Collapse of a granular raft: Transition from single particle falling to collective creasing

Abstract

Particles can aggregate on a fluid surface through capillary interactions, a phenomenon famously known as the Cheerios effect. Despite their ubiquity, few studies have considered the dynamics of the rafts comprising heavy granular particles. We experimentally test the collapse of granular rafts upon biaxial compression and observe two unexpected failure modes: individual particle expulsion for small particles and collective creasing for large particles. By combining potential energies of the raft and liquids, we calculate the shape of the particle-laden interface, which quantitatively matches our experiments.