Paper Number
EF18 

Session
Emulsions, Foams, and Interfacial Rheology

Title
Stokesian dynamics simulations of interfacial colloidal aggregation under shear flow

Presentation Date and Time
October 10, 2017 (Tuesday) 11:30

Track / Room
Track 3 / Crystal C

Authors (Click on name to view author profile)

1. Laal-Dehghani, Nader (Texas Tech, Mechanical Engineering)
2. Christopher, Gordon F. (Texas Tech, Mechanical Engineering)

Author and Affiliation Lines (in printed abstract book)
Nader Laal-Dehghani and Gordon F. Christopher
Mechanical Engineering, Texas Tech, Lubbock, TX 79409

Speaker / Presenter 
Laal-Dehghani, Nader

Text of Abstract
Controlling the formation of colloidal aggregates at fluid interfaces is important due to the prevalence of Pickering emulsions and particle laden interfaces in commercial applications and industrial processes. As a result, recent experimental studies have focused on microstructure formation of particle laden interfaces undergoing surface flow. However, there is a wide phase space of parameters that affect these systems, making it difficult to generalize experimental results. Computational approaches are well suited to address this problem through use of non-dimensional control parameters and allow explicit characterization of the effect of underlying physical mechanisms.

In this study, colloidal aggregation at an air-water interface under shear flow is explored by means of 2D Stokesian dynamics simulations. Monodisperse, spherical, charged particles are modeled on an interface with dominant attractive inter-particle interactions balanced by solvent-mediated interactions, including hydrodynamic and Brownian forces. Two initial configurations of particles, crystal packed and randomly placed, are subjected to a surface Couette flow and aggregation kinetics are monitored. Particles form anisotropic aggregates extended by the subjected shear flow for both initial configurations. However, initial positioning of the particles changes kinetics and structural properties of these aggregates. In particular, randomly positioned particles aggregate faster, forming denser less open structures. Furthermore, fractal dimension of aggregates depends primarily on shear rate and secondarily on surface coverage. The simulation results indicate that controlling surface microstructure of such systems through flow is a viable strategy in manipulating properties of interface.