The effect of air on sand near the jamming point

Static granular matter is traditionally studied in terms of contact forces between the particles only. Recent experimental evidence shows that this framework is insufficient to describe loosely packed fine granular matter: The influence of the interstitial air needs to be taken into account. This influence becomes particularly strong where the contact forces between the grains become vanishingly small, i.e., close to the jamming point. The objective of this project is to study in detail how the ambient, interstitial air influences the structure of loosely packed, static granular matter close to the jamming point. In particular, we want to clarify the following, questions:

In one of the first experiments we measure the pressure difference over and the air flow through the sand bed during the events caused by an impacting ball: splash and penetration, jet formation, and granular eruption. The used setup allows for fluidization of the sand bed to create a loose packing (41%). The experiments are done at different container pressures and different release heights.

Figure 1: Experimental setup

Info: Devaraj van der Meer

Researchers: Tess Homan, Detlef Lohse, Devaraj van der Meer.
Embedding: JMBC
Sponsors: FOM

Max Planck Gesellschaft