2D stokesian simulation of particle aggregation at quiescent air/oil-water interfaces

Aggregation of particles on a liquid interface is controlled by inter-particle forces and hydrodynamic interactions. Previous experimental work has shown atypical structures despite diffusion limited cluster aggregation like behavior. It is likely that this is primarily due to the role of capillary quadrupoles in allowing particle repositioning after aggregation, which is tested here.

Using Stokesian dynamics and inter-particle forces unique to particles at liquid interfaces, aggregation of particles adsorbed to a liquid interface is studied. Simulations' parameters are adjusted to control hydrodynamic interaction strength, initial particle position, and inter-particle forces magnitudes to compare to existing experimental results and hypothesis.

It is found that initial particle position plays a small role on equilibrium interfacial microstructure but has a significant impact on aggregation kinetics. Interfacial hydrodynamic interactions and inter-particle forces have a strong impact on equilibrium microstructure by altering the amount particles can reposition, which is consistent with published results. Capillary forces that allow significant repositioning after contact appear to play a key role in previously observed fractal dimensions of particle laden interfaces.