Cluster Formation and Relaxation in Particle Rafts under Uniform Radial Expansion

Abstract

Particle rafts floating at an air-liquid interface exhibit a variety of behaviors when interfacial flow is introduced. Motivated by previous experimental observations, the failure pattern of particle rafts under uniform radial expansion is reported in this paper. The expansion process is specifically designed to expand the system affinely in the radial direction and to keep the velocity gradient constant throughout. A strong resemblance to the results of particle rafts under uniform uniaxial expansion[1] is found. The size of the cluster emerging as the rafts are pulled apart scales inversely with the pulling velocity. This is a result of two competing velocities: the inter-particle separation speed provided by the flow and a size-dependent relaxation speed for clustering. A model, generalized from a one-dimensional linear (in)stability calculation, is in agreement with the failure morphology found for this radially expanded system. Nonlinear relaxation and particle rearrangement is observed after the initial clustering occurs. This is a feature unique to a two-dimensional system. With its easily accessible particle dynamics at the microscopic level, this system provides insights into the morphology controlled by two competing mechanisms in two or higher dimensions and across different scales.

References in corpus (10)

• Formation of Galaxy Clusters
• The 'Cheerios effect'
• Elasticity of an interfacial particle raft
• Granular Character of Particle Rafts
• Aggregation of frictional particles due to capillary attraction
• Wrinkles, folds and plasticity in granular rafts
• Microbial range expansions on liquid substrates
• Shock driven jamming and periodic fracture of particulate rafts
• Amorphous to amorphous transition in particle rafts
• Strain localization and failure of disordered particle rafts with tunable ductility during tensile deformation