waves, consist of two distinct processes. First, the movements sharply increase while the particles are colliding with a bottom plate, where the duration of the collisions is very short compared to the period of the vibration. Next, the movements gradually decrease between the collisions, during which the particles move through the material. We also find that the horizontal velocity field after the collisions is strongly correlated to the surface profile before the collisions.