(102j) Role of Tangential Interactions in Breakage and Restructuring of Colloidal Aggregates in Laminar Flows

Harshe, Y. M., ETH Zurich
Lattuada, M., ETH Zurich
Morbidelli, M., Institute of Chemical and Bioengineering, ETH Zurich

Abstract: In the processing of colloidal suspensions the suspended particle aggregates undergo different mechanisms, namely aggregation, breakage, and restructuring. The steady state size and structure of the final aggregate is governed by the interplay of these mechanisms. The extent of these mechanisms is decided by both the fluid forces exerted on individual particle and the inter-particle forces. The hydrodynamic interactions account for the hydrodynamic fluid forces whereas the inter-particle forces are represented by the DLVO interactions. Recently, Pantina and Furst (2005) experimentally demonstrated the presence of tangential forces between touching particles, which are capable of withstanding the bending moments. Their proposed theory was modeled by Becker and Briesen (2008) to develop a suitable model for computer simulations. The significance of all interactions except the tangential forces has been studied in different ways in the literature. In the present study we have used Stokesian dynamics (Brady and Bossis, 1989) model to investigate the motion of fractal aggregates under different flow conditions. The inter-particle forces are incorporated through the DLVO theory and tangential interactions as described by Becker and Briesen (2008). By switching on and off the role of tangential interactions was quantified for wide size range and morphologies of aggregates under different flow conditions after analyzing the steady-state structures of the resulting aggregates.

Reference: Pantina, J. P. and Furst, E. M. Elasticity and critical bending moment of model colloidal aggregates. Phys Rev Lett, Vol. 94, (2005)

Becker, V. and Briesen, H. Tangential-force model for interactions between bonded colloidal particles. Phys Rev E, Vol. 78, - (2008)

Brady, J. F. and Bossis, G. Stokesian dynamics. Annual Review of Fluid Mechanics, Vol. 20, 111-157 (1988)