(375b) The Effect of Hydrodynamic Interactions on the Aggregation of Colloidal Suspensions

Developing a quantitative understanding for the behavior of colloidal suspensions under the effect of repulsive and attractive interactions, under high concentrations, in the presence of gravity of shear forces, has been a challenging endeavor. Simulations strategies, such as Brownian Dynamics, have proved to be one of the key elements to clarify aspects of the fate of suspensions that can otherwise be difficult to probe experimentally. The mechanistic insights provided by simulations on the competition of the various forces at play has allowed to reach a better understanding of the physics at play. But one of the aspects that in early works has been often neglected is the effect of hydrodynamic interactions. Notoriously difficult to account for, hydrodynamic interactions have been often considered of marginal importance, compared to other factors. Only with the introduction of computational methods such as Stokesian dynamics, some light about the role of hydrodynamics has been shed. The objective of this presentation is to show instead how only by accounting for hydrodynamic interactions the behavior of colloidal suspensions can be properly described, especially under those conditions (high concentrations, gravity, shear), where complex many body effects are relevant. Through a series of examples, this works aims at showing how only with hydrodynamics can explain the behavior of suspensions under sedimentation, how the presence of hydrodynamic interactions sometimes accelerates and sometimes slows down the aggregation of particles, and how strongly not only the kinetics but also the structure of colloidal suspension dynamics differs with vs. without these elusive interactions.

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