Granular Impact Dynamics: Acoustics and Fluctuations

TL;DR

This study investigates the impact dynamics of granular media, revealing that force fluctuations are driven by acoustic pulses from grain collisions, with energy dissipated through grain networks, enhancing understanding of granular impact behavior.

Contribution

It introduces detailed high-speed visualization and analysis of acoustic and fluctuation phenomena during granular impact, highlighting the role of grain clusters and energy propagation networks.

Findings

Force fluctuations are strongly correlated with acoustic pulses.

Collisions with grain clusters dominate the fluctuation dynamics.

Energy is dissipated along networks of grains.

Abstract

In the corresponding fluid dynamics video, created for the APS DFD 2012 Gallery of Fluid Motion, we show high-speed videos of 2D granular impact experiments, where an intruder strikes a collection of bidisperse photoelastic disks from above. We discuss the force beneath the intruder, which is strongly fluctuating in space and time. These fluctuations correspond to acoustic pulses which propagate into the medium. Analysis shows that this process, in our experiments, is dominated by collisions with grain clusters. The energy from these collisions is carried into the granular medium along networks of grains, where is it dissipated.